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LIBRARY
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University

 

 

 

This is to certify that the

dissertation entitled

Late Transition Metal Polychalcogenides:
Synthesis, Structure, and Applications

presented by

Kan g-Woo Kim

has been accepted towards fulfillment
of the requirements for

PhD . Chemis try
degree 1n

 

 

 

 

Major professor

Date 10/14/93

 

MSU is an Affirmative Action/Equal Opportunity Institution 0-12771

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MSU Is An Affirmative Action/Equal Opportunity Institution

 

 

LATE TRANSITION METAL POLYCHALCOGENIDES: SYNTHESIS,
STRUCTURE, AND APPLICATIONS

By

Kang-Woo Kim

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Chemistry

1993

 

ABSTRACT

LATE TRANSITION METAL POLYCHALCOGENIDES: SYNTHESIS,
STRUCTURE, AND APPLICATIONS

By

Kang-Woo Kim

The chemistry of late transition metal (Group 10, 11, and 12)
polychalcogenides has been developed quite extensively during the
last decade, particularly in the field of heavier polychalcogenides (Se
and Te). Both conventional solution and hydro(methano)thermal
synthetic methods have been sucessfully employed for the synthesis
of these metal polychalcogenides. As a result, a number of new
compounds with interesting structures have been prepared and
structurally charaterized by single crystal X—ray diffraction study.
These compounds include KdeSelo, (RMe3N)[M(Te4)] (M=Cu, Ag;
R=Me, Et), (Et4N)4[Hg7Se9], (Et4N)4[Hg7Selo], (Mew)2[Hg(Se4)2]-
0-5DMF, (Me4N)2[Hg(Se4)2], {(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2],
(Et4N)4[Cd4Te12], (Me4N)4[Hg4Teizl, K4lPt4822l'4H20, K4[Pt45622],
(Ph4P)2[Pt(S4)2], and (Ph4P)4[Pt(S4)(Ss)2][Pt(S5)3]. The structures of
these compounds are diverse and range from simple molecular to
interpenetrating 3D polymeric types. The most notable ones are, (l)

K2PdSe1o which is the first metal polychalcogenide with an

 

 

interpenetrating framework structure and one of the earliest
examples that demonstrate the effectiveness of the hydrothermal
method for the synthesis of metal polychalcogenides; (2)
(RMe3N)[M(Te4)] which possesses a 2D layered structure and
implicates the possibility of intercalation chemistry on metal
polychalcogenide layers. Physicochemical properties of these
compounds have been studied using far—IR, UV/Vis, and TGA.
Optical and electrical properties are also reported where available.
The late transition metal polychalcogenides have been studied
as precursors for the synthesis of electronically important
semiconductor compounds. Soluble metal polychalcogenides can be
decomposed to the corresponding binary metal chalcogenides under
mild conditions using chalcogen abstracting reagents such as R3P and
CN'. Nanometer-sized particles of CdSe and a metastable phase of y—
MnSe can be prepared by this method. Using a mixture of
[Cd(Se4)2]2' and [Mn(Se4)2]2‘ as precursors, we could obtain Cd1_
anxSe in the whole range of x, for the first time. Magnetic

properties of Cd1-anxSe and y-MnSe compounds have been studied.

 

 

To My Wife and Sons

iv

 

ACKNOWLEDGMENT

I most sincerely thank my research advisor, Professor Mercouri
G. Kanatzidis. Without his patient guidance, encouragement,
dedication and support, none of the work described in this

dissertation would have been possible.

I also thank Professor J. A. Cowen for magnetic susceptibility
measurements with helpful suggestions and comments, Professor C.
R. Kannewurf for charge transport property measurements, Professor
K. Klomparens for assistance in TEM experiments, Dr. D. Ward for

precious discussions on single crystal X—ray diffraction studies.

Appreciation is also extended to Professor H. A. Eick, Professor
J. L. Dye, and Professor J. McCracken for serving as members of my

research committee.

My special thanks go to each member in the Kanatzidis group
fOF their kindness and friendship, which gave me such an enjoyable

experience of just being a co—member.

Finally, I would like to express my deepest gratitude to my
Wife, Mi—Jung and sons, Sang—Bin and Sang—Woon for their

Understanding and encouragement throughout this thesis work.

Financial support given by a BASF fellowship (1992—1993),
National Science Foundation, Center for Fundamental Materials
Research, and Department of Chemistry at Michigan State University

is gratefully acknowledged

vi

 

TABLE OF CONTENTS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Page
LIST OF TABLES xii
LIST OF FIGURES x vii
ABBREVIATIONS xxii
CHAPTER] INTRODUCTION 1
I. Background and Objective 1
II. Synthetic Methods 7
II-l. Conventional solution methods ......................................... 7
(1) Use of polychalcogenide aninm R
(2) Extraction from metal/chalcogen alloys ............... 9
(3) Use of elemental chalcogens 9
(4) Use of hydrogen chalcogenides ............................. 10
(5) Use of trialkylsilyl 1 D ‘ 11
(6) Use of chalcogen—abstracting reagents ............... 12
II—2. Molten salt synthesis 12
Il—3. Hydro(solvato)thermal Synthesis 13
111. Application of Metal Polychalcogenides as Precursors
to Solid State Materials 1S
LIST OF REFERENCES 18
CHAPTER 2 GROUP 12 METAL POLYSELENIDE CHEMISTRY:

STUDIES ON (Me4N)2[Hg(Se4)2]-0.5DMF,

(M64N)2[Hg(Se4)2],

{(CH3)N(CH2CH2)3N(CH3)}[113(364)2],

(Et4N)4[Hg7Se10], AND (Et4N)4[Hg7Seg] .................................. 26
ABSTRACT 77
INTRODUCTION 79
EXPERIMENTAL SECTION 20

Reagents 30

Physicochemical Methods 31

Synthesis 2’)
Sodium diselenide, NazSez 27
Bis(tetramethylammonium)
bis(tetrase1enido)-mercurate(II) 0.5—DMF,
(Me4N)2[Hg(Se4)2]'0.5DMF 3%

vii

'una’xga-- ~ -'

 

 

Bis(tetramethylammonium)
bis(tetraselenido)—mercurate(II),

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Me4N)2[Hg(Se4)2] s4
Dimethyl(triethylene)diammonium
bis(tetraselenido)—mercurate(II),
{(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2] ............................... 34
Tetra(tetraethylammonium) (diselenido)—
octa(selenido)—heptamercurate(II),
(Et4N)4[Hg7(Sez)(Se)sl as
Tetra(tetraethylammonium) nona(selenido)—
heptamercurate(II), (Et4N)4[Hg7Se9] ............................ 36
X—ray Crystallographic Studies 36
RESULTS AND DISCUSSION 5?
1. Synthesis 5’)
2. PhySiCOChemical Studies SS
2.1 UV/Vis spectroscopy SS
2.2 Far—IR spectroscopy SS
2.3 Thermal Gravimetric Analysis 58
3. Description of Structures 64
3.1 Structure of [Hg(Se4)2]2' 64
3.2 Structure of [Hg7Se10]4' 66
3.3 Structure of [Hg7Se9]n4n- 75
LIST OF REFERENCES R4
CHAPTER 3 GROUP 12 METAL POLYTELLURIDE CHEMISTRY:
STUDIES ON (Et4N)4[Cd4Te12] AND
(Me4N)4[Hg4T612] 27
ABSTRACT 88
INTRODUCTION >29
EXPERIMENTAL SECTION 90
Reagents 90
Physicochemical Methods 91
Synthesis 91
Tetra(tetraethylammonium) di(tellurido)—
di(ditellurido)—di(tritellurido)—
tetracadmate(II),
(Et4N)4[Cd4(Te)2(T62)2(T63)21 91
Tetra(tetramethylammonium) di(tellurido)-
di(ditellurido)~di(tritellurido)—
tetramercurate(II),
(Me4N)4[Hg4(Te)2(Tez)2(T63)2] 92
X-ray Crystallographic Studies 92
RESULTS AND DISCUSSION 100

 

viii

 

 

1. Synthesis 100

 

 

 

 

2. Physicochemical Studies 101

2.1 UV/Vis spectroscopy 101

2.2 Far-IR spectroscopy 102

2.3 Thermal Gravimetric Analysis ............................ 102

3. Description of Structures 105

LIST OF REFERENCES 1 13

 

CHAPT ER 4 GROUP 11 METAL POLYTELLURIDE CHEMISTRY:
THE LAYERED METAL POYTELLURIDES,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(RMe3N)[M(Te4)] (M=Cu, Ag; R=Me, Et) ............................. 115
ABSTRACT 116
INTRODUCTION 118
EXPERIMENTAL SECTION 1 19

Reagents 119
Physicochemical Methods 119
Synthesis 121
Tetramethylammonium tetratellurido-
CUprateG), (Me4N)[CU(Te4)] 121
Tetramethylammonium tetratellurido—
argenate(I), (M64N)[Ag(Te4)l 121
Ethyltrimethylammonium tetratellurido-
cuprate(I), (EtMe3N)[Cu(Te4)] 122
Ethyltrimethylammonium tetratellurido—
argenate(I), (EtMe3N)[Ag(Te4)] 122
X—ray Crystallographic Studies 123
RESULTS AND DISCUSSION 1'37
1. Synthesis 137
2. Physicochemical Studies 138
2.1 Far-IR spectroscopy 138

2.2 UV/Vis diffuse reflectance spectroscopy ....... 142
2.3 Conductivity and thermopower

 

 

measurements 142
3. Description of Structures 147
LIST OF REFERENCES 162

 

CHAPTER 5 GROUP 10 METAL POLYCHALCOGENIDE CHEMISTRY:
STUDIES ON K2PdSe1o, K4[Pt4822]-4H20, K4[Pt48622],
(Ph4P)2[Pt(S4)2]'CH3OH, AND
(Ph4P)4[Pt(S4)(Ss)2][Pt(Ss)3l 165

 

‘1!» 2w-

 

PARTI Hydrothermal Synthesis of K2PdSelO: Coexistence
of Two Large Interpenetrating Three—Dimensional

 

 

 

 

 

 

 

 

 

 

Frameworks of [Pd(Se4)2]2' and [Pd(Se6)z]2‘ ..................... 166
ABSTRACT 166
INTRODUCTION 168
EXPERIMENTAL SECTION 169

Reagents 169

Physicochemical Methods 169

Synthesis 170

Dipotassium (tetraselenido)-(hexaselenido)-
palladate(II), K2[Pd(Se4)(Se6)] ..................................... 170

X—ray Crystallographic Studies 170
RESULTS AND DISCUSSION 178

1. Physicochemical Studies 178

1.1 Far—IR spectroscopy 173

1.2 UV/Vis diffuse reflectance spectroscopy .....

178

 

 

 

 

 

 

 

 

 

 

 

 

 

2. Description of Structure 181
3. Synthesis 194
LIST OF REFERENCES 196
PART II Synthesis and Characterization of New Platinum
Polysulfide(selenide)s: K4[Pt4Szz]'4H20, K4[Pt4Se22],
(Ph4P)2[Pt(S4)2]-CH3OH, and
(Ph4P)4[Pt(S4)(Ss)2l[Pt(Ss)3l 7m
ABSTRACT 700
INTRODUCTION 7m
EXPERIMENTAL SECTION 7m
Reagents 7m
Physicochemical Methods 702
Synthesis 7114
Tetrapotassium hexa(trisulfido)-
tetra(sulfido)~tetraplatinate(IV) tetrahydrate,
K4[Pt4(S)4(Ss)6l'4H20 704
Tetrapotassium hexa(triselenido)—
tetra(selenido)—tetraplatinate(IV),
K4[Pt4(Se)4(Se3)6] 704
Di(tetraphenylphosphonium) di(tetrasulfido)-
platinate(11) monomethanolate,
(Ph41’)2[Pt(S4)2l-CH30H 70s
Tetra(tetraphenylphosphonium)
(tetrasulfido)—penta(pentasulfido)-
diplatinate(IV), (Ph4P)4[Pt(S4)(S5)2][Pt(Ss)3] ......... 205

 

r

X—ray Crystallographic Studies ................................................ 206
RESULTS AND DISCUSSION .................................................................... 223
1. Synthesis ..................................................................................... 223
2. Physicochemical Studies ....................................................... 227
2.1 UV/Vis spectroscopy .............................................. 227
2.2 Far—IR spectroscopy ................................................ 227
3. Description of Structures ...................................................... 235
3.1 Structure of [Pt4822]4' in (II) ............................... 235
3.2 Structure of [Pt(S4)2]2' in (IV) ............................ 238
3.3 Structure of [Pt(Ss)2(S4)]2' and [Pt(85)3]2'
in(V) .............................................................................. 244
LIST OF REFERENCES ................................................................................. 250

CHAPTER 6 THE USE OF SOLUBLE METAL POLYCHALCOGENIDES
AS LOW TEMPERATURE PRECURSORS TO
NAN OCRYSTALLINE BINARY AND TERNARY

 

METAL CHALCOGENIDES .......................................................... 253
ABSTRACT ..................................................................................................... 254
INTRODUCTION ........................................................................................... 255
EXPERIMENTAL SECTION ....................................................................... 256

Reagents ............................................................................................ 256
Physicochemical Methods .......................................................... 257
Synthesis ........................................................................................... 259
Preparation of CdSe, using KCN ................................... 260
Preparation of CdSe, using (n-Bu)3P ......................... 260
Preparation of HgSe, using KCN ................................... 260
Preparation of HgSe, using (n-Bu)3P ......................... 261
Preparation of SnSe, using KCN ................................... 261
Preparation of HgTe, using (n-Bu)3P ......................... 262
Preparation of Cdo,5Mno,5Se, using (n-Bu)3P ......... 262
Preparation of y-MnSe, using (n-Bu)3P .................... 263
RESULTS AND DISCUSSION .................................................................... 264

CdSe crystallites ................................................................. 266

HgSe crystallites ................................................................. 273

SnSe and HgTe crystallites ............................................ 277

Cd1-anxSe and y—MnSe crystallites ......................... 281

LIST OF REFERENCES ................................................................................. 295

xi

 

LIST OF TABLES

Page
Table 1.1. Various Coordination Modes of Polychalcogenide
Ligands (sz') in Metal Polychalcogenide

Complexes ............................................................................................ 2
Table 2.1. Summary of Crystallographic Data for

(Me4N)2[Hg(Se4)2]'O.5DMF (I) and

 

(Me4N)2[Hg(Se4)2] (II) ................................................................. 39
Table 2.2. Summary of Crystallographic Data for
(Et4N)4[Hg7Se1o] (IV) and (Et4N)4[Hg7Se9] (V) .................. 40

Table 2.3. Fractional Atomic Coordinates and Beq Values for

(Me4N)2[Hg(Se4)2]-O.5DMF (I) with Their Estimated
Standard Deviations in Parentheses ...................................... 41
Table 2.4. Fractional Atomic Coordinates and Bag Values for
(Me4N)2[Hg(Se4)2] (II) with Their Estimated
Standard Deviations in Parentheses ...................................... 42
Table 2.5. Fractional Atomic Coordinates and Beq Values for
(Et4N)4[Hg7Se10] (IV) with Their Estimated
Standard Deviations in Parentheses ...................................... 43
Table 2.6. Fractional Atomic Coordinates and Bag Values for
(Et4N)4[Hg7Se9] (V) with Their Estimated Standard

Deviations in Parentheses .......................................................... 45

Table 2.7. Calculated and Observed X—ray Powder Diffraction
Pattern of (Me4N)2[Hg(Se4)2]-O.5DMF (I) ............................. 48

Table 2.8. Calculated and Observed X—ray Powder Diffraction
Pattern of (Me4N)2[Hg(Se4)2] (II) ........................................... 49

Table 2.9. Calculated and Observed X-ray Powder Diffraction
Pattern of (Et4N)4[Hg7Se1o] (IV) .............................................. 50

Table 2.10. Calculated and Observed X—ray Powder Diffraction
Pattern of (Et4N)4[Hg7Se9] (V) .................................................. 51

Table 2.11. Far—IR Spectral Data for (Me4N)2[Hg(Se4)2]-O.5DMF

(I), (Me4N)2[Hg(Se4)2l (II),
{(CH3)N(CH2CH2)3N(CH3)}ng(Se4)2l (HI),
(Et4N)4[Hg7Seiol (IV), and (Et4N)4[Hg7Se9] (V). ................ 58
Table 2.12. TGA Data for (Me4N)2[Hg(Se4)2]'O.5DMF (I),
(Me4N)2[Hg(Se4)2] (H),
{(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2l (HI),
(Et4N)4[TIg7Se1o] (IV), and (Et4N)4[Hg7Seg] (V). ................ 63

xii

 

Table 2.13.

Table 2.14.

Table 2.15.

Table 2.16.

Table 2.17.
Table 2.18.

Table 2.19.

Table 3.1.

Table 3.2.

Table 3.3.

able 3.4.
able 3.5.
able 3.6.

able 3.7.

able 3.8.

ble 3.9.

 

 

 

Average Bond Distances (A) and Angles (deg) in

the [Hg(Se4)2]2' Anions of

(Me4N)2[Hg(Se4)2l°0.5DMF (I), (Me4N)21Hg(Se4)2l

(II), [Na(1S—crown-5)]2[Hg(Se4)2], and
(Ph4P)2[Hg(Se4)2] ........................................................................... 65
Selected Bond Distances (A) and Angles (deg) in

the [Hg(Se4)2]2‘ Anion of (Me4N)2[Hg(Se4)2]'0.5DMF

(I) ......................................................................................................... 69
Selected Bond Distances (A) and Bond Angles (deg)

in the [Hg(Se4)2]2' Anion of (Me4N)2[Hg(Se4)2]

(II) ....................................................................................................... 70
Selected Bond Distances (<3.35 A) between Se and

H Atoms in (Me4N)2[I-Ig(Se4)2]°0.5DMF (I) ........................... 72
Se1ected Bond Distances (A) in the [Hg7Se1o]4-

Anion .................................................................................................. 77
Selected Bond Angles (deg) in the [Hg7Se10]4-

Anion .................................................................................................. 78
Selected Bond Distances (A) and Bond Angles (deg)

in the [Hg7Se9]4* Anion ............................................................... 83
Summary of Crystallographic Data for

(Et4N)4[Cd4Te12] (I) and (Me4N)4[Hg4Te12] (II) ................ 95

Fractional Atomic Coordinates and Beq Values for
(Et4N)4[Cd4Te12] (I) with Their Estimated Standard
Deviations in Parentheses .......................................................... 96
Fractional Atomic Coordinates and Beq Values for
(Me4N)4[Hg4Te12] (II) with Their Estimated

Standard Deviations in Parentheses ...................................... 97
Calculated and Observed X—ray Powder Diffraction
Pattern of (Et4N)4[Cd4Te12] (I) ................................................. 99
Calculated and Observed X-ray Powder Diffraction
Pattern of (Me4N)4[Hg4Te12] (II) ......................................... 100
TGA Data for (Et4N)4[Cd4Te12] (I) and

(Me4N)4[Hg4Te12] (II) ............................................................... 105

Comparison of Average M—Te and Te-Te Distances

(A) in [M4Te12]4‘ Clusters of (Et4N)4[Cd4Te12] (I),
(Me4N)4[Hg4T6121 (II), (BU4N)4[Hg4Te12] and
[Na(15-Crown—5)]4[Cd4Te12]-8DMF ...................................... 110
Selected Bond Distances (A) and Bond Angles (deg)

in the [Cd4Te12]4‘ Anion .......................................................... 111
Selected Bond Distances (A) and Bond Angles (deg)

in the [I-Ig4T612]4’ Anion .......................................................... 112

xiii

 

 

 

 

Table 4.1.

Table 4.2.

Table 4.3.

Table 4.4.

Table 4.5.

Table 4.6.

Table 4.7.

Table 4.8.

Table 4.9.

Table 4.10.

Table 4.11.

Table 4.12.

Table 4.13.

Table 4.14.

Table 4.15.

 

Summary of Crystallographic Data for

(Me4N)[Cu(Te4)] (I) and (EtMe3N)[Cu(Te4)] (III) ........... 125
Summary of Crystallographic Data for

(Me4N)[Ag(Te4)] (II) and (EtMe3N)[Ag(Te4)] (IV) ........ 126
Fractional Atomic Coordinates and Beq Values for
(Me4N)[Cu(Te4)] (I) with Their Estimated Standard
Deviations in Parentheses ....................................................... 127
Fractional Atomic Coordinates and Beq Values for
(Me4N)[Ag(Te4)] (II) with Their Estimated

Standard Deviations in Parentheses ................................... 128
Fractional Atomic Coordinates and BBQ Values for
(EtMe3N)[Cu(Te4)] (III) with Their Estimated

Standard Deviations in Parentheses ................................... 129
Fractional Atomic Coordinates and Beq Values for
(EtMe3N)[Ag(Te4)] (IV) with Their Estimated

Standard Deviations in Parentheses ................................... 130
Calculated and Observed X—ray Powder Diffraction
Pattern of (Me4N)[Cu(Te4)] (I) .............................................. 132
Calculated and Observed X—ray Powder Diffraction
Pattern of (Me4N)[Ag(Te4)] (II) ............................................ 134
Calculated and Observed X-ray Powder Diffraction
Pattern of (EtMe3N)[Cu(Te4)] (III) ...................................... 135
Calculated and Observed X—ray Powder Diffraction
Pattern of (EtMe3N)[Ag(Te4)] (IV) ...................................... 136

Comparison of Mean Standard Deviations and

Te(2) Atom Distances from the Plane Defined by

M(1), Te(l), Te(3), and Te(4) in a MTe4 Ring of
(Me4N)[CU(Te4)] (I), (Me4N)[Ag(Te4)] (11),
(EtMe3N)[Cu(Te4)] (III), and (EtMe3N)[Ag(Te4)]

(IV) ................................................................................................... 150
Comparison of Some Selected Bond Distances (A)

in the [Cu(Te4)]- Anions of (Me4N)[Cu(Te4)] (I) and
(EtMe3N)[Cu(Te4)] (III) ............................................................ 153
Comparison of Some Se1ected Bond Angles (deg) in

the [Cu(Te4)]' Anions of (Me4N)[Cu(Te4)] (I) and
(EtMe3N)[Cu(Te4)] (III) ............................................................ 154
Comparison of Some Se1ected Bond Distances (A)

in the [Ag(Te4)]' Anions of (Me4N)[Ag(Te4)] (II)

and (EtMe3N)[Ag(Te4)] (IV) ................................................... 155
Comparison of Some Selected Bond Angles (deg) in

the [Ag(Te4)]' Anions of (Me4N)[Ag(Te4)] (II) and
(EtMe3N)[Ag(Te4)] (IV) ............................................................ 156

xiv

 

Table 4.16.

Table 5.1.

Table 5.2.

Table 5.3.
Table 5.4.

Table 5.5.

Table 5.6.

Table 5.7.

Table 5.8.

Table 5.9.

Table 5.10.
Table 5.11.
Table 5.12.

Table 5.13.

 

Table 5.14.

Dimensions of 14-Membered Rings in the
[M(Te4)]' Layers of (Me4N)[Cu(Te4)] (I),
(Me4N)[Ag(Te4)] (II), (EtMe3N)[Cu(Te4)] (III), and
(EtMe3N)[Ag(Te4)] (IV)
Summary of Crystallographic Data for K2PdSe10

(I)

l 72

 

Fractional Atomic Coordinates and Beq Values for
K2PdSe10 (I) with Their Estimated Standard

 

Deviations in Parentheses
Calculated and Observed X—ray Powder Diffraction
Pattern of K2PdSe10 (I)

173

175

 

Se1ected Bond Distances (A) and Bond Angles (deg)

in the [Pd(Se4)(Se6)]2— Anion of (I) .................................

Summary of Crystallographic Data for

K4[Pt4822]-4H20 (II) and (Ph4P)2[Pt(S4)2]'CH3OH
(IV)
Summary of Crystallographic Data for
(Ph4P)4[Pt(S4)(SS)2][Pt(Ss)3] (V)

...183

709

210

 

Fractional Atomic Coordinates and Beq Values for
K4[Pt4822]-4H20 (II) with Their Estimated Standard
Deviations in Parentheses

211

 

Fractional Atomic Coordinates and Beq Values for

(Ph4P)2[Pt(S4)2]-CH3OH (IV) with Their Estimated
Standard Deviations in Parentheses

212

 

Fractional Atomic Coordinates and Beq Values for
(Ph4P)4[Pt(S4)(Ss)2][Pt(SS)3] (V) with Their

Estimated Standard Deviations in Parentheses ...........

Calculated and Observed X—ray Powder Diffraction
Pattern of K4[Pt4822]'4H20 (II)

..214

719

 

Calculated and Observed X—ray Powder Diffraction

Pattern of (Ph4P)2[Pt(S4)2]-CH3OH (IV) ............................

Calculated and Observed X-ray Powder Diffraction

Pattern of (Ph4P)4[Pt(S4)(Ss)2][Pt(85)3] (V) ...................

Far—IR Spectral Data for K4[Pt4Szz]-4H20 (II),
K4[Pt43622] (III), (Ph4P)2[Pt(S4)2l'CH3OH (IV),
(Ph4P)4[Pt(S4)(Ss)2][Pt(Ss)3] (V), and

(Ph4P)2[Pt(Ss)3]
TGA Data for K4[Pt4822]-4H20 (II),
(Ph4P)2[Pt(S4)2]'CH3OH (IV), and
(Ph4P)4[Pt(S4)(SS)2][Pt(55)3] (V)

XV

..220

..222

230

734

 

__WW

Table 5.15.
Table 5.16.

Table 5.17.

Table 5.18.

Table 5.19.

Table 6.1.

Table 6.2.

 

 

Selected Bond Distances (A) and Bond Angles (deg)

in the [Pt4822]4' Anion of (II) ................................................ 237
Selected Bond Distances (A) and Bond Angles (deg)
in the [Pt(s4)2]2~ Anion of (IV) ............................................. 242

Comparison of s—s Bond Distances (A) in the Pt(S4)
Ring Containing Compounds with Estimated

Standard Deviations in Parentheses ................................... 243
Selected Bond Distances (A) in the [Pt(S4)(Ss)2]2‘

and [Pt(Ss)3]2‘ Anions of (V) ................................................. 248
Selected Bond Angles (deg) in the [Pt(S4)(Ss)2]2'

and [Pt(Ss)3]2' Anions of (V) ................................................. 249
Binary And Ternary Metal Chalcogenides Prepared
Using the Chalcogen Abstraction Method ........................ 281
Magnetic Freezing Temperatures for Various Cd1_
anxSe ............................................................................................ 292

xvi

 

 

 

2igure 2.1.

iigure 2.2.

7igure 2.3.
iigure 2.4.
2igure 2.5.
2igure 2.6.
2igure 2.7.

igure 2.8.

igure 2.9.

gure 2.10.
gure 2.11.
ure 2.12.
ure 2.13.

ure 2.14.

ure 2.15.

 

LIST OF FIGURES

UV/Vis spectra, in DMF, of (Et4N)4[Hg7Se10] (IV)
(A) freshly prepared and (B) several days later.

(C) UV/Vis spectra of DMF solution of NazSez .............

Far—IR spectra of (A) (Me4N)2[Hg(Se4)2]°0.5DMF (I),
(B) (Me4N)2[Hg(Se4)2l (H), and (C)

Page

..... 56

 

 

 

(III)

 

 

 

 

 

 

 

 

 

 

{(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2] (III) ............................. 57
Far-IR spectra of (A) (Et4N)4[Hg7Se10] (IV) and (B)
(Et4N)4[Hg7Se9] (V) 59
TGA diagrams of (A) (Me4N)2[Hg(Se4)2]-O.5DMF (I)
and (B) (Me4N)2[Hg(Se4)2] (H) 6“
TGA diagram of {(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2]

61
TGA diagrams of (A) (Et4N)4[Hg7Selo] (IV) and (B)
(Et4N)4[Hg7Se9] (V) 57
ORTEP representation of the [Hg(Se4)2]2' anion in
(I) and (II) with labeling scheme 65
Unit cell packing diagrams (stereoview) of (A)
(Me4N)2[Hg(Se4)2]'0.5DMF (I) and (B)
(Me4N)2[Hg(Se4)2l (11) 67
H atom environments around Se atoms of the
[Hg(Se4)z]2' anion in (Me4N)2[Hg(Se4)2]‘0.5DMF
(I) 70
ORTEP representation (two views) of the
[Hg7Se10]4' cluster with labeling scheme 72
The one—dimensional mode of interconnecting
[Hg7Se10]4' clusters 74
Unit cell packing diagram (stereoview) of
(Et4N)4[Hg73610] (IV) 76
ORTEP representation of the [Hg7Se9]4‘
asymmetric unit with labeling scheme 79
(A) The two—dimensional structure of the
[Hg7Se9]n4n‘ framework. (B) A View of a large
hole itself with its dimensions an
(A) Side-view and (B) top—View (stereoview) of
the [Hg7Seg]n4n' layered structure with Et4N+
cations in the unit cell R1

 

xvii

 

 

 

 

 

 

 

 

 

2igure
iigure
figure
iigure

2igure

3igure

iigure
iigure

2igure

Iigure

igure
igure
'gure

gure

 
 
   

3.1.
3.2.
3.3.
3.4.

3.5.

4.1.

4.2.
4.3.

4.4.

4.5.

4.6.
4.7.
4.8.

4.9.

ure 4.10.

ure 4.11.

Far-IR spectra of (A) (Et4N)4[Cd4Te12] (I) and (B)

(Me4N)4[Hg4Te12] (II) ............................................................... 103
TGA diagrams of (A) (Et4N)4[Cd4Te12] (I) and (B)
(Me4N)4[Hg4T612] (II) ............................................................... 104
ORTEP representation (two views) of the

[Cd4Te12]4“ cluster with the labeling scheme ................. 106
ORTEP representation of the [Hg4Te12]4* cluster

with the labeling scheme ........................................................ 107

The packing diagrams (stereo—view) of (A)
((Et4N)4[Cd4T612] (I) and (B) (Me4N)4[Hg4T6121 (11)

in the unit cell .............................................................................. 109
XRD powder patterns of (A)

{(benzyl)Me3N}[Cu(Te4)], (B) {(n-

hexy1)Me3N}[Cu(Te4)], and (C) (Me4N)[Cu(Te4)] (I) ...... 139
Far—IR spectra (CsI pellet) of (A) (Me4N)[Cu(Te4)]

(I) and (B) (EtMe3N)[Cu(Te4)] (III) ..................................... 140
Far—IR spectra (CsI pellet) of (A) (Me4N)[Ag(Te4)]
(II) and (B) (EtMe3N)[Ag(Te4)] (IV) ................................... 141

Optical absorption spectra of (A) (Me4N)[Cu(Te4)]
(I) and (B) (EtMe3N)[Cu(Te4)] (III), derived from
diffuse reflectance measurements ...................................... 143
Optical absorption spectra of (A) (Me4N)[Ag(Te4)]
(II) and (B) (EtMe3N)[Ag(Te4)] (IV), derived from

diffuse reflectance measurements ...................................... 144
Variable temperature electrical conductivity of
(EtMe3N)[Cu(Te4)] (III) ............................................................ 145
Variable temperature thermoelectric power of
(EtMe3N)[Cu(Te4)] (III) ............................................................ 146
Variable temperature electrical conductivity of
(Me4N)[Ag(Te4)] (II) .................................................................. 148

ORTEP representation (50% ellipsoids) and labeling
scheme of [M(Te4)]' layer in the (Me4N)[Cu(Te4)]

(I), (Me4N)[Ag(Te4)] (11), (EtMe3N)[Cu(Te4)] (III),

and (EtMe3N)[Ag(Te4)] (IV), viewed along the a-

axis .................................................................................................... 149
Side-view of the layered structure of

(Me4N)[Cu(Te4)] (I) and (Me4N)[Ag(Te4)] (II)

viewed along the b—axis .......................................................... 158
Side—view of the layered structure of
(EtMe3N)[Cu(Te4)] (III) and (EtMe3N)[Ag(Te4)] (IV)
viewed along the b-axis .......................................................... 159

xviii

 

 

r r

iigure 4.12.

iigure 4.13.

3igure 5.1 .

2‘igure 5.2.

2igure 5.3.

:igure 5.4.

3igure 5.5.

2igure 5.6.

igure 5.7.

igure 5.8.

'gure 5.9.

gure 5.10.

ure 5.11.

 

 

 

 

 

 

 

 

 

Top—view of the layered structure of

(Me4N)[Cu(Te4)] (1) and (Me4N)[Ag(Te4)] (11)

viewed along the a-axis ........................................................... 160
Top-view of the layered structure of

(EtMe3N)[Cu(Te4)] (III) and (EtMegN)[Ag(Te4)] (IV)

viewed along the a-axis ........................................................... 161
Far-IR spectrum (CsI pellet) of K2PdSe10 (I) .................. 179
Optical absorption spectrum of KdeSelo (1),

derived from diffuse reflectance measurements ......... 180

(A) Schematic representation of a single 3D

framework of [Pd(Sex)2]2‘. (B) Schematic view of

the interpenetrating behavior (stereoview) of
[Pd(Se4)2]2~ and [Pd(Se6)2]2' frameworks ........................ 182
ORTEP representation and labeling scheme of the
repeating units in (A) [Pd(Se4)2]2' and (B)

[Pd(Se6)2]2' .................................................................................... 186
Stereoview of the individual substructures of (A)
[Pd(Se4)2]2' and (B) [Pd(Se6)2]2‘ looking down the

c-axis ................................................................................................ 187
Stereoview of both [Pd(Se4)2]2‘ and [Pd(Se6)2]2'
frameworks as they interpenetrate, looking down

(A) the c-axis and (B) the a—axis .......................................... 188
Stereoview of the [Pd(Se4)2]2‘ substructure

looking down (A) the a—axis and (B) the b—axis,
illustrating the large one-dimensional channels .......... 189
Stereoview of the [Pd(Se6)2]2' substructure

looking down (A) the a—axis and (B) the b—axis,
illustrating the large one-dimensional channels .......... 190
Stereoview of (A) [Pd(Se4)2]2' and (B) [Pd(Se6)2]2-
frameworks with K+ atoms included looking down

the a-axis ....................................................................................... 191
(A) Stable assembly of mutually screened Ph4P+

cations and [Pd(Se4)2]2‘ anions. (B) Substitution of
large Ph4P+ for K“ results in short anion-anion

contacts (poor screening), developing destabilizing
repulsive interactions. (C) A stable assembly is
possible by converting chelated Sexz' ligands to

bridges ............................................................................................ 193
UV/Vis spectrum of (Ph4P)4[Pt(S4)(Ss)2][Pt(85)3]
(V)in CH3CN .................................................................................. 228

xix

 

 

Figure

Figure
Figure

Figure
Figure

Figure
Figure

Figure

Figure

iigure
ligure
'igure
i gure
igure

gure

gure
gure
:ure

UI'C

Lll'C

5.12.

5.13.
5.14.

5.15.
5.16.

5.19.

5.20.

5.21.
6.1.
6.2.
6.3.
6.4.

6.5.

6.6.
6.7.
6.8.
6.9.

6.10.

 

 

Far-IR spectra (CsI pellet) of K4[Pt4822]-4H20 (II),

(Ph4P)2[Pt(S4)2]-CH3OH (IV), and

(Ph4P)4[Pt(S4)(Ss)2][Pt(85)3] (V) ........................................... 229
Far—IR spectrum (CsI pellet) of K4[Pt4Se22] (III) .......... 231

TGA diagrams of (A) K4[Pt4822]-4H20 (II) and (B)

(Ph4P)2[Pt(S4)2]'CH3OH (IV) .................................................... 232
TGA diagram of (Ph4P)4[Pt(S4)(Ss)2][Pt(85)3] (V) .......... 233

ORTEP representation and labeling scheme of

[Pt482214’ ......................................................................................... 236
The packing diagram of K4[Pt4822]-4H20 (II) .................. 239

. ORTEP representation and labeling scheme of
[Pt(S4)2]2' in two views ............................................................ 240

The packing diagram (stereo-view) of

(Ph4P)2[Pt(S4)2]-CH3OH (IV) .................................................... 241
ORTEP representation and labeling scheme of

[Pt(Ss)3]2' and [Pt(Ss)2(S4)]2’ in
(Ph4P)4[Pt(S4)(Ss)2][Pt(Ss)3] (V) ........................................... 246
The packing diagram (stereo-view) of
(Ph4P)4[Pt(S4)(Ss)2][Pt(85)3] (V) ........................................... 247
Schematic representation for the structures of
[M(Q4)]2' and [Sn(Se4)3]2‘ precursor complexes ............ 265
X—ray powder diffraction pattern of CdSe obtained
using KCN as a chalcogen abstracting reagent ............... 267

X—ray powder diffraction pattern of CdSe obtained
using (n-Bu)3P as a chalcogen abstracting reagent ..... 268
TEM micrograph of the CdSe particles obtained

using (n-Bu)3P as a chalcogen abstracting reagent ..... 270
SAED (Selected Area Electron Diffraction) pattern

of the CdSe particles obtained using (n~Bu)3P as a

chalcogen abstracting reagent .............................................. 271
Evolution of the CdSe particle growth in DMSO

solution monitored by UV/Vis spectroscopy ................. 272
X—ray powder diffraction pattern of HgSe obtained
using KCN as a chalcogen abstracting reagent ............... 274
TEM micrograph of HgSe crystallites obtained

using KCN as a chalcogen abstracting reagent ............... 275

X-ray powder diffraction pattern of HgSe,
obtained using (n-Bu)3P as a chalcogen abstracting

reagent and passivated with CH3I ...................................... 277
X-ray powder diffraction pattern of SnSe obtained
using KCN as a chalcogen abstracting reagent ............... 279

XX

 

 

Figure

Figure

Figure
Figure
Figure

Figure
Figure

Figure

Figure

6.11.

6.12.

6.13.
6.14.
6.15.

6.16.
6.17.

6.18.

6.19.

 

 

X—ray powder diffraction pattern of HgTe obtained
using (n—Bu)3P as a chalcogen abstracting reagent ..... 280

X—ray powder diffraction pattern of y—MnSe
obtained using (n-Bu)3P as a chalcogen abstracting

reagent ............................................................................................ 283
The phase diagram of the CdSe-MnSe system

(adopted from ref. 21) ............................................................. 284
X—ray powder diffraction patterns for a series of
Cd1-anxSe solid solutions ..................................................... 286
Plot of (A) a- and (B) c— lattice parameters of Cd1_
anxSe solid solutions as a function of x ......................... 287
TGA diagram of y-MnSe ........................................................... 288
Optical absorption spectra of Cd1_anxSe solid
solutions ......................................................................................... 290
Plot of bandgap energies of Cd1-anxSe solid

solutions as a function of x ..................................................... 291
Variable temperature magnetic susceptibility data

for y-MnSe annealed at various temperatures .............. 293

xxi

 

 

 

 

BU4N+
Bu3P

15 -crown~5
DMF
dmpe
DMSO

e n

Et4N+
Me4N+
N ~MeIm
Ph3P
Ph4P+
PPN+
THF

 

 

ABBREVIATIONS

tetra-n-butylammonium(l +)
tri-n-butylphosphine

1,4,7, 1 0, l 3-pentaoxacyclopentadecane
N,N'-dimethylformamide
l,2-bis(dimethylphosphino)ethane
dimethylsulfoxide
ethylenediamine
tetraethylammonium(l +)
tetramethylammonium(1+)
N—methylimidazole
triphenylphosphine
tetraphenylphosphonium(1+)

bis(triphenylphosphoranylidene)ammonium(l +)

tetrahydrofuran

xxii

 

 

CHAPTER 1

INTRODUCTION

I. Background and Objective

All chalcogen atoms (S, Se and Te) tend to catenate giving rise
:0 polychalcogenide ligands, sz- (Q=S, x=2-7, 9; Q=Se, x=2—9; Q=Tea
{=2-5). These polychalcogenide ligands can coordinate to virtually
.11 metal ions, leading into the fascinating field of metal
tolychalcogenide chemistry},2 By virtue of the versatile
oordination modes of these ligands (see Table 1.1), the metal
Olychalcogenide chemistry is rich and diverse, particularly in terms
F structure.
In the last two decades considerable progress has been made in
6 area of metal polysulfide Chemistry. Interest in this area is
ainly driven by its relevance to some important systems such as
)deling of active sites in metalloproteins and metalloenzymes,3 and
talytic processes of hydrodesufurization (HDS) and hydrogenation.4
1 the contrary, no such applicability can be claimed for the heavier
YChalcogenides (Se and Te). This could be one of the reasons for
delayed development in the chemistry of metal polyselenides

l polytellurides.

 

2

Table 1.1. Various Coordination Modes of Polychalcogenide
Ligands (sz') in Metal Polychalcogenide Complexes.

T e Re resentative Exam 1e

Reference

/Q [U(Se2)414- 5
M

\Q

/Q\ (n5-C5H5)2Cr2(CO)4(Sez) o
M M
M

\Q/ M [Ni8(T62)2(C0)12]2' 7
/ \
M M

\(t/
M/ \M

/Q/M [(n5-C5M65)R6(C0)212(T62) s
M I

\Q

/Q——-M (C0)5W(T62)[W(C0)512 9
u\l

Q\M

Q/M [Hg2T6(T62)212‘ 1 0
l
2

\M

Q/M [(n5-C5H4Me)2Ti12(Sez)2 1 1

 

 

 

 

 

 

 

 

 

 

Table 1.1. (cont'd).
Type Representative Example Reference
(‘2 [(CO)6Fe2Te(Te2)]2" 1 2
Q
M/ \M
M\Q [t(nS—CsHs)(CO)2Fe}3(Se2)1+ l 3
Q
M/ \M
\Q/ M [M4T€2(T€2)2(T63)2l4‘ (M=Hg, Cd) 10,14
Q
M/ \M
/Qx-2 x=3 [W2594(Se3)212' l 5
0\ \Q x=4 [Pd(Te4)212' 16
M/ x=5 [F62Q2(Q5)2]2' <Q=s, Se) 17
x_3_6 9 x=6 tHg<Ss>12- 18
’ x=9 [M(so)]- (M==Au, Ag) 19
/Qt-g x=3 [moment'- (Q=s, Se) 20
Q Q x=4 [Pd2(Se4)(Ses)]n2n- 21
11W / x=5 [In2(Se4)4(Ses)]2- 22
x=3-8M x=6 [M(Seo)21nn' (Q=Ga, In, T1) 23
x=7 [Pd2(S7)4]4' 2 4
x=8 [CU2(So)2(Ss)14‘ 2 5
a... :fig‘ifif :2
X: -
K /Q\ g2 6 2
M M

 

 

 

 

 

 

 

Table 1.1. (cont‘d).
Type Representative Example Reference
/Qx-g B-[Cu(84)]nn‘ 2 8
[CU(So)lnn' 2 9
/0\ /Q\
M M
x=4, 6
Qx-2 -
/ [Ag(395)lnn 3 0
Q\ \Q--Q
/ / \
M
x:
M
/ a-[CU(Q4)]nn' (Q=S, Se) 2 8
Q...
/
K /Q\
M M
M\Q [M(Te4)]' (M=Cu, Ag) 3 1
/ Q)
O\ /Q\
M M
/Q"‘Q\ [Cuo(S4)3(Ss)lZ“ 3 2
/
M). f).
/Q\ Q/ Q\ (Me3P)3Os(S7) 3 3
Q‘Q\ 1 /Q’Q
M
/Q\ [CU6(S4)3(SS)12‘ 3 2

 

 

 

 

 

 

Recent events, however, have indicated an increasing utility of the
heavier polychalcogenides for a variety of applications. For example,
they can be used as precursors to the corresponding binary and
ternary metal selenides and tellurides,34 which provide industrial
applications such as IR detection and imaging (e.g. Hg1-xCdee),35
solar cells (e.g. CuInSez, CdTe),36 electroluminescent devices (e.g. ZnS,
CdSe),37 optoelectronics (e.g. T13AsSe3),38 and high energy density
rechargeable batteries (e.g. LixTi52).39

There seem to be two other reasons for the delayed progress in
the heavier polychalcogenide chemistry. First, no convenient
synthesis route to such compounds was available, until recently. In
the synthesis of metal polysulfides, H28 was traditionally used to
produce polysulfide ligands, but this method is not suitable for
)olyselenides and polytellurides. Both HgSe and HgTe are extremely
)oisonous and H2Te is also highly unstable. However, recent
levelopments in synthetic methodologies involving polyselenide and
olytelluride ligands have allowed their chemistry to grow at a rapid
ite. Second, there was an initial perception that the chemistry of
le metal heavier chalcogenides will be similar to that of
)lysulfides. In fact, early in the development of the heavier
ilychalcogenide chemistry some compounds were found to be
alogous to the polysulfides. Examples are [M(Q4)2]2‘ (M=Zn, Cd, Hg,
. Pd, Q=S, Se; M=Hg, Pd, Q=Te),16t4O [Fe2Q2(Q5)2]2' (Q=S, Se),17 and
0Q(Q4)2]2“ (QzS, Se).41 Later, however, it turned out to be that the
tctures of the metal heavier polychalcogenides were distinct and
61 on their own. Typical examples include [V28e13]2",42 [NbTe10]3'
lCr3(Q4)6l3‘ (Q=Se, T 9),44 [M04T616(en)412',45 [WxSeylz' (x=2, y=9,

 

 

 

 

 

 

10; x=3, y=9),15 [Ni(592)(WS<=4)]2‘,46 [AU2(T62)212‘,47 [ngTeslzzlo and
[Hg4Te12]4-.10 This deviation is suggested to be largely due to
differences between sulfur and the heavier chalcogens in size,
equilibria of the various QXZ' species, and redox potentials of the
Q/sz‘ system.2(a)t(e)

In the study of late transition (Group 10, 11, and 12) metal
polychalcogenide chemisty, our main interest was the exploration of
new compounds exhibiting unprecedented, especially polymeric or
multinuclear cluster type structures. On the other hand, molecular
species with less interesting but simpler structures were found to be
useful for application as low temperature precursors to binary and
ternary metal chalcogenides (vide infra). Specifically, the binary and
ternary late transition metal chalcogenides are important
semiconducting materials, enjoying wide practical applications. A
more detailed introduction to this aspect of the work will be
presented later in this chapter.

One of our goals in this research was to explore 2D or 3D
frameworks of late transition metal polychalcogenides stabilized with
large organic counter-cations. Because of large cavities occupied by
organic cations, the anionic frameworks might serve as microporous
materials, provided that the organic cations could be removed
without destruction of the open framework, by either ion exchange
or thermal decomposition. Oxide-based microporous materials such
as zeolite and AlPO4 have been used extensively in industry as size-
:xclusive molecular sieves.48 It could be expected that chalcogenide-

based such materials would be multifunctional materials and possess

 

 

 

 

 

 

 

their own electronic, optical, and catalytic properties, in addition to
the microporosity required for size exclusion.

Various synthetic strategies were employed in order to explore
such materials. One approach was to utilize the structural
dependence of anionic complexes on the counter—cations, as had been
witnessed in many cases.2(a),10,30 Smaller cations usually favor
higher dimensional, that is, polymeric structures, because large
molecular anions could not be well separated by too small spacer
cations unless they are very highly charged. The destabilizing
repulsive force between large discrete anions in close contact can be
dissipated by connecting themselves through bonding interactions.

Another approach was the employment of shorter chain
polychalcogenide ligands (sz‘, x=l-3). It seems that shorter
)olychalcogenide ligands prefer to bridge multiple metal centers,
'esulting in multinuclear cluster or polymeric structures. So far no
nolecular anion of [M(Q2)2]n‘ or [M(Q3)2]n' has been isolated, though
M(Qx)2]n“ (x=4-6) were frequently encountered. With the
forementioned rationale in mind, we adopted several synthetic
tethods including conventional solution and hydro(solvato)therma1
:ethods to proceed in this work. In the following section various
rported synthetic methods for the preparation of metal

llychalcogenides will be described in detail.

Synthetic Methods

II-l. Conventional solution methods

 

 

 

 

(1) Use of polychalcogenide anions

The convenient source of polychalcogenide ligands as a Zintl
salts, A2Qx (A==Alkali metal; Q=S, Se, Te; x=2-6) has contributed
significantly to the development of metal polychalcogenide
chemistry. These salts can be readily prepared either by dissolving
the elemental chalcogen and alkali metal in liquid ammonia, or by
melting a mixture of them. Zintl AzQx salts are quite stable to air and
easily handled without special precautions. These are very soluble in
common polar organic solvents such as DMF and CH3CN. When these
polychalcogenide salts dissolve in solution, it is known that several
different QXZ' species of various chain lengths are present in

equilibrium, as shown in eq (1.1).

2(Qx)2' ___—___, (Qx-1)2’ + (Qx+l)2‘ ............................................. eq. (1.1)

n most reactions it appears that the metal ions choose a
>olychalcogenide chain of desired length from the various QXZ'
pecies in solution. Once metal ions favor one species of a certain
hain length, the equilibrium will shift to produce more of that
pecies.

Zintl polychalcogenide salts are convenient reagents for the
'eparation of metal polychalcogenide complexes, notwithstanding
eir complexity in solution. They often readily react with metal
Its in a metathetical fashion, as some typical reactions are shown in

. 1.2 and 1.3.44,26
rCl3+6K23e4 __QM_F__> [CI’3(SE4)6]3" ....................................... eq (12)

v03 + K2864 DMF . [Ag(Se4)]nn- ........................................ eq. (1.3)

 

 

 

 

2) Extraction from metal/chalcogen alloys

Several interesting metal polychalcogenide complexes have
een extracted from metal/chalcogen alloys by Haushalter et a1. (see

q. 1.4 and 1.5).10,47

 

 

 

 

. Bu NBr
.gHg2T63 en 4 V (BU4N)4[H84T€12]
Ph PB
4 I‘ ’ (Ph4P)2[Hg2TC5] ................... eq. (14)
AuTe2 en, PPNCI > (PPN)2[Au2Te4] .............................. eq. (15)

)me ternary metal tellurides (AxMyTez: A=alkali metal; M=Hg, Au)
:re found to dissolve in highly polar organic solvents. Concurrently
aduced polytelluride ligands and metal ions react in situ to yield
:tal polytelluride complexes, which can be isolated as organic
iion salts. This synthetic process was developed in the early stage
the heavier polychalcogenide chemistry, but it has not been
vadly applied as a general synthetic method, mainly due to the

ited source of such soluble alloys.

Use of elemental chalcogens

The use of elemental chalcogens as reagents. has proven to be
e effective, specially in derivatizing metal chalcogenide
plexes. Elemental chalcogens were readily incorporated into
3 metal monochalcogenides to yield derivative complexes

Lining polychalcogenide ligands (see eq. 1.6 and 1.7).15,41

CH3CN

 

c4]2-' + 868 > [WZSeIOJZ- .............................. eq. (1.6)

 

 

 

 

10

)Q4]2' 4, Q8 My [MoQ(Q4)2]2-' (st, Se) ........................ eq. (1.7)

ently, Rauchfuss et al. have reported that N-alkylimidazole can
ciently enhance the reactivity of elemental Se towards metal

tents such as zinc dust, as shown in eq. 1.8.49

N—MeIm * ..........................
100 °c > [Zn(Se4)(N—Melm)2] eq. (18)

 

Seg

lar reactivity enhancement was also observed with pyridine, as
(Ss)2(py)4] was isolated upon reaction of copper metal and
ental sulfur at r.t..50 The strong coordinating ability of these
nts is believed to promote the dissolution of both sparingly

1e reactants and to make them available for reaction.

se of hydrogen chalcogenides
In the beginning of metal polysulfide chemistry, the
tlfide ligands were mainly produced by the use of hydrogen

, as shown in eq. (1.9).

DH- + (n-I)S ___—___> 802'- .................................................. eq. (19)

1g H28 gas into aqueous base such as an ammoniacal solution
es polysulfide anions, which can then react with appropriate
ons. A great number of metal polysulfides has been obtained
synthetic method.1 This approach, however, can not be easily
:1 to the heavier congeners. Compared to H28 which can be
with relative ease, ste is extremely toxic, malodorous, and

e, and HgTe is very unstable in addition to suffering all the

 

 

 

 

 

 

—’—‘ 5""

11

isadvantages of HgSe. Although the general use of both HgSe and
nge as routine reagents is not promising, they have been employed
)oradically to yield compounds such as (n5—C5H4Me)2V2Se(Se2)2 and
115-C5Me5)Re(CO)2]2(Te2).51a8 For the synthesis of the latter, HzTe
as generated in situ, because of its instability, by the reaction of

2Te3 with HCl.

. Use of trialkylsilyl reagents

It is known that trialkylsilyl compounds, (Me3Si)2S, can be used
place of H28 for the syntheses of sulfide complexes.52 Similarly,
Si)2Q (Q=Se, Te) have proven to be suitable substitutes for the HzQ
=Se, Te). Fenske et al. have used this reagent to synthesize a large
leI‘ of remarkable metal selenide clusters, one example of which

hown in eq. 1.10.53

[2(PPh3)2 + 2(Messi)28e 4111, Ni345622(PPh3)10 eq. (1.10)

this stage no metal telluride complex has been made in this
on, even though appropriate trialkylsilyl compounds such as (t-
ezsi)2Te are available.54 It should be pointed out that these
:nts are basically monochalcogenide reagents, therefore a redox
ss must occur to generate polychalcogenide ligands.

One interesting related reagent, containing a ditelluride unit, is
:2. It was recently used by Dahl et al. for the preparation of
hedral cluster compounds of [Ni3(Te2)2(CO)12]2' and
Te2)Te(CO)15]2-.7 The solubility of thTez and the silylated
ts in nonpolar organic solvents certainly widens the range of

t choices.

 

 

 

 

 

—7—‘ i h" J 3" "-‘T‘fl‘m '

12

3) Use of chalcogen-abstracting reagents

If there is a way to remove internal chalcogen atoms in the
)lychalcogenide ligands of M(Qx) complexes, it will lead to the
:rivatives containing shorter polychalcogenide ligands. R3P
=Phenyl, n—Butyl, etc.) and CN' are reported to be excellent
alcogen-abstracting reagents. Some examples that use these

.gents are shown in eq. 1.11 and 1,12,55,11

 

CI-I3CN
mpe)21r(Se4)]" + 2Ph3P _ 2Ph3PSe* [(dmpe)2lr(Se2)]' eq. (1.11)

CH C1
S_C5H4Me)2Ti(Ses) + 6Bu3P - 6Bu23PSe ’

 

[(ns-C5H4Me)2Ti12(Se2)2 6(1- (1.12)

 

:his type of reaction, the resulting monomeric intermediates with
shorter ligands are quite often unstable, and thus condense into a

inuclear cluster.

II-2. Molten salt synthesis

Molten salts have been important as solvents in solid state
istry. Use of molten salts for the synthesis of metal
halcogenides was accomplished rather recently.56 Molten
metal polychalcogenide salts can act as a solvent as well as a
at. These polychalcogenide salts melt at moderate
ratures (150-500 °C) and offer an intermediate reaction-
ature regime which can not be accessed by either classical

emperature direct methods or conventional solution synthesis.

 

 

_fi—

13

method allows for the exploration of new compounds such as
tically stable phases and otherwise hardly attainable species. As
sult, most metal polychalcogenides prepared by this molten salt
nique present novel and unique structures which range from
ete molecular clusters to extended polymeric structures. One of

arliest example is shown in the following equation:57

375 0C

 

2Nazse4 > NaZTIZSe8 ........................................... Cq (113)

Recently, in our group organic—cation polychalcogenide salts

 

(Ph4P)2Sex) were used successfully for the preparation of
)2[M(Se6)2] (M==Ga, In, T1), remarkable layered structural
)unds.23 This new type of molten salt not only broadens the
oire of this synthetic technique, but also opens up a new
3 for accommodating organic cations in extended framework
res. A barrier that remains to be overcome, however, is that
of these organic polychalcogenide salts decompose at the
atures where they melt. Other potential molten salts include
—cation halide salts which melt without decomposition. (n-
’ (X=Br, Cl) and (n-Bu4N)Br have been known to be good
; for some regioselective reactions in organic synthesis.58
alts behave similar to polar aprotic solvents, specifically DMF,

reaction temperature could be lowered to less than 100 °C.

-3. Hydro(solvato)thermal Synthesis

- _——“—n—‘_.* _.., _

 

 

 

 

—_-..—~—- _ _ .. _
. - HM -3 “4. .

 

l4

Hydro(solvato)therma1 synthesis usually refers to
terogeneous reactions in water (solvent) media above its boiling
int and atmospheric pressure. The previously common distinction
tween conditions below and above the critical point is no longer
de, because little discontinuity is observed upon exceeding the
'tical condition.59 Under hydro(solvato)thermal conditions,
ringly soluble reactants can dissolve and act as highly reactive
cies often with the help of "mineralizers" (complexing agents).
neralizers, which can be the solvent itself or additives such as
roxide or carbonate anions, not only increase the dissolution of
tants but also facilitate crystal growth. Hydro(solvato)thermal
thesis, in contrast to conventional synthetic methods, offers a
tety of advantages such as: (1) crystal growth of sparingly soluble
mounds, (2) stabilization of metal oxidation states difficult to
eve, and (3) synthesis of phases stable only at low temperatures
metastable compounds.59 In the field of metal-oxides,
sphates, and —chalcogenides, this hydrothermal technique has
en to be an excellent synthetic tool.60,61
It came to our attention that metal polychalcogenide complexes
1 be also obtained by the hydrothermal technique, when
:halcogenide ligands were used as reagents as well as
'alizers. As the first example, some novel Mo polychalcogenide

)unds were successfully prepared in our group, as shown in eq.
32

 

2K28e4 172321;: > K12[M012898(Sez)18(Ses)4] °°°°°°°°° 6(1- (1-14)

 

 

 

 

 

15

ollowing these, numerous interesting compounds emerged to
plicate that this technique could be generally applicable for the
nthesis of various metal polychalcogenidesfioaz1,63 Other solvents
ch as methanol could also be employed to extend its versatile
nthetic capability even more. In addition, organic cations survive
thout decomposition in mild hydro(solvato)therma1 conditions, to
1d numerous novel compounds which enjoy the template effect of
go cations. This synthetic approach is still in its infancy, but there
no doubt about its significant contribution to the development of

tal polychalcogenide chemistry in the future.

Application of Metal Polychalcogenides as Precursors to Solid

te Materials

Recently, extremely small semiconductor particles, called
itum dots, Q-particles, nanoclusters, and so on, have attracted a
of interest not only because they represent a transition state
een bulk semiconductor materials and molecular compounds,
also because of the potential application in the field of
catalysis, non—linear optical materials and optoelectronic
'als.64 If the size of the semiconductor particle becomes small
h to be in the nanometer size range (1—10 nm), a blue-shift in
bsorption spectrum can be observed and interpreted in terms of
ntum size effect.65 An electron and a positive hole of the
n, confined to the potential energy wells of nanometer scale

sion in small particles, have been known to cause a

 

 

 

 

_fi— »—.~~----— — ~- .
_ IA -_ — *Ad-qfi—i—_u'-/—Iu _.., . . _

l6

 

ntization of energy levels and a blue-shifted absorption
ctrum.

The achievement of size—controlled and mono—dispersed
iconductor particles is considered to be one of the important
hetic barriers to be overcome. Various synthetic methods have

applied to attain size—modified semiconductor particles. These
ods include a method of structured media (zeolites,66 Langmuir—
gett films,57 inverted micelles,68 etc.), a surface modification
od,69 and an arrested precipitation method.70
We have established another notable synthetic approach for

materials. It has been found that soluble metal
halcogenides could be used as excellent low temperature non-

ytic precursors to the nanometer-sized corresponding binary or

 

ry metal chalcogenides, which are mostly important
onductors. Upon using chalcogen—abstracting reagents such as
and CN“ to remove excess chalcogen atoms, metal
alcogenides easily lead to the simple binary metal

enides. A representative reaction is shown in eq. 1. 15.34

 

 

2‘ DMF + 6Bu3P (or 6CN') >
)2] reflux - 6Bu3PSe (or 6SeCN')
CdSe + 862" -- eq. (1.15)

ethod is very effective especially in stabilizing otherwise
sible and little known metastable phases such as v—MnSe. A
metal chalcogenide, CuInSez has been also successfully
using an appropriate mixture of [In3Se15]3' and [Cu4Se12]2'

rs in our group.34(b)a(°) Furthermore, this method can be

 

 

—

l7

plied for the preparation of multinary solid solutions. Nanometer—
:ed particles of Cd1-anxSe, which is one of the important DMS
iluted Magnetic Semiconductor) materials, was obtained for the
st time in the whole range of x. This material is of both scientific
d technological interest, due to the dependence of its
ysicochemical properties on the concentration of x.

In the following chapters, we will present the synthesis,
ucture, and physicochemical characterizations of new late
nsition metal polychalcogenide complexes, and then the
plication of soluble metal polychalcogenides as molecular
:cursors to solid state materials. For convenience, the metal
lychalcogenide complexes being reported here will be arranged in

:h chapter, according to the periodic groups of their metals.

 

 

_fi—r
18

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(a) Herron, N.; Wang, Y.; Eckert, H. .1. Am. Chem. Soc. 1990, 112,
1322-1326. (b) Steigerwald, M. L.; Alivisatos, A. P.; Gibson, J.
M.; Harris, T. D.; Kortan, R.; Muller, A. J.; Thayer, A. M.; Duncan,
T. M.; Douglass, D. C.; Brus, L. E. J. Am. Chem. Soc. 1988, 110,

3046-3050.

Kuczynki, J. P.; Milosavljevic, B. H.; Thomas, J. K. J. Phys. Chem.
1984, 88, 980-984.

 

 

 

 

CHAPTER 2

GROUP 12 METAL POLYSELENIDE CHEMISTRY: STUDIES ON
(Me4N)2[Hg(Se4)2]°0.5DMF, (Me4N)2[Hg(S€4)21a
{(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2], (Et4N)4[Hg7SemL AND
(Et4N)4[Hg7Se9]

 

26

 

 

 

 

27

ABSTRACT

(Me4N)2[Hg(Se4)2]-0.5DMF was produced by the reaction of
[gC12 with Na28e4 at room temperature in DMF, in the presence of
Ie4NCl. When NazSez was used instead of NazSe4, solvent-free
VIe4N)2[Hg(Se4)2] was obtained in a different crystallographic form.
rle4N)2[Hg(Se4)2]-0.5DMF crystallizes in the monoclinic space group
Z/c (no. 15) with a=33.722(10) A, b=10.658(3) A, c=13.96l(3) A,
=98.05(2)°, V=4969(2) A3 and Z28, whereas (Me4N)2[Hg(Se4)2]
ystallizes in the orthorhombic space group Pbca (no. 61) with
15.898(2) A, b=15.321(2) A, c=l8.523(3) A, V=4512(1) A3 and 228.
1th (Me4N)2[Hg(Se4)2]'0.5DMF and (Me4N)2[Hg(Se4)2] are composed
the molecular [Hg(Se4)2]2' anion and the non—interacting Me4N+
“anic counter cations. The molecular anion [Hg(Se4)2]2‘ can be also
)ilized with the doubly charged cation, {(CH3)N(CH2CH2)3N(CH3)}2+.
'H3)N(CH2CH2)3N(CH3)}[Hg(Se4)2] was prepared from the reaction of
312, NazSe4 and {(CH3)N(CH2CH2)3N(CH3)}12 in a 1:2:1 ratio.
H3)N(CH2CH2)3N(CH3)}[Hg(Se4)2] crystallizes in the monoclinic
:e group P21/c (no. 14) with a=9.538(l4) A, b==10.537(12) A,
9.744(10) A, e=100.02(7)°, V=1954(3) A3 and 2:4.

Reaction of HgClz with NazSez in DMF gave [Hg7Selo]4“, which
isolated as a Et4N+ salt. The use of Nazse instead of Nazsez in the
6 reaction yielded [Hg7Se9]n4n‘, which was also obtained as a
+ salt. (Et4N)4[Hg7Se10] crystallizes in the triclinic space group P1

a=12,231(4) A, b=12.555(6) A, c=21.155(6) A, o=96.15(3)°,
.48(2)°, y=107.84(3)°, V=3031(2) A3 and 2:2, whereas

l)4[Hg7Se9] crystallizes in the orthorhombic space group Pna21

 

 

 

 

 

28

with a=16.066(5) A, b=14.594(3) A, c=24.754(7) A, V=5804(2) A3
and 2:4. [Hg7Se10]4' is a cluster containing eight Sez' and one 5e22-

These clusters interact weakly to form a pseudo 1D chain

ligands.
structure. [Hg7Se9]n4n' is an anionic framework with a 2D layered
structure. The layers are perforated with large holes composed of

30-membered rings of alternating Hg and Se atoms.
UV/Vis and Far—IR spectroscopic studies on all compounds are
reported. TGA studies show that all the compounds thermally

decompose in the temperature range of 130—550 °C without leaving

ny residue material.

 

29

INTRODUCTION

During the last two decades, research on metal
polychalcogenide chemistry has been extensive, especially in the
area of polysulfide chemistry.l Compared to polysulfide chemistry,
relatively less effort has been given to metal polyselenide and
olytelluride chemistry.2 This is partly due to the early belief that
item] polyselenide and polytelluride chemistry would be analogous
o polysulfide chemistry. The presence of the series of [M(Q4)2]2-
M= Zn, Cd, Hg for Q= S, Se and M: Cd, Hg for Q=Te)2(3)t3 complexes
upports this assumption. However, Haushalter recently reported
no interesting mercury polytelluride compounds [Hg4Te1214‘ and
Flnge5]2', whose polysulfide and polyselenide analogs have not been
10wn.4 In addition, [Hg4Te1214‘ is a large cluster and [Hg2Te5]2‘ is a
D polymer, which is quite unusal because all the previously known
roup 12 metal polyselenide and polytelluride compounds such as
1(Q4)212‘, [Hg2(Se4)31232(a) and [Zn(Se4)(Seo)12',5 are simple
)lecular compounds.

It has been known that the structures of metal
lychalcogenide anions are often dependent on the size of the
mic counter-cations. Typical examples can be found in silver
yselenide chemistry where numerous different structural
lpounds that range from molecular clusters to 1D polymers have
71 prepared by using different organic cations.6 T o explore new
ctural chemistry in mercury polyselenide compounds, we
,ded to examine the structural dependence of metal

chalcogenides on the size of organic counter-cation. Until this

 

 

 

 

30

work, the known molecular anions [Hg(Se4)2]2‘ and [Hg2(Se4)3]2* were
only stabilized with the relatively large Ph4P+ and crown ether-alkali
metal complex cations. Here we employed smaller organic cations
such as Me4N+ and the divalent cation, {(CH3)N(CH2CH2)3N(CH3)}2+, in
the hope that different structural complexes of [HgSe,dn' might
result.

In order to achieve'cluster or quasi—dimensional polymeric
ompounds, we investigated the Hg2+/Sex2' system using shorter
ex?” (x=1, 2) ligands in ratios intermediate between 1:2 and 1:1. Use
f shorter-chain polychalcogenides appears to favor larger clusters or
olymeric structures, for example, in the case of [Hg4Te12]4' (2
Hg4(Te)2(T92)2(T93)212') and [ngTeslz‘ (= [Hg2(Te)(T62)2]2‘).

In this chapter we report the synthesis, structural
haracterization, and some physicochemical properties of
W64N)2[Hg(Se4)2l'0.5DMF (I), (Me4N)2[Hg(Se4)2] (II),
'CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2l (III), (Et4N)4[Hg7Setol (IV),7 and
1t4N)4ng7Se91 (V)-7

EXPERIMENTAL SECTION

agents

The chemicals in this research were used as obtained without
her purification: Mercuric chloride, analyzed reagent, J. T. Baker
, Phillipsburg, New Jersey; Sodium metal, analyzed reagent,
linckrodt Inc., Paris, Kentucky; Selenium (-100 mesh, 99.5+%),

aethylammonium bromide (98%), l,4-Diazabicyclo[2.2.2]octane

 

 

 

 

31

(97%) Aldrich Chemical Company Inc., Milwaukee, Wisconsin;
Tetramethylammonium chloride (98+%), Lancaster Synthesis Inc.,
Windham, New Hampshire; Methyl iodide (98%) J. T. Baker Inc.,
Phillipsburg, New Jersey. DMF (A.C.S. grade, EM Science, Gibbstown,
New Jersey) was distilled under reduced pressure after being stored
over KOH for more than a week and over 4A Linde molecular sieves
for several days. Diethyl ether (A.C.S. anhydrous, Columbus Chemical
Industries Inc., Columbus, Wisconsin) was distilled after refluxing
over potassium metal in the presence of benzophenone and

triethylene-glycol—dimethyl ether for several hours.

Physicochemical Methods
Far—IR spectra were measured using Csl pellets of compounds
on a Nicolet 740 FT -IR spectrometer. Each sample was ground along
with CsI to a fine powdery form and a translucent pellet was made
3y applying about 12,000 psi pressure to the ground powder.
UV/Vis spectra were measured on a Hitachi U-2000
pectrophotometer. The molar extinction coefficients were calculated
ccording to Beer-Lambert law:
A = log 10/1, 2 set
'here A is absorbance, e is molar extinction coefficient, c is the
>ncentration in moles per liter, and l is the path length in cm.
Thermal Gravimetric Analysis (TGA) was performed on a
timadzu TGA-50. The samples were heated to 900 °C at a rate of 5
10 °C/min. under a steady flow of dry N2 gas.
Semi-quantitative elementary analysis were done by the

M/EDS (Scanning Electron Microscopy/ Energy Dispersive

 

 

 

 

32

Spectroscopy) technique on a JEOL JSM-35C microscope equipped
with a Tracor Northern TN 5500 X-ray microanalysis attachment.
Single crystals of each sample were mounted on an aluminum stub
with conductive carbon paint not only for their adhesion to the stub,
ut also for the dissipation of charge developed on the sample.
ypical experimental conditions for SEM/EDS analysis are as follows:
ccelerating voltage, 20 KeV; Detector window, Beryllium; Take-off
ngle, 27 deg; Accumulation time, 30 sec. A standardless
uantitative analysis program (SQ analysis) was used to analyze
uantitatively the characteristic X-ray peaks of elements present in
e sample. The X-ray peaks of the elements below atomic number
1 could not be detected because these were absorbed by the
sryllium window of detector. The analysis results reported here
'e the average of three to five measurements on several different
ngle crystals of each compound. A correction factor for Se element
x 1.8) was determined and applied because the Se ratio is always
derestimated due to an artifact of the quantitative analysis

ogram.

nthesis
All experiments and manipulations were performed under an

osphere of dry nitrogen using either a Vacuum Atmosphere Dri-

glove box or a Schlenk line.

Sodium diselenide, Na2Se2 An amount of 16.00 g (0.203
of elemental selenium and 4.66 g (0.203 mol) of sliced pieces of

am metal were charged into a 250 ml round-bottomed flask

 

 

 

33

equipped with a cold finger condenser. A dry ice-acetone bath was

placed beneath the flask and in the cold finger of the condenser.

Ammonia gas was condensed until the flask was about 2/3 full. The

liquid ammonia solution was stirred with a magnetic stirrer for

several hours until the sodium metal dissolved completely and

reacted with selenium. After the reaction was completed, the liquid

ammonia was evaporated off by allowing the solution to warm

:lowly to room temperature under a steady flow of dry nitrogen.
The resulting reddish brown solid was kept in vacuo overnight and
he flask was heated with a mild flame

to remove any residual

mmonia. This solid was ground to fine powder and used without

thher characterization.

Preparations of NazSe4 and NazSe were accomplished by

illowing the same procedure as that for NazSez, with appropriate

oichiometric ratios of elemental selenium and sodium metal.
Bis(tetramethylammonium) bis(tetraselenido)-

ercuratefll) 0.5-DMF, (Me4N)2[Hg(Se4)2]'0.5DMF (I) To
50 ml DMF solution of 0.53 g (1.5 mmol) NazSe4 and 0.16 g (1.5
001) Me4NCl, a 10 ml DMF solution of 0.20 g (0.74 mmol) HgC12 was
led dropwise over a 15 min period. After all the HgC12 solution
1 been added, the color of the resulting solution became dark
dish brown. A 60 ml ether was slowly layered over the filtrate
ution to induce crystallization, after removing undissolved
3ipitates by filtration. Upon standing at room temperature for
day, Slightly reddish black chunky crystals had been formed.

SC crystals were isolated and washed with ether several times.

 

34

More crystals were obtained upon layering an additional 30 ml ether
over the solution after isolation of the first cr0p of crystals. The
yield was 54%. SEM/EDS analysis on these crystals showed the Hg:Se
ratio as 126.9. The density of crystals was measured to be 2.66

g/cm3 with a mixture of CHBr3 and n-heptane.

Bis(tetramethylammonium) bis(tetraselenido)-
mercuratefll), (Me4N)2[Hg(Se4)2] (II) To a 50 ml DMF
solution of 0.45 g (2.2 mmol) NazSez and 0.24 g (2.2 mmol) Me4NCl, a
10 ml DMF solution of 0.30 g (1.1 mmol) HgClz was added dropwise
over a 30 min period. A dark reddish brown color developed while
the HgClz solution was being added. After removing about 0.4 g of
undissolved precipitates (NaCl and insoluble binary phase of Hg/Se)
by filtration, 150 ml ether was layered over the filtrate solution.
Upon standing at room temperature for three days, black platelet
crystals were obtained. These crystals (5 % yield, based on the Hg
metal ion content used) were isolated and washed with ether several
times. SEM/EDS analysis on these crystals showed the Hg:Se ratio as
1:7.7. The density of crystals was measured to be 2.74 g/cm3 with a
mixture of CHBr3 and CCl4.

Dimethyl(triethylene)diammonium bis(tetraselenido)-
nercurateaI), {(CH3)N(CH2CH2)3N(CH3)}IHg(Se4)2] (In) To
50 ml DMF solution of 0.30 g (0.76 mmol) K28e4 and 0.15 g (0.38
mol) {(CH3)N(CH2CH2)3N(CH3)}12 (prepared by the reaction of 1,4-
iazabicyclo[2.2.2]octane and excess methyl iodide in acetone and

1rified by recrystallization in MeOH), a 10 ml DMF solution of 0.10 g

 

 

 

35

).37 mmol) HgClz was added dropwise over 10 min. A dark reddish
rown color appeared upon addition of the HgC12 solution. 5 ml
lethanol was layered over the filtrate solution after removing
ndissolved precipitates by filtration. Upon standing at room
:mperature for three days, black rectangular platelet crystals were
btained. These crystals were isolated and washed with ether
everal times. The yield was 28%. SEM/EDS analysis on these
rystals showed the Hg:Se ratio as 1:6.3. The density of crystals was

leasured to be 3.15 g/cm3 with a mixture of CH212 and CCl4.

Tetra(tetraethylammonium) (diselenido)-octa(selenid0)-
eptamercuratefll), (Et4N)4[Hg7(Se2)(Se)3] (IV) To a 50
11 DMF solution of 0.45 g (2.2 mmol) NazSez and 0.47 g (2.2 mmol)
it4NBr, a 15 ml DMF solution of 0.40 g (1.5 mmol) HgClz was added
ropwise over 20 min. Upon addition of the entire HgC12 solution the
:action solution became reddish brown. 80 ml ether was layered
ver the filtrate solution after removing undissolved precipitates by
ltration. Upon standing at room temperature for a day, a light
own microcrystalline material was obtained. This microcrystalline
aterial was dissolved back in DMF and recrystallized by layering
th ether, to yield light-red rectangular platelet crystals. These
Istals were isolated and washed with ether several times. The
51d was 9%, based on the Hg metal ion content used. These air—
tsitive crystals turned black after exposure to the air for several
lrs. SEM/EDS analysis on these crystals showed the Hg:Se ratio as

The microcrystalline material obtained before recrystallization

36

is a different (Et4N)ngySez phase, which has different XRD pattern

and a Hg:Se ratio of 4:7 as determined by SEM/EDS.

Tetra(tetraethylammonium) nona(selenido)-
heptamercurate(ll), (Et4N)4[Hg7Se9] (V) To a 50 ml DMF

solution of 0.14 g (1.1 mmol) NazSe and 0.16 g (0.76 mmol) Et4NBr, a
10 ml DMF solution of 0.20 g (0.74 mmol)

over 30 min.

HgC12 was added dropwise
Upon addition of the entire HgC12 solution the reaction

:olution became reddish brown. The reddish black undissolved

irecipitates were removed by filtration and the filtrate solution was
but into several long test tubes. A total volume of 50 ml ether was

arefully added to the filtrate solution without a cloudy layer being

)rmed. Upon standing at room temperature for a week, transparent
ght-yellow hexagonal platelet crystals were isolated and washed
ith ether several times. The yield was 54%, based on the Hg metal
'n content used. These crystals turned black immediately upon
:posure to air, especially when they were ground. SEM/EDS
alysis on these crystals showed the Hg:Se ratio as 5:6. The density

crystals was measured to be 3.2 g/cm3 with a mixture of CH2I2
ClCCl4.

ray Crystallographic Studies

Single crystals of (I), (II), and (III) were mounted on the tip of
SS fibers with epoxy adhesive and coated with KrylonTM to protect
m from exposure to air. The crystals of (IV) and (V) were placed
d6 glass capillaries sealed with a flame. The crystallographic data

(I), (IV) and (V) were collected on a Nicolet P3 four-circle

 

 

 

 

37

automated diffractometer. The data for (II) were collected at
Analytical Diffraction Services, Notre Dame, Indiana, on an Enraf—
Nonius CAD4 diffractometer, while the data for (III) were collected
on a Rigaku AFC6S four—circle automated diffractometer. The
accurate unit cell parameters were determined from the 26, w, d), and
x angles of 15 to 25 centered reflections. The intensities of three
standard reflections were checked every 100 or 150 reflections to
monitor crystal and instrument stability. No serious decay was
observed during the data collection period. An empirical absorption
correction based on 1p scans of three strong reflections with X ~90°
was applied to each data set. The structures were solved by direct
methods using the SHELXS—86 software program and refined with
iull—matrix least squares techniques. After isotropic refinement of
lll atoms, a DIFABS correction was applied.8 All calculations were
ierformed on VAXstation 2000 and 3100/76 computers with the
‘EXSAN crystallographic software package of Molecular Structure
jorporation9 or the SHELXS—86 and SDP combined package of
rystallographic programs.10 All the atoms in the anions of
3mpounds were refined anisotropically. The hydrogen positions
ere calculated but not refined.

In the structures of (I) and (II), only N atoms of Me4N+ cations
ere refined anisotropically and the C atoms were refined
)tropically. All non—hydrogen atoms of DMF molecules in (I) were
fined isotropically. The 0(1) and N(3) atoms of DMF are located on
Z-fold axis (1/2, y, 1/4) and C(9) atoms are disordered between
0 positions related by the 2—fold axis (1/2, y, W). with equal

iupancies. The structure of (III) could not be completed, due to a

38

oor data set. Even though [Hg(Se4)2]2' anion was easily found, at
est only two N and two C atoms in the organic cation,
(CH3)N(CH2CH2)3N(CH3)}2+ could be found and the R/RW value was
bout 0.25/0.30 at this stage.

The N atoms of Et4N+ cations in the structure of (IV) were
:fined anisotropically while the C atoms were refined isotropically.
.11 atoms of the Et4N+ cations in the structure of (V) were refined
:otropically.

Tables 2.1-2.2 show the crystal data and details of the
tructure analysis of all compounds except (III). The fractional
oordinates and temperature factors (Beq) of all atoms with their

stimated standard deviations are given in Tables 2.3-2.6.

 

39

 

 

Table 2.1. Summary of Crystallographic Data for
(Me4N)2mg(Se4)2]'0.5D1\4F (I) and (Me4N)2[Hg(Se4)2] (11)-

, (I) (II)
Compound (Me4N)2[Hg(Se4)2]-0.5DMF (Me4N)2[Hg(Se4)2]
Formula C10.5H27.500.5N2.5Hg398 C8H24N2Hg398
FW 1017.11 980.56
Crystal shape polyhedral chunky chunky platelet

Crystal color
Crystal size (mm)
Temperature (°C)
Crystal system
Space group

a (A)

b (A0

C 0A)

9 (deg)

6 (deg)

v (deg)

v'oA3yzz

(1 (cm'l) M0(Ka)
dcalc (g/Cm3)
Scan Method
26max ((198)

No. of reflections
collected

No. of reflections,
Fo2 > 3C5(1:“o)2

No. of variables
Max. shift/esd
Phasing method
i/Rw (%)

reddish black
0.18x0.23x0.32
23
monoclinic
C2/c (No. 15)
33.722(10)
10.658(3)
13.961(3)
90

98.05(2)

90

4969(2), 8
178.0

2.719

0/20

45

3517

1730

144

0.00

direct methods
6.0/6.1

reddish black
0.19x0.31x0.37
23
orthorhombic
Pbca (No. 61)
15.898(2)
15.321(2)
18.523(3)

90

90

90

4512(2), 8
196.0

2.887

03/20

45

6411

1479

13 2

0.00

direct methods
3 .7/3 .2

 

t==X||Fo|-lli'cl-II/lel’1'ol

aw: [z w(|Fo|-|Fcl)2/£ Wall)” 2

 

able 2.2.

40

:V) and (Et4N)4[Hg7Se9] (V).

L

Summary of Crystallographic Data for (Et4N)4[Hg7Se10]

 

. (IV) (V)

ompound (Et4N)4[Hg7Seiol (Et4N)4[Hg7Se9]
ormula C32H80N4Hg7Se10 C32H30N4Hg7Seg
W 2714.75 2635.79

lrystal shape rectangular platelet hexagonal platelet
irystal color light red light yellow

irystal size (mm)

0.08x0.26x0.70

0.09x0.22x0.3l

 

'emperature (°C) 2 3 -107
frystal system triclinic orthorhombic
pace group P1 (no. 2) Pna21 (no. 33)
(A) 12.281(4) 16.066(5)
(A) 12.555(6) 14.594(3)
(A) 21.155(6) 24.754(7)
. (deg) 9615(3) 90
(deg) 9848(2) 90
(deg) 107.84(3) 90
' (A3), 2 3031(2), 2 5804(2), 4
(cm-1) MO(K0t) 2 3 6 2 4 1
:alc (g/cm3) 2.97 3.02
can Method 6/26 6/26
lmax (deg) 4 3 4 5
o. of reflections 74 1 3 42 8 1
illected
). of reflections, 4727 2563
2 > 30(Fo)2
). of variables 317 288
ix. shift/esd 0.00 0.00
asing method direct methods direct methods
1w (‘76) 6.4/7.5 5.3/6.5
T 1/2
ZIIFoI-IFcII/XIFoI Rw={): w(|Fol-IFcD2/XWIF0|2}

 

41

Table 2.3. Fractional Atomic Coordinates and Beq Values for

(Me4N)2[Hg(Se4)2]-0.5DMF (I) with Their Estimated Standard
Deviations in Parentheses.

I;

 

 

gatom x y z 13611 (A2”
Hg(1) 0.36676(3) 0.0640(1) 0.60318(9) 3.44(6)
Se(1) O.32867(8) -0.0586(3) 0.4500(2) 3.8(1)
Se(2) 0.3073(1) 0.2324(3) 0.5324(3) 4.5(2)
Se(3) 0.3612(1) -O.2694(3) 0.6543(2) 4.0(2)
Se(4) O.36151(9) -0.0875(3) 0.7476(2) 3.9(2)
Se(5) 0.33571(9) 0.2901(3) 0.6320(2) 3.9(2)
Se(6) 0.3885(1) 0.4178(3) 0.6033(2) 4.7(2)
Se(7) 0.4155(1) 0.3099(4) 0.4824(3) 5.1(2)
Se(8) 0.43782(8) 0.1252(3) 0.5582(2) 4.2(2)
0(1) 1/2 0.420(6) 1/4 16(1)
N(1) 0.2245(6) 0.098(2) 0.655(2) 4(1)
N(2) 0.0592(6) 0.219(2) 0.098(2) 4(1)
N(3) 1/2 0.227(4) 1/4 5.1(9)
C(l) 0.246(1) 0.059(3) 0.573(3) 5.7(8)
C(2) 0.214(1) 0.233(4) 0.641(3) 8(1)
C(3) 0.250(1) 0.083(5) 0.746(4) 11(1)
C(4) 0.186(1) 0.032(4) 0.647(3) 8(1)
(1(5) 0.1009(8) 0.168(3) 0.114(2) 4.7(7)
(3(6) 0.031(1) 0.133(5) 0.138(3) 10(1)
C(7) 0.057(2) 0.339(6) 0.139(4) 14(2)
0(8) 0.045(1) 0.237(5) 0.003(4) 11(1)
C(9) 0.529(2) 0.299(7) 0.232(5) 6(1)
C(10) 0.525(1) 0.116(8) 0.217(6) 22(1)

 

1 Anisotropically refined atoms are given in the form of the isotropic
Equivalent displacement parameter defined as Beq= (8n2/3)[a2B11 +
’2322 + 02B33 + ab(cosv)B12 + ac(cosB)B13 + bc(cos01)Bz3]. The
inisotropic temperature factor expression is exp[--2712(B11a"‘2h2 + +
3312a*b*hk + ...)].

42

'able 2.4. Fractional Atomic Coordinates and Beq Values for

Me4N)2[Hg(Se4)2] (II) with Their Estimated Standard Deviations in
'arentheses.

I_

 

9m x y 2 BBC! (A2)a
[g(1) 0.30492(6) 0.10367(7) 0.71874(6) 404(5)
6(1) 0.1711(1) 0.1797(2) 0.7715(2) 4.2(2)
6(2) 0.1755(1) 0.1189(2) 0.8852(2) 3.8(2)
6(3) 0.3135(2) 0.1468(2) 0.9243(1) 4.0(1)
Le(4) 0.3942(2) 0.0723(2) 0.8405(2) 4.8(2)
:e(5) 0.3130(2) 0.0542(2) 0.6608(2) 5.0(2)
:e(6) 0.3558(2) 0.0158(2) 0.5453(2) 4.8(2)
16(7) 0.4503(1) 0.0981(2) 0.5650(2) 5.2(2)
:e(8) 0.3627(2) 0.2040(2) 0.6142(2) 4.6(2)
1(1) 0.617(1) 0.360(1) 0.494(1) 4(1)
1(2) 0.426(1) 0.375(1) 0.794(1) 3(1)
:(1) 0.620(2) 0.283(2) 0.450(2) 7.0(6)
3(2) 0.692(2) 0.360(2) 0.543(2) 6.4(6)
3(3) 0.538(2) 0.359(2) 0.535(2) 6.0(6)
3(4) 0.621(2) 0.439(2) 0.450(2) 6.0(6)
‘(5) 0.482(1) 0.303(1) 0.771(1) 3.5(5)
(6) 0.437(2) 0.391(2) 0.872(2) 7.6(6)
(7) 0.338(2) 0.354(2) 0.783(2) 6.4(6)
(8) 0.446(2) 0.452(2) 0.752(2) 7.5(6)

 

 

Anisotropically refined atoms are given in the form of the isotropic
(uivalent displacement parameter defined as Beg: (8n2/3fla2311 +
B22 + c2B33 + ab(cosy)B12 + ac(cos[3)Bl3 + bc(cosa)Bz3]. The
isotropic temperature factor expression is exp[-27r2(B11a*2h2 + +
’~12a*b*hk + ...)].

I..‘J]]‘((((((((((((

43

 

 

 

”able 2.5. Fractional Atomic Coordinates and Beq Values for
Et4N)4[Hg7Se10] (IV) with Their Estimated Standard Deviations in
’arentheses.

Loni x )7 Z Bea (A2)a
[g1 0.4056(2) 0.4756(1) 0.71790(9) 352(4)
1g2 0.7256(2) 0.5211(1) 0.82346(9) 368(4)
[g3 0.6520(2) 0.1923(1) 0.80304(9) 365(4)
Ig4 0.3325(2) 0.1509(2) 0.6966(1) 4.19(5)
IgS 0.5972(2) 0.3266(2) 0.67408(8) 351(4)
Ig6 0.6056(2) 0.7337(2) 0.80952(9) 362(4)
Ig7 0.4144(2) 0.0552(2) 0.76906(9) 377(5)
:61 0.4921(3) 0.4338(3) 0.8385(2) 257(9)
:62 0.4499(3) 0.2363(3) 0.8247(2) 2.7(1)
:63 0.6364(4) 0.5285(4) 0.6844(2) 3.8(1)
:64 0.5620(5) 0.1262(4) 0.6632(2) 4.4(1)
:65 0.8259(4) 0.3724(4) 0.8327(2) 3.3(1)
:66 0.2699(5) 0.2979(4) 0.6441(3) 4.5(1)
:67 0.4045(4) 0.6810(3) 0.7504(2) 3.3(1)
:68 0.7947(4) 0.7363(4) 0.8666(3) 4.7(1)
:69 0.6056(4) 0.0081(4) 0.8390(3) 4.0(1)
1610 0.2339(4) 0.0595(4) 0.7016(3) 4.6(1)
11 0.323(3) 0.677(3) 0.970(2) 3.9(9)
I2 0.011(3) 0.441(3) 0.346(2) 4(1)
[3 0.043(3) 0.129(3) 0.836(2) 4(1)
'4 0.520(3) 0.782(3) 0.553(1) 4(1)

1 0.331(4) 0.785(4) 1.011(2) 5(1)

2 0.335(8) 0.887(8) 0.970(5) 13(3)

3 0.422(5) 0.687(5) 0.936(3) 7(1)

4 0.549(5) 0.737(5) 0.983(3) 7(2)

5 0.320(6) 0.610(6) 1.024(4) 9(2)

5 0.304(6) 0.478(5) 0.986(3) 8(2)

7 0.209(5) 0.631(5) 0.918(3) 7(2)

% 0.098(7) 0.631(7) 0.947(4) 10(2)

’ 0.033(5) 0.421(5) 0.278(3) 7(2)
.0 0.050(6) 0.321(6) 0233(3) 8(2)

.1 0.009(5) 0.341(5) 0380(3) 7(1)

2 0.109(7) 0.299(7) 0383(4) 11(3)

3 0.109(5) 0.449(5) 0.344(3) 6(1)

 

44

Table 2.5. (cont'd).

 

 

atom x y z Beg (A2)a
C14 0.127(7) 0.488(6) 0.413(4) 10(2)
C15 0.104(5) 0.549(5) 0.385(3) 7(2)
C16 0.105(5) 0.656(5) 0.360(3) 7(1)
C17 0.020(6) 0.175(6) 0.903(3) 8(2)
C18 0.083(6) 0.086(6) 0.926(4) 9(2)
C19 0.148(5) 0.219(5) 0.821(3) 6(1)
C20 0.125(5) 0.319(5) 0.806(3) 7(1)
C21 0.057(5) 0.017(5) 0.831(3) 7(2)
C22 0.150(7) 0.012(7) 0.887(4) 10(2)
C23 0.071(5) 0.114(5) 0.787(3) 6(1)
C24 0.064(6) 0.085(6) 0.715(4) 9(2)
C25 0.604(6) 0.758(6) 0.606(4) 10(2)
C26 0.669(5) 0.857(5) 0.662(3) 6(1)
C27 0.581(8) 0.886(8) 0.522(5) 13(3)
C28 0.687(6) 0.880(6) 0.503(3) 8(2)
C29 0.469(6) 0.679(6) 0.501(3) 9(2)
C30 0.406(8) 0.567(8) 0.519(4) 12(3)
C31 0.424(6) 0.806(6) 0.581(4) 10(2)
C32 0.326(6) 0.809(5) 0.535(3) 8(2)

 

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beqz (4/3)[a2B11 +
b2B22 + CZB33 + ab(cosy)B12 + ac(cosfi)Bl3 + bC(COSO()BZS]-

 

45

Table 2.6. Fractional Atomic Coordinates and Beq Values for

(Et4N)4[Hg7Se9] (V) with Their Estimated Standard Deviations in
Parentheses.

 

 

[atom x y z Bea (A2“
Hgl 0.8767(2) 0.0547(2) 0.986 229(5)
Hg2 0.8116(2) 0.1053(2) 0.8375(1) 237(5)
Hg3 0.8570(2) 0.1395(2) 0.8801(1) 2.15(5)
Hg4 0.8081(1) 0.3218(2) 0.9796(1) 207(4)
HgS 0.8589(2) 0.5105(2) 1.0895(1) 239(5)
Hg6 0.9038(2) 0.2793(2) 1.0396(1) 217(5)
Hg7 0.8120(2) 0.5679(2) 1.2212(1) 226(5)
SCI 0.9052(5) 0.1136(4) 0.9760(3) 3.2(1)
$62 0.8251(5) 0.1840(4) 0.9258(3) 3.2(1)
863 0.8320(4) 0.0518(5) 0.7952(3) 2.7(1)
$64 0.8116(4) 0.3176(4) 0.8814(3) 2.2(1)
565 0.7913(4) 0.6688(4) 1.0781(3) 2.4(1)
$66 0.8938(4) 0.4310(5) 1.0003(3) 3.1(2)
367 0.9144(4) 0.1291(5) 1.0809(2) 2.7(1)
$68 0.8845(5) 0.4386(5) 1.1814(3) 3.3(2)
369 0.7478(4) 0.2073(5) 0.7573(3) 2.7(1)
N1 0.668(3) 0.809(3) 0.173(2) 0.9(8)
N2 0.415(3) 0.907(3) 0.410(2) 1.4(9)
N3 0.635(3) 0.571(3) 0.889(2) 1.5(8)
N4 0.492(3) 0.673(4) 0.662(2) 2(1)
C1 0.695(6) 0.892(6) 0.145(4) 5(2)
C2 0.664(4) 0.976(5) 0.172(3) 4(2)
C3 0.697(5) 0.727(6) 0.143(4) 5(2)
C4 0.666(7) 0.710(7) 0.085(5) 8(3)
3 0.565(5) 0.793(5) 0.174(3) 4(2)
36 0.533(4) 0.707(5) 0.198(3) 3(1)
37 0.695(4) 0.811(5) 0.232(3) 3(1)
'38 0.784(4) 0.820(5) 0.238(3) 3(1)
39 0.488(3) 0.971(4) 0.387(2) 1(1)
:10 0.456(5) 1.044(6) 0.345(4) 6(2)
:11 0.340(3) 0.959(4) 0.432(3) 3(1)
:12 0.364(6) 1.016(6) 0480(4) 6(2)
113 0.457(4) 0.848(4) 0.446(3) 3(1)
314 0.401(4) 0.777(4) 0465(2) 3(1)

 

46

 

 

ble 2.6. (cont'd).

)m x y Z Bea (A2”
5 0.385(4) 0.860(5) 0.355(3) 3(1)
6 0.444(5) 0.802(5) 0.322(3) 4(2)
7 0.681(4) 0.556(4) 0.948(2) 2(1)
8 0.629(6) 0.518(6) 0.991(4) 6(2)
9 0.607(5) 0.486(6) 0.866(4) 5(2)
0 0.577(5) 0.495(6) 0.812(3) 5(2)
,1 0.564(3) 0.635(3) 0.906(2) 0.4(9)
,2 0.578(7) 0.720(7) 0.925(5) 7(3)
,3 0.694(6) 0.632(6) 0.860(4) 6(2)
4 0.777(5) 0.579(6) 0.834(4) 5(2)
,5 0.430(4) 0.732(4) 0.638(2) 2(1)
,6 0.459(6) 0.825(7) 0.610(4) 6(2)
.7 0.446(4) 0.592(4) 0.687(2) 2(1)
.8 0.403(6) 0.533(6) 0.645(4) 6(2)
:9 0.556(4) 0.643(4) 0.623(2) 2(1)
»0 0.620(5) 0.586(5) 0.649(3) 4(2)
1 0.531(4) 0.741(5) 0.706(3) 4(2)
2 0.484(5) 0.780(5) 0.743(3) 4(2)

 

 

\nisotropically refined atoms are given in the form of the isotropic
livalent displacement parameter defined as Beg: (4/3)[a2B11 +
‘22 + 02333 + ab(cosy)B12 + ac(cosB)B13 + bc(cosa)B23].

47

XRD (X—ray Powder Diffraction) patterns were obtained on
ther a Phillips XRG-3000 computer-controlled powder
ffractometer or a Rigaku-Denki/RW4OOF2 (Rotaflex) rotating anode
wder diffractometer. Ni-filtered, Cu radiation was used at the
ndition of 35 KV, 35 mA for Phillips XRG-3000, and 45 KV, 100 mA
r Rigaku-Denki/RW4OOF2 (Rotaflex) powder diffractometer. The
ystals of each compound were ground to fine powder and put on a
ass slide with a double-sided sticky tape. Based on the atomic
ordinates from the X-ray single crystal diffraction study, X-ray
1wder patterns for all compounds were calculated by either the
ftware package CERIUS11 or the program POWD—IOIZ. The
served X-ray powder patterns were in good agreement with those
lculated, assuring the homogeneity and purity of the compounds.
[lculated and observed X-ray powder patterns that show d-spacings
d intensities of strong hkl reflections are compiled in Tables 2.7-

[0.

 

48

Calculated and Observed X-ray Powder Diffraction

:m of (Me4N)2[Hg(Se4)2]-O.5DMF (I).

e 2.7.

 

I/Imax (obs, %)

dobs (A)

dcalc (A)

l

f

 

 

44009820505845613634
12041123221111122111

1

170817442692983290
51360870631088744321
60877666444433333333
11

50213975370209.4190
72370970631098844321
60877666444433333333
11

000042Q2£03222334QOQ

01011000011020123122

2.778 34

3.10
2 785
2.784

31.53

233

 

49

ble 2.8. Calculated and Observed X-ray Powder Diffraction
ttem of (Me4N)2[Hg(Se4)2] (II).

I‘

 

[1 k l dcalc (A) dobs (A) I/Imax (Obs, 70)
. 1 1 9.48 9.44 30
D 0 2 9.26 9.22 15
’. 0 0 7.95 7.89 20
D 2 1 7.08 7.05 100
l 1 1 6.59 6.55 40
l 0 2 6.03 6.00 16
l 2 l 5.29 5.28 30
l 3 2 3.90 3.88 17
i 1 3 3.89
i 4 0 3.83 3 82 14
. 3 3 3.82
1 0 4 3.49 3.48 13
l l 3 3.27 3.26 10
1 2 5 3.26
5 3 3 3.16 3.15 9
Z 3 4 3.15
. 4 4 2.902 2.90 11
i 2 1 2.901
"- 2 5 2.823 2.82 12
2 6 2.818 18
1 3 2.780 2.78 13
3 4 2.597 2.59 21
5 3 2.595
5 3 2.259 2.26 9

 

 

50

.e 2.9. Calculated and Observed X-ray Powder Diffraction
am of (Et4N)4[Hg7Selo] (IV).

 

rk 1 defile (A) dobs (A) I/Imax (obs, %)
0 0 11.5 11.5 72
0 2 10.3 10.4 100
0 2 8.52 8.39 70
0 4 5.08 5.08 30
—1 4 4.69 4.70 10
0 2 3.83 3.85 5
0 6 3.44 3.41 15
0 6 3.14 3.10 20
-4 1 3.13

—4 1 2.987 2.98 15
-1 7 2.977

4 2 2.886 2.88 50
-4 3 2.884

4 2 2.884

2 1 2.712 2.71 15
—4 3 2.651 2.64 15
-4 3 2.627 2.62 20
-1 3 2.620

4 4 2.535 2.53 10
-1 9 2.324 2.32 5

 

 

51

.e 2.10. Calculated and Observed X-ray Powder Diffraction
3111 of (Et4N)4[Hg7Se9] (V ).

 

 

. k l dcalc (A) dobs (A) I/Imax (Obs, %)
0 2 12.4 12.6 15
1 1 9.90 10.2 45
1 2 8.14 8.34 20
0 0 8.03
0 1 7.64 7.81 100
1 3 7.18 7.35 12
2 0 6.64 6.84 15
1 2 6.12 6.24 9
1 3 5.35 5.43 12
2 1 5.28
1 2 4.66 4.74 43
2 0 4.32 4.37 12
3 3 4.06 4.08 24
1 5 4.05
0 0 4.02
1 0 3.87 3.88 21
0 2 3.82
3 4 3.72 3.75 9
0 3 3.61 3.66 15
2 0 3.52 3.57 11
2 7 3.12 3.16 19
1 1 3.11
3 4 3.11
0 8 3.09 3.13 22
4 3 3.08
3 6 2.930 2.97 17
3 7 2.860 2.89 27
5 1 2.853
2 8 2.805 2.83 17
5 2 2.678 2.72 17

 

 

52

RESULTS AND DISCUSSION

Synthesis

The synthesis of (I) and (III) was accomplished by the

ction of HgClz and NazSe4 in a 1:2 ratio, in the presence of

)ropriate organic cation salts such as Me4NCl

 

and
H3)N(CH2CH2)3N(CH3)}12 in DMF, as represented in eq. (2.1).
DMF
:12 + 2NazSe4 + 2Me4NCl (or {(CH3)N(CH2CH2)3N(CH3)}12) m —>
(Me4N)2[I-Ig(Se4)2]-O.5DMF + 4NaCl (or 4NaI) --------- eq. (2.1)

(0r {(CH3)N(CH2CH2)3N(CH3)} [11336020

: we used the small organic cation, Me4N+ or the divalent cation,
I3)N(CH2CH2)3N(CH3)}2+ of even smaller size per charge, to balance
negative charge on [Hg(Se4)2]2'. The rationale behind using small
nic cations was that large discrete [Hg(Se4)2]2‘ anions might not
)creened properly by these small cations. Instead, they might
different (possibly polymeric) structural compounds, in order to
i repulsive interactions among closely contacted anions.
aver, even with these cations discrete monomeric [Hg(Se4)2]2'
.s were obtained, implying that these cations are not yet small
{h to cause a structural change in the [Hg(Se4)2]2' anion. Even
3r divalent cations such as {H3NCH2CH2NH3}2+ were also tried in

bove reaction, but did not give crystalline mercury polyselenide

ounds.

 

 

 

53

While this study was under way, the hydrothermal synthetic
ethod allowed successful preparation of K4[Pd(Se4)2][Pd(Se6)2]13
)ssessing bridging Sexz' ligands and a 2D layered structure (see
1apter 5). We employed this hydrothermal method for the
nthesis of alkali metal salts of [Hg(Se4)2]2', speculating that alkali
etal ions are small enough to cause the structural changes of the
[g(Se4)2]2', but no crystalline compound except binary HgSe has
:en isolated. This synthetic approach was also applied to the
12+/Se42' system and gave similar results.

The stability of the molecular [Hg(Se4)2]2‘ anion was attested
we again as (11) was obtained upon the reaction of HgC12 and
azSez in a 1:2 ratio, in the presence of Me4NC1. The Se42' ligands in
[g(Se4)2]2' were supplied through the equilibrium among different
1ain-length polyselenide ligands in solution, from the NazSez
agent. It is quite difficult to prepare pure (11), instead a mixture
(1) and (II) was obtained in most cases.

When HgC12 reacted with NazSez in a 2:3 ratio, in the presence
Et4N+ organic cation, a microcrystalline product (Et4N)ngySez (yzz
4:7 by SEM/EDS) was obtained. This microcrystalline product
34N)ngySez was then recrystallized in DMF/ether, to give good
gle crystals of (IV), which was found to contain a large
ltinuclear cluster of [Hg7Se10]4' by a X-ray single crystal study.
are have been numerous attempts to get single crystals of the
ial (Et4N)ngySez product before recrystallization by varying the
:tion and crystallization condition, without success. Interestingly,

use of a 1:2 ratio of HgC12 and NazSez, instead of a 2:3 ratio,

ded again the molecular [Hg(Se4)2]2‘.

 

54

The presence of eight monoselenide and only one diselenide in

[Hg7(Se)3(Se2)]4' cluster of (IV) encouraged us to use the

)noselenide reagent Nazse instead of Na28e2, to see if we can

)duce any analogous compound without a diselenide ligand. The

ction of HgClz and NazSe in a 2. 3 ratio, in the presence of Et4NBr,

 

lded (V) containing a layered framework of [Hg7Se9]n4n' with
noselenide ligands only, as described in eq. (2.2).
DMF
{C12 + 3NazSe + 2Et4NBr r t
(Et4N)4[Hg7Se9] + 4NaCl + 2NaBr ------------------- eq. (2.2)

the preparation of (V), it is important to strictly follow the

hetic procedure, in order to reproduce the product in good yield.

example, no product except red fluffy precipitates was obtained

cloudy layer was allowed to form when the reaction solution was

ed with ether. The single crystals of (V) are transparent light

1w and very sensitive to air, in which they turn opaque dark red.
When Pr4N+ was used instead of Et4N+ in the above reaction,
red transparent crystals of (Pr4N)ngySeZ (y:z = 5:7, by
/EDS) were isolated. Preliminary X—ray single crystal study
ed unit cell parameters as follows: tetragonal (Primitive),
047(5) A, b=16.072(5) A, c=58.321(24) A, V=lSO4l(9) A3. The
ly diffracting nature of these crystals did not allow a data

:tion to be accomplished.

 

 

 

55

Physicochemical Studies

1 UV/Vis spectroscopy
DMF solutions of (I), (II), and (III) give featureless UV/Vis
ectra. (IV) is sparingly soluble in DMF and gives a transparent
ght orange solution with a tinge of green color. Upon standing for
veral days under N2 atmosphere, DMF solutions of (IV) develop a
uch more intense green color and colloidal red precipitates form.
the UV/Vis spectra taken immediately after the solution was
epared, there is only one small peak at 400 nm (e=4.2x103 cm'lM'
(see Figure 2.1(A)). However, several days later, a new strong
arp peak appears at 590 nm (8:6.8X103 cm'lM‘l). The 400 nm
:ak also grows with higher extinction coefficient (8:7.2X103 cm‘lM‘
(see Figure 2.1(B)). These two peaks can be found at the same
:quencies in the UV/Vis spectra of free diselenide in DMF (see
gure 2.1(C)). Therefore, these peaks might be due to Sc)?" anions
)duced as (IV) slowly decomposed in DMF. Compound (V) is
loluble, but decomposes to a black material in polar organic

vents such as DMF.

Far-IR spectroscopy

In the far-IR spectra of (I), (II), and (III) (see Figure 2.2), the
1 peaks in the region of 240 and 270 cm“1 could be assigned to Se—
vibration modes. Similar assignments have been made in the far-
Spectra of other known metal polyselenide and free polyselenide
lplexes such as [F62Se1212' (VSe-Se=258 cm'l),l4 [SnSelzlz' (V36-
273 and 256 cm‘l),15 [AgSexl‘ (x=4, 5) (VSe-Se="265 CHI-9,6

 

56

 

 

 

 

 

 

 

 

 

 

 

 

 

 

a) (A)
U
c
m
_c:
L.
0
U)
_o
<
I I 1
200 400 600 800
q’ (B) 400
‘c’ 590
m
.o
L
0
U)
.9
<1
I I
200 400 600 800
3 (C)
c
m
.n
L
o
(I)
.0
<1
I I
200 400 600 800
Wavelength (nm)
Fe 2.1. UV/Vis spectra, in DMF, of (Et4N)4[I-Ig7Selo] (IV) (A)

2y prepared and (B) several days later.
solution of NazSez.

(C) UV/Vis spectra of

In

 

MOEt-Em ZELI

57

(A)

(B)

(C)

 

 

 

00 340 280 220 160 T10
WAVENUMBER

re 2.2. Far-IR spectra of (A) (Me4N)2[Hg(Se4)2]-0.5DMF (I),
MC4N)2[Hg(Se4)2] (11), and (C) {(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)21

58

’dSe8]2“ (VSe-Se=247 cm‘l),l6 [InxSey]2' (x=2, y=10, 21;
Se-Se=~268 and ~256 CIII'

x=3, y=15)
1),17 [MSe12]' (M=Ga, In, Tl) (Vge-se=~265
0'1),18 [Sex]2' (x=2-6) (VSe-Se=258 cm'l),19 and cyclo-Se6 (VSe-
=253 cm‘l).20 The rest of the peaks in the 140-170 cm'1 range, are

ndidates for the tetrahedral Hg-Se vibration modes.

As shown in Figure 2.3, the far-IR spectra of (IV) and (V) show
'ee peaks in the region of 260, 200, and 180 cm-1, which could be
Ligned for the linear and trigonal Hg—Se vibration modes. A weak

2 cm'1 peak in the spectra of (IV), is a candidate for the

:ahedral Hg—Se vibration mode. The summary of these spectral

a is shown in Table 2.11.

do 2.11. Far-IR Spectral Data for (Me4N)2[Hg(Se4)2]-0.5DMF
(Me4N)2[Hg(Se4)2] (H), {(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2l (HI),
LN)4[Hg7Selol (IV), and (Et4N)4[Hg7Se9] (V)-

 

gEound Vibration Frequency (cm-1)
4N)2[Hg(Se4)2]-0.5- 271 (s)*, 243 (m), 159 (m), 143 (w), 140 (w)
P (I)

de4N)2[Hg(Se4)2] (II) 270 (s), 243 (m), 159 (m), 143 (w), 141 (w)
I3)N(CH2CH2)3N(CH3)} 268 (s), 238 (m), 165 (w), 144 (w), 141 (w)
:(Se4)2] (III)

N)4[Hg78610] (IV) 260 (m), 197 (m), 178 (w), 162 (w)
‘1)41Hg7869] (V) 259 (s), 202 (m), 179 (m)

P;

strong, m: medium, w: weak.

Thermal Gravimetric Analysis

TGA results for all compounds are summarized in Table 2.12
shown in Figures 2.4-2.6. Above 500 °C, all Hg polyselenide

)ounds of (I)-(V) completely lost their weight without leaving

 

 

 

w02<t~§mz<m|~1 rfi. 01V

59

(A)

(B)

MW

 

 

 

& o 340 280 220 160 100
wmeNUMBER

lure 2.3. Far-IR spectra of (A) (Et4N)4[Hg7Se10] (IV) and (B)
1N)4[Hg7Se9] (V).

 

60

 

 

 

 

 

 

 

 

 

 

 

 

(A)
00 " .4
80 *- q
9 -(
60 7 a
L -1
4o — ‘
b -1
20 r -
b ‘1
O 1 l -J L 1? ~3=§
0 200 400 600 800
Temp. (C)
(B)
00 - a
.1
80 -
L -1
.J
80 b
10 - ~
20 1" .1
° 1 ' L ' i 66
0 200 400 600 8
Temp. (C)

re 2.4. TGA diagrams of (A) (Me4N)2[Hg(Se4)2]°0.5DMF
(B) (Me4N)2[Hg(Se4)2] (II).

(I)

 

61

 

 

 

 

 

 

100 ' I I I

8O ' :1

60 ‘

40 - -

20 "

0' . . . . 1======1
O 200 400 600 800

mm 2.5. TGA diagram of {(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2]
I).

 

 

62

 

 

 

 

 

 

 

 

 

 

 

 

(A)

100 - _
8O — _
60 - _
4o - ,
zo - _
O l I l l I l l

O 200 400 600 800
Temp. (C)
(B)

100 ~ -
8O “ -
60 r 7
4o - —
20 1. ‘
0 1 1 r 1 L . L 1 I

0 200 400 600 800
Temp. (C)

gure 2.6. TGA diagrams of (A) (Et4N)4[Hg7Se1o] (IV) and (B)

4N)4[Hg7Se9] (V).

 

 

63

my binary phase of Hg/Se. During pyrolysis, redox reactions occured
)etween Hg2+ metal ions and (poly)selenide anions to form volatile
I-Ig and Se elements. For compounds (I), (II), (IV), and (V), there are
wo steps of weight loss in the temperature ranges of 151-232 and
190-523 °C. Organic cations were lost as organoselenides (ste) and
{3N in the first step, while Hg and Se were lost in the second step. In
he case of (III), the early two weight-loss steps can be attributed to
he loss of organic species while the final step is due to the loss of Hg
1nd Se. From the above thermal decomposition study we can point
)ut that these compounds would not be useful as precursors for the

:orresponding binary Hg/Se compounds.

.‘able 2.12. TGA Data for (Me4N)2[Hg(Se4)2]°O.5DMF (I),
M64N)2[Hg(Se4)2] (II), {(CH3)N(CH2CH2)3N(CH3)}[Hg(Se4)2] (III),
Et4N)4[Hg7Se1()] (IV), and (Et4N)4[Hg7Se9] (V).

g

 

Limpound Temperature range (°C) Weight loss (%)
.Vle4N)2[Hg(se4)2].0.5_ 188 - 218 31.3
’MF (1) 290 — 485 67.7
-(Me4N)2[Hg(Se4)2] (II) 178 - 215 31.2
305 - 493 67.7
CH3)N(CH2CH2)3N(CH3)} 138 — 189 12.3
Hg(Se4)2] (III) 226 - 248 3.4
335 — 507 83.3
1t4N)4[Hg7Selo] (IV) 151 - 232 34.9
333 - 503 62.4
t4N)4[Hg7Se9] (V) 192 - 224 27.7

371 — 523 70.8

k

 

64

3. Description of Structures

31 Structure of [Hg(Se4)2]2' in (I) and (II)

Figure 2.7 shows the structure of the [Hg(Se4)2]2‘ anion
in (I) and (II). The Hg atom is tetrahedrally coordinated by two
chelating tetraselenide ligands. The average Hg-Se and Se-Se
distances, respectively, are 265(3) and 233(1) A for (I), and 265(4)
and 232(2) A for (II). These Hg-Se and Se-Se distances are Virtually
the same as those of the [Hg(Se4)2]2‘ stabilized with much bigger
:ounter cations such as [Na(15—crown-5)]+ and Ph4P+.3(C),(f)
lnterestingly, no structural shrinkage or distortion in the [Hg(Se4)2]7—'

mion was caused by the smaller Me4N+ (see Table 2.13). The closest

7able 2.13. Average Bond Distances (A) and Angles (deg) in the
Hg(Se4)2]2‘ Anions 0f (Me4N)2[Hg(Se4)2]'0.5DMF (I), (Me4N)2[Hg(Se4)2]
11), [Na(15-Crown-5)l2[Hg(Se4)2], and (Ph4P)2[Hg(Se4)2]-

~

Intrachelate Interchelate

 

Eimpound Hg-Se Se-Se Se-Hg—Se Se-Hg-Se
VIe4N)2[Hg(Se4)2]— 265(3) 233(1) 103(2) 113(6)

5DMF(I)

464N)2[Hg(s64)2] 265(4) 232(2) 102(1) 114(13)
'I)

Jams-crown- 265(2) 233(1) 108(1) 111(14)
]2[Hg(Se4)2la

'h4P)2[Hg(s64)2]b 265(2) 232(2) 102(3) NA

¥

Reference 3(e). b Reference 3(0)-

 

 

 

65

 

 

Figure 2.7. ORTEP representation of the [Hg(Se4)2]2' anion in (I)
and (II) with labeling scheme.

 

 

66

ntermolecular Se-Se distances are 3.537(5) and 3.397(4) A,
'espectively, for (I) and (II). Figures 2.8(A) and (B) show the
)acking diagrams of (I) and (II) in the unit cell. Selected bond
listances and angles in the [Hg(Se4)2]2' of (I) and (II) are
:ummarized in the Tables 2.14 and 2.15, respectively.

A solid state 7786 NMR study of metal (poly)selenide complexes
Ias been hindered by the very long relaxation time of 77Se nuclei.
Recently, we have found that the application of a cross-polarization
nethod using the H nuclei of Me4N+ ion can solve the problem of long
'elaxation times.21 Thus, for an accurate interpretation of NMR
:pectra of these complexes, it is necessary to scrutinize not only the
:oordination, but also the H atom environments around each Se site.
Figure 2.9 shows the H atom environments around all Se atoms in (I),
Vhere the Se-"H distances are less than the sum of the van der Waals
'adii22 of H and Se atoms, 3.35 A. The shortest Se---H intermolecular

:ontact is 2.820 A. Selected Se---H distances are summarized in Table

1.16.

.2 Structure of [Hg7Se10]4' in (IV;

As shown in Figure 2.10, [Hg7Se10]4' is odd shaped. It contains
)ur tetrahedral Hg2+ and three linear Hg2+ metal ions, which are
31d together by one diselenide and eight monoselenide ligands.
hUS, [Hg7(Se2)(Se)3]4‘ is a more descriptive formulation. The
1873610]4' cluster is reasonably described as a cage with two
1ndles. The Se(7)-Hg(6)-Se(8) and Se(9)—Hg(7)-Se(10) pseudo—
Iear fragments on either side of the cage represent the handles.

1e central cage is composed of two oppositely placed planar

 

67

 

 

 

 

 

 

 

 

(B)

 

 

 

 

 

 

 

 

 

 

Figure 2.8. Unit cell packing diagrams (stereoview) of (A)
.MC4N)2[Hg(Se4)2]-0.5DMF (I) and (B) (Me4N)2[Hg(Se4)2] (II).

 

HHHH

S1

S1

S1

S1

81

SI

68

 

 

Table 2.14. Selected Bond Distances (A) and Angles (deg) in the
[Hg(Se4)2]2' Anion of (Me4N)2[Hg(Se4)2]-0.5DMF (1). Standard
Deviations Are Given in Parentheses.a
Hg(l)-Se(1) 2.677(3) Se(l)-Se(2) 2.347(5)
Hg(1)-Se(4) 2.609(3) Se(2)-Se(3) 2.344(5)
Hg(1)-Se(5) 2.680(3) Se(3)-Se(4) 2.335(5)
Hg(l)—Se(8) 2.642(3) Se(5)-Se(6) 2.320(5)
Se(6)-Se(7) 2.330(5)
Se(7)-Se(8) 2.311(5)
Hg-Se (mean) 265(3) Se-Se (mean) 2.33(1)
Se(l)-Hg(l)-Se(4) 103.8(1) Hg(1)—Se(l)-Se(2) 98.0(1)
Se(1)-Hg(1)-Se(5) 113.9(1) Hg(1)-Se(4)—Se(3) 94.5(1)
Se(1)-Hg(1)-Se(8) 106.3(1) Hg(1)-Se(5)—Se(6) 100.1(1)
Se(4)-Hg(l)—Se(5) 111.7(1) Hg(1)-Se(8)-Se(7) 94.1(1)
Se(4)-Hg(1)-Se(8) 119.9(1) Se(l)-Se(2)-Se(3) 103.2(1)
Se(5)-Hg(1)-Se(8) 101.5(1) Se(2)-Se(3)-Se(4) 102.0(2)
Se(5)-Se(6)-Se(7) 102-9(2)
Se(6)—Se(7)-Se(8) 102.9(2)

a The estimated standard deviations in the mean bond distances were
calculated by the equation 01 = {in(ln-l)2/n(n-I)}1/2, where In 18 the
distance of the nth bond, 1 is the mean bond distance, and n is the

number of bonds.

th

HHHH

69

Fable 2.15. Selected Bond Distances (A) and Bond Angles (deg) in
.he [Hg(Se4)2]2- Anion of (Me4N)2[Hg(Se4)2] ([1).
Are Given in Parentheses.a

Standard Deviations

 

Hg(1)-Se(1) 2.614(3) Se(1)-Se(2) 2.305(4)
I-Ig(1)—Se(4) 2.708(3) Se(2)—Se(3) 2.350(4)
Hg(1)—Se(5) 2.649(3) Se(3)—Se(4) 2.315(4)
Hg(1)-Se(8) 2.638(3) Se(5)—Se(6) 2.321(4)
Se(6)—Se(7) 2.331(4)

Se(7)—Se(8) 2.324(4)

Hg—Se (mean) 265(4) 86—86 (mean) 232(2)
Se(l)-Hg(1)—Se(4) 101.19(9) Hg(l)—Se(1)—Se(2) 97.9(1)
Se(1)-Hg(l)-Se(5) 126.69(9) Hg(1)—Se(4)—Se(3) 100.4(1)
Se(1)-Hg(1)-Se(8) 107.37(9) Hg(l)-Se(5)—Se(6) 99.0(1)
Se(4)-Hg(1)-Se(5) 9862(9) Hg(1)—Se(8)—Se(7) 95.2(1)
Se(4)—Hg(1)—s6(8) 122.17(9) Se(l)—Se(2)—Se(3) 103.6(1)
36(5)-Hg(1)—Se(8) 102.57(9) Se(2)—Se(3)—Se(4) 102.8(1)
Se(5)—Se(6)—Se(7) 103.6(1)
Se(6)—Se(7)—Se(8) 101.4(1)

 

The estimated standard deviations in the mean bond distances were
alculated by the equation a) = {in(ln—l)2/n(n—I)}1/2, where In is the
istance of the nth bond, 1 is the mean bond distance, and n is the
umber of bonds.

70

 

 

Figure 2.9. H atom environments around Se. atoms of the
[Hg(Se4)2]2- anion in (Me4N)2[Hg(Se4)2]°0.5DMF (I).

 

 

S.
S.
S.
8.
S1
81
S.
81
81
S1

 

_fi—
71

Table 2.16. Selected Bond Distances (<3.35 A) between Se and H
Atoms in (Me4N)2[Hg(Se4)2]-0.5DMF (I).

 

Se(1)—H(15) 2.997 Se(5)-H(2) 3.142
Se(l)-H(8) 3.273 Se(5)-H(8) 3.256
Se(l)-H(1) 3.321 Se(6)-H(13) 3.094
Se(l)-H(3) 3.343 Se(6)—H(l 1) 3.095
Se(2)-H(l) 2.973 Se(6)-H(14) 3.192
Se(2)-H(15) 3.269 Se(7)-H(14) 3.162
Se(3)-H(10) 3.063 Se(7)-H(ll) 3.321
Se(3)-H(6) 3.175 Se(8)—H(21) 3.132
Se(4)-H(6) 2.820 Se(8)-H(22) 3.197
Se(5)-H(3) 2.981 Se(8)—H(l6) 3.220
Se(5)-H(5) 3.021 Se(8)-H(20) 3.345
Se(5)-H(l3) 3.068

 

 

 

 

 

72

 

.0828 $533 :33 .8320
-vBEanw: 05 ..o $363 03: :3330353 Amity—O .cud 0.53%

a:

 

 

 

aom

 

 

 

 

_fi—

73

rhombic Hg28e2 units fused with two five-membered and two six-
membered rings. All members in the planar rhombic Hg2$e2 units
are lying in a least—square plane with an average displacement of
0.101 A. A molecular C2 axis passes through the Hg(5) atom and
bisects the diselenide Se(l)-Se(2) bond. Four mercury atoms, Hg(l),
Hg(2), Hg(3), and Hg(4), lie in a plane with Hg(5) lying 2.349 A above
it, while Hg(6) and Hg(7) lie 0.546 and 0.828 A below it, respectively.
The dimensions of a cluster are 9.36x7.12x3.88 A.

There are four distorted tetrahedral Hg centers and two
distorted linear Hg centers in the [Hg7Se10]4‘ cluster. The fluctuations
in Hg-Se bond distances and angles around tetrahedral Hg atoms
range from 2.508(6) to 3.101(7) A and from 88.1(1) to l36.0(2)°,
respectively, indicative of severe distortions in the tetrahedral
geometry around Hg. Long Hg-Se bonds are found between
tetrahedral Hg atoms and the diselenide ligand (average 280(2) A)
and between tetrahedral Hg atoms and the Se(4)—Hg(5)-Se(3) linear
unit (average 299(8) A).

Although the bond angle around Hg(5) is 178.9(2)”, the average
angle around the two-coordinate Hg(6) and Hg(7) is 167(1)°,
considerably smaller than the ideal 180°. The reason for this
distortion stems from the weak interactions between [Hg7Se10]4-

clusters through long ternary Hg-Se intercluster bonds. These

 

interactions result in a linear chain of clusters, running parallel to the
crystallographic [110] direction, as shown in Figure 2.11. The Hg-Se
distances between the clusters, Hg(6)-Se(9)' and Hg(7)-Se(7)’, are
3.256(5) and 3.235(5) A, respectively. These distances are shorter
than the sum of the van der Waals radii of Hg and Se atoms, 3.40 A,

 

 

74

 

 

 

 

 

 

 

 

 

 

Figure 2.11. The one-dimensional mode of interconnecting
[Hg7Se10]4' clusters. Filled circles represent Hg atoms.

 

—7—
75

but much longer than normal Hg-Se bonds. There are no Hg—Hg
bonds in the cluster, as the shortest Hg—Hg distance is 3.440(3) A.
Figure 2.12 shows the packing diagram of (IV) in the unit cell.
Selected bond distances and angles in the [Hg7Se10]4' cluster are

summarized in Tables 2.17 and 2.18.

3.3 Structure of [Hg7Se9]n4n' in (V)

 

Compound (V) consists of [Hg7Se9]n4n", with an unprecedented
layered structure, and non-interacting Et4N+ cations. An asymmetric
unit in the [Hg7Se9]n4n' framework is shown in Figure 2.13. These
asymmetric units are combined together to form a 2D layered
structure, as shown in Figure 2.14(A). An intriguing feature in the
structure is that the layers are perforated with large holes composed
of 30-membered rings of alternating Hg and Se atoms. One such
large hole and its dimensions are shown in Figure 2.14(B). These
holes are large enough to be comparable to those typically found in
zeolite and AlPO4 structures, particularly those of AlPO4—523 and
VPI-524.

Figure 2.15(A) shows a side View of the layered structure with
Et4N+ cations. The layers are corrugated and run parallel to the

crystallographic (011) plane. The average distance between the

 

layers is 8.03 A. As we can see from the top view of the layers
(Figure 2.15(B)), the large holes of 30-membered rings are eclipsed
with other [Hg73691n4n' layers above and below, avoiding the
formation of long channels. The Et4N+ cations are located between
the layers and some alkyl chains of these cations are penetrating into

the large holes.

76

 

 

Figure 2.12. Unit cell packing diagram (stereoview) of
(Et4N)4[Hg7Se10] (IV).

 

 

HHHHHHHHHHH

S.

CE

di

Table 2.17.

Standard Deviations Are Given in Parentheses.al

Selected Bond Distances (A) in the [Hg7Se10]4- Anion.

 

 

Hg(l)—Se(1) 2.783(5) Hg(3)-Se(9) 2.625(5)
Hg(1)-Se(3) 2.919(5) Hg(4)—Se(2) 2.801(4)
Hg(l)-Se(6) 2.530(4) Hg(4)-Se(4) 3.101(7)
Hg(l)-Se(7) 2.601(5) Hg(4)-Se(6) 2.508(6)
Hg(2)-Se(l) 2.819(4) Hg(4)-Se(10) 2.567(5)
Hg(2)-Se(3) 3.005(5) Hg(5)—36(3) 2.411(5)
Hg(2)-Se(5) 2.541(5) Hg(5)-Se(4) 2.399(5)
Hg(2)-Se(8) 2.587(5) Hg(6)—Se(7) 2.452(5)
Hg(3)-Se(2) 2.793(5) Hg(6)—Se(8) 2.443(6)
Hg(3)-Se(4) 2.934(5) Hg(7)-Se(9) 2.447(5)
Hg(3)-Se(5) 2.531(4) Hg(7)-Se(10) 2.435(6)

Hg-Se (mean) 2.65(21)
Se(l)-Se(2) 2.349(6)

 

a The estimated standard deviations in the mean bond distances were
calculated by the equation a) = {in(ln-l)2/n(n—I)}1/2, where ln IS the
distance of the nth bond, 1 is the mean bond distance, and n IS the

number of bonds.

S.

S.

S.

S.

S.

S.

S.

S.

S.

S.

S.

S.

S.

Table 2.18.

Standard Deviations Are Given in Parentheses.

Selected Bond Angles (deg) in the [Hg7Se10]4- Anion.

 

Se(l)-Hg(1)-Se(3)
Se(1)-Hg(1)—Se(6)
Se(1)-Hg(1)-Se(7)
Se(3)—Hg(1)-Se(6)
Se(3)-Hg(1)—Se(7)
Se(1)-Hg(2)-Se(3)
Se(1)—Hg(2)—Se(5)
Se(l)-Hg(2)-Se(8)
Se(3)-Hg(2)-Se(5)
Se(3)-Hg(2)-Se(8)
Se(5)-Hg(2)-Se(8)
Se(2)-Hg(3)-Se(4)
Se(2)-Hg(3)-Se(5)
Se(2)-Hg(3)-Se(9)
Se(4)-Hg(3)-Se(5)
Se(4)-Hg(3)-Se(9)
Se(5)-Hg(3)-Se(9)
Se(2)-Hg(4)-Se(4)
Se(2)-Hg(4)-Se(6)
Se(2)-Hg(4)—Se(10)
Se(4)-Hg(4)-Se(6)
Se(4)-Hg(4)-Se(10)
Se(6)—Hg(4)-Se(10)
Se(3)-Hg(5)-Se(4)
Se(7)-Hg(6)-Se(8)
Se(9)—Hg(7)-Se(10)

906(1)
112.8(2)
99.7(1)
109.1(2)
136.0(2)
88.1(1)
110.8(1)
106.6(2)
111.4(2)
98.3(2)
132.3(2)
922(2)
110.4(2)
98.2(2)
113.6(2)
100.3(1)
133.7(2)
88.5(1)
111.5(2)
102.1(2)
113.8(2)
96.3(2)
134.6(2)
178.9(2)
166.0(2)
168.1(2)

Hg(1)-Se(1)-Hg(2)
Hg(3)-Se(2)-H8(4)
Hg(1)-Se(3)-Hg(2)
Hg(1)-Se(3)-Hg(5)
Hg(2)-Se(3)-Hg(5)
Hg(3)-Se(4)-Hg(4)
Hg(3)-Se(4)-Hg(5)
Hg(4)—Se(4)-Hg(5)
Hg(2)-Se(5)-Hg(3)
Hg(1)-Se(6)-Hg(4)
Hg(1)-Se(7)-Hg(6)
Hg(2)-Se(8)-Hg(6)
Hg(3)-Se(9)-Hg(7)

Hg(4)-Se(10)-Hg(7)

Hg(1)—Se(1)—Se(2)
Hg(2)—Se(1)-Se(2)
Hg(3)-Se(2)-Se(l)
Hg(4)-Se(2)-Se(1)

93.0(1)
93.6(1)
866(1)
84.0(1)
825(2)
84.9(2)
79.8(1)
76.7(2)
100.7(2)
99.9(2)
89.5(2)
86.3(1)
86.2(2)
87.8(1)
104.5(2)
104.9(2)
107.3(2)
106.9(2)

 

Figu
asym

79

b, Se7
898 C Hg6
gr
Hg7
(' Hgs
Se9 (I ‘9 Se6
SeS
’O‘

 

‘9 Se9,

Figure 2.13. ORTEP representation of the [Hg7Se9]4"
asymmetric unit with labeling scheme.

 

 

 

80

 

 

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Figu
the [

81

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(B) . o

 

 

 

 

 

 

Figure 2.15. (A) Side-view and (B) top-view (stereoview) of
the [Hg78e9]n4n' layered structure with Et4N’r cations in the unit cell.

 

ar
co
lit

16

015
ex

f0

pe

r

82

In the asymmetric unit of [Hg7Se9]n4n' (see Figure 2.13), there
are three linearly coordinated Hg and four trigonal-planarly
coordinated Hg atoms. The average Hg—Se bond distances around the
linear and trigonal—planar Hg atoms are 243(1) and 257(8) A,
respectively. Another example of a mercury chalcogenide complex
that contains trigonal-planar Hg atoms can be found in the polymeric
[ngTe5]n20'.4 Selected bond distances and angles in the [Hg7Se9]n4n-
are summarized in Table 2.19.

Recently, a new family of metal—sulfide based materials with
open 3D frameworks such as (Me4N)[Sb3Ss] was reported.25 Another
example of a 2D framework structure in the metal-sulfide system is
found in (NH4)2[PdS11]~2HzO.26 The existence of such materials
persuades us to search for the next family of Open 3D framework
structural compounds based on heavier chalcogenides. The success
in synthesizing [Hg7Se10]4‘ and [Hg7Se9]n4n' is another indication that

it may be possible to get open 3D framework structures by using

appropriate templating counter-cations.

r

83

Selected Bond Distances (A) and Bond Angles (deg) in

Table 2.19.
Standard Deviations Are Given in Parentheses.a

the [Hg7Se9] 4‘ Anion.

 

Hg(1)-Se(1) 2.511(7) Hg(4)-Se(4) 2.431(7)
Hg(1)-Se(2) 2.537(7) Hg(4)-Se(5) 2.456(7)
Hg(1)-Se(7) 2.666(7) Hg(5)—Se(5) 2.569(7)
Hg(2)-Se(2) 2.479(8) Hg(5)-Se(6) 2.555(8)
Hg(2)-Se(3) 2.542(7) Hg(5)—Se(8) 2.538(8)
Hg(2)-Se(9) 2.685(7) Hg(6)-Se(6) 2.424(7)
Hg(3)-Se(1) 2.527(8) Hg(6)-Se(7) 2.425(7)
Hg(3)-Se(3) 2.493(7) Hg(7)-Se(8) 2.427(8)
Hg(3)-Se(4) 2.700(6) Hg(7)-Se(9) 2.422(7)
Hg—Se (mean) 252(9)

Se(l)-Hg(1)-Se(2) 137.1(3) Hg(1)-Se(1)-Hg(3) 100.3(2)
Se(1)-Hg(1)—Se(7) 116.1(2) Hg(1)—Se(2)—Hg(2) 101.5(2)
Se(2)ng(1)-Se(7) 106.7(2) Hg(2)-Se(3)-Hg(3) 97.9(2)
Se(2)-Hg(2)—Se(3) 140.4(2) Hg(3)—Se(4)-Hg(4) 92.5(2)
Se(2)-Hg(2)—Se(9) 115.4(2) Hg(4)—Se(5)-Hg(5) 96.5(2)
Se(3)-Hg(2)-Se(9) 104.2(2) Hg(5)—Se(6)-Hg(6) 94.7(3)
Se(l)-Hg(3)-Se(3) 139.9(2) Hg(1)-Se(7)-Hg(6) 88.8(2)
Se(l)-Hg(3)-Se(4) 102.4(2) Hg(5)-Se(8)-Hg(7) 88.1(2)
Se(3)-Hg(3)-Se(4) 117.4(2) Hg(2)~Se(9)-Hg(7) 87.6(2)
Se(4)-Hg(4)-Se(5) 174.7(2)

Se(5)—Hg(5)—Se(6) 114.0(2)

Se(5)-Hg(5)—Se(8) 122.6(2)

Se(6)-Hg(5)-Se(8) 123.4(3)

Se(6)—Hg(6)-Se(7) 178.7(3)

Se(8)-Hg(7)-Se(9) 173.7(3)

 

a The estimated standard deviation in the mean bond distance was
calculated by the equation 0) = {Enfln‘UZ/”(n-1)}I/2, where In is the
distance of the nth bond, 1 is the mean bond distance, and n is the

number of bonds.

r

(1)

(2)

(3)

(4)

(5)

(6)

8 4
LIST or REFERENCES

(a) Draganjac, M.; Rauchfuss, T. B. Angew. Chem, Int. Ed. Engl.
1985, 24, 742—757. (b) Miiller, A. Polyhedron 1986, 5, 323-
340. (c) Mfiller, A.; Diemann, E. Adv. Inorg. Chem. 1987, 31,

89—122.

(a) Kanatzidis, M. G. Comments Inorg. Chem. 1990, 10, 161-
195. (b) Ansari, M. A.; Ibers, J. A. Coord. Chem. Rev. 1990, 100,
223-266. (c) Kolis, J. W. Coord. Chem. Rev. 1990, 105, 195-

219.

(a) Miiller, A.; Krickemeyer, E.; B6gge, H.; Clegg, W.; Shelderick,
G. M. Angew. Chem, Int. Ed. Engl. 1983, 22, 1006-1007. (b)
Coucouvanis, D.; Patil, P. R.; Kanatzidis, M. G.; Detering, B.;
Baenziger, N. C. Inorg. Chem. 1985, 24, 24-31. (c) Banda, R. M.
H.; Cusick, J.; Scudder, M. L.; Craig, D. C.; Dance, 1. G. Polyhedron
1989, 8, 1995—1998. ((1) Ansari, M. A.; Mahler, C. H.;
Chorghade, G. S.; Lu, Y.-J.; Ibers, J. A. Inorg. Chem. 1990, 29,
3832-3839. (e) Magull, S.; Neumiiller, B.; Dehnicke, K. Z.
Naturforsch. 1991, 463, 985—991. (f) Adel, J.; Weller, F.;
Dehnicke, K. Z. Naturforsch. 1988, 433, 1094-1100. (g)
Krauter, G.; Weller, F.; Dehnicke, K. Z. Naturforsch. 1989, 443,
444-454. (h) Magull, S.; Dehnicke, K.; Fenske, D. Z. Anorg. Allg.

Chem. 1992, 608, 17—22.

Haushalter, R. C. Angew. Chem. Int. Ed. Engl. 1985, 24, 433-
435.

Fenske, D.; Magull, S.; Dehnicke, K. Z. Naturforsch. 1991, 468,
1011—1014.

(a) Kanatzidis, M. G.; Huang, S.—P. J. Am. Chem. Soc. 1989, 111,
760-761. (b) Huang, S.-P.; Kanatzidis, M. G. Inorg. Chem. 1991,

30, 1455—1466.

(7)

(8)

(9)

(10)

(11)

(12)

(13)

(14)

(15)

(16)

(17)

 

85
Kim, K.-W.; Kanatzidis, M. G. Inorg. Chem. 1991, 30, 1966-1969.

DIFABS: "An Empirical Method for Correcting Difiractometer
Data for Absorption Effects" Walker, N.; Stuart, D. Acta
Crystallogr., 1983, A39, 158-166.

TEXSAN: Single Crystal Structure Analysis Software, Version
5.0, Molecular Structure Corporation, The Woodlands, Texas.

(a) Sheldrick, G. M. in “Crystallographic Computing 3”; Sheldrick,
G. M.; Kruger, C.; Doddard, R. Oxford University Press 1985, pp.
175-189. (b) Frenz, B. A. The Enraf-Nonius CAD4 SDP System

in “Computing in Crystallography”; Delft University Press, Delft
Holland, 1978, pp. 64-71.

CERIUS: Molecular Modeling Software for Materials Research,
Version 3.1, Molecular Simulations Inc., Cambridge, UK.

Smith, D. K.; Nichols, M. C.; Zolenski, M. E. "POWDIO: A Fortran
IV Program for Calculating X—ray Powder Difiraction Pattern",
Version 10, Pennsylvania State University, 1983.

Kim, K.—W.; Kanatzidis, M. G. J. Am. Chem. Soc. 1.992, 114, 4878-
4883.

Strasdeit, H.; Krebs, B.; Henkel, G. Inorg. Chim. Acta 1984, 89,
L1-Ll3.

Huang, S. P.; Dhingra, S.; Kanatzidis, M. G. Polyhedron 1990, 9,
1389-1395.

Kréiuter, G.; Dehnicke, K.; Fenske, D. Chem.—Ztg. 1990, 114, 7—9_

Dhingra, S. Ph.D. Thesis; Michigan State University, 1992;
Chapter 2.

 

 

(18)

(19)

(20)

(21)

(22)

(23)

(24)

(25)

(26)

86

Dhingra, S. Ph.D. Thesis; Michigan State University, 1992;
Chapter 5.

Weller, F.;.Ade1, J.; Dehnicke, K. Z. Anorg. Allg. Chem. 1987, 548,
125-132.

Nagata, K.; Tshibashi, K.; Miyamoto, Y. Jpn J. Appl. Phys. 1980,
19, 1569-1573.

Barrie, P. J.; Clark, R. J. H.; Withnall, R.; Chung, D.; Kim, K.—W.;
Kanatzidis, M. G. Manuscript in preparation.

Huheey, J. E. Inorganic Chemistry, 3rd ed.; Harper & Row: New
York, 1983; pp 258-259.

Wilson, S. T.; Lok, B. M.; Messina, C. A.; Cannan, T. R.; Flanigen, E.
M. J. Am. Chem. Soc. 1982, 104, 1146-1147.

Davies, M. E.; Saldarriaga, C.; Montes, C.; Garces, J.; Crowder, C.
Nature, 1988, 331, 698—699.

(a) Parise, J. B. Science 1991, 251, 293-294. (b) Bedard, R. L.;
Wilson, S. T.; Vail, L. D.; Bennett, E. M.; Flanigen, E. M. Zeolites:
Facts, Figures, Future; Jacobs, P. A., van Santen, R. A. Eds.;
Elsevier Science Publishers B. V.: Amsterdam, 1989; pp 375-

387.

Haradem, P. S.; Cronin, J. L.; Krause, R. A.; Katz, L. Inorg. Chim.
Acta 1977, 25, 173-179.

 

GRt

CHAPTER 3

GROUP 12 METAL POLYTELLURIDE CHEMISTRY: STUDIES ON
(Et4N)4[Cd4Telzl AND (Me4N)4[Hg4Te121

87

 

an

an

01

611

88

ABSTRACT

Cluster anions, [M4Te12]4' (M=Cd, Hg) were isolated with Et4N+
and Me4N+ ions, respectively. (Et4N)4[Cd4Te12] (I) was prepared by
the reaction of CdIz, K2Te2 and Et4NBr in a 2:3:2 molar ratio, in DMF.
The black chunky polyhedral crystals of (I) were grown upon
addition of ether to the reaction solution. (I) crystallizes in the
orthorhombic space group Cmca (no. 64) with a=15.482(5) A,
b=22.563(4) A, c=18.027(4) A, v=6297(5) A3, and 2:4. The black
rectangular platelet crystals of (Me4N)4[Hg4Te12] (II) were obtained
from the reaction of HgClz and KzTe in a 2:5 molar ratio in DMF,
followed by addition of Me4NCl in methanol to the reaction solution.
(11) crystallizes in the monoclinic space group P21/n (no. 14) with
a=10.324(3) A, b=21.851(6) A, c=ll.125(4) A, 6:110.63(3)°,
V=2348(3) A3, and 2:2.

[M4Te12]4' is a cluster with two Te2', two Te22' and two Te32'
ligands connecting a planar array of four tetrahedral M2+ metal
centers. Its shape may be described as a basket, consisting of a
{M4(T62)Te2} core with two side Te32' handles. The average M—Te
and Te-Te distances are 285(8) and 274(2) A, respectively, for (I)
and 2.86(12) and 273(1) A, respectively, for (II).

In the Far-IR spectra there are two peaks at 173 and 160 cm“1
for (I) and two at 167 and 148 cm'1 for (11). TGA studies show that

elemental Te is the only residue material at 900 0C for both (I) and

(II).

 

 

sh

11V

 

 

 

89

INTRODUCTION

Compared to metal polysulfide and polyselenide chemistry,
metal polytelluride chemistry is less explored. For the late transition
(Group 10, 11 and 12) metals, [Ni4Te23]4*,1 [M(Te4)2]2' (M=Pd,2 Cd,
Hg),3 [MT 6713‘ (M=Zn, Hg),4 [Hg4T61214',5 [ngT6512‘,5 [M2T612l4‘ (M=Cu,
Ag),6 [M(Te4)]‘ (M=Cu, Ag),7 [AuzTe4]2',8 and [AuTe7]3‘ 9 are the only
known metal polytelluride compounds, so far. One common
fascinating feature in most of these compounds is the novelty of their
structures, for which sulfide or selenide analogs do not exist.

The structures of metal polychalcogenide anions are often
dependent on the size of organic counter-cations. A typical example
can be found in silver polyselenide chemistry where different
structural compounds ranging from molecular clusters to 1D
polymers have been prepared using different organic cations.10 The
trend continues in mercury polytelluride chemistry where two
different [Hg4Te12]4' and [ngTe5]2' complexes have been isolated
from the same ethylenediamine extract of the K2Hg2Te3 alloy as n-
Bu4N+ and Ph4P+ salts, respectively.5 A similar reaction with an alloy
of composition KHgTe and 2,2,2-cryptand has yielded the linear
[HgTe2]2‘ anion as a salt of 2,2,2—crypt—KJ'.11 In our search for new
mercury (or cadmium) polytelluride compounds we investigated
smaller organic cations such as Me4N+ and Et4N+. In addition,
shorter-chain polytelluride ligands, Tex?" (x=1, 2) were employed to

avoid forming the stable [M(Te4)2]2" (M=Cd, Hg) anion.

 

IE

cllai

11011

furth
Prod
reag.
anal)
Utes]
'Tetre
Inc.
Lane
grade
reduc

and 1

W180
P1686
Seven

J 913 e)

 

———
90

In this chapter, we report the synthesis, structural

characterization, and some physicochemical properties of

(Et4N)4[Cd4T612] (I) and (Me4N)4[Hg4T612] (II)-

EXPERIMENTAL SECTION

Reagents

The chemicals in this research were used as obtained without
further purification: Cadmium(II) iodide (-40 mesh, 99.5%), Alfa
Products, Ward Hill, Massachusetts; Mercuric chloride, analyzed
reagent, J. T. Baker Inc., Phillipsburg, New Jersey; Potassium metal,
analyzed reagent, Mallinckrodt Inc., Paris, Kentucky; Tellurium (-200
mesh, 99.5+%), Cerac Inc., Milwaukee, Wisconsin;
Tetraethylammonium bromide (98%), Aldrich Chemical Company
Inc., Milwaukee, Wisconsin; Tetramethylammonium chloride (98+%),
Lancaster Synthesis Inc., Windham, New Hampshire. DMF (A.C.S.
grade, EM Science, Gibbstown, New Jersey) was distilled under
reduced pressure after being stored over KOH for more than a week

and over 4A Linde molecular sieves for several days. Diethyl ether

 

(A.C.S. anhydrous, Columbus Chemical Industries Inc., Columbus,
Wisconsin) was distilled after refluxing over potassium metal in the
presence of benzophenone and triethylene—glycol—dimethyl ether for
several hours. MeOH (A.C.S. grade, EM Science, Gibbstown, New

Jersey) was distilled after refluxing over CaHz.

 

 

Phys

8an

atmos
Lab 1
vvere
1121231

eleme

di(te
tetra.
40 111]
mmol)
added
addedE
solutic
f1112.1 .
undiss
solutic
199161
Stand 1
Obufine

 

 

91

Physicochemical Methods
see Chapter 2.

Synthesis

All experiments and manipulations were performed under an
atmosphere of dry nitrogen using either a Vacuum Atmosphere Dri—
Lab glove box or a Schlenk line. Preparations of K2Tez and KzTe
were accomplished by following the same procedure as that used for
NazSez (see Chapter 2), with appropriate stoichiometric ratios of

elemental tellurium and potassium metal.

Tetra(tetraethylammonium)
di(tellurido)-di(ditellurid0)-di(tritellurid0)-
tetracadmate(II), (Et4N)4[Cd4(Te)2(Te2)2(Te3)2] (I) To a
40 ml DMF solution of 0.37 g (1.1 mmol) K2Te2 and 0.23 g (0.75
mmol) Et4NBr, a 35 ml DMF solution of 0.27 g (0.74 mmol) Cdlz was
added dropwise over 20 min. After all the Cdlz solution had been
added, the purple color was no longer present in the reaction
solution, implying the absence of unreacted polytelluride anion. The
final reaction solution showed a dark brownish black color. After
undissolved black precipitates had been filtered out, the filtrate
solution was placed into several long test tubes and ether was
layered over the filtrate solution. Upon allowing the solution to
stand for a week, black polyhedral chunky crystals (24% yield) were
obtained. SEM/EDS analysis on these crystals showed the Cd:Te ratio
as 1:3.5.

 

di(
teti
(123

solu
addi
filte
laye
grev
wen
1011
phas
resul

8110“

X-ra

fiben
fro m

Colle

 

 

_7—

92

Tetra(tetramethylammonium)
di(tellurido)-di(ditellurido)~di(tritellurido)-
tetramercuratefll), (Me4N)4[Hg4(Te)z(Te2)2(Te3)2] (II) To
0.23 g (1.1 mmol) K2Te in 20 ml DMF, a 15 ml DMF solution of 0.12 g
(0.44 mmol) HgClz was added dropwise over 15 min. KzTe is not
soluble in DMF, but dissolved to give a dark brownish solution upon
addition of HgC12 solution. After undissolved precipitates had been
filtered out, a 80 ml MeOH solution of 0.05 g (0.46 mmol) Me4NCl was
layered to the filtrate solution. Black rectangular platelet crystals
grew upon allowing the solution to stand for a week. These crystals
were isolated and washed with ether several times. The yield was
10%, based on the Hg metal ion content used. An amorphous binary
phase of Hg/Te and elemental Te were obtained as by-products, to
result in the yield being low. SEM/EDS analysis on these crystals
showed the ngTe ratio as 1:2.7.

X-ray Crystallographic Studies

Single crystals of (I) and (II) were mounted on the tip of glass
fibers with epoxy adhesive and coated with KrylonTM to protect them
from exposure to air. The crystallographic data for (I) and (II) were
collected on Rigaku AFC6S four-circle automated diffractometers.
Accurate unit cell parameters were determined from the 20, 00, (I), and
X angles of 15 to 25 centered reflections. The intensities of three
standard reflections were monitored every 150 reflections. No
serious decay was observed during the data collection period. An
empirical absorption correction based on 1p scans of three strong

reflections with X ~90° was applied to each data set. The structures

 

vve
p11
Af‘
aPI
311
pac
ani

hyd

sihi
plat

indc

aSynl
8in...
1104)
01 C

 

_—

93

were solved by direct methods using the SHELXS-86 software
program and refined with a full-matrix least squares technique.
After isotropic refinement of all atoms, DIFABS corrections were
applied.12 All calculations were performed on VAXstation 2000 and
3100/76 computers with the TEXSAN crystallographic software
package of Molecular Structure Corporation.13 All atoms in the
anions of both compounds were refined anisotropically. The
hydrogen atom positions were calculated but not refined.

An asymmetric unit in the structure of the [Cd4Te12]4' anion of

(I) has one Cd atom and five Te atoms. While Cd and T e(5) atoms are

 

sitting in general positions, Te(l), Te(2), and Te(4) are in a mirror

plane (0, y, z), and Te(3) is on a 2-fold axis (x, 0, 0). The two

 

independent Et4N+ cations in the structure of (I) are completely
disordered and atomic coordinates of all C atoms had to be fixed
during the final refinement of the structure. Atom N(l) lies on a 2—
fold axis (1/4, y, 1/4), while atom N(2) is in a mirror plane (0, y, z).
The carbon atoms associated with the N(l) atom are in general
positions, but disordered except for C(4). The second Et4N+ cation
was modeled with two orientations having a common nitrogen atom,
N(2). One orientation was assigned with 4/5 occupancy while the
other with only 1/5. Both N atoms were refined anisotropically and
all C atoms were refined isotropically.

In the structure of (11), only a half of (Me4N)4[Hg4Te12] is an
asymmetric unit and the other half can be generated by a center of
symmetry situated in the center of the [Hg4Te12]4‘ cluster. For
M64N+ organic cations, the N atoms were refined anisotropically and

all C atoms were refined isotrOpically.

 

 

analy:
temps:

deviati

 

————

94

Table 3.1 shows the crystal data and details for the structure
analyses of both compounds. The fractional coordinates and
temperature factors (Beq) of all atoms with their estimated standard

deviations are given in Tables 3.2—3.3.

 

 

 

0011:

F02 :
No.

Max.
Phas:

11:2

 

Table 3.1.

95

(I) and (Me4N)4[Hg4Te12] (II)-

Summary of Crystallographic Data for (Et4N)4[Cd4Te12]

 

 

(I) (11)
Compound (Et4N)4[Cd4Te12] (Me4N)4[Hg4Teizl
Form 11 1 a C32H80N4Cd4Te 12 C 16H43N4Hg4Te12
FW 2501.82 2630.14

Crystal shape
Crystal color
Crystal size(mm)
Temperature (°C)
Crystal system
Space group

a (A)

b (A)

c (A)

a (deg)

[3 (deg)

11 (deg)

\I(A3):z

u (cm'l) Mo(K01)
dcalc (g/cm3)
Scan Method
2emax (deg)

No. of reflections
collected

No. of reflections,
Fo2 > 301130)2

No. of variables
Max. shift/esd
Phasing method
R/Rw (%)

chunky polyhedral
black
0.26x0.22x0.10
23
orthorhombic
Cmca (no. 64)
15.482(5)
22.563(4)
18.027(4)

90

90

90

6297(5), 4
68.2

2.639

w/20

45

2313

1335

7 0

0.00

direct methods
5 . 1 /6 .5

rectangular platelet
black
0.05x0.10x0.21
23

monoclinic
P21/n (no. 14)
10.324(3)
21.851(6)
11.125(4)

90

110.63(3)

90

2348(3), 2
203.8

3.719

w/20

45

3409

1700

123

0.00

direct methods
5 .8/5 .7

 

R=Z “Fol ‘ chll/Z lFol

M: I): w(lFoI-|FcDZ/Z WWI“

 

 

 

 

 

96

Table 3.2. Fractional Atomic Coordinates and Beq Values for

(Et4N)4[Cd4Te12] (I) with Their Estimated Standard Deviations in
Parentheses.

 

 

atom x y Z Bea (A03
Cd(1) 0.1240(1) 0.07896(7) 0.0220(1) 4.32(8)
Te(l) 0 0.0758(1) 0.1010(1) 4.0(1)
Te(2) 0 0.0435(1) 0.1357(1) 4.4(1)
Te(3) 0.2548(1) 0 0 4.5(1)
Te(4) 0 0.2145(1) 0.1255(1) 5.8(1)
Te(5) 0.1445(1) 0.20230(7) 0.0407(1) 6.3(1)
N(1) 1/4 0.118(1) 1/4 6(2)
N(2) 0 0.138(1) 0.376(2) 9(2)
C(1) 0.2026 0.1762 0.2034 8(1)
C(2) 0.2251 0.2286 0.2448 18(2)
C(1') 0.2174 0.0668 0.2075 9(1)
C(2') 0.2881 0.0101 0.2229 8(1)
C(3) 0.3442 0.1233 0.2372 12(2)
C(3') 0.2263 0.1292 0.3380 9(1)
C(4) 0.3557 0.1252 0.1470 15(1)
C(5) 0.0822 0.1248 0.3216 12(1)
C(5') 0.1005 0.1512 0.4150 11(1)
C(6) 0.1755 0.1341 0.3315 23(2)
C(6') 0.1405 0.0838 0.4318 37(1)
C0) 0 0.0855 0.4343 19(1)
C(7') 0 0.0795 0.3452 4(2)
C(8) 0 0.0300 0.3914 14(2)
C(9) 0 0.1965 0.4223 20(1)
(3(9) 0 0.1821 0.2963 4(1)
C(10) 0 0.2449 0.3502 15(2)

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beg: (81r2/3)[a2B11 +
b2B22 + c2B33 + ab(cosy)B12 + ac(cos[3)B13 + bc(cos01)B23]. The
anisotropic temperature factor expression is exp[-2712(B11a*2h2 + +
2B12a*b*hk + ...)].

 

97

Table 3.3. Fractional Atomic Coordinates and Beq Values for

(Me4N)4[Hg4Te12] (II) with Their Estimated Standard Deviations in
Parentheses.

 

 

 

atom x y z Bea (A2)a
Hg(l) 0.0382(2) 0.03566(8) 0.2443(2) 334(7)
Hg(2) 0.0959(2) 0.11111(8) 0.1004(2) 339(7)
Te(l) 0.1464(2) 0.0741(1) 0.3455(3) 3.0(1)
Te(2) 0.1879(2) 0.0847(1) 0.0793(3) 2.7(1)
Te(3) 0.2245(2) 0.0236(1) 0.0287(3) 27(1)
Te(4) 0.1391(2) 0.2253(1) 0.0116(3) 3.0(1)
Te(5) 0.0651(2) 0.2215(1) 0.2258(3) 3.4(1)
Te(6) 0.0235(3) 0.1388(1) 0.3625(3) 3.2(1)
N(1) 0.542(3) 0.218(1) 0.189(3) 3(1)
N(2) 0.615(3) 0.061(2) 0.336(4) 4(2)
C(1) 0.643(4) 0.265(2) 0.222(5) 36(9)
C(2) 0.404(4) 0.245(2) 0.136(5) 4(1)
C(3) 0.549(5) 0.172(2) 0.299(6) 6(1)
C(4) 0.552(4) 0.173(2) 0.077(5) 5(1)
C(5) 0.609(4) 0.081(2) 0.470(5) 6(1)
C(6) 0.761(4) 0.050(2) 0.347(4) 3.6(9)
C(7) 0.549(6) 0.100(3) 0.229(7) 10(1)
(3(8) 0.542(4) 0.002(2) 0.296(5) 5(1)

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beq= (8712/3)[a2B11 +
b21322 + 02B33 + ab(cosy)B12 + ac(cos[3)B13 + bc(cosa)B23]. The
anisotropic temperature factor expression is exp[-27r2(B11a*2h2 + +
2B12a’1‘b’1‘hk + ...)].

eithc
dfiiiz
powd
condi
for I
crysta
ghus

coord
powd.
soflhu
X-ray
and p.
paherr

are C0

98

XRD (X—ray Powder Diffraction) patterns were obtained on
either a Phillips XRG-3000 computer—controlled powder
diffractometer or a Rigaku-Denki/RW400F2 (Rotaflex) rotating anode
powder diffractometer. Ni-filtered, Cu radiation was used at the
condition of 35 KV, 35 mA for Phillips XRG—3000, and 45 KV, 100 mA
for Rigaku-Denki/RW400F2 (Rotaflex) powder diffractometer. The
crystals of each compound were ground to fine powder and put on a
glass slide using a double-sided sticky tape. Based on the atomic
coordinates from the X-ray single crystal diffraction study, X-ray
powder patterns for all compounds were calculated with the
software package CERIUS”. The good agreement between observed
X-ray powder patterns and those calculated assured the homogeneity
and purity of the compounds. Calculated and observed X—ray powder
patterns showing d—spacings and intensities of strong hkl reflections

are compiled in Tables 3.4—3.5.

 

99

Table 3.4. Calculated and Observed X-ray Powder Diffraction
Pattern of (Et4N)4[Cd4Te12] (I).

 

 

h k l dcalc (A) dobs (A) I”max (ObS, %)
10.42 10.34 100
9.01 8.91 45
7.36 7.30 10

.89 3.86 74
.86
.38 3.37 25
.36
.20 3.19 28
.19
.19
.11 3.11 57
.936 2.929 38
.931 35
.732 2.715 20
579 2.571 29
.569
.488 2.490 28
.314 2.310 22
.210 2.209 16
189 2.186 44
.185
.178
.160 2.160 13
.034 2.030 20
.935 1.937 14
1.810 18

HO-hUlUtv—‘NN-hUJUIONWUI-hr—‘UJO-h-ROUJANNH

\IOOA#on-hAwhwmw-P-I—OANUJNWNHOH
\IooooxxlwcoooxxiNI—H—H—Iouoxh-hHow—tOv—oh-t

y—a
00
_l
A

 

 

Tal
Pat

o
-—e<:>
—-

l\.)

N

N

/

molar

2C012

1..., .
[C140

 

100

Table 3.5. Calculated and Observed X—ray Powder Diffraction
Pattern of (Me4N)4[Hg4Te12] (II).

h k l dcalc (A) dobs (A) I/lmax (0133, %)

0 2 0 10.93 10.85 15
0 1 1 9.40 9.35 29
l 1 0 8.84 8.81 100
1 0 —1 8.79 8.77 36
1 1 —l 8.16 8.17 13
2 1 1 3.83 3.82 10
2 3 —2 3.76 3.76 8
2 4 2 3.43 3.42 8

m

RESULTS AND DISCUSSION
1. Synthesis

(1) was prepared by the reaction of CdI2 and K2Te2 in a 2:3

molar ratio, in the presence of Et4NBr, as shown in eq. (3.1).

DMF
ZCdIZ + 3K2Te2 + 2Et4NBr T’
1/2(Et4N)4[Cd4Te12] + 4K1 + ZKBr ----------------------- eq. (3.1)

The monotelluride and tritelluride ligands in the [Cd4Te12]4' (=
[Cd4(Te)2(Te2)2(Te3)2]4') anion are generated from ditelluride ligands

through the equilibrium in the DMF solution, as shown in eq. (3.2)

2Tez2

Recei

[Cd4l

nuflar
isohne
be 80
adOpt
l
reactit
Interes
sane
(Me4N)
fiher i

[HgT62

101

2Te22' m Tez' + Te32' ................................................ eq. (32)

Recently, Dehnicke et a1. independently prepared the same
[Cd4Te12]4‘ complex as a Na(15—crown—5)+ salt in DMF.15

In a similar reaction using CdIz, NazTez, and Ph4PCl in a 1:2:2
molar ratio, the familiar metal octachalcogenide [Cd(Te4)2]2' was
isolated as a Ph4P+ salt. The Cd analog of (Ph4P)2[Hg2Te5]5 could not
be stabilized, possibly due to the unwillingness of Cd2+ centers to
adopt the required trigonal planar coordination.

In the preparation of (II), methanol was layered to the
reaction solution to induce crystallization of the product.
Interestingly, when ether instead of methanol was layered to the
same solution, transparent light yellow thin platelet crystals of
(Me4N)2[HgTe2] were isolated as a main product. Faster diffusion of
ether into the reaction solution seems to favor isolating discrete
[HgTe2]2' anions before they combine with themselves and free
polytelluride ligands to form the cluster, [Hg4Te12]4'. Haushalter's
(BU4N)4[Hg4Te12] was also prepared upon layering methanol to the
ethylenediamine extract of K2Hg2Te3.5 It is noteworthy that both
Bu4N+ and the much smaller Me4N+ cations can stabilize the same
[Hg4Te12]4‘ cluster, while 1D polymeric [ngTe5]2' is stabilized with

Ph4P+ cations.

2. Physicochemical Studies

2.1 UV/Vis spectroscopy

gi‘
blz

inc

2.2

2.3

and

Orgai
range
(527.
the f
10 1e;
Semi.
decon

fI‘Om .

102

DMF and CH3CN solutions of (I) show a dark brown color and
give featureless UV/Vis spectra. They slowly decompose to give
black precipitates in several hours. (II) is insoluble in most solvents,

including DMF.

2.2 Far-IR spectroscopy

In the far—IR spectra of (I) and (II) (see Figure 3.1), two peaks
exist at 160, 173 and 148, 167 cm'1 for (I) and (II), respectively.
These peaks are assigned to Te—Te and M—Te (M=Cd, Hg) Vibration
modes. Frequencies of some previously assigned Te—Te vibration
modes range from 188 to 219 cm‘l, as found in metal polytelluride
and free polytelluride complexes such as [PdTngZ‘ (VTe-Te=200 cm'
1),2(c) [AuzTe4]2' (vTe-Te=188 cm-I),16 and [Te412- (vTe_Te=219, 188

cm‘l).17

2.3 Thermal Gravimetric Analysis

TGA results for both compounds are summarized in Table 3.6
and shown in Figure 3.2. (I) begins to lose its organic species as
organotellurides (R2Te), Et3N, and other products in the temperature
range of 188—231 °C. Some Te was lost in the next step of weight loss
(527—678 ”C) to give an intermediate with a formula of Cd4Te6. In
the final step of weight loss (678—900 °C), Cd metal evaporated away
10 leave elemental Te as the final residue. This was confirmed by
semi—quantitative analysis using SEM/EDS. The thermal
decomposition behavior of (Me4N)4[Hg4Te12] (II) is little different
from (I), mainly due to the difference in the boiling points of Cd and

Hg metals (765 and 357 °C, respectively). (II) lost its

TRANSMI—FTANCE

11!

Fig.1“
(M04N

 

103

 

 

(A)

LL]

0

E

E (B)

E

1.

L. 0 3110 260 253 1&1 T00
WAVENUMBER
Figul'e 3.1. Far-IR spectra of (A) (Et4N)4[Cd4Te12] (I) and (B)

(Me4N)4[Hg4T612] (11)-

100 '-

80~

60‘

W (%)

4o-

20‘

 

.o. 1:

 

me4N)4m84Te

 

 

 

 

 

 

 

 

 

 

 

 

(A)
100
80

’2?

§ so
40
20
0

0 200 400 600 800
Temp. (C)
(B)
100 [ _
80 - _

A —

5Q _

g 60 - —
4O - _
20 ~ 4
o __.__ l A l A I l l

O 200 400 600 800
Temp. (C)

Figure 3.2. TGA diagrams of (A) (Et4N)4[Cd4Telz] (I) and (B)
(Me4N)4[Hg4Te12] (II).

tetramethyl.
285 °C), ar
°C). Final]
°C, to give
binary M/I‘.
(I) and (II)

Table 3,6.

\

Mm

(E1411 l4lCd4l

(Me4N141Hg4

3' Descripti.

1" (I) a
non-interacting

structura1 con

BU4N+ Salt t

[M4T612]4~ 1 S

00111160th thI‘(

1W0 T022- and

105

tetramethylammonium cation in the first step of weight loss (186—
285 °C), and then the Hg metal evaporated in the next step (300-460
°C). Finally, some Te was lost in the temperature range of 493-636
°C, to give the residue of elemental Te. It is interesting to note that
binary M/Te (M=Cd, Hg) are not the final decomposition products of
(I) and (II).

Table 3.6. TGA Data for (Et4N)4[Cd4Te12] (I) and (Me4N)4[Hg4Te12] (II).

 

 

Compound Temperature range (°C) Weight loss (%)
(Et4N)4[Cd4Te12] 188 - 231 28.4

527 - 678 24.0

678 - 900 20.4
(Me4N)4[Hg4Te12] 186 -285 9.9

300 — 460 44.0

493 - 636 26.6

 

3. Description of Structures

In (I) and (II), [M4Te12]4' (M=Cd, Hg) anions are stabilized with
non-interacting organic counter—cations. These anions are the same
structural complexes as the [Hg4Te12]4' which was prepared as a
BU4N+ salt by Haushalter.5 As shown in Figures 3.3 and 3.4,
[M4Te12]4" is a cluster anion in which four M2+ metal ion centers are
connected through three different kinds of Texz' ligands, two Te2',

two Te22' and two Te32‘. So a more descriptive formula for thlS

 

T936

 

T92 T91

Figure 3.3. ORTEP representation (two views) of the [Cd4Te12]4'
cluster with the labeling scheme. '

“We 34.

Te1

 

Te5

Figlfl‘e 3.4. ORTEP representation of the [Hg4Te12]4' cluster with
the labeling scheme.

 

 

cluster w0
the shape
two side 1
planar arr
geometry.
center of
bisecting it
only a nys
11184161211
1“) in the 1
[M4Tt
ralllacing si.

ligands with

In the

distances are

1W0~(3001‘dinat6

COOrdinate

HaUShalterts [I-

 

 

———-:——W 1

108

cluster would be [M4(Te)2(Te2)2(Te3)2]4". It is tempting to describe
the shape of the cluster as a basket having a {M4(Te2)Te2} core with
two side Te32' handles. In the cluster, four metal centers are in a
planar arrangement and have distorted tetrahedral coordination
geometry. There is a crystallographic center of symmetry in the
center of [Cd4Te12]4‘ cluster and a crystallographic mirror plane
bisecting it through Tel, Te2, Te4, Te4', Te2', and Tel' atoms, while
only a crystallographic center of symmetry is present in the center of

[Hg4Te12]4‘ cluster. Figure 3.5 shows the packing diagrams of (I) and

 

(II) in the unit cell.
[M4Te12]4‘ can be structurally related to [Hg7Selo]4‘ by
replacing side Te32' ligands with Se—Hg-Se units and one of 114-T622'

ligands with a linear Se-Hg-Se unit.18 This is shown in Scheme (A).

 

 

 

 

Scheme (A)

In the [Cd4Te12]4' cluster, the average Cd-Te and Te-Te bond
distances are 285(10) and 274(3) A, respectively. There are two
different groups of Cd—Te bonds, that is, shorter bonds from Cd to
two-coordinate Te (277(7) A) and longer bonds from Cd to three-
coordinate Te (293(1) A). This behavior was first seen in

Haushalter's [Hg4Te12]4' cluster. It can be also seen in the [Hg4Te12]4-

 

 

 

 

 

 

Figure 3.5.

(EhN)4[Cd4Tt

 

 

 

 

.{

 

a ' .p
. .-‘_- I. a '

(£13278

I
JD
.
‘ -—-". ‘6}.' .;.Li
'1'.
S
7 ..
I. .9“ .4

r

u
'l

(A)

 

 

 

 

(B)

 

 

 

 

 

 

 

 

Figure 3.5. The packing diagrams (stereo-view) of (A)
(Et4N)4[Cd4Te12] (I) and (B) (Me4N)4[Hg4Te12] (II) in the unit cell.

   

 

 

 

cluster of
shorter b0
bonds fror.
Te and
respectively
can be
(BU4N)4[Hg
Table 3.7.

  
  
 
 
   
    

clusters of

Table 3.7.
[M4T61214‘
(Bu4N)4[Hg
Deviations

Compoun

 

(Et4N)4[Cd41

[Na(15-Crov
5)]41Cd4Te12

(11640411184
(314N)41Hg4

(a) The e:
equation 01
nth bond, 1
(b) Referencl

 

 

flu :4 74.7 4.- .

110

cluster of (II), as there are two different groups of Hg—Te bonds,
shorter bonds from Hg to two-coordinate Te (275(4) A) and longer
bonds from Hg to three—coordinate Te (296(2) A). The average Hg—
Te and Te—Te bond distances are 2.86(12) and 273(1) A,
respectively. The average M—Te and Te—Te distances in (I) and (II)
can be compared reasonably well with those found in
(Bu4N)4[Hg4Te12] and [Na(15-Crown—5)]4[Cd4Te12]'8DMF, as shown in
Table 3.7. Some selected bond distances and angles in the [M4Te12]4-

clusters of (I) and (II) are summarized in the Tables 3.8 and 3.9.

Table 3.7. Comparison of Average MeTe and Te—Te Distances (A) in
[M4T61214‘ Clusters of (Et4N)4[Cd4T6121 (I), (Me4N)4ng4T6121 (II).
(Bu4N)4[Hg4Te12] and [Na(l5—Crown—5)]4[Cd4Te12]'8DMF. Standard
Deviations Are Given in Parentheses.(a)

 

 

Compound M-Te, two M-Te, three Te—Te
coordinate coordinate
(Et4N)4[Cd4Te12] (1) 277(7) 293(1) 274(3)
[Na(15—Crown- 278(5) 291(2) 273(2)
5)]4[Cd4Te12]'8DMF(b)
(Me4N)4[Hg4Te12] (II) 275(4) 296(2) 273(1)
(BU4N)4[Hg4Te12](C) 274(5) 295(4) NA

 

(a) The estimated standard deviations were calculated by the
equation a) = {in(ln—l)2/n(n—1)}1/2, where 1,, is the distance of the
nth bond, 1 is the mean bond distance, and n is the number of bonds.
(b) Reference 15. (c) Reference 5. NA: Not Available.

 

   

 

 

 

 

Table 3.8.
the [Cd4T

 

Cd-Te(l)
Cd-Te(2)
Cd-Te(3)
Cd—Te(5)

Cd—Te (me:

 

1 The estim
calculated b
distance of
number of l

Table 3.8.

the [Cd4Te12]4' Anion.

 

 

—f——_—_

Selected Bond Distances (A) and Bond Angles (deg) in
Standard Deviations Are Given in Parentheses.a

 

 

Cd-Te(l)
Cd-Te(2)
Cd—Te(3)
Cd—Te(5)

Cd-Te (mean)

Te(1)-Cd—Te(2)
Te(1)-Cd-Te(3)
Te(1)-Cd-Te(5)
Te(2)—Cd—Te(3)
Te(2)—Cd-Te(5)
Te(3)-Cd-Te(5)

2.933(2)
2.920(2)
2.727(2)
2.821(2)

285(10)

9537(7)
111.13(7)
100.81(7)
114.29(7)
105.13(8)
125.31(8)

Te(1)—Te(2)
Te(4)-Te(5)

Te-Te (mean)

Cd—Te(l)—Cd
Cd-Te(2)-Cd
Cd-Te(3)-Cd
Cd-Te(1)-Te(2)
Cd—Te(2)-Te(1)
Cd—Te(5)—Te(4)

2.764(3)
2.725(2)

274(3)

8174(8)
8221(9)
84.0(1)
101.21(7)
9622(7)
9422(8)

Te(5)-Te(4)-Te(5) 110.4(1)

 

‘1 The estimated standard deviations in the mean bond distances were
calculated by the equation oz = {in(ln-l)2/n(n—I)}1/2, where l” is the
distance of the nth bond, 1 is the mean bond distance, and n is the

number of bonds.

 

 

 

 

 

Table 3.9.

 

it 34 1|. Ill/llll llllll .0
66666 m (((((1222222 u o 0
TTTTTRRR ( 888888.81188.188. 8. Elmer
)rxr)).l.).. HHHHHHHHHH.HH eace
1111227.0\l. C \./)\l\.}\.../)\tl . “Mm
g I. /I\ ( ( (\ ( m4. .1. l( 1.. 2 2 3 1|. 1|... 1.. 2\./ 2x.) 1 H C m 0“
06000800060000 g 000069900060 Mud—.11“- n

 

if

112

Table 3.9. Selected Bond Distances (A) and Bond Angles (deg) in
the [Hg4T612]4' Anion. Standard Deviations Are Given in Parenthesesa

 

 

Hg(1)-Te(1) 2.716(3) Te(2)—Te(3) 2.740(4)
Hg(1)-Te(2) 2.984(3) Te(4)-Te(5) 2.740(4)
Hg(1)—Te(3) 2.932(3) Te(5)—Te(6) 2.719(4)
Hg(1)—Te(6) 2.794(3)

Hg(2)—Te(1) 2.713(4) Te—Te (mean) 2.73(l)
Hg(2)—Te(2) 2.964(3)

Hg(2)—Te(3) 2.970(3)

Hg(2)-Te(4) 2.778(3)

Hg-Te (mean) 2.86(12)

 

Te(1)—Hg(1)—Te(2) 110.22(9) Hg(1)—Te(1)—Hg(2) 86.6(1)
Te(1)-Hg(1)-Te(3) 112.7(1) Hg(l)-Te(2)—Hg(2) 8321(8)
Te(1)-Hg(l)-Te(6) 130.2(1) Hg(l)—Te(2)-Te(3) 98.1(1)
Te(2)-Hg(1)-Te(3) 9339(9) Hg(2)-Te(2)—Te(3) 97.4(1)
Te(2)—Hg(1)-Te(6) 104.68(9) Hg(1)-Te(3)—Hg(2) 84.0l(8)
Te(3)-Hg(l)—Te(6) 99.13(9) Hg(1)-Te(3)-Te(2) 101.9(1)
Te(1)-Hg(2)—Te(2) 114.5(1) Hg(2)—Te(3)-Te(2) 100.9(1)
Te(1)—Hg(2)-Te(3) 109.5(1) Hg(2)—Te(4)—Te(5) 98.6(1)
Te(1)-Hg(2)—Te(4) 128.9(1) Hg(1)—Te(6)-Te(5) 95.5(1)
Te(2)-Hg(2)-Te(3) 93.01(9) Te(4)-Te(5)—Te(6) 105.3(1)
Te(2)-Hg(2)-Te(4) 100.36(9)

Te(3)-Hg(2)-Te(4) 104.6(1)

 

a The estimated standard deviations in the mean bond distances were
calculated by the equation 01
distance of the nth bond, 1 is the mean bond distance, and n is the

number of bonds.

{in(ln-l)2/n(n-I)}1/2, where In is the

 

 

 

 

 

 

McC
1992

(a) A
Poly)
Clysz
K.; I
1991,

Mfille
Anor

Haus
435 .

(21) Fe
1993,
A. [M

Kim, I
5872.

(a) Ha
Kanat:
1992,

Ansari
115,

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

113

LIST OF REFERENCES

McConnachie, J. M.; Ansari, M. A.; Ibers, J. A. Inorg. Chim. Acta
1992, 198, 85-93.

(a) Adams, R. D.; Wolfe, T. A.; Eichhorn, B. W.; Haushalter, R. C.
Polyhedron 1989, 8, 701—703. (b) Kanatzidis, M. G. Acta
Crystallogr. 1991, 47C, 1193-1196. (c) Wolkers, H.; Dehnicke,
K.; Fenske, D.; Khassanov, A.; Hafner, S. S. Acta Crystallogr.
1991, 47C, 1627-1632.

Kanatzidis, M. G. Comments Inorg. Chem. 1990, 10, 161—195.

Miiller, U.; Grebe, C.; Neumiiller, B.; Schreiner, B.; Dehnicke, K. Z.
Anorg. Allg. Chem. 1993, 619, 500—506.

Haushalter, R. C. Angew. Chem. Int. Ed. Engl. 1985, 24, 433—
435.

(a) Fenske, D.; Schreiner, B.; Dehnicke, K. Z. Anorg. Allg. Chem.
1993, 619, 253—260. (b) Ansari, M. A.; Bollinger, J. C.; Ibers, J.
A. Inorg. Chem. 1993, 32, 1746-1748.

Kim, K.—W.; Kanatzidis, M. G. J. Am. Chem. Soc. 1993, 115, 5871—
5872.

(a) Haushalter, R. C. Inorg. Chim. Acta 1985, 102, L37—L38. (b)
Kanatzidis, M. G.; Huang, S.~P. Phosphorus, Sulfinr and Silicon
1992, 64, 153—160.

Ansari, M. A.; Bollinger, J. C.; Ibers, J. A. J. Am. Chem. Soc. 1993,
115, 3838—3839.

 

(10) (a) l
760-
30,

(11) Burn

(12) DIFlA
Data
Crysz

(13) TEX!
5.0 :

9

(14) CERI
Versh

(15) SChI‘e;
1993,

(16) Huang
Chapt.

(17) Wolke
Natur}

(18) Kim, 1

(10)

(11)

(12)

(13)

(14)

(15)

(16)

(17)

(18)

114

(a) Kanatzidis, M. G.; Huang, S.—P. J. Am. Chem. Soc. 1989, 111,
760—761. (b) Huang, S.—P.; Kanatzidis, M. G. Inorg. Chem. 1991,
30, 1455—1466.

Burns, R. C.; Corbett, J. D. Inorg. Chem. 1981, 20, 4433—4434.
DIFABS: "An Empirical Method for Correcting Difi‘ractometer
Data for Absorption Efiects" Walker, N.; Stuart, D. Acta

Crystallogr., 1983, A39, 158-166.

TEXSAN: Single Crystal Structure Analysis Software, Version
5.0, Molecular Structure Corporation, The Woodlands, Texas.

CERIUS: Molecular Modeling Software for Materials Research,
Version 3.1, Molecular Simulations Inc., Cambridge, UK.

Schreiner, B.; Dehnicke, K.; Fenske, D. Z. Anorg. Allg. Chem.
1993, 619, 1127—1131.

Huang, S. P. Ph.D. Thesis; Michigan State University, 1993;
Chapter 2.

Wolkers, H.; Schreiner, B.; Staffel, R.; Miiller, U.; Dehnicke, K. Z.
Naturforsch. 1991, 46B, 1015—1019.

Kim, K.-W.; Kanatzidis, M. G. Inorg. Chem. 1991, 30, 1966—1969.

GROI
LAYERE]

CHAPTER 4

GROUP 11 METAL POLYTELLURIDE CHEMISTRY: THE
LAYERED METAL POYTELLURIDES, (RMe3N)[M(Te4)] (M=Cu,
Ag; R=Me, Et)

115

 

(
of (Pb;
cube-sh
the rea
prepare
Space
0:12.00
in the
c=12.16

T1
with Etl
(IV) art
and Etl
platelet
P21/c (1
5402.3
Polyhedr
a=9.577(
V=1348(

(1)
A8) and
The basi<
Te42~ lig
polymeri‘

atom is

 

—:—

116

ABSTRACT

(Me4N)[Cu(Te4)] (I) has been prepared in DMF by the reaction
of (Ph3P)3CuCl, K2Te4, and Me4NCl in a 1:1:1 molar ratio. The black
cube—shaped crystals of (I) were obtained upon addition of ether to
the reaction solution. The Ag analog (Me4N)[Ag(Te4)] (II) can be
prepared similarly using AgBF4. (I) crystallizes in the monoclinic
space group P21/c (no. 14) with a=9.519(7) A, b=11.240(6) A,
c=12.007(5) A, 5:103.73(4)° and V=1248(1) A3, while (II) crystallizes
in the same space group with a==9.357(2) A, b=ll.494(3) A,
c=12.l64(2) A, p=102.06(2)° and V==1279.3(5) A3.

The anionic layered [M(Te4)]‘ (M=Cu, Ag) can be also stabilized
with EtMe3N+ cations. (EtMe3N)[Cu(Te4)] (III) and (EtMe3N)[Ag(Te4)]
(IV) are prepared by the reaction of (Ph3P)3CuCl (or AgNOg), KzTe4
and EtMe3NI in a 1:1:1 molar ratio, in DMF. The black chunky
platelet crystals of (III) crystallize in the monoclinic space group
P21/c (no. 14) with a=9.684(2) A, b=11.429(2) A, c=12.131(2) A,
p=loz.38(1)°, and V=1311.5(6) A3, while the black chunky

 

polyhedral crystals of (IV) also crystallize in P21/c (no. 14) with
a=9.577(4) A, b=11.775(3) A, e=12.199(2) A, p=101.46(2)°, and
V=1348(1) A3.

(I) and (II) are composed of anionic layered [M(Te4)]' (M=Cu,
Ag) and non—interacting Me4N+ cations situated between the layers.
The basic layer building block is the five-membered MTe4 ring. The
Te42‘ ligand is the longest polytelluride ligand stabilized in a
polymeric structure. The tetrahedral geometry around the metal

atom is quite distorted and short contacts between metal atoms are

 

 

 

 

found to
(I) and
~0.80 am
The
the same
interspacil
~02 A h.
[M(Te4)l‘
are also :
0.85 eV,
crystals 0
r00m tem

S/Cm, res

77f

117

found to be 2.735(4) and 2.901(1) A for (I) and (II), respectively.
(I) and (II) are semiconductors with optical energy band gaps of
~0.80 and 0.90 eV, respectively.

The structure of the anionic [M(Te4)]- layer remains virtually
the same upon changing the cation from Me4N+ to EtMe3N+. The
interspacing distance between the [M(Te4)]* layers increased by only
~0.2 A because the ethyl group of EtMe3N+ is oriented parallel to the
[M(Te4)]‘ layer instead of being perpendicular to it. (III) and (IV)
are also semiconductors with optical energy band gaps of ~0.75 and
0.85 eV, respectively. Conductivity measurements on the single
crystals of (III) and (II) confirm that they are semiconductors with

room temperature electrical conductivities of ~1x10'4 and ~lx10'5

S/cm, respectively.

 

 

 

 

 

16pm

metal

 

 

 

118

INTRODUCTION

The presence of long (2,} (Q=S, Se, Te; x >3) chains as building
blocks or linking units for metal atoms in extended frameworks is
only a recent phenomenon. Compounds with these characteristics
are more likely to have low-dimensional or open structures.1 Despite
the abundance of molecular metal polychalcogenide complexes,
analogs with extended solid state structures are still rare with a few
notable examples. These include the alkali metal salts of a- and ['3-
KCuQ4 (Q=S, Se),2 KdeSelo,3 KAuQ5 (Q: S, Se),4 K3AuSe134 and
K28n283.5 Polymeric structures with organic counterions are even
fewer with (Ph4P)[AgSe4],6 (Me4N)[AgQ5] (Q=S,7 Se8),
(H3NCH2CH2NH3)[Cu281o],9 and (Ph4P)[MSe12] (M=Ga, In and T1).10
Prior to this work, no polymeric metal tetratelluride compound is
known. The longest known Texz‘ ligand is the Te32" found in
K4M3,Te1711 (M=Zr, Hi) and the binary compound CrTe3.12 Here we
report (RMe3N)[M(Te4)] (M=Cu, Ag; R==Me, Et), the first polymeric
metal tetratelluride compound with a layered structure.

Intercalation chemistry with metal polychalcogenide
frameworks has been limited due to the lack of such frameworks. In
the structure of (Me4N)[M(Te4)], the Me4N+ cations are assembled
nicely as a double layer between the layers of [M(Te4)]', raising the
possibility of ion exchange with other cations (vide infra). Upon
employing RMe3N+ (R=Et, Benzyl, and n—Hexyl) cations, we prepared
(RMe3N)[M(Te4)] compounds which appear to retain the layered

structure of [M(T64)1'-

 

 

EX

Reagent
Thr
further
(97% pu:
nitrate (S
Milwauke
stoichiom
described
purity) .
Hampshir
Company
was from
grade, 5}
reduced p:
and Over
(A'C-S- a:
Wisconsin]
PresenCe ‘

SCVEral hC

PhySicoch
Far~1
on a Nicol
with Csl
applying al

 

 

 

119

EXPERIMENTAL SECTION

Reagents

The chemicals in this research were used as obtained without
further purification. Tris(triphenylphosphine)copper(I) chloride
(97% purity), Silver(I) tetrafluoroborate (97% purity), and Silver(I)
nitrate (99+% purity) were from Aldrich Chemical Company Inc.,
Milwaukee, Wisconsin. K2Te4 was prepared by dissolving the
stoichiometric amounts of the elements in liquid ammonia, as
described in Chapter 2. Tetramethylammonium chloride (98+%
purity) was from Lancaster Synthesis Inc., Windham, New
Hampshire. Dimethylethyl amine was from Aldrich Chemical
Company Inc., Milwaukee, Wisconsin. Methyl iodide (98% purity)
was from J. T. Baker Inc., Phillipsburg, New Jersey. DMF (A.C.S.
grade, EM Science, Gibbstown, New Jersey) was distilled under
reduced pressure after being stored over KOH for more than a week
and over 4A Linde molecular sieves for several days. Diethyl ether
(A.C.S. anhydrous, Columbus Chemical Industries Inc., Columbus,
Wisconsin) was distilled after refluxing over potassium metal in the
presence of benzophenone and triethylene—glycol-dimethyl ether for

several hours.

Physicochemical Methods

Far—IR spectra were measured with CS] pellets of compounds
on a Nicolet 740 FT-IR spectrometer. Each sample was ground along
with C31 to fine powder and a translucent pellet was made by

applying about 12,000 psi pressure.

 

 

Shi
spe
pov
pov

absl

whe
and
coel
for

user
extr;

(his

SEhl

mas
and

00nd
mefll
Voha

wifll

if

120

UV/Vis/Near—IR diffuse reflectance spectra were obtained on a
Shimadzu UV—3101PC double-beam, double-monochromator
spectrophotometer, in the wavelength range of 200-2500 nm. BaSO4
powder was used as reference and base material, on which ground
powder sample was coated. Reflectance data were converted to
absorbance data using the Kubelka—Munk equationzl3

a/S = (I—R)2/2R

where or is the absorption coefficient, S is the scattering coefficient,
and R is the reflectance at a given wavelength. The scattering
coefficient has been shown to be practically wavelength independent
for particles larger than 5 pm, a condition easily met with the sample
used here. The bandgap energy value was determined by
extrapolation from the linear portion of the absorption edge in a
(or/S) vs E plot.

Semi-quantitative analyses of the compounds were done by
SEM/EDS as described in Chapter 2.

Variable temperature conductivity and thermopower
measurements were made on single crystals by Prof. C. R. Kannewurf

and coworkers at Northwestern University. The dc electrical

 

conductivity was measured using the conventional four-probe
method with 60 and 25 um diameter gold wires for the current and
voltage electrodes, respectively. Conductivity data were obtained
with the computer-automated system described elsewhere.14
Thermoelectric power measurements were performed using a slow
ac technique15 with 60 um gold wires to support and conduct heat to
the sample, as well as to measure the voltage resulting from the

applied temperature gradient. The gold wires used in these

 

 

measur
paste.

heated

Synth
A
atmospl

Lab glo

T
(Me4N)
mmd)1
of 0.30
Period <
addition
Precipita
into Sev
solutionS
fOrmed.
times. '

ratio as

Te
(Me4N)[
mmOI) K;
of 0.10 g

reaCthH

 

 

 

121

measurements were attached to the sample with a conductive gold
paste. Mounted samples were placed under vacuum (10'3 Torr) and

heated to 320 K for 2—4 hours to cure the gold contacts.

Synthesis
All experiments and manipulations were performed under an
atmosphere of dry nitrogen using either a Vacuum Atmosphere Dri—

Lab glovebox or a Schlenk line.

Tetramethylammonium tetratellurido-cuprate(l),
(Me4N)[Cu(Te4)] (I) To a 30 ml DMF solution of 0.199 g (0.34
mmol) K2Te4 and 0.037 g (0.34 mmol) Me4NCl, a 20 ml DMF solution
of 0.30 g (0.34 mmol) (Ph3P)3CuCl was added dropwise over a 30 min
period of time. The reaction solution became brownish black upon
addition of the (Ph3P)3CuCl solution. After undissolved black
precipitates had been filtered out, the filtrate solution was placed
into several long test tubes and 80 ml ether was layered over the
solutions. During the course of a week black cube—shaped crystals
formed. These crystals were isolated and washed with ether several
times. The yield was 70% and SEM/EDS analysis showed the CuzTe

ratio as 1531.

Tetramethylammonium tetratellurido-argenate(I),
(Me4N)[Ag(Te4)] (II) To a 30 ml DMF solution of 0.302 g (0.51
mmol) K2Te4 and 0.056 g (0.51 mmol) Me4NCl, a 20 ml DMF solution
0f 0.10 g (0.51 mmol) AgBF4 was added dropwise over 15 min. The

reaction solution became brownish black upon addition of the AgBF4

sol

the

chi
wa:

ana

ace
sell
20

of

Wer
sev:
solu
The.
The

(Ell
(0.51
solut

min.

 

 

 

 

 

 

122

solution. After undissolved black precipitates had been filtered out,
the filtrate solution was placed into several long test tubes and 100
ml ether was layered over them. During the course of a week black
chunky square crystals formed. These crystals were isolated and
washed with ether several times. The yield was 50% and SEM/EDS
analysis showed the Ange ratio as 1:5.2.

Ethyltrimethylammonium tetratellurido-cuprate(l),
(EtMe3N)[Cu(Te4)] (III) To a 30 ml DMF solution of 0.199 g
(0.34 mmol) KzTe4 and 0.073 g (0.34 mmol) EtMe3NI (prepared by
the reaction of dimethylethyl amine and excess methyl iodide in
acetone and purified by recrystallization in MeOH), a 20 ml DMF
solution of 0.30 g (0.34 mmol) (Ph3P)3CuCl was added dropwise over
20 min. The reaction solution became brownish black upon addition
of the (Ph3P)3CuCl solution. After undissolved black precipitates
were removed by filtration, the filtrate solution was placed into
several long test tubes and 80 m1 ether was layered over the
solutions. During the course of a week black chunky crystals formed.
These crystals were isolated and washed with ether several times.
The yield was 30% and SEM/EDS analysis showed the Cu:Te ratio as
1225.

Ethyltrimethylammonium tetratellurido-argenate(l),
(EtMe3N)[Ag(Te4)] (IV) To a 30 m1 DMF solution of 0.302 g
(0.51 mmol) KzTe4 and 0.110 g (0.51 mmol) EtMe3NI, a 20 ml DMF
solution of 0.087 g (0.51 mmol) AgNO3 was added dropwise over 15

min. A typical color change to brownish black was observed upon

 

 

addit
were
sevez
solut
cryst
with

show

X-ra

was
coate
The
AFCt

1'63th

reSpe.

123

addition of the AgNO3 solution. After undissolved black precipitates
were removed by filtration, the filtrate solution was placed into
several long test tubes and 100 ml ether was layered over the
solutions. During the course of a week black chunky polyhedral
crystals were obtained. These crystals were isolated and washed
with ether several times. The yield was 20% and SEM/EDS analysis
showed the Ange ratio as 1:5.0.

X-ray Crystallographic Studies

A single crystal of each compound, (I), (II), (III), and (IV),
was mounted on the tip of a glass fiber with epoxy adhesive and
coated with KrylonTM to protect it from prolonged exposure to air.
The crystallographic data for (I) and (IV) were collected on Rigaku
AFC6S four~circle automated diffractometers at r.t. and -100 °C,
respectively. The data for (II) and (III) were collected on a Nicolet
P3 four-circle automated diffractometer at —115 “C and r.t.,
respectively. Accurate unit cell parameters were determined from
the 26, to, (b, and x angles of 15 to 25 centered reflections. The
intensities of three standard reflections were checked every 100 or
150 reflections to monitor crystal and instrument stability. No
appreciable decay was observed during the data collection period.
An empirical absorption correction based on tp scans of three strong
reflections with X ~90“ was applied to each data set. The structures
Were solved by direct methods using the SHELXS—86 software
Program and refined with full—matrix least squares techniques.
After isotropic refinement of all atoms, a DIFABS correction was

applied.16 All calculations were performed on a VAXstation 3100/76

compl

Molec

crystal
the sa
in (1),
Ag a.
hydrog

calculi

analys
temper

deviati

124

computer using the TEXSAN crystallographic software package of
Molecular Structure Corporation.17

(1), (II), (III), and (IV) are isostructural to each other, as they
crystallize in the same space group, P21/c. The EtMe3N+ cations have
the same orientation in both (III) and (IV). All non-hydrogen atoms
in (I), (II), and (III) were refined anisotropically, while in (IV) only
Ag and Te atoms were refined anisotropically with other non-
hydrogen atoms refined isotropically. Hydrogen atom positions were
calculated but not refined.

Tables 4.1-4.2 show the crystal data and details for structure
analysis of all compounds. The fractional coordinates and
temperature factors (Beq) of all atoms with their estimated standard

deviations are given in Tables 4.3—4.6.

 

Tab]
and

Con
FOI'I

125

Table 4.1. Summary of Crystallographic Data for (Me4N)[Cu(Te4)] (I)
and (EtMe3N)[Cu(Te4)] (III).

 

Compound
Formula

FW

Crystal shape
Crystal color
Crystal size (mm)
Temperature (°C)
Crystal system
Space group

a (A)

b (A)

c (A)

a (deg)

6 (deg)

v (deg)

v (A3), 2

ll (cm'l) M0(Ka)
dcalc (g/cm3)
Scan Method
26max (deg)

No. of reflections
collected

No. of reflections,
Fo2 > 30(Fo)2

No. of variables
Max. shift/esd
Phasing method
R/Rw (%)

(I)
(Me4N)[CU(Te4)]
C4H12NCuTe4
648.09
chunky cube
black
0.06x0.06x0.08
23
monoclinic
P21/c (no. 14)
9.519(7)
11.240(6)
12.007(5)
90

103.73(4)
90

1248(1), 4
109.04
3.449

w/26

50

2472

1292

9 1

0.00

direct methods
3 .3/3 .6

(III)
(EtMe3N)[Cu(Te4)]
C5H14NCuTe4
662.12
chunky platelet
black
0.10x0.l3x0.21
23

monoclinic
P21/c (no. 14)
9.684(2)
11.429(2)
12.131(2)

90

102.38(1)

90

1311.5(6), 4
103.79

3.353

(.0/26

50

2604

1704

100

0.00

direct methods
4 .3/5 .0

 

R=2 IIFoI - IFcII/Z IFol

Rw= {X w(|Fo|-IFCD2/Z WlFolZlU 2

 

Cor
For

 

126

Table 4.2. Summary of Crystallographic Data for (Me4N)[Ag(Te4)]
(II) and (EtMe3N)[Ag(Te4)] (IV).

 

Compound
Formula

FW

Crystal shape
Crystal color
Crystal size (mm)
Temperature (°C)
Crystal system
Space group

a (A)

b (A)

c (A)

or (deg)

[3 (deg)

v (deg)

v (A3), 2

u (cm‘l) M0(Ka)
dcale (g/Cm3)
Scan Method
26max (deg)

No. of reflections
collected

No. of reflections,
1:02 > 30(Fo)2

No. of variables
Max. shift/esd
Phasing method
mw (%)

(11)
(Me4N)[Ag(Te4)]
C4H12NAgTe4
692.41
chunky cube
black
0.10x0.13x0.18
-115
monoclinic
P21/c (no. 14)
9.357(2)
11.494(3)
12.164(2)
90

102.06(2)
90

1279.3(5), 4
104.86
3.595

w/20

50

3297

1868

91

0.00

direct methods
2.5/3 .3

(IV)
(EtMe3N)[Ag(Te4)]
C5H14NAgTe4
706.44
polyhedral chunky
black
0.12x0.14x0.20
-100
monoclinic
P21/C (no. 14)
9.577(4)
11.775(3)
12.199(2)

90

101.46(2)

90

1348(1), 4
99.54

3.480

03/20

45

2011

1142

7 O

0.00

direct methods
10.4/11.6

 

R=2 IIFol - chlVZ IFol

Rw=[2w(lFoI-|FcD2/2WlFOlzll/2

 

 

 

 

 

Table
(Me4N
Parent

 

atom

 

127

Table 4.3. Fractional Atomic Coordinates and B3q Values for
(Me4N)[Cu(Te4)] (I) with Their Estimated Standard Deviations in
Parentheses.

 

 

atom x y Z Beq (AZJa
Cu(1) 0.4690(2) 0.0342(2) 0.8875(2) 2.77(8)
Te(l) 0.2770(1) 0.45550(8) 0.51552(8) 2.14(4)
Te(2) 0.3276(1) 0.22317(8) 0.58899(8) 217(4)
Te(3) 0.4258(1) 0.26646(8) 0.82355(8) 209(4)
Te(4) 0.6352(1) 0.43030(8) 0.80586(8) 2.39(4)
N(1) —0.126(1) 0.134(1) 0.675(1) 3.0(5)
C(1) -0.056(2) 0.172(2) 0.792(1) 4.8(9)
C(2) —0.286(2) 0.110(2) 0.665(1) 3.7(8)
C(3) -0.118(2) 0.234(2) 0.595(2) 6(1)
C(4) ~0.061(2) 0.025(2) 0.643(2) 8(1)

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beq= (8n2/3)[a2B11 +
b7-B22 + c2B33 + ab(cosy)B12 + ac(cos[3)B13 + bc(cosor)B23]. The
anisotropic temperature factor expression is exp[-27r2(B11a*2h2 + +
2312a*b*hk + ...)].

Tab
(Me
Par

at01

aniso

128

Table 4.4. Fractional Atomic Coordinates and Beq Values for
(Me4N)[Ag(Te4)] (II) with Their Estimated Standard Deviations in
Parentheses.

 

 

atom x y z Bea (A2)a
Ag(l) 0.46715(7) 0.03850(5) 0.88387(5) 1.56(2)
Te(l) 0.25375(5) 0.45269(4) 0.52368(4) 1.26(2)
Te(2) 0.32471(5) 0.23263(4) 0.60353(4) 1.20(2)
Te(3) 0.41600(5) 0.2823l(4) 0.83157(4) 124(2)
Te(4) 0.63773(6) 0.43467(5) 0.82267(4) 1.43(2)
N(1) -0.1299(7) 0.1521(6) 0.6726(5) 1.5(3)
C(1) -0.048(1) 0.186(1) 0.7859(8) 2.7(4)
C(2) -0.284(1) 0.1226(8) 0.6758(8) 2.3(3)
C(3) —0.128(1) 0.2505(8) 0.5948(7) 2.4(4)
C(4) -0.061(1) 0.0476(9) 0.630(1) 2.9(4)

 

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beg: (8n2/3)[a7-B11 +
b2B22 + 02333 + ab(cosy)B12 + aC(CosB)B13 + bc(cosa)B23]. The
anisotropic temperature factor expression is exp[-2112(Blla*2h2 + +
2B12a*h*hk + ...)].

Table
(EtMe;
Parent

 

atom

 

Table 4.5 . Fractional

129

Atomic Coordinates

and Beq Values for
(EtMe3N)[Cu(Te4)] (III) with Their Estimated Standard Deviations in

 

 

Parentheses.

atom x y z Beq (A2)a
Cu(1) -0.0269(2) 0.0295(2) 0.3899(1) 2.97(8)
Te(l) 0.2147(1) 0.06136(8) 0.48311(8) 236(4)
Te(2) 0.1608(1) 0.28642(8) 0.40318(8) 250(4)
Te(3) 0.0502(1) 0.23970(8) 0.17644(7) 238(4)
Te(4) -O.1485(1) 0.07790(8) 0.20968(8) 273(4)
N(1) 0.635(1) 0.082(1) 0.823(1) 4.0(6)
C(1) 0.576(3) 0.139(2) 0.715(1) 6(1)
C(2) 0.792(2) 0.089(2) 0.851(1) 3.8(7)
C(3) 0.588(2) -0.054(2) 0.814(2) 5(1)
C(4) 0.572(2) 0.121(3) 0.912(2) 8(1)
C(5) 0.614(2) 0.255(2) 0.934(2) 5(1)

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beq= (8n2/3)[a2311 +
b2B22 + c2333 + ab(cosy)B12 + ac(cosB)B13 + bc(cosa)B23]. The
anisotropic temperature factor expression is exp[-27r2(B11a"‘2h2 + +
2B12a"‘b"‘hk + ...)].

 

Tal
(Et
Pal

ato

equi

311181
2812

130

Table 4.6. Fractional Atomic Coordinates and Beq Values for
(EtMe3N)[Ag(Te4)] (IV) with Their Estimated Standard Deviations in
Parentheses.

 

 

 

atom x y Z Bea (A03
Ag(1) 0.4728(5) 0.0352(3) 0.8839(3) 3.1(2)
Te(l) 0.2622(5) 0.4409(3) 0.5229(2) 3.2(2)
Te(2) 0.3328(4) 0.2268(2) 0.6027(2) 2.7(1)
Te(3) 0.4309(4) 0.2738(2) 0.8290(2) 3.0(2)
Te(4) 0.6408(5) 0.4277(2) 0.8149(2) 3.2(2)
N(1) -O.148(8) 0.135(5) 0.671(5) 8(2)
C(1) —0.056(8) 0.176(5) 0.784(5) 5(1)
C(2) -0.298(7) 0.104(4) 0.661(4) 4(1)
C(3) 0.129(7) 0.257(5) 0.581(4) 5(1)
C(4) -0.077(8) 0.062(5) 0.615(5) 5(1)
C(5) 0058(8) -0.043(5) 0.682(5) 5(1)

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beq= (8n2/3)[a2311 +
b2B22 + c2333 + ab(cosy)B12 + ac(cos0)B13 + bc(cosa)Bz3]. The
anisotropic temperature factor expression is exp[—2rr2(B11a’*‘2h2 + +
2B12a"‘b*hk + ...)].

Rig
diff
45

fine
Bas
diff
calc
pow
assu
and

intel

131

XRD (X-ray Powder Diffraction) patterns were obtained on a
Rigaku-Denki/RW400F2 (Rotaflex) rotating anode powder
diffractometer. Ni-filtered, Cu radiation was used at the condition of
45 KV and 100 mA. The crystals of each compound were ground to
fine powder and put on a glass slide using a double-sided sticky tape.
Based on the atomic coordinates from the X-ray single crystal
diffraction study, X-ray powder patterns for all compounds were
calculated with the software package CERIUS.18 The observed X-ray
powder patterns were in good agreement with those calculated,
assuring the homogeneity and purity of the compounds. Calculated
and observed X-ray powder patterns showing d-spacings and

intensities of strong hkl reflections are compiled in Tables 4.7-4.10.

 

Table 4.7.

132

Calculated and Observed X-ray Powder Diffraction
Pattern of (Me4N)[Cu(Te4)] (I).

 

 

h k 1 defile (A) dobs (A) I/ImaL (obs, %)
1 0 0 9.25 9.33 100
0 l 1 8.09 8.14 11
1 1 0 7.14 7.19 18
-1 1 1 6.66 6.68 13
-1 0 2 5.56 5.59 13
-1 2 1 4.65 4.68 20
2 1 0 4.28 4.29 33
1 1 2 4.16 4.18 15
-2 0 2 4.13 4.15 25
-2 1 2 3.88 3.90 8
2 1 1 3.76 3.78 24
0 1 3 3.67 3.69 28
0 3 1 3.57 3.58 16
1 3 0 3.47 3.48 19
-2 1 3 3.25 3.27 17
2 1 2 3.14 3.15 15
3 0 0 3.08 3.10 26
2 3 0 2.911 2.919 20
1 3 2 2.873 2.885 14
0 1 4 2.823 2.841 19
-2 0 4 2.782 2.785 16
-2 3 2 2.775

_1 4 1 2.660 2.651 20
-1 2 4 2.641

0 2 4 2.588 2.592 15
1 4 1 2.581

1 1 4 2.541 2.550 10
-2 3 3 2.518 2.524 7
3 3 0 2.380 2.380 27—
-3 1 4 2.370

-3 3 2 2.360 2.356 35
—4 o 2 2.348

-1 1 5 2.348

-4 1 1 2.326 2.333 18
2 4 1 2.297 2.303 21
-2 1 5 2.267 2.277 10

 

Table

l. nZ4IAE/ul‘.”

l I. .

2132412_v543214.34 .405

\

133

 

 

Table 4.7. (cont'd).

h k 1 defile (A) dob, (A) 1/1Inai (obs, %)
—2 4 3 2.166 2.171 10
1 3 4 2.141 2.143 24
3 1 3 2.137

2 2 4 2.079 2.088 23
—1 4 4 2.048 2.056 13
1 5 2 2.009 2.013 21
—3 4 3 1.967 1.970 17
—5 0 2 1.897 1.904 25
4 2 2 1.878 1.885 15
3 4 2 1.864 1.861 24
-2 2 6 1.856

1 6 0 1.836 1.835 9
-4 4 1 1.815 1.810 26
—3 5 2 1.807

3 2 4 1.804

—4 4 2 1.802

0 5 4 1.780 1.785 13
-3 2 6 1.761 1.747 11
—4 1 6 1.681 1.687 9
-3 5 4 1.649 1.653 11
5 1 2 1.636 1.635 9

 

 

Table

Patter

I

(1]..(rll1(1113311010033140414401422

10111121222001412133021002121244222

Table 4.8.

134

Calculated and Observed X—ray Powder Diffraction
Pattern of (Me4N)[Ag(Te4)] (II).

 

 

h k l dcalc (A) dob. (A) I/Imax (obs, %)
1 0 0 9.15 9.13 100
0 1 1 8.27 8.25 10
1 1 0 7.15 7.16 15
1 1 —1 6.63 6.62 8
1 0 —2 5.54 5.55 5
1 2 —1 4.69 4.70 10
2 1 0 4.25 4.26 20
1 1 2 4.25

2 o —2 4.06 4.08 6
2 1 —2 3.83 3.84 5
2 1 1 3.78 3.78 8
o 1 3 3.75 3.75 10
0 3 1 3.65 3.67 6
1 3 -1 3.46 3.48 5
—2 1 3 3.23 3.23 8
2 1 2 3.18 3.18 6
1 0 —4 3.02 3.02 9
3 1 —1 3.01

3 0 —2 2.978 2.988 6
0 0 4 2.974

2 3 0 2.937 2.947 10
1 3 2 2.936

0 1 4 2.879 2.890 6
o 4 0 2.874

2 0 —4 2.772 2.779 5
1 4 0 2.742 2.751 5
2 1 -4 2.695 2.701 5
1 4 1 2.636 2.651 .7
2 4 1 2.334 2.340 6
4 0 —2 2.302 2.316 7
4 1 -1 2.292 2.301 5
2 4 -3 2.185 2.197 7
2 2 4 2.123 2.128 10
2 2 -6 1.869 1.873 6

 

Tabl

Table 4.9.

135

Pattern of (EtMe3N)[Cu(Te4)] (III).

Calculated and Observed X—ray Powder Diffraction

 

 

 

h k 1 dcalc (A) dob, (A) I/I%(obs, %)
1 0 0 9.46 9.38 100
0 1 1 8.23 8.14 11
1 1 0 7.29 7.24 10
1 1 —1 6.72 6.67 15
1 0 —2 5.59 5.56 14
1 2 —1 4.71 4.69 13
2 1 0 4.37 4.35 23
1 1 2 4.27 4.24 15
2 0 —2 4.16 4.14 24
2 1 1 3.86 3.84 18
0 1 3 3.73 3.72 10
0 3 1 3.63 3.62 9
2 1 —3 3.27 3.26 12
2 1 2 3.22 3.21 10
1 3 -2 3.15 3.14 15
2 3 0 2.967 2.957 19
3 1 —2 2.965

1 3 2 2.933 2.919 10
0 1 4 2.868 2.857 13
2 3 —2 2.808 2.786 10
1 4 —1 2.702 2.695 10
4 o —2 2.379 2.373 11
2 4 1 2.344 2.340 11
4 1 -2 2.329 2.324 10
2 2 4 2.133 2.127 8
3 3 —4 2.052 2.047 12
1 5 2 2.047

 

 

 

Table 4.10.

 

’i—

136

Pattern of (EtMe3N)[Ag(Te4)] (IV).

Calculated and Observed X—ray Powder Diffraction

 

 

h k 1 4,3,1, (A) dob. (A) mm (obs, %)
1 0 0 9.39 9.34 100
0 1 1 8.39 8.40 16
1 1 0 7.34 7.32 19
1 1 -1 6.74 6.75 22
1 0 -2 5.57 5.58 13
1 2 —1 4.79 4.80 14
2 1 0 4.36 4.34 40
1 1 2 4.32

2 0 —2 4.11 4.12 20
2 1 -2 3.88 3.87 13
2 l 1 3.87

0 1 3 3.77 3.78 9
0 3 1 3.73 3.74 6
2 1 —3 3.26 3.24 15
2 1 2 3.25 6
2 3 0 3.01 3.00 25
1 3 2 3.00

3 1 —2 2.935 2.944 15
0 1 4 2.897 2.908 11
1 4 1 2.699 2.703 12
2 4 1 2.391 2.399 22
1 1 -5 2.385

4 0 -2 2.349 2.348 30
4 1 —1 2.346

2 4 -3 2.222 2.230 15
2 2 4 2.159 2.163 10
1 5 2 2.100 2.106 11
3 4 —3 2.005 2.015 9
2 5 2 1.932 1.933 15
2 2 -6 1.878 1.888 10
3 2 4 1.872 1.874 14

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RESULTS AND DISCUSSION
1. Synthesis
The syntheses of (I), (II), (III), and (IV) were accomplished
by the reaction of (Ph3P)3CuCl (or AgBF4, AgNO3), KzTe4, and Me4NC1

(or EtMe3NI) in DMF at r.t., as represented in eq. (4.1).

DMF

 

(Ph3P)3CuC1 + K2Te4 + Me4NCl T.
(or AgBF4, AgNO3) (or EtMe3NI)
(RMe3N)[M(Te4)] + 2KC1 + 31>th ----------------- eq. (4.1)

(M=Cu’ Ag; RzMe’ E‘) (or KI + KBF4(or KNO3))
Sometimes elemental Te was obtained as a by—product. In such a
case it was necessary to treat the products with n-Bu3P in DMF to
remove the Te impurity.

In the structure of (I) and (II) the Me4N+ ions form a double
layer between the [M(Te4)]‘ layers (vide infra). Considering the
charge density of the [M(Te4)]‘ layer (33.7 and 35.0 A2 per charge,
respectively, for (l) and (11)), cations larger than Et4N+ should not be
accommodated in the structure. Therefore, we tried RMe3N+ (R=Et,
benzyl, n-hexyl) cations which might be fit into the space between
the layers. The rationale is that RMe3,N+ cations have a common
group with the Me4N+ and thus, in a certain orientation, will have
equal projections on the [M(Te4)]' layer. Indeed this hypothesis
proved correct for yielding (III) and (IV), and according to X-ray

 

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powder diffraction and elemental analytical evidence, also for
(benzy1)Me3N’r and (n-hexy1)Me3N+. The EtMe3N+ salts are
isostructural compounds to the Me4N+ salts as determined by X—ray
single crystal studies. When n—hexyl- or benzyltrimethylammonium
cations were employed the layer d—spacing increased by 2.9 and 3.7
A, respectively, based on the powder XRD patterns (see Figure 4.1),
but no single crystal has yet been obtained. Direct ion exchange of
Me4N+ ions with RMe3N+ ions and other smaller cations including
alkali metal ions was attempted without success so far.

When Ph4P+ and Et4N+ organic cations were adopted to produce

new Cu or Ag polytellurides, molecular complexes of [M2(Te4)3]4'

 

(M=Cu, Ag) were only obtained.19 This proves that the large Ph4P+
and Et4N+ cations can not be fit between the [M(Te4)]' layers and the
templating RMe3N+ cations are responsible for the stabilization of the

[M(Te4)]’ layered structure.

2. Physicochemical Studies

2.1 Far-IR spectroscopy
In the far—IR spectra of (Me4N)[Cu(Te4)] (I) and

 

(EtMe3N)[Cu(Te4)] (III) a strong peak exists at 165 cm"1 with several
shoulders in the 140-160 cm‘1 range, whereas the far-IR spectra of
(Me4N)[Ag(Te4)] (II) and (EtMe3N)[Ag(Te4)] (IV) show a strong peak
at 175 cm'1 (see Figures 4.2 and 4.3). These peaks could be assigned
to either M—Te or Te—Te vibration modes. Frequencies of some
previously assigned Te-Te vibration modes range from 167 to 219

cm'l, as found in metal polytelluride and free polytelluride

 

139

 

 

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800 380 360 280 260 180 100
WAVENUMBER

Figure 4.2. Far-IR spectra (Csl pellet) of (A) (Me4N)[Cu(Te4)] (I)
and (B) (EtMe3N)[Cu(Te4)] (III).

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Figure 4.3. Far-IR spectra (Csl pellet) of (A) (Me4N)[Ag(Te4)]
(II) and (B) (EtMe3N)[Ag(Te4)] (IV).

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complexes such as [Cd4Te12]4‘ (VTe-Te=173 cm-l),20 [Hg4Te12] (VTe-
Te=l67 cm-1)920 [PdTe3]2' ("Te-Te:200 CHI-0,21 [AU2T3412' ("Te-Te:188
cm'l),22 and [Te4]2‘ (VTe-Te:219a 188 cm'l).23

2.2 UV/Vis diffuse reflectance spectroscopy

All compounds, (I), (II), (III), and (IV) start to steeply absorb
light in the near-infrared region, as can be seen in their optical
spectra (see Figures 4.4 and 4.5). The bandgap of each compound
ranges from 0.75 to 0.90 eV. It is noteworthy that Ag analogs have
slightly higher bandgaps than do Cu analogs. The other thing to be
noted is that the bandgaps of the Me4N+ salts are a little higher than
those of the EtMe3N+ salts.

2.3 Conductivity and thermopower measurements

The conductivity data of (EtMe3N)[Cu(Te4)] (III) show
semiconductor behavior in the temperature range of 320—80 K with a
room temperature electrical conductivity of ~1x10'4 S/cm, see Figure
4.6. A hump at ~250 K might be due to a phase transition.
Thermoelectric power data represent p-type metallic behavior at
temperatures above ~250 K with S”, ~230 uV/K, as shown in Figure
4.7. However, considering the large value of the Seebeck coefficient
and the observation that the temperature dependence of
thermopower is relatively flat at the temperatures below ~250 K, in
addition to the conductivity result, ([11) is believed to be a
semiconductor. The conductivity and thermopower data of
(Me4N)[Cu(Te4)] (I) also show similar behavior to (III) with a much

lower conductivity of ~le0‘6 S/cm and a Seebeck coefficient

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Figure 4.4. Optical absorption spectra of (A) (Me4N)[Cu(Te4)] (I)
and (B) (EtMe3N)[Cu(Te4)] (III), derived from diffuse reflectance
measurements. The tangent line to the Energy axis represents an
extrapolation of the absorption edge.

 

 

 

 

 

144

 

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a/s

 

 

 

 

 

 

2.0-

(B)

a/s

 

 

 

 

 

Energy (eV)

Figure 4.5. Optical absorption spectra of (A) (Me4N)[Ag(Te4)]
(II) and (B) (EtMe3N)[Ag(Te4)] (IV), derived from diffuse reflectance
measurements. The tangent line to the Energy axis represents an
extrapolation of the absorption edge.

 

 

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~300(i 50) uV/K at r.t.. The silver analog, (Me4N)[Ag(Te4)] (II) also
shows semiconducting behavior with a r.t. electrical conductivity of
~1x10'5 S/cm (see Figure 4.8). However, the conductivity data on
various selected crystals were not consistent. Further study is

needed to clarify this problem.

3. Description of Structures

(RMe3N)[M(Te4)] (M=Cu, Ag; R=Me, Et) contain anionic [M(Te4)]-
layers and noninteracting Me4N+ cations situated between the layers.
As shown in Figure 4.9, the layers form by interconnection of five-
membered MTe4 rings via a new bridging mode of the Te42' ligand
which holds three Cu atoms together. Scheme (A) shows four
different bridging modes of a Q42" ligand known to result in
polymeric [M(Q4)]' structures which include or— and B-[Cu(Q4)]' (Q=S,
Se) and [Ag(Se4)]'.216 Variations in connectivity of Q42' and M+ atoms

determines the dimensionality of the structures.

M M
—. __03 \QZ —— Q3

Q1 Q4 Q1 Q4 Qt Q4 Qt Q4
/ \ / \ \M/ \M \M/ \M \M/ \M

in fi-[Cu(Q4)]' in or-[Cu(Q4)]' .in [Ag(Se4)]' in [Cu(Te4)]'

Scheme (A)

 

 

 

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Figure 4.9. ORTEP representation (50% ellipsoids) and labeling
scheme of [M(Te4)]' layer in the (Me4N)[CuTe4] (I), (Me4N)[AgTe4]
(II), (EtMe3N)[CuTe4] (III), and (EtMe3N)[AgTe4] (IV), viewed along
the a-axis. One 14-membered ring hole in the layer is shaded for
clarity and its dimension is defined by dotted lines connecting
opposite Te(2) and Te(4) atoms. Partially filled ellipsoids represent
Cu atoms and crossed ellipsoids represent Te atoms.

 

 

 

———

150

As the MTe4 rings come together to build layers, they form
planar [MzTez] rhombic units located at the center of symmetry. The
Cu-Cu distances in the [CuzTez] units are 2.735(4) and 2.695(4) A for
(I) and (111), respectively, shorter than the sum of the van der
Waals radii of Cu atoms, 2.80 A, and somewhat longer than the
distances found in B—[Cu(S4)]‘ (2.607(1) and 2.661(1) A). The Ag—Ag
distances in the [Angez] units (2.901(1) and 2.897(6) A for (11) and
(IV), respectively) are much shorter than the sum of the van der
Waals radii of Ag atoms, 3.40 A. These dlo-d10 interactions between
metal atoms might be the driving force to form the dimeric unit of
[MzTez]. The five-membered ring of MTe4 adopts an envelope

conformation as the M(1), Te(l), Te(3) and Te(4) atoms lie in a plane

 

with the Te(2) atom lying above it. Table 4.11 shows the mean
deviation of the atoms defining a plane and the Te(2) atom distance

from the plane for all the compounds of (I), (II), (III), and (IV).

Table 4.11. Comparison of Mean Standard Deviations and Te(2)
Atom Distances from the Plane Defined by M(1), Te(l), Te(3), and
Te(4) in a MTe4 Ring of (Me4N)[Cu(Te4)] (I), (Me4N)[Ag(Te4)] (II),
(EtMe3N)[Cu(Te4)] ([11), And (EtMe3N)[Ag(Te4)] (IV).

 

Compound Mean standard Te(2) atom distance (A)
__ deviation (A)

(Me4N)[Cu(Te4)] 0.01 l .50
(Me4N)[Ag(Te4)] 0.03 1 .55
(EtMe3N) [Cu(Te4)] 0.04 l .4 4
(EtMe3N) [Ag (Te4)] 0.004 1 .49

¥

 

 

 

 

’i—

151

The Cu-Te distances in the [Cu(Te4)]“ anions of (I) and (III) fall in
two categories. Shorter distances involve the terminal Te atoms,
Te(l) and Te(4), and longer distances are associated with the internal
Te atom, Te(3) of the Te42" chain. This behavior was also seen in 01—
[Cu(Q4)]‘ (Q=S, Se), but interestingly was not observed in the
[Ag(Te4)]- of (II) and (IV). The comparison of M-Te and Te—Te bond
distances and selected bond angles for each compound are listed in
Tables 4.12-4.15.

The most interesting feature of the layers is the presence of
large holes made of 14-membered rings (see Figure 4.9). The
dimensions of the rings as defined by the closest Opposite Te atoms
for each compound are shown in Table 4.16. The conformation of
this ring is puckered with the four Te atoms (two Te(4) and two
Te(2)) pointed inwards and defining a square planar site. The Me4NJr
cations assemble nicely as a double layer between the [M(Te4)]'
layers instead of sitting inside l4—membered rings of the layer (see
Figure 4.10). This raises an interesting possibility for ion-exchange
with other kinds of cations. The layered structural motif is retained
with the EtMe3N+ cation, as (EtMe3N)[M(Te4)] is isostructural to
(Me4N)[M(Te4)], suggesting the possible existence of a whole family
of isostructural lamellar (RMe3N)[M(Te4)] materials. The interspacing
distance between the [M(Te4)]‘ layers increased by as little as ~0.2 A
upon replacing the Me4N+ cation to the EtMe3N+. The reason for this
is that the ethyl group of EtMe3N+ does not point toward the layer,
instead it favors the equatorial position as shown in Figure 4.11. The

top—views of the [M(Te4)]' layer, including the Me4N+ and EtMe3N+

 

 

’t—
152

cations, suggest that RMe3N+ cations with even larger R group can
also be fit in the structure (see Figures 4.12 and 4.13).
(RMe3N)[M(Te4)] represents a new addition to the already
known broad AMQX family (A: Ph4P, Me4N, K, Rb, Cs; M: Cu, Ag, Au;
Q=- S, Se, Te), all of which feature low—dimensional polymeric
structures. With the stable layered structure of [M(Te4)]- (M: Cu, Ag)
we find further support for the notion that sz' ligands can provide

the structural elements for building a variety of open semiconductor

frameworks.

 

 

 

 

Tab
the
(111

Cu-
Cu-
Cu-
Cu—

Cu-’

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Te(i

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the

 

 

’i—

153

Table 4.12. Comparison of Some Selected Bond Distances (A) in
the [Cu(Te4)]' Anions of (Me4N)[Cu(Te4)] (I) and (EtMe3N)[Cu(Te4)]
(111). Standard Deviations Are Given in Parentheses.a

 

(Me4N)[CU(Te4)l (EtMe3N)[CU(Te4)l

Cu-Te(l) 2.655(3) 2.649(2)
Cu—Te(1)' 2.578(3) 2.588(2)
Cu-Te(3) 2.725(3) 2.753(2)
Cu-Te(4) 2.578(2) 2.563(2)
Cu—Te (mean) 2.63(7) 264(8)

Te(1)-Te(2) 2.762(2) 2.759(1)
Te(2)-Te(3) 2.791(2) 2.781(1)
Te(3)—Te(4) 2.759(2) 2.760(1)
Te—Te (mean) 2.77(2) 2.77(1)

Cu-Cu' 2.735(4) 2.695(4)

a The estimated standard deviations in the mean bond distances
were calculated by the equation 01 = {Znfln—lfl/nm—I )}1/2, where In
is the distance of the nth bond, 1 is the mean bond distance, and n is
the number of bonds.

 

 

 

Table 4.13.
the [Cu(Te.
(111). Star.

 

l

154

Table 4.13. Comparison of Some Selected Bond Angles (deg) in
the [Cu(Te4)]“ Anions of (Me4N)[Cu(Te4)] (I) and (EtMe3N)[Cu(Te4)]
(111). Standard Deviations Are Given in Parentheses.

 

(Me4N)[Cthe4)] (EtMe3N)[CU(Te4)]

Te(1)-Cu-Te(l)' 116.99(8) 118.07(7)
Te(1)-Cu-Te(3) 9244(7) 9085(6)
Te(1)-Cu-Te(4) 111.76(9) 108.34(8)
Te(l)'-Cu-Te(3) 121.24(8) 121.46(8)
Te(l)'-Cu-Te(4) 111.76(8) 112.8l(7)
Te(3)-Cu-Te(4) 100.38(7) 102.45(7)
Cu-Te(1)-Cu' 6301(8) 6193(7)
Cu-Te(l)-Te(2) 97.73(6) 103.35(6)
Cu-Te(l)'-Te(2) 96.10(6) 97.78(6)
Cu-Te(3)-Te(2) 9627(5) 95.47(5)
Cu-Te(3)-Te(4) 126.70(7) 131.98(6)
Cu-Te(4)-Te(3) 103.94(7) 103.78(6)
Te(1)-Te(2)-Te(3) 9855(4) 9993(4)
Te(2)-Te(3)-Te(4) 9653(5) 9672(4)

 

 

 

 

 

 

Table 4.14.
the [Ag(Te.
(IV). Stan

Ag-Te
Ag-Te
Ag-Te
Ag-Te

1)
1)’

A
A
A

A

4)

Ag‘TC (me:

is the distan

155

Table 4.14. Comparison of Some Selected Bond Distances (A) in
the [Ag(Te4)]' Anions of (Me4N)[Ag(Te4)] (II) and (EtMe3N)[Ag(Te4)]
(IV). Standard Deviations Are Given in Parenthesesa

 

(Me4N) [Ag(T64)1 (EtMe3N)[Ag(Te4)]

Ag-Te(l) 2.882(1) 2.895(6)
Ag—Te(1)' 2.798(1) 2.797(6)
Ag-Te(3) 2.891(1) 2.897(4)
Ag-Te(4) 2.7692(9) 2.760(4)
Ag—Te (mean) 284(6) 284(7)

Te(l)-Te(2) 2.7409(9) 2.739(4)
Te(2)-Te(3) 2.7857(9) 2.790(4)
Te(3)—Te(4) 2.7344(8) 2.738(5)
Te-Te (mean) 275(3) 276(3)

Ag-Ag' 2.901(1) 2.897(6)

 

a The estimated standard deviations in the mean bond distances
were calculated by the equation 01 = {in(ln-l)2/n(n-1)}1/2, where 1,,
is the distance of the nth bond, 1 is the mean bond distance, and It IS

the number of bonds.

 

 

 

 

 

Table 4.15
the [Ag(T e
(IV). Star

 

I

156

Table 4.15. Comparison of Some Se1ected Bond Angles (deg) in
the [Ag(Te4)]' Anions of (Me4N)[Ag(Te4)] (II) and (EtMe3N)[Ag(Te4)]
(IV). Standard Deviations Are Given in Parentheses.

 

(Me4N)[Ag(Te4)] (EtMe3N)[Ag(Te4)]

Te(l)-Ag-Te(l)' 118.60(3) 118.8(1)
Te(l)-Ag—Te(3) 8957(2) 87.7(1)
Te(l)-Ag—Te(4) ll3.ll(3) 111.1(2)
Te(l)'—Ag-Te(3) 121.85(3) 123.5(2)
Te(l)'-Ag-Te(4) 109.69(3) 110.0(2)
Te(3)-Ag—Te(4) 101.95(3) 103.2(1)
Ag—Te(1)-Ag’ 61 .40(3) 61.2(1)
Ag-Te(l)-Te(2) 9546(2) 98.4(2)
Ag-Te(1)'-Te(2) 92.65(3) 94.6(2)
Ag-Te(3)—Te(2) 9130(2) 92.3(1)
Ag-Te(3)—Te(4) 122.50(3) 125.9(2)
Ag-Te(4)—Te(3) 100.60(3) 101-1(2)
Te(1)-Te(2)—Te(3) 99.49(2) 100.4(1)

Te(2)-Te(3)—Te(4) 9974(2) 100.1(1)

 

 

 

Table 4.16
Layers t
(EtMe3N)[C

 

Compound

(Me4N)[Cu(
(Me4N)[Ag1
(EtMesNHC
(EtMe3N) [A

 

\

 

157

Table 4.16. Dimensions of l4-Membered Rings in the [M(Te4)]‘
Layers of (Me4N)[CU(Te4)l (I), (Me4N)[Ag(Te4)] (11),
(EtMe3N)[Cu(Te4)] (III), and (EtMe3N)[Ag(Te4)] (IV).

 

 

Compound Dimensions (A)

(Me4N)[Cu(Te4)] 6.043(3) x 6.621(3)
(Me4N)[Ag(Te4)] 5.670(2) x 7.011(2)
(EtMe3N)[Cu(Te4)] 6.496(2) x 6.603(2)

(EtMe3N) [Ag(Te4)] 5.951 (8) x 6.947(7)

 

 

 

158

 

 

 

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(Me4N)[Cu(Te4)] (I) and (Me4N)[Ag(Te4)] (II) viewed along the b-

axis.

Ellipsoids are drawn with 50% probability.

 

 

 

 

 

 

 

159

 

 

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(EtMe3N)[Cu(Te4)] (III) and (EtMe3N)[Ag(Te4)] (IV) viewed along the
b-axis. Ellipsoids are drawn with 50% probability.

 

 

 

 

Figure 4.]

(Me4N)[Cu(1
ElliPSOIds a]

 

a..._A__-_- .__..r.._.

160

 

 

 

 

 

 

 

 

 

Figure 4.12. Top-view of the . layered structure of
(Me4N)[Cu(Te4)] (I) and (Me4N)[Ag(Te4)] (11) viewed along the a-axrs.
Ellipsoids are drawn with 50% probability.

 

 

 

 

 

 

 

 

 

Figure 4

(EtMe3N)[CI

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4.13. Top-view of the layered structure of
(EtMe3N)[Cu(Te4)] (III) and (EtMe3N)[Ag(Te4)] (IV) viewed along the
a-axis. Ellipsoids are drawn with 50% probability.

 

 

 

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162

LIST OF REFERENCES

(a) Haradem, P. S.; Cronin, J. L.; Krause, R. A.; Katz, L. Inorg.
Chim. Acta 1977, 25, 173-179. (b) Kanatzidis, M. G. Chem.
Mater. 1990, 2, 353-363. (c) Park, Y.; Liao, J.-H.; Kim, K.-W.;
Kanatzidis, M. G. in Inorganic and Organometallic Polymers and
Oligomers ; J. F. Harrod and R. M. Laine (eds). Kluwer Academic
Publishers 1991, pp. 263-276.

Kanatzidis, M. G.; Park, Y. J. Am. Chem. Soc. 1989, III, 3767—
3769.

Kim, K.—W.; Kanatzidis, M. G. J. Am. Chem. Soc. 1992, 114, 4878—
4883.

Park, Y.; Kanatzidis, M. G. Angew. Chem. Int. Ed. Engl. 1990, 29,
914-915.

Liao, J.—H.; Kanatzidis, M. G. Inorg. Chem. 1993, in press.

Kanatzidis, M. G.; Huang, S.-P. J. Am. Chem. Soc. 1989, 111,
760—761.

Banda, R. M. H.; Craig, D. C.; Dance, 1. G.; Scudder, M. L.
Polyhedron 1989, 8, 2379-2383.

Huang, S.-P.; Kanatzidis, M. G. Inorg. Chem. 1991, 30, 1455—
1466.

Kiel, G.; Gattow, G.; Dingeldein, T. Z. Anorg. Allg. Chemie 1991,
596, 111-119.

(10) Dhingra, S.; Kanatzidis, M. G. Science 1992, 258, 1769—1772.

(11) Keane, P. M.; Ibers, J. A. Inorg. Chem. 1991, 30, 1327—1329.

 

 

 

 

 

5.0, ]

Versit

<19) (a) F<
1993,
A. In

(20) See C

(21) Wolke
Acta

(22) Huang

Chaptt

 

 

(12) Klepp, K. 0.; Ipser, H. Angew. Chem. Int. Ed. Engl. 1982, 21, 911.

(13) (a) Wendlandt, W. W.; Hecht, H. G. Reflectance Spectroscopy;
Interscience Publishers: New York, 1966, and references
therein. (b) Kotfim, G. Reflectance Spectroscopy; Springer—
Verlag: New York, 1969. (c) Tandon, S. P.; Gupta, J. P. Phys.
Status Solidi 1970, 38, 363-367.

 

(14) Lyding, J. W.; Marcy, H. 0.; Marks, T. J.; Kannewurf, C. R. IEEE
Trans. Instrum. Meas. 1988, 37, 76-80.

(15) Marcy, H. 0.; Marks, T. J.; Kannewurf, C. R. IEEE Trans. Instrum.
Meas. 1990, 39, 756-760.

 

(16) DIFABS: "An Empirical Method for Correcting Difiractometer
Data for Absorption Effects" Walker, N.; Stuart, D. Acta
Crystallogr., 1983, A39, 158—166.

(17) TEXSAN: Single Crystal Structure Analysis Software, Version
5.0, Molecular Structure Corporation, The Woodlands, Texas.

(18) CERIUS: Molecular Modeling Software for Materials Research,
Version 3.1, Molecular Simulations Inc., Cambridge, UK.

 

(19) (a) Fenske, D.; Schreiner, B.; Dehnicke, K. Z. Anorg. Allg. Chem.
1993, 619, 253-260. (b) Ansari, M. A.; Bollinger, J. C.; Ibers, J.
A. Inorg. Chem. 1993, 32, 1746-1748.

(20) see Chapter 3.

(21) Wolkers, H.; Dehnicke, K.; Fenske, D.; Khassanov, A.; Hafner, S. S.
Acta Crystallogr. 1991, 47C, 1627-1632.

 

(22) Huang, S. P. Ph.D. Thesis; Michigan State University, 1993;
Chapter 2.

 

 

 

 

(23) Wolkers, H.; Schreiner, B.; Staffel, R.; Mfiller, U.; Dehnicke, K. Z.
Naturforsch. 1991, 468, 1015-1019.

 

 

 

 

 

 

 

CHAPTER 5

 

GROUP 10 METAL POLYCHALCOGENIDE CHEMISTRY: STUDIES
ON K2Pd8610, K4[Pt4522]‘4H20, K4[Pt4Se22],
(Ph4P)2[Pt(S4)2]‘CH30H1 and (Ph4P)4[Pt(S4)(Ss)2][Pt(Ss)3]

 

 

 

 

Hydrotl
Large I

ABS’

Kde
an interpe;
hydrotherm;
°C, in the 3
(I) are ins.
in the ortl
11. b=15.92
C0mposed
[Pd(se6)2];
K4[Pd(3€4)2
In the [pc
ligands C0
diam0nd~lil
frameworks
hameW0rk
crystallogra.
atom is S

 

 

 

PART I

Hydrothermal Synthesis of KdeSeloz Coexistence of Two
Large Interpenetrating Three-Dimensional Frameworks of

[Pd(Se4)2]2' and [Pd(Se6)2]2‘

ABSTRACT

KdeSem (I), the first metal polychalcogenide compound with
an interpenetrating 3D framework structure, was produced by the
hydrothermal reaction of PdC12 and K28e4 in a 1:5 molar ratio at 110
°C, in the presence of KOH. The black rectangular chunky crystals of
(I) are insoluble in water and most organic solvents. (I) crystallizes
in the orthorhombic space group 1212121 (No. 24) with a=15.872(9)
A, b=15.922(9) A, c=12.885(8) A, V=3256(6) A3, and 2:8. (I) is
composed of two independent frameworks of [Pd(Se4)2]2‘ and
[Pd(Se6)2]2‘ besides non-interacting K+ ions. Therefore,
K4[Pd(Se4)2][Pd(Se6)2] could be a more self-descriptive formulation.
In the [Pd(Se4)2]2' and [Pd(Se6)2]2' frameworks, Se42‘ and 8e62—
ligands connect tetrahedrally arranged Pd atoms to result in
diamond—like frameworks. Remarkably, these two different 3D
frameworks interpenetrate each. other to fill their void spaces. Each
framework contains large tunnels running parallel to the a- and b-
crystallographic axes. The coordination geometry around the Pd
atom is square planar as usual. The average Pd—Se and Se-Se

distances are 2.462(5) A and 235(2) A, respectively. The closest

166

 

 

 

 

 

distances l
and 3.75(2
by UV/Vi:

 

————

167

distances between K+ ions and Se atoms are in the range of 327(2)
and 3.75(2) A. The bandgap energy for (I) is 1.48 eV, as determined
by UV/Vis/NIR diffuse reflectance Spectroscopy.

 

 

 

 

 

INT.

Rec:
synthesis
polychalcc
technique
chalcophili
elements 1
extent at
produce a
0f the cati
Was founc
structures
3‘33), (H3NI
that other
containing
COUnteriong
Products fr
on a Signil
COUntefion
recognized.
modificatioi
Canse Inajc
strUCtUre 0
explore ne.
structural, l

e"counter

 

 

 

168

INTRODUCTION

Recently, it was shown in our group that hydrothermal
synthesis can be applied to the preparation of some novel Mo
polychalcogenide compounds.1 To explore the generality of this
technique for other metals, we turned our attention to the more
chalcophilic late transition metal elements. The reactions of such
elements with polychalcogenide ligands have been explored to some
extent at ambient temperature and pressure, and were found to
produce a number of interesting molecular compounds.2 In the case
of the cation/M/Q (M=Cu, Ag; Q=S, Se) and cation/Hg/Te systems it
was found that some cations could stabilize polymeric 1D chain
structures such as those of (Ph4P)[Ag(Se4)],3 (Me4N)[Ag(Qs)] (Q=S4,
Se3), (H3NCH2CH2NH3)[Cu2(Ss)2],5 and (Ph4P)2[Hg2Te5].6 This suggests
that other interesting polychalcogenide-based polymeric structures
containing various metals may be also prepared. A particular set of
counterions with which it is difficult to obtain pure crystalline
products from solution are the alkali metal ions. Furthermore, based
on a significant body of experimental evidence the importance of the
counterion in determining the structure of [MQXP‘ anions is now well
recognized.2,3 For example, our group has shown that minor
modifications in the size of the counterions (Me4N+, Pr4N+, Ph4P+) can
cause major geometric and electronic reorganization of the anionic
structure of silver polyselenide compounds.3 This motivated us to
explore new counterions (e.g. alkali metal ions) in search of new
structural, particularly polymeric [MQx]n‘ compounds. Since we often

encounter difficulties in isolating crystalline polymeric compounds

 

 

 

using amb
the hydrot
Palla
such explo
(NH4)2[Pd5
with 852'
compound
structure.
(I), the

interpenetrz
EXP]

Reagents

The
further pur
Ward Hill,
Chemical 1
by dissolv
aIllmonia a:

bubbllng W

PhlSicoch,
Far-I]

On a N i901:

with C81 ':
applyng at

 

f

169

using ambient temperature and pressure conditions, we resorted to
the hydrothermal synthetic technique.

Palladium metal chemistry seemed particularly attractive for
such exploration because the first known Pd polysulfide compound,
(NH4)2[PdSl1]7 was reported to have a polymeric layered structure
with 852' and S62" ligands. The corresponding polyselenide
compound is unknown and expected to represent a different
structure. Herein we report the hydrothermal synthesis of KdeSelo
(I), the first metal polychalcogenide compound with an

interpenetrating 3D diamond-like framework structure.

 

EXPERIMENTAL SECTION

Reagents

The chemicals in this research were used as obtained without
further purification. PdClz (99% purity) was from Alfa Products,
Ward Hill, Massachusetts. KOH (A.C.S. grade) was from Columbus
Chemical Industries Inc., Columbus, Wisconsin. K28e4 was prepared
by dissolving stoichiometric amounts of the elements in liquid
ammonia as described in Chapter 2. Distilled water was degassed by

bubbling with nitrogen.

 

Physicochemical Methods

Far-IR spectra were measured with C31 pellets of compounds
on a Nicolet 740 FT-IR spectrometer. The sample was ground along
with C51 to fine powder and a translucent pellet was made by

applying about 12,000 psi pressure to the powder. UV/Vis/Near—IR

 

 

 

 

 

 

diffuse
and St

using 5

Synth
l
atmosp

Lab glt

pallad;
mmol)

KOH 2
thick-w
heated

(70% ;
amount
0rganic

SISM/131
X~ray

four-cir
K01 radi
with .
determll
The int

 

—’—

170

diffuse reflectance spectra were obtained as described in Chapter 4,
and semi-quantitative analyses of the compounds were performed

using SEM/EDS as described in Chapter 2.

Synthesis
All experiments and manipulations were performed under an
atmosphere of dry nitrogen using either a Vacuum Atmosphere Dri—

Lab glovebox or a Schlenk line.

Dipotassium (tetraselenido)—(hexaselenido)-
palladate(II), K2[Pd(Se4)(Se6)] (I) An amount of 0.050 g (0.28
mmol) of PdClz, 0.552 g (1.40 mmol) of K25e4, 0.079 g (1.41 mmol) of

 

KOH and 0.2 ml distilled water were charged in a 9 mm diameter
thick-walled Pyrex tube. The tube was sealed off under vacuum and
heated at 110 °C for a day. Shiny black rectangular chunky crystals
(70% yield) were isolated by filtration and washed with copious
amount of water. These crystals are insoluble in water and most
organic solvents. Semiquantitative analysis of the crystal by the

SEM/EDS technique showed the K:Pd:Se atomic ratio as 2.1:1.0:10.8.

 

X-ray Crystallographic Studies

The crystallographic data were collected on a Rigaku AFC6S
four-circle automated diffractometer using a 03/26 scan mode and Mo
Koc radiation. A single crystal was mounted on the tip of a glass fiber

with epoxy adhesive. Accurate unit cell parameters were

determined from the 26, to, d), and x angles of 20 centered reflections.

The intensities of three standard reflections were checked every 150

 

 

 

 

 

reflec
decay
absor
with

by c
refint

isotrc

beuei
its u
tetrag
zdso

Synnr

enant

Were
differ
Pd(2)
3/4,

POShi
aIlaly
(Beq)

in Ta

171

reflections to monitor crystal and instrument stability. No serious
decay was observed during the data collection period. An empirical
absorption correction based on 1p scans of three strong reflections
with X ~90° was applied to each data set. The structure was solved
by direct methods using the SHELXS-86 software program and
refined with a full-matrix least squares technique. After the
isotropic refinement of all atoms a DIFABS correction was applied.8
All calculations were performed on a VAXstation 3100/76 computer
with the TEXSAN crystallographic software package of Molecular
Structure Corporation.9

We carefully checked the structure of (I) to see if it could be
better refined in the tetragonal unit cell, because the a and b axis of
its unit cell were nearly equal. However, the refinement in the
tetragonal unit cell was not successful. The MISSYM program was
also applied to ensure the absence of any possible overlooked
symmetry. All atoms including K were refined aniostropically. The
enantiomorph was also refined to completion but gave slightly higher
R values (~0.3%) and estimated standard deviations (esds). There
were no significant residual peaks in the final electron density
difference map. In the structure of (I) two independent Pd(l) and
Pd(2) atoms are found sitting on 2-fold axes (1/2, 1/4, 2) and (1/2,
3/4, Z+1/2), respectively, while the Sc and K atoms are in general
positions. Table 5.1 shows crystal data and details of the structure
analysis. The final fractional coordinates and temperature factors

(Beq) of all atoms with their estimated standard deviations are given

in Table 5.2.

 

 

 

 

 

coll

172

Table 5.1. Summary of Crystallographic Data for K2PdSe10 (I).

 

Compound
Formula

FW

Crystal shape
Crystal color
Crystal size (mm)

Temperature (°C)
Crystal system
Space group

a (A)

b (A)

c (A)

a (deg)

6 (deg)

v (deg)

v (A3), 2

u (cm'l) M0(K0t)
dcalc (g/cm3)
Scan Method

20max (deg)

No. of reflections
collected

No. of reflections,
1:02 > 300:0)2

No. of variables
Max. shift/esd

Phasing method
R/RW (%)

(I)
K2[Pd(Se4)(Seo)l
K2PdSe10
974.20
rectangular chunky
black
0.07x0.09x0.13
23
orthorhombic
1212121 (no. 24)
15.872(9)
15.922(9)
12.885(8)

90

90

90

3256(6), 8
237

3.97

w/20

45

1976

881

1 19

0.00

direct methods
6 .5/7 .8

 

R=z IIFoI - IFcll/Z IFol

Rw= {2 wGFol-IFcD2/2 wlFolzim

 

 

 

 

Tablt
K2Pt
Pare

aton

Pdl
Pd2
Sel
Se2
Se3
Se4
SeS
Se6
Se7
Se8
Se9
Se10

173

Table 5.2. Fractional Atomic Coordinates and Beq Values for

K2PdSe10 (I) with Their Estimated Standard Deviations in
Parentheses.

 

 

atom x y Z Bea (A03
Pdl 1/2 1/4 0.8741(7) 2.4(4)
Pd2 1/2 3 /4 1.1255(7) 2.0(4)
Sel 0.4405(5) 0.3932(5) 0.8713(6) 3.4(4)
$62 0.5490(6) 0.4879(5) 0.8395(6) 4.0(5)
Se3 0.6432(6) 0.3091(5) 0.8777(6) 3.3(4)
864 0.7385(6) 0.2014(6) 0.9087(6) 4.1(5)
565 0.5113(5) 0.5961(4) 1.1306(6) 2.6(4)
Se6 0.8569(5) 0.4440(5) 0.5698(6) 2.9(4)
Se7 0.7642(5) 0.4322(6) 0.7127(6) 4.0(5)
Se8 0.6546(5) 0.7593(5) 1.1212(6) 2.8(4)
Se9 0.6957(5) 0.8938(5) 1.1820(6) 3.1(5)
Se10 0.8178(7) 0.0136(5) 0.5388(7) 4.3(5)
K1 0.095(2) 0.848(1) 0.630(2) 8(2)
K2 0.403(1) 0.659(2) 0.870(2) 9(2)

 

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beq= (8n2/3)[a2311 +

b2322 + c2B33 + ab(cosy)B12 + ac(cosB)B13 + bc(cos0t)B23]. The
anisotropic temperature factor expression is exp[-2712(B11a"‘2h2 + +
2312a*b*hk + ...)].

 

 

 

l
Phillip
Graphit
35 KV
single
using 1
was in
X-ray
hkl refl

174

An XRD (X—ray Powder Diffraction) pattern was obtained on a
Phillips XRG-3000 computer—controlled powder diffractometer.
Graphite-monochromated, Cu radiation was used at the condition of
35 KV and 35 mA. Based on the atomic coordinates from the X-ray
single crystal diffraction data, a X-ray powder pattern was calculated
using the program POWD-lO.10 The observed X—ray powder pattern
was in good agreement with that calculated. Calculated and observed
X—ray powder patterns showing d-spacings and intensities of strong

hkl reflections are compiled in Table 5.3.

 

T abl

Patti

h
11
— — n303230413141204024034502251415235\

 

 

 

175

Calculated and Observed X-ray Powder Diffraction

Table 5 .3.

Pattern of K2PdSe10 (I).

 

I/Ima1x (obs, %)

dobs (A)

dcalc (A)

l

j;

 

 

01 4 4 3 1 0 08 7 8 1 4 5
01 2 1 1 1 1 61 5 4 3 9 3
1
4 5 0
07 6 2 2 4 2 95 2 4 0 3 5
70 9 2 0 7 4 21 1 0 9 8 7.
55 4 4 4 3 3 33 3 3 2 2 2
65141703584
93219778776098898211999888877610922
50098119999766633211000099888888777
55544443333333333333333322222222222

2001111110022113322422111144113322400
131130324031412140042543020524151253

11303230413141204024034502251415235

 

Table :

k

h

 

61.4354526251616471153637043736282354

163445252615164017135360734372628345

\

 

 

 

Table 5 .3.

(cont'd).

176

 

3‘

MhUJOONONNflW-hUJQOONUJMUJF—‘flHQ-PQF-‘Mt—‘QNLIINLII-h-P-UJQt—t

Pr

hmmNOONONQO-hOflmmwmv—H—KQAGHQHMNQNm-hmmhr—ON

N

UIU'IChOO-D-ANNMMWWWWh-RQNNOOmW-b#NNUJUJt—‘r—wmr—‘h-t

dome (A)

2.565
2.558
2.556
2.555
2.439
2.437
2.435
2.431
2.344
2.339
2.242
2.239
2.235
2.230
2.206
2.204
2.126

HHHi—‘HF‘HHHNNNNNNNNN
O
O
[\D

dobs (A)

2.588

2.459

2.366

2.274

2.226

2.144

2.101

2.030

2.007

1.946

1.862
1.816

I/ImaL (obs, %)

25

31

21

18

10

46

21

35

34

15

12
22

 

 

Tabl

 

 

 

 

Table 5.3.

(cont'd).

177

 

3“

OOAQ\I-P-OOUINOQMQOCQALAOOOOUJQQNOHMr—I\I&ll

N

-I>OO\IAQUIOOONUIONONQkMQQQWNOOQQOH©HMUIQ

N

k#Nmmwmoooommwwb—t-hr—t-hAmt—wt—HHQOQQNN

dcalc (A)

Hp—Lp—Ap—Ap—spip—dpdp—ip—Li—AHp—sy—‘Hp—ip—ny—AHHy—ay—sp—ap—an—AHp—‘p—nH

.777
.776
.769
.768
.758
.753
.711
.709
.709
.709
.707
.706
.619
.604
.603
.602
.600
.600
.600
.598
.597
.579
.579
.570
.568
.567
.565
.558
.557
.555

dobs (A)
1.794

1.775

1.726

1.639
1.612

1.586

1.578

I/Imalé (obs, %)
2 1

36

31

18
23

17

25

 

 

 

 

 

 

liOt

infra
The
mate

flan]

 

 

 

 

 

178

RESULTS AND DISCUSSION
1. Physicochemical Studies

1.1 Far-IR spectroscopy

In the far-IR spectrum of (I) (see Figure 5.1) two peaks at 261
and 245 cm‘1 could be assigned to Se—Se vibration modes. Similar
assignments have been made in the far-IR spectra of other known
metal polyselenide and free polyselenide complexes such as
[FezSe12]2- (VSe-Se=258 cm'l),12 [SnSe12]2‘ (VSe-Se=273 and 256 cm-1
),13 [AgSex]' (x=4, 5) (vs.._Se=~265 em-l),3 [PdSegP' (vSe-s.,=247 em-l
).14 [InxSeyP‘ (x=2, y=10, 21; x=3, y=15) (VSe-Se=”268 and ~256 cm'1
).15 [MSe12]' (M=Ga, In, T1) (vs.-s.,=~265 em-l),11 [Sex]2' (x=2-6) (vs..-
se=258 cm‘l),16 and cyclo-Se6 (VSe-Se=253 cm'l).17 The peak at 228
cm‘1 might be due to a Pd-Se vibration. Some additional broad peaks
that exist in the higher energy region, at 490, 389, and 342 cm‘l, can

not be assigned for certain at this moment.

1.2 UV/Vis diffuse reflectance Spectroscopy
Compound (I) starts to steeply absorb light in the near-
infrared region, as we can see in its optical Spectrum (see Figure 5.2).
The bandgap of ~1.48 eV suggests that it would be a semiconductor
material. For comparison, another known anionic metal poyselenide

framework, [In(Se6)2]',11 shows a similar bandgap of 1.42 eV.

 

 

NOEt—EWZELI

 

 

 

 

 

800

Fig

 

 

TRANSMITTANCE

 

 

179

 

 

 

o 516 s32 318 26s 180
WAVENUMBER
Figure 5.1. Far—IR spectrum (CsI pellet) of K2PdSe10 (I).

86

 

 

 

6.0'

4.0'

a/s

2.0-

 

0.0-

 

 

 

 

 

 

 

 

   

 

 

 

180
1 I L I l L L l J L _1 L L
6.0- L
.. t-
4.0— ‘
2.0~ ’
" lEg= 1.48 eVI "
0.0 I [ 1 T F I D T f l V I W
O 1 2 3 4 5 6 7
Energy (eV)

Figure 5.2. Optical

absorption spectrum of KdeSelo (1),

derived from diffuse reflectance measurements. The tangent line to
the Energy axis represents an extrapolation of the absorption edge.

if
181

2. Description of Structure

The Spectacular structure of KdeSew (I) is composed of K+
ions and two remarkable PdSexz' macroanions of [Pd(Se4)2]2' and
[Pd(Se5)2]2". Therefore, K4[Pd(Se4)2][Pd(Seg)2] is a more descriptive
formulation. Both [Pd(Se4)2]2' and [Pd(Se6)2]2‘ macroanions resemble
diamond—like frameworks assembled one inside the other and are
shown schematically in Figure 5.3(A). The polyselenide ligands, 8642'
and Se62', serve as long bridges between the Pd metal centers. The
individual [Pd(Sex)2]2‘ is topologically equivalent to the structure of
cristobalite, Si02 (Pd atoms occupy the Si sites and Sexz' ligands
occupy the 0 Sites). It is also interesting to note that the square—
planar Pd atoms in a single framework are arranged in space in the
same way as carbon atoms in diamond. The average distance
between the Pd metal centers in both frameworks is 8.577(6) A.
Remarkably, [Pd(Se4)2]2' and [Pd(Se6)2]2' interpenetrate each other
to fill their void spaces, as shown in Figure 5.3(B). In this
architecture the PdSe4 square planes from one framework stack
directly above and below those of the other, Spaced 6.44 A apart
along the c—axis. There are no covalent or ionic bonds between the
two frameworks, and thus one can never cross, through bonds, from
one to the other. The shortest contact between the frameworks is in
the van der Waals bond range of 3.45(1) A, between Se(4) and 86(9).
The angles around the Pd atoms are 90°. The average Pd—Se and Se-
Se distances are 2.462(5) A and 235(2) A, respectively. The closest
distances between K+ ions and Se atoms are in the range of 327(2)

and 3.75(2) A. Selected bond distances and angles for (I) are given

 

 

 

/Pd
Pd/(Sex) / \(SGQ Pd
(Sex) I

/ (Sex)

 

(Sex

)
l Pd l (A)

Pd Pd
S /
fl (ex) \Pd/(Sex) / \
ex

Pd//(SBX>/ Pd\<Sex>

 

(Sex)

\Pd

(B)

 

Figure 5.3. (A) Schematic representation of a Single 3D
framework of [Pd(Sex)2]2'. The tetrahedral depiction of Pd atoms
signifies the disposition and connectivity pattern of the Sex} ligands,
not their actual coordination geometry. (B) Schematic View of the
interpenetrating behavior (stereoview) of [Pd(Se4)2]2' and
[Pd(Se6)2]2' frameworks. This model is topologically equivalent to
the Cu20 (cuprite) structure in which the Cu atoms correspond to the
36x2' chains and the 0 atoms to the Pd2+ atoms.

 

 

Table 5.4
the [Pd(E
Parenthe

 

 

 

 

 

 

 

———

183

Table 5.4. Se1ected Bond Distances (A) and Bond Angles (deg) in
the [Pd(Se4)(Se6)]2' Anion of (1). Standard Deviations Are Given in
Parentheses.a

 

Pd(l)—Se(1) 2.468(8) Se(l)—Se(2) 2.33(1)
Pd(1)-Se(3) 2.461(9) Se(2)-Se(2') 2.34(2)
Pd(2)-Se(5) 2.458(7) Se(3)-Se(4) 232(1)
Pd(2)—Se(8) 2.459(8) Se(4)—Se(4') 2.38(2)
Se(5)-Se(6) 2.32(1)
Pd-Se (mean) 2.462(5) Se(6)-Se(7) 2.36(1)
Se(7)—Se(7') 236(2)
Se(8)-Se(9) 2.37(1)
Se(9)—Se(10) 2.37(1)
Se(10)-Se(10') 2.37(2)
Se-Se (mean) 2.35(2)
Se(1)-Pd(1)-Se(1') 178.3(6) Pd(1)—Se(1)-Se(2) 108.6(4)
Se(1)-Pd(1)-Se(3) 90.0(3) Pd(1)—Se(3)-Se(4) 108.8(4)
Se(1)-Pd(1)-Se(3') 90.0(3) Pd(2)-Se(5)-Se(6) 109.3(4)
Se(l')—Pd(1)—Se(3) 90.0(3) Pd(2)—Se(8)-Se(9) 108.7(4)
Se(l')-Pd(1)—Se(3') 90.0(3) Se(1)-Se(2)—Se(2') 106.3(4)
Se(3)-Pd(1)—Se(3') 177.9(6) Se(3)-Se(4)-Se(4') 105.7(4)
Se(5)-Pd(2)-Se(5') 177.0(5) Se(5)-Se(6)-Se(7) 106.1(4)
Se(5)—Pd(2)-Se(8) 89.3(3) Se(6)—Se(7)-Se(7‘) 104.2(5)
Se(5)-Pd(2)-Se(8') 90.8(3) Se(8)-Se(9)—Se(10) 106.2(4)
Se(5')-Pd(2)-Se(8) 90.8(3) Se(9)—Se(10)-Se(10') 104.2(5)

Se(5')-Pd(2)—Se(8') 89.3(3)
Se(8)-Pd(2)-Se(8') 177.4(6)

 

a The estimated standard deviations in the mean bond distances
were calculated by the equation 01 = {in(ln-l)2/n(n-I)}1/2, where In
is the distance of the nth bond, 1 is the mean bond distance, and n is
the number of bonds.

 

 

 

 

 

 

 

in Table
framewor
verbally
arrangem
stereovier
both [1
inteipene
The dia1
figands 1
structure
Wh
with mu1
0- and t
by 11 A
tunnels
[”0602
running 1
in Figure
0f each f

Intt

rare in r.
[Cu{NC((
exanlple
the orga,
key diffe
struCtUral

 

184

in Table 5.4. Figure 5.4 shows the repeating units in the individual
frameworks of [Pd(Se4)2]2‘ and [Pd(Se6)2]2'. Since it is not easy to
verbally convey the proper impression of the gordian crystal
arrangement of the Sexz‘ chains and Pd atoms in (I), we Show two
stereoviews of each framework separately in Figure 5.5. The view of
both [Pd(Se4)2]2‘ and [Pd(Se6)2]2' frameworks together as
interpenetrating each other, can be hardly clarfied (see Figure 5.6).
The diamondoid arrangement of metal centers and polyselenide
ligands in (I) explains the lack of a center of symmetry in the
structure.

When considered alone, framework [Pd(Se4)2]2‘ is perforated
with mutually perpendicular large tunnels running parallel to both
a— and b—axes. The approximate dimensions of these tunnels are 8
by 11 A, large enough to accomodate small organic molecules. The
tunnels of [Pd(Se4)2]2‘ are shown in Figure 5.7. Framework
[Pd(Se6)2]2' is also perforated with mutually perpendicular tunnels
running parallel to both the a— and b—axes. These tunnels are shown
in Figure 5.8. Non-interacting K+ ions are located inside the tunnels
of each framework, as shown in Figure 5.9.

Interpenetrating 3D diamond—like framework Structures are
rare in nature; examples include C020,18 M(CN)2 (M 2 Cd, Zn),19
[Cu{NC(CH2)4CN}2]N03,20 and several borate anions.21 An interesting
example of multiple identical diamondoid frameworks comes from
the organic compound adamantane—l,3,5,7—tetracarboxylic acid.22 A
key difference in (I) is that its frameworks are chemically and
structurally inequivalent, whereas in the known examples the

frameworks are identical. The conformational flexibility of the

 

 

 

 

 

polychalt
two verj
different
atoms.
must "fol
inside th
Th.
framew01
cage. 1
structure
and [Pd(.
greater a
creating
come tog
“1868 an
Viewed 1
micropon
A
CryStallizc
Composec
1igands.
determinii
0f the 5
explanatit
(Ph4P)2[P
pack in t

Cation is

 

185

polychalcogenide chains is beautifully manifested by the fact that
two very different polyselenide ligands, Se42' and Se62' each in
different frameworks serve as bridges between equally spaced Pd
atoms. This means that the potentially larger [Pd(Se6)2]2‘ framework
must "fold" or contract (by folding of the Se62‘ chains) in order to fit
inside the smaller [Pd(Se4)2]2' framework.

The distance between Pd atoms in the 3D diamond—like
framework structure determines the size of the adamantane-like
cage. Compared to the distance between 0 atoms in the CuzO
structure (3.7 A),18 the distance between Pd atoms in [Pd(Se4)2]2'
and [Pd(Se6)2]2' frameworks (8.6 A) is much longer creating a much
greater adamantane—like cage. In order to avoid the disadvantage of
creating too much empty Space in the structure, two frameworks
come together and coexist in such a way as to fill each other‘s empty
cages and tunnels. Alternatively, each individual framework can be
viewed as a host framework, raising the intriguing possibility of
microporosity in this type of frameworks.

A molecular form of [Pd(Se4)2]2‘ was reported recently to
crystallize as its Ph4P+ salt.14 The Structure of this complex is simple,
composed of a square—planar Pd2+ centers chelated by two Se42'
ligands. Although it illustrates the importance of the counterion in
determining the anion structure, it does not explain why the K+ salt
of the same composition is polymeric. The origin of such an
explanation must lie in the packing arrangement of the molecular
(Ph4P)2[Pd(Se4)2] compound. In the latter, the anions and cations
pack in such a way as to screen each other. When the large Ph4P+

cation is changed to the drastically smaller K+, the [Pd(Se4)2]2' anions

 

_——L

 

 

 

 

 

Figure 5
repeating

 

 

 

186

802' 361'

(A)

 

Se4

 

Figure 5.4. ORTEP representation and labeling scheme of the
rePeating units in (A) [Pd(Se4)2]2' and (B) [Pd(Se6)2]2‘.

 

in.

 

 

 

 

 

 

Figure 1

cirCIeS re

 

 

187

 

 

 

 

 

(B)

 

 

 

 

Figure 5.5. Stereoview of the individual substructures of (A)
[Pd(Se4)2]2' and (B) [Pd(Se6)2]2' looking down the c-axis. Filled
circles represent Pd atoms.

 

 

 

 

 

 

Figure ‘

 

188

s array-15138.0

.' Eilil’i’vii‘ m ~-

. (Wit &t{{k*lmé)flm
' «m‘fllfl’ are) -'~’

 

Figure 5.6. Stereoview of both [Pd(Se4)2]2‘ and [Pd(Se6)2]7-'
frameworks as they interpenetrate, looking down (A) the c-axis and
(B) the a-axis. The K“ atoms are omitted for clarity.

 

 

 

 

 

 

 

 

“a. r”! Lt. nil

P?

??

Figure
“W“ (A
dimensiot

 

189

 

 

 

 

 

 

 

 

 

. (A)

I I"
91 ‘3'.

. "'-.

 

 

 

 

 

Figure 5.7 . Stereoview

of the [Pd(Se4)2]2' substructure looking
down (A) the a-axis and (B) the b-axis, illustrating the large one-
dimensional channels.

 

 

 

 

 

Figure .
dOWn (A

 

 

 

 

 

 

 

Figure 5.8. Stereoview of the [Pd(Se6)2]2‘ substructure looking
down (A) the a-axis and (B) the b-axis, illustrating the large one-
dimensional channels.

 

 

 

 

 

3’13
.yo

@

 

Figure
frameWor'
filled Cir ‘

 

191

 

 

 

 

 

Figure 5.9. Stereoview of (A) [Pd(Se4)2]2‘ and (B) [Pd(Se6)2]2'
frameworks with K+ atoms included looking down the a-axis. Half—
filled circles represent K+ atoms.

 

 

 

 

 

 

 

 

 

can no lor
repulsions.
the system
convert the
neighboring
In this fash
remain const
repulsive in
lattice energ
used to pre
P01ymeric ar
n0n-interacti1
where the s
(NH4)2
a P01ymeric
Possesses a
atoms and d
the tetrag0n
i“mile/netrati
NH4+, the d
the ever in
ChemiStry art
EVen 1
do "0t exist
Of a micrt
PhotoconduCt

Hove] tilpes

 

 

 

192

can no longer be effectively screened, resulting in destabilizing
repulsions. If the stoichiometry is to remain the same, one way for
the system to respond and avoid these destabilizing repulsions is to
convert the Se42' ligands from chelating one Pd atom to bridging two
neighboring Pd atoms. This is shown schematically in Figure 5.10.
In this fashion the number and type (i.e., Pd—Se, Se-Se) of bonds
remain constant, and thus there is no cost in enthalpy. However, the
repulsive interactions transform into attractive ones and lead to a
lattice energy gain (in the Madelung sense). This concept can be
used to predict or eliminate possible structures for molecular or
polymeric anions upon changing the nature and Size of corresponding
non—interacting counterions. It should be broadly applicable in cases
where the structural framework of interest is relatively labile.

(NH4)2[Pd811],7 the polysulfide analogue of (I), also represents
a polymeric structure. However, it is not isostructural to (I) and
possesses a unique layered structure composed of square—planar Pd
atoms and disordered 852' and 862‘ ligands. NH4+ ions fill voids in
the tetragonal network of [PdS11]2'. (NH4)2[PdS11] exhibits no
interpenetrating behavior. Given the similar dimensions of K+ and
NH4+, the different architectures of (I) and (NH4)2[PdS(1] underscore
the ever increasing conviction that polysulfide and polyselenide
chemistry are divergent more often than not.

Even though microporous metal polychalcogenide compounds
do not exist yet, they are of considerable interest. The combination
of a microporosity and unique catalytic, semiconducting or
photoconducting properties of metal chalcogenides23 could result in

novel types of multifunctional materials. .. Progress towards this goal

 

 

1311413+

Se.
a/A/

Pd
S: \ Sc/ \Se'

1311413+

Se/ SC

 

Figllre 5.11
Cations and

reSuits in s
dCStabilizin

dotted lines,
ex‘ lisands
extended lait‘
and sz+ ion

 

 

 

 

 

 

56 Se (A )
/ \
Sc/Se\ /Se\5e SC \ / SC

\
\
.. (B)
‘0 " ‘\Isc SC \

 

‘1
Se 5
\5c I e\ /5¢
® ‘Pd—Sc pd ®
/
Ste-~54e Sel:\ 53‘33 \Sc—Sc
Sc~é¢ SC 5 S \S 5°
C_ e 8“-
Se\ / s/ l \ /5°
\ c‘-1>d\S Pd C
/ Se I c / \
5° 1 S°“‘Sc 1 Se 75° 5‘
Sc \5 / Sc/ ‘5. 5°~stt
CK) ’6 sc~5° 8’
SC / C
\P \ ® Sc/Pd ®
/ Sc Sc
Sc

 

Figure 5.10. (A) Stable assembly of mutually screened Ph4P+
cations and [Pd(Se4)2]2' anions. (B) Substitution of large Ph4P+ by K+
results in short anion-anion contacts (poor screening), developing
destabilizing repulsive interactions. The latter are represented by
dotted lines. (C) A stable assembly is possible by converting chelated
Sexz‘ ligands to bridges. The repulsive interactions disappear and an

extended lattice of lower energy is formed by the association of Sexz'
and Pd2+ ions.

ll:

 

 

 

 

was report
(Me4N)[Sb3t

compounds
3. Synthe

The 1
reaction of 1

represented

In the abov
PTOduct, bu
Similar re
p01yselenide
Structural A
for (1).

The N
of QXZ— Spe
Prefer quan
COOrdination

[M13603 (1

this Convieti

 

 

 

 

 

 

194

was reported recently with the syntheses of (Me4N)[GeSx],24
(Me4N)[Sb3S5],25 (Et4N)4[I—Ig7Se9],26 and (Ph4P)[M56121 (M=Ga, In, T1)“

compounds.
3. Synthesis
The synthesis of (I) was accomplished by the hydrothermal

reaction of PdC12 and KzSe4 in a 1:5 ratio, in the presence of KOH, as

represented in eq. (5.1).

 

KOH 110°C .
PdClZ + SKZSCA’ Water + 1 day
KZPdSeIO + ZKCI + 3K2$Cx ........................ Cq (51)

In the above reaction elemental Se was sometimes obtained as a by-
product, but its formation could be suppressed by adding KOH.
Similar reactions with the other alkali metal ion salts of
polyselenides, AZSex (A=Na, Cs; x=2—4) did not yield the same
structural A2PdSe10 compound, indicating the templating role of K+
for (I).

The reaction reported here Should be general. The combination
of Q?" species with proper counterions and divalent cations which
prefer square-planar (i.e., Ni, Pd) or tetrahedral (e.g., Zn, Cd, Hg, In)
coordination geometries should give new compounds with related
framework structures. The recent report of layered networks of
[M(Se6)2]' (M=Ga, In, Tl),11 as stabilized with Ph4P+ cations, supports

this conviction.

 

 

 

 

We 2
and [Pd(Se.
such as
{(CH3)N(CE
Based on
cations or
present in 1
0f cage als
charged, spl
to stabilize
The reactior

Structurally

195

We attempted to stabilize both interpenetrating [Pd(Se4)2]2'
and [Pd(Se6)2]2‘ frameworks of (I), separately with organic cations
such as R4N+, Ph4P+, and the divalent cations of
{(CH3)N(CH2CH2)3N(CH3)}2+ and (H3NCH2CH2NH3)2+, without success.
Based on the requirement for charge balance, two monovalent
cations or one divalent cation would be needed for each large cage
present in the framework of [Pd(Se4)2]2‘ or [Pd(Se6)2]2‘. The shape
of cage also suggests that it would be preferable to have a doubly
charged, spherical cation. So far, no such ideal cation has been found
to stabilize the individual framework of [Pd(Se4)2]2' or [Pd(Se6)2]2‘.
The reaction with Ph4P+ yielded a new compound, but it could not be

structurally characterized due to its poor crystallinity.27

 

 

 

 

(a) L:
7400-
31, 4:
1992,

 

———

(1)

(2)

(3)

(4)

(5)

(6)

(7)

 

(8)

(9)

196

LIST OF REFERENCES

(a) Liao, J.-H.; Kanatzidis, M. G. J. Am. Chem. Soc. 1990, 112,
7400-7402. (b) Liao, J.-H.; Kanatzidis, M. G. Inorg. Chem. 1992,
31, 431-439. (c) Kim, K.-W.; Kanatzidis, M. G. J. Am. Chem. Soc.
1992, 114, 4878—4883.

(a) Kanatzidis, M. G. Comments Inorg. Chem. 1990, 10, 161-
195. (b) Ansari, M. A.; Ibers, J. A. Coord. Chem. Rev. 1990, 100,
223—266. (c) Kolis, J. W. Coord. Chem. Rev. 1990, 105, 195—
219.

(a) Kanatzidis, M. G.; Huang, S.-P. J. Am. Chem. Soc. 1989, 111,
760-761. (b) Huang, S.-P.; Kanatzidis, M. G. Inorg. Chem. 1991,
30, 1455-1466.

Banda, R. M. H.; Craig, D. C.; Dance, I. G.; Scudder, M. L.
Polyhedron 1989, 8, 2379-2383.

Kiel, G.; Gattow, G.; Dingeldein, T. Z. Z. Anorg. Allg. Chem. 1991,
596, 111-119.

Haushalter, R. C. Angew. Chem. Int. Ed. Engl. 1985, 24, 433-
435.

Haradem, P. S.; Cronin, J. L.; Krause, R. A.; Katz, L. Inorg. Chim.
Acta 1977, 25, 173-179 and references therein.

DIFABS: "An Empirical Method for Correcting Difi‘ractometer
Data for Absorption Effects" Walker, N.; Stuart, D. Acta
Crystallogr., 1983, A39, 158—166.

TEXSAN: Single Crystal Structure Analysis Software, Version
5.0, Molecular Structure Corporation, The Woodlands, Texas.

 

 

 

(10) Smith
[V P.
Versi

(ll) Dhing

(12) Strasc
Ll-L

(13) Huang
1389

(14) Kréiut.

(15) Dhing
Chapt

116) Welle.
125-1

117) Nagat.
19, 1

(18) Wells,
Press:

 

(10)

(11)

(12)

(13)

(14)

(15)

(16)

(17)

(18)

(19)

(20)

(21)

(22)

 

———

197
Smith, D. K.; Nichols, M. C.; Zolenski, M. E. “POWDIO: A Fortran
IV Program for Calculating X-ray Powder Dificraction Pattern",
Version 10, Pennsylvania State University, 1983.

Dhingra, S.; Kanatzidis, M. G. Science 1992, 258, 1769-1772.

Strasdeit, H.; Krebs, B.; Henkel, G. Inorg. Chim. Acta 1984, 89,
L1-L13.

Huang, S. P.; Dhingra, S.; Kanatzidis, M. G. Polyhedron 1990, 9,
1389-1395.

Kriiuter, G.; Dehnicke, K.; Fenske, D. Chem.-Ztg. 1990, 114, 7—9.

Dhingra, S. Ph.D. Thesis; Michigan State University,
Chapter 2.

1992;
Weller, F.;.Adel, J.; Dehnicke, K. Z. Anorg. Allg. Chem. 1987, 548,
125-132.

Nagata, K.; Tshibashi, K.; Miyamoto, Y. Jpn J. Appl. Phys. 1980,
19, 1569-1573.

Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon
Press: Oxford, UK, 1984; pp 127-129, pp 1072-1078.

Hoskins, B. F.; Robson, R. J. Am. Chem. Soc. 1990, 112, 1546—
1554.

Kinoshita, Y.; Matsubara, I.; Higuchi, T.; Saito, Y. Bull. Chem. Soc.
Japan 1959, 32, 1221—1226.

(a) Krogh—Moe, J. Acta. Crystallogr. 1974, B30, 747-752. (b)
Krogh-Moe, J.; Ihara, M. Acta. Crystallogr. 1967, 23, 427—430.

Ermer, O. J. Am. Chem. Soc. 1988, 110, 3747-3754.

 

 

(23) (a) R
with
Publ.

226-2
303—3
Multi

47. (
A. 11
7th C
Socie'
D.; F
Tang,
Anger
D: A
Yama
Takac
Phys.

124) Bedar.

M. Ze
Eds.;
3753

(25) PariSe

126) Kim,
1969,

(27) The 1
pr6pal
and 1
Semiq
the p

 

(23)

(24)

(25)

(26)

(27)

(a) Rouxel, J. In Crystal Chemistry and Properties of Materials
with Quasi One—Dimensional Structures; Rouxel, J., Ed.; Reidel
Publ. Co.: 1986; references therein. (b) Chianelli, R. R.; Pecoraro,
T. A.; Halbert, T. R.; Pan, W.—H.; Steifel, E. I. J. Catal. 1984, 86,
226—230. (c) Whittingham, M. S. J. Solid State Chem. 1979, 29,
303—310. (d) Mickelsen, R. A.; Chen, W. S. In Ternary and
Multinary Compounds, Proceedings of the 7th Conference, Deb,
S. K., Zunger, A., Eds; Materials Research Society: 1987; pp 39—
47. (e) Steward, J. M.; Chen, W. S.; Devaney, W. E.; Mickelsen, R.
A. In Ternary and Multinary Compounds, Proceedings of the
7th Conference, Deb, S. K., Zunger, A., Eds; Materials Research
Society: 1987; pp 59—64. (1‘) Ballman, A. A.; Byer, R. L.; Eimerl,
D.; Feigelson, R. S.; Feldman, B. J.; Goldberg, L. S.; Menyuk, N.;
Tang, C. L. Applied Optics 1987, 26, 224-227. (g) Eckert, H.
Angew. Chem. Int. Ed. Engl. 1989, 28, 1723—1732. (h) Strand,
D.; Adler, D. Proc. SPIE Int. Soc. Opt. Eng. 1983, 420, 200. (i)
Yamada, N.; Ohno, N.; Akahira, N.; Nishiuchi, K.; Nagata, K.;
Takao, M. Proc. Int. Symp. Optical Memory, 1987, Jpn. J. Appl.
Phys. 1987, 26, Suppl. 26—4, 61.

Bedard, R. L.; Wilson, S. T.; Vail, L. D.; Bennett, E. M.; Flanigen, E.
M. Zeolites: Facts, Figures, Future; Jacobs, P. A., van Santen, R. A.
Eds.; 1989; Elsevier Science Publishers B. V.: Amsterdam; pp
375—387.

Parise, J. B. Science 1991, 251, 293—294.

Kim, K.— W.; Kanatzidis, M. G. Inorg. Chem. 1991, 30, 1966-
1969.

The polyhedral chunky black crystals of this compound were
prepared by the hydrothermal reaction of PdClz, K28e4, Ph4PCl,
and KOH in a l:2:2:2 ratio, at 130 °C for several days.
Semiquantitative analysis by the SEM/EDS technique Showed
the P:Pd:Se atomic ratio as 0.5:1.0:4.0. A preliminary single

fil-

 

 

 

(nysu
grout
c=23.
coupl
defiet

 

———
199

crystal study Shows that it crystallizes in the monoclinic space
group C2/c (No. 15) with a=28.291(9) A, b=18.848(7) A,
=23.578(6) A, 6:98.76(2)°, V=12425(7) A3. A poor data set,
coupled with serious decay of the crystal during data collection,
defied a complete structural characterization.

 

 

 

 

Synt
PolySI
(Ph4P)2[

ABST

K4[Pt
reaction of
analog K4[
reaction of
presence of
soluble in
black hexag
most organi
1110111) F431
whereas (H
176) with
[Pt4Q22]4‘ ((
conneeting
[P14322]4~ is
in the clus
methanotherr
ratio at 80°(

soluble in I:

 

 

PART II

Synthesis and Characterization of New Platinum
Polysulfide(selenide)s: K4[Pt4Szz]'4H20, K4[Pt4Se22],
(Ph4P)2[Pt(S4)2]‘CH30H1 and (Ph4P)4[Pt(S4)(Ss)2l[Pt(Ss)3]

ABSTRACT

K4[Pt4Szz]-4H20 (II) was prepared by the hydrothermal
reaction of K2PtC14 and K284 in a 1:5 molar ratio at 130 °C. The Se
analog K4[Pt4Se22] (III) was also obtained by the hydrothermal
reaction of K2PtCl4 and KzSe4 in a 1:2 molar ratio at 110 °C, in the
presence of KOH. The black trigonal prismatic crystals of (II) are
soluble in water and polar organic solvents such as DMF, but the
black hexagonal platelet crystals of (III) are insoluble in water and
most organic solvents. Compound (II) crystallizes in the cubic Space
group F43m (no. 216) with a=14.964(4) A, v=3351(2) A3, and 2:8,
whereas (III) crystallizes in the hexagonal space group P63/m (no.
176) with a=10.642(6) A, c==39.377(20) A, and v=3862(6) A3.
[Pt4022]4' (Q=S, Se) is a PtW4-Q4 cubane cluster with six Q32: ligands
connecting diagonal pairs of Pt atoms. The Pt—Pt distance in
[Pt4822]4“ is 3.478(4) A, indicating the absence of Pt-Pt metal bonding
in the cluster. (Ph4P)2[Pt(S4)2]-CH3OH (IV) was produced by the
methanothermal reaction of K2PtCl4, K284 and Ph4PBr in a 1:3:2 molar
ratio at 80°C. The reddish orange rectangular rod crystals of (IV) are

soluble in DMF, but insoluble in water. Compound (IV) crystallizes in

200

 

 

the orthorl
b=10.163(l(
a new the
possessing
chelating S
by the rear
‘waun; foHc
nucrocryst
recrystallize
(V0 crysta
a=13.264(9
5:105 .76(5;

independent

 

—7—

201

the orthorhombic space group Pna21 (no. 33) with a=26.888(11) A,
b=10.163(10) A, c=17.630(3) A, V=4818(8) A3, and 2:8. [Pt(S4)2]2‘ is
a new member of the well known metal octachalcogenide family
possessing a square-planar Pt metal center coordinated by two
chelating S42“ ligands. (Ph4P)4[Pt(S4)(85)2][Pt(Ss)3] (V) was obtained
by the reaction of (NH4)2[Pt(Ss)3] with KCN in a 1:7 molar ratio in
water, followed by the addition of Ph4P+ cations. A reddish brown
microcrystalline material was isolated as a precipitate and
recrystallized in DMF to yield dark red platelet crystals. Compound
(V) crystallizes in the triclinic space group P1 (no. 1) with
a=13.264(9) A, b=19.311(5) A, c=11.879(6) A, a=94.26(3)°,
[3:105.76(5)°, y=95.42(4)°, and V=2899(3) A3. (V) contains two

independent molecular anions of [Pt(S4)(Ss)2]2‘ and [Pt(Ss)3]2'.

 

 

 

 

 

 

 

INTI

The
preparation
the recogn
use this s
metal pol
previously
which we

Prepa
among iht
However, i
Group 10 I
36.5; M=Pd
[Ni4Te4(Te;
911360312:
reaction 01
Organic 80]
91139212“ .
CN' ions st
CWStallogra
S(lllare Plan
011 the abs

the flV€~m

 

 

 

202

INTRODUCTION

The continuing success of hydrothermal synthesis in the
preparation of several new metal polychalcogenide compounds1 and
the recognition that its applicability might be general, urged us to
use this synthetic method for the exploration of possible new Pt
metal polychalcogenide compounds. Indeed, we found some
previously unrecognized species, [Pt4022]4‘ (Q=S, Se) and [Pt(S4)2]2’,
which we report here.

Prepared in the early 1900's, [PdS11]2‘ 2 and [PtS15]2‘ 3 are
among the earliest known metal polychalcogenide compounds.
However, it is merely a recent achievement to synthesize a set of
Group 10 metal polychalcogenide compounds: [M(Q4)2]2' (M=Ni, Q=S,4
Se,5; M=Pd, Q=S,4(a) Se,5(b)16 Te7; M=Pt, Q=Se6), [Ni4Se4(Se3.)5(Se4)]4',8
[Ni4Te4(T62)2(T63)4l4‘.9 [Pd2(S7)4l““,10 [Pd(365)2]2',11 [Pt(S6)3]2',12 and
[Pt(Se4)3,]2'.lla13 All of these compounds have been prepared by the
reaction of metal ions and polychalcogenide ligands in the polar
organic solvents, DMF and CH3CN. A previous report3(c)sl4 that
[Pt(Ss)2]2‘ can be prepared from [Pt(S5)3]2‘ by removing S atoms with
CN' ions stimulated us to repeat this work in View of the absence of a
crystallographic work. The [Pt(Ss)2]2‘ ion was proposed to be a
square planar Pt(II) complex chelated with two 852‘ ligands. Based
on the absence of a structural characterization and the notion that
the five-membered ring MS4 (M=Ni(II), Pd(II), and Pt(II)) is
considerably preferred to the six-membered ring MSs, we set out to

obtain crystals of the [Pt(85)2]2' complex. Instead, we isolated and

 

 

 

 

 

 

 

structural];

reported 1
EXP)

Reagents
The

further put:
(98% purit
130., Milwa
Chemical I
Prepared b;
licluid amr
degassed b;
Science, G
CaHZ- Dit
Inca Colu
POtassium

glycol-dime

Phl’Sicoch.

Far-I]
chapter. 1
I‘litachi u_

(TGA) Was

heated Up t:

 

 

 

203

structurally characterized (Ph4P)4[Pt(S4)(S5)2][Pt(Ss)3] which is

reported here.

EXPERIMENTAL SECTION

Reagents

The chemicals in this research were used as obtained without
further purification. K2PtCl4 (98% purity), KCN (97% purity), Ph4PBr
(98% purity), and Ph4PCl (98% purity) were from Aldrich Chemical
Co., Milwaukee, Wisconsin. KOH (A.C.S. grade) was from Columbus
Chemical Industries Inc., Columbus, Wisconsin. K28e4 and K254 were
prepared by dissolving the stoichiometric amounts of the elements in
liquid ammonia, as described in Chapter 2. Distilled water was
degassed by bubbling with a nitrogen gas. MeOH (A.C.S. grade, EM
Science, Gibbstown, New Jersey) was distilled after refluxing over
CaHz. Diethyl ether (A.C.S. anhydrous, Columbus Chemical Industries
Inc., Columbus, Wisconsin) was distilled after refluxing over
potassium metal in the presence of benzophenone and triethylene—

glycol—dimethyl ether for several hours.

Physicochemical Methods

Far—IR spectra were measured as described in Part I of this
chapter. UV/Vis spectra for the liquid sample were measured on a
Hitachi U—2000 Spectrophotometer. Thermal Gravimetric Analysis
(TGA) was performed on a Shimadzu TGA—50. The samples were
heated up to 900 °C at a rate of 10 °C/min. under a steady flow of dry

 

 

 

 

N2. Sem
SEM/EDS,

Synthesh
All
atmosphere

Lab gloveb

Tetr
tetraplatil

An 8
mmol) of
tube. The
for a day.
on the qua
being kept
and “(3.3th
DMF, and :

Tctr.
tetralllatir.
0°50 8 (0

(0.61 mmo:
Pyrex tube.
110 0C for

based on t

and WaShec

 

f—

204

N2. Semi-quantitative analysis of the compounds were done by

SEM/EDS, as described in Chapter 2.

Synthesis
All experiments and manipulations were performed under an
atmosphere of dry nitrogen using either a Vacuum Atmosphere Dri-

Lab glovebox or a Schlenk line.

Tetrapotassium hexa(trisulfido)-tetra(sulfido)-
tetraplatinate(IV) tetrahydrate, K4[Pt4(S)4(S3)6]°4H20 (II)
An amount of 0.050 g (0.12 mmol) of K2PtCl4, 0.124 g (0.60

 

mmol) of K284 and 0.4 ml distilled water were charged in a Pyrex
tube. The tube was sealed off under vacuum and heated at 130 °C
for a day. Reddish black trigonal prismatic crystals (50% yield, based
on the quantity of Pt metal used) grew while the reaction tube was
being kept at r.t. for several days. They were isolated by filtration
and washed with ethanol. These crystals are soluble in water and

DMF, and slightly soluble in methanol and CH3CN.

Tetrapotassium hexa(triselenido)-tetra(selenido)-
tetraplatinate(IV), K4[Pt4(Se)4(Se3)6] (III) An amount of
0.050 g (0.12 mmol) of K2PtCl4, 0.095 g (0.24 mmol) of K28e4, 0.034 g
(0.61 mmol) of KOH and 0.4 ml distilled water were charged in a

 

Pyrex tube. The tube was sealed off under vacuum and heated at
110 °C for two days. Black hexagonal platelet crystals (60% yield,
based on the quantity of Pt metal used) were isolated by filtration

and washed with water and methanol. These crystals are insoluble

 

 

 

 

in water a

SEM/EDS

Di(t
platinatef

An 2
mmol) of
were char;
vacuum an
rod crystal:
isolated by
crystals art
analysis by
l.7:l.0:8.0,

Tetr
Denta(pe]
(Ph4P)4[p(

T0 1
1NH4)2[Pt(t
ml aqueout
Solution wa
ml a(illeou:
yield immt
isolated by
ether. Da

qUantity 0f

205

in water and most organic solvents. Semiquantitative analysis by the

SEM/EDS technique Showed the K:Pt:Se atomic ratio as l.0:1.0:5.5.

Di(tetraphenylphosphonium) di(tetrasulfido)-
platinate(II) monomethanolate, (Ph4P)2[Pt(S4)2]-CH3OH (IV)

An amount of 0.050 g (0.12 mmol) of K2PtCl4, 0.124 g (0.60
mmol) of K2S4, 0.100 g (0.24 mmol) of Ph4PBr and 0.5 ml methanol
were charged in a Pyrex tube. The tube was sealed off under
vacuum and heated at 80 °C for a day. Reddish orange rectangular
rod crystals (40% yield, based on the quantity of Pt metal used) were
isolated by filtration and washed with water several times. These
crystals are soluble in DMF but insoluble in water. Semiquantitative
analysis by the SEM/EDS technique showed the P:Pt:S atomic ratio as
l.7:l.0:8.0.

Tetra(tetraphenylphosphonium) (tetrasulfido)-
penta(pentasulfido)-diplatinate(IV),
(Ph4P)4[Pt(S4)(S5)2][Pt(S5)3] (V)

To a 10 ml aqueous solution of 0.050 g (0.070 mmol)
(NH4)2[Pt(S5)3] (prepared by following a reported procedure),3(C) a 5
ml aqueous solution of 0.032 g (0.49 mmol) KCN was added. This
solution was heated at 60 °C for 10 min. To the reaction solution a 30
ml aqueous solution of 0.059 g (0.14 mmol) Ph4PCl was added to
yield immediately a reddish brown precipitate. This precipitate was
isolated by filtration and recrystallized from DMF by layering with
ether. Dark red—brown platelet crystals (21% yield, based on the

quantity of Pt metal used) were obtained. Semiquantitative analysis

 

 

 

 

by the S
l.8:l.0:l3.

contains le:

X-ray C1
A si1
glass fiber
were coate
collected
using a
determined
reflections.
Checked e
instrument
collection
Scans of ti”.
set. The:
86 SOftWar
technique.
COrrection
VAXSlatior
software pt
the aniOn
in Which C

pOSlthns “

206

by the SEM/EDS technique showed the P:Pt:S atomic ratio as
18:10:13. The reddish brown precipitate before recrystallization

contains less S as its P:Pt:S atomic ratio is around l.7:l.0212.

X-ray Crystallographic Studies

A single crystal of each compound was mounted on the tip of a
glass fiber with epoxy adhesive. The crystals are air sensitive and
were coated with KrylonTM to protect them from air. All data were
collected on Rigaku AFC6S four—circle automated diffractometers
using a Mo radiation. Accurate unit cell parameters were
determined from the 20, co, (1), and x angles of 15 to 25 centered
reflections. The intensities of three standard reflections were
checked every 100 or 150 reflections to monitor crystal and
instrument Stability. No serious decay was observed during the data
collection period. An empirical absorption correction based on 11)
scans of three strong reflections with X ~90° was applied to each data
set. The structures were solved by direct methods using the SHELXS—
86 software program and refined with a full—matrix least squares
technique. After isotropic refinement of all atoms a DIFABS
correction was applied.15 All calculations were performed on a
VAXstation 3100/76 computer with the TEXSAN crystallographic
software package of Molecular Structure Corporation.16 All atoms in
the anion of each compound were refined anisotropically except (V),
in which only Pt atoms were refined anisotropically. Hydrogen atom

positions were calculated but not refined.

 

 

 

In ti
symmetry
and 8(3)
respectivel;
between tv
x). The
Among the
and K(2)) ;
(1, 1, 1/2:
disordered
(3/4, y, 3/.
a 43m syr

The
though the
ana10g of 1
Sure and t]

In th
of Ph4p+ ‘
an ideal p
COCustaniz.
Was C0l‘tfirr
Were rtifine
methanol 11
atoms in H
atoms in u

Table

 

207

In the structure of (II), Pt and 8(1) atoms are located in 3m
symmetry positions (x, x, x) and (x, f, x), respectively, while 8(2)
and 8(3) atoms are on mirror planes (x, z, x) and (x, z, i),
respectively. The S(3) atom is disordered with half occupancies
between two positions which are generated by a mirror plane (x, Z,
x). The distance between the two disordered S(3) atoms is 0.59 A.
Among the four K+ ions in the structure of (II), two of them (K(l)
and K(2)) are found on 4—3m symmetry positions (3/4, 3/4, 3/4) and
(1, 1, 1/2), respectively. The other two K+ ions (atom K(3)) are
disordered with four water molecules at 2mm symmetry positions
(3/4, y, 3/4), sitting in the vertices of an octahedron whose center is
a 43m symmetry position (3/4, 1, 3/4).

The structure of (111) could not be completely refined. Even
though the [Pt4Se22]4' anion was reasonably established to be an
analog of the [Pt4S22]4' of (II), only two K atoms could be found for
sure and the R/RW values at this stage were 0.21/0.24.

In the structure of (IV), the carbon atoms in the phenyl rings
of Ph4P+ were refined as a group, with their geometry restricted to
an ideal planar six-membered ring. One methanol was found as a
cocrystallized solvent molecule in the structure of (IV). Its existence
was confirmed by TGA analysis. The Patoms in the two Ph4P+ ions
were refined anisotropically, while the C atoms and all atoms in the
methanol were refined isotropically. In the structure of (V) carbon
atoms in the phenyl rings of Ph4P+ were also refined as a group. All
atoms in the four Ph4P+ ions were refined isotropically.

Tables 5.5-5.6 Show crystal data and details of the structure

analysis for all compounds except (III). The fractional coordinates

 

 

 

 

and temp

standard 0

208

and temperature factors (Beq) of all atoms and their estimated

standard deviations are given in Tables 5.7-5.9.

I!

 

Table 5 .5.

209

(II) and (Ph4P)2[Pt(S4)2]'CH3OH (IV).

Summary of Crystallographic Data for K4[Pt4S22]'4H2O

 

 

(I I ) (IV)
Compound K4[Pt48221'4H20 (Ph4P)2[Pt(S4)2] “CH3OH
Form u l a H304K4Pt4S22 C49H44OP2Pt83
FW 1714.13 1162.40

Crystal shape
Crystal color
Crystal Size (mm)

Temperature (°C)
Crystal system
Space group

a (A)

b (A)

C (A)

0 (deg)

6 (deg)

17 (deg)

v (A3), 2

11 (cm'l) MO(KOt)
dcalc (g/cm3)
Scan Method
26max (deg)

No. of reflections
collected

No. of reflections,
Fo2 > 30(Fo)2

No. of variables
Max. shift/esd
Phasing method
R/Rw (%)

trigonal prism
reddish black
0.08x0.08x0.08
23

cubic

F43m (no. 216)
14.964(4)
14.964(4)
14.964(4)

90

90

90

3351(2), 8
187

3.414

03/20

50

678

172*

2 3

0.00

direct methods
4 .6/5 .1

rectangular rod
reddish orange
0.06x0.08x0.35
23
orthorhombic
Pna21 (no. 33)
26.888(11)
10.163(10)
l7.630(3)

90

90

90

4818(8), 4
33.8

1.602

w/20

45

3553

1435

168

0.00

direct methods
8.8/10.9

 

R=2 llFol - IFcll/Z IFoI

Rw= {>3 w(|Fo|-|FcD2/>Z Wlele 2

* No. of reflections, F02 > 2003102

 

210

Table 5.6. Summary of Crystallographic Data for

(Ph4P)4[Pt(S4)(SS)2][Pt(35)3] (V).

 

Compound
Formula

FW

Crystal shape
Crystal color
Crystal size (mm)
Temperature (°C)
Crystal system
Space group

a (A)

b (A)

c (A)

0 (deg)

6 (deg)

r (deg)

V (A3),z

11 (cm'l) M0(I<a)
dcalc (g/cm3)
Scan Method

26max (deg)

No. of reflections
collected

No. of reflections,
Fo2 > 300:0)2

No. of variables
Max. shift/esd
Phasing method

R/Rw (%)

(1V)
(Ph4P)4[Pt(S4)(55)2l [Pt(35)3]
C96H80P4Pt2$29
2677.50
platelet

dark; red
0.04x0.l4x0.26
23

triclinic

Pl(no. 1)
13.264(9)
19.311(5)
11.879(6)
94.26(3)
105.76(5)
95.42(4)
2899(3), 1
30.3

1.53

w/20

4()

5908

3109

260

0.00

direct methods
8.3/11.1

 

R=2 IIFoI - IFcII/r. IFoI

12w: [2 w(IFol-|FcD2/£ thoIZl" 2

 

211

 

 

Table 5.7. Fractional Atomic Coordinates and Beq Values for
K4[Pt4S22]'4H2O (II) with Their Estimated Standard Deviations in
Parentheses.

atom x y 2: Ben ((312)a
Pt 0.9178(1) 0.9178 0.9178 5.8730(8)
S(1) 0.9253(8) —0.9253 0.9253 6.75(1)
S(2) 0.918(1) 0.762(1) 0.918 8.10(1)
5(3) 1.028(2) 0.711(1) —1.028 12(1)
K(l) 3/4 3/4 3/4 6.322(5)
K(2) 1.0000 1.0000 1/2 18.8(6)
K(3) 3/4 1.115 3/4 19(1)
0(1) 3/4 1.115(3) 3/4 15.0

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beg: (8n2/3)[a2B11 +
b2B22 + o21333 + ab(cosy)B12 + ac(cos[3)B13 + bc(cosot)B23]. The
anisotropic temperature factor expression is exp[—2712(B11a"‘2h2 + +

2312a*b*hk +

...)].

212

Table 5.8. Fractional Atomic Coordinates and Beq Values for

(Ph4P)2[Pt(S4)2]-CH3OH (IV) with Their Estimated Standard Deviations
in Parentheses.

 

 

atom x y Z Bea (A2)a
Pt 0.13030(9) 0.8220(3) 0.8351 3.6(1)
S(l) 0.0952(8) 0.647(2) 0.761(1) 5(1)
S(2) 0.0765(8) 0.729(2) 0.664(1) 5(1)
S(3) 0.140(1) 0.827(3) 0.640(1) 9(2)
8(4) 0.1417(7) 0.960(2) 0.735(1) 5(1)
8(5) 0.1167(7) 0.698(2) 0.939(1) 6(1)
5(6) 0.1713(7) 0.744(2) 1.019(2) 5(1)
8(7) 0.1552(9) 0.932(3) 1.018(1) 7(2)
5(8) 0.1745(7) 0.975(2) 0.904(1) 5(1)
P(1) 0.0815(6) 0.582(2) 1.239(1) 2.7(8)
P(2) 0.1620(6) 0.109(2) 0.440(1) 4(1)
0(1) 0.618(3) 019(1) 0.816(4) 2(2)
0(2) 0.615(4) 0.10(1) 0.908(8) 5(2)
C(1) 0.045(1) 0.715(3) 1.205(2) 1.2(7)
C(2) 0.013(2) 0.788(5) 1.250(2) 7.5(7)
C(3) 0.017(1) 0.885(4) 1.218(3) 5.3(7)
C(4) —0.015(1) 0.909(4) 1.140(3) 3.9(7)
C(5) 0.017(2) 0.836(5) 1.095(2) 9.2(7)
C(6) 0.048(1) 0.740(4) 1.127(2) 3.0(7)
C(7) 0.066(1) 0.555(4) 1.342(2) 2.4(5)
C(8) 0.0974(9) 0.575(3) 1.404(2) 09(5)
C(9) 0.079(1) 0.557(5) 1.477(2) 5.4(5)
C(10) 0.030(2) 0.520(5) 1.489(2) 4.9(5)
C(11) 0.001(1) 0.501(5) 1.426(3) 5.4(5)
C(12) 0.017(1) 0.518(4) 1.353(2) 4.7(5)
C(13) 0.080(2) 0.449(4) 1.183(2) 4.3(7)
C(14) 0.052(2) 0.342(5) 1.208(2) 4.8(7)
C(15) 0.045(2) 0.234(4) 1.160(3) 5.4(7)
C(16) 0.066(2) 0.233(4) 1.088(3) 3.6(7)
C(17) 0.094(2) 0.340(5) 1.063(2) 7.7(7)
C(18) 0.101(1) 0.448(4) 1.110(3) 2.5(7)
C(19) 0.146(1) 0.630(4) 1.237(2) 1.1(6)
C(20) 0.183(2) 0.536(3) 1.251(2) 4.7(6)
C(21) 0.233(1) 0.572(4) 1.249(3) 5.9(6)

 

 

Table 5.8.

213

 

 

(cont'd).
atom x y z Bea (A2)a
C(22) 0.246(1) 0.702(5) 1.233(3) 5.6(6)
C(23) 0.210(2) 0.796(4) 1.220(3) 6.0(6)
C(24) 0.160(1) 0.760(3) 1.222(2) 2.4(6)
C(25) 0.186(1) 0.147(3) 0.349(2) 1.8(6)
C(26) 0.237(1) 0.165(4) 0.341(2) 2.8(6)
C(27) 0.258(1) 0.179(5) 0.269(3) 5.6(6)
C(28) 0.227(2) 0.176(5) 0.205(2) 6.6(6)
C(29) 0.176(2) 0.158(5) 0.213(2) 4.8(6)
C(30) 0.155(1) 0.144(4) 0.285(2) 4.1(6)
C(31) 0.099(1) 0.064(5) 0.437(3) 4.9(8)
C(32) 0.067(2) 0.157(4) 0.406(3) 3.7(8)
C(33) 0.017(2) 0.125(5) 0.395(3) 8.3(8)
C(34) —0.001(1) 0.001(5) 0.415(3) 5.0(8)
C(35) 0.031(2) —0.092(4) 0.446(3) 5.2(8)
C(36) 0.081(2) —0.061(5) 0.457(3) 7.1(8)
C(37) 0.164(2) 0.245(4) 0.507(2) 4.3(7)
C(38) 0.135(2) 0.243(4) 0.573(3) 3.7(7)
C(39) 0.141(2) 0.342(5) 0.627(2) 5.6(7)
C(40) 0.175(2) 0.443(4) 0.615(2) 3.3(7)
C(41) 0.204(1) 0.445(4) 0.549(3) 5.9(7)
C(42) 0.198(1) 0.346(5) 0.495(2) 3.3(7)
C(43) 0.201(1) —0.019(4) 0.474(2) 2.2(6)
C(44) 0.231(2) -0.005(4) 0.539(2) 4.0(6)
C(45) 0.266(1) —0.101(4) 0.558(2) 3.9(6)
C(46) 0.272(1) -0.210(4) 0.511(2) 2.8(6)
C(47) 0.243(2) —0.224(3) 0.446(2) 4.7(6)
C(48) 0.208(1) —0.128(4) 0.427(2) 3.1(6)

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beq= (8n2/3)[a2B11 +
b23122 + c2B33 + ab(cosy)B12 + ac(cosfi)B13 + bc(cosor)B23]. The
anisotropic temperature factor expression is exp[—2712(B11a*2h2 + +
2B12a*b*hk + ...)].

214

Table 5.9. Fractional Atomic Coordinates and Beq Values for
(Ph4P)4[Pt(S4)(S5)2][Pt(S5)3] (V) with Their Estimated Standard
Deviations in Parentheses.

 

 

atom x y Z Bed (6281
Pt(l) 0.7213 0.9791 0.2435 2.6(3)
Pt(2) 1.1596(3) 0.4822(2) 0.2030(3) 2.8(3)
S(1) 0.674(3) 1.067(2) 0.370(3) 5(1)
S(2) 0.543(2) 1.032(1) 0.396(2) 2.5(5)
S(3) 0.549(2) 0.944(1) 0.493(2) 3.8(5)
8(4) 0.559(2) 0.868(1) 0.369(2) 3.1(4)
8(5) 0.714(2) 0.883(1) 0.360(2) 4.2(7)
5(6) 0.754(2) 0.886(2) 0.104(2) 4.6(8)
S(7) 0.729(4) 0.909(2) 0.045(4) 11(2)
8(8) 0.590(3) 0.909(2) —0.127(4) 6(1)
3(9) 0.530(4) 0.982(2) —0.042(4) 5(1)
S(10) 0.548(3) 0.970(2) 0.135(3) 6(1)
S(ll) 0.906(2) 0.979(1) 0.345(2) 2.9(6)
S(12) 0.962(2) 1.071(2) 0.448(2) 4.1(7)
S(13) 0.980(3) 1.140(2) 0.327(3) 4.9(9)
S(14) 0.834(3) 1.156(2) 0.245(3) 3.4(8)
S(15) 0.764(2) 1.077(1) 0.138(2) 2.4(7)
S(16) 1.115(3) 0.399(2) 0.314(3) 5(1)
S(l7) 1.060(3) 0.303(2) 0.186(4) 6(1)
S(18) 0.903(3) 0.312(2) 0.097(3) 6(1)
S(19) 0.940(3) 0.379(2) —0.020(3) 6(1)
S(20) 0.986(2) 0.473(2) 0.067(3) 5.2(8)
S(21) 1.343(2) 0.506(1) 0.322(2) 0.9(5)
S(22) 1.356(4) 0.476(2) 0.479(4) 5(1)
S(23) 1.314(3) 0.565(2) 0.570(3) 6(1)
S(24) 1.141(2) 0.537(1) 0.495(2) 1.8(5)
S(25) 1.100(2) 0.561(1) 0.324(2) 2.7(6)
S(26) 1.200(2) 0.406(1) 0.061(2) 2.4(6)
S(27) 1.336(2) 0.458(2) 0.026(2) 5.1(7)
S(28) 1.255(3) 0.535(2) -0.043(3) 8.5(8)
S(29) 1.215(2) 0.582(2) 0.111(2) 4.6(7)
P(l) 0.818(3) 0.625(2) 0.510(3) 4(1)
13(2) 0.078(3) 0.840(2) 0.951(3) 2.7(8)
P(3) 0.264(3) 0.173(2) 0.852(2) 1.5(6)

 

 

 

 

 

215

 

 

Table 5.9. (cont'd).

atom x y Z Beq (A2)a
13(4) 0.628(3) 0.291(2) 0.609(3) 4(1)
C(1) 0.899(7) 0.694(4) 0.459(9) 9(2)
C(2) 1.001(9) 0.694(4) 0.531(7) 9(2)
C(3) 1.080(5) 0.747(5) 0.532(6) 9(2)
C(4) 1.057(7) 0.801(4) 0.460(8) 9(2)
C(5) 0.954(8) 0.801(4) 0.387(6) 9(2)
C(6) 0.875(5) 0.748(5) 0.387(7) 9(2)
C(7) 0.732(5) 0.674(3) 0.566(6) 5(1)
C(8) 0.735(5) 0.747(3) 0.576(6) 5(1)
C(9) 0.676(5) 0.779(2) 0.639(6) 5(1)
C(10) 0.612(5) 0.739(3) 0.693(5) 5(1)
C(11) 0.609(5) 0.667(3) 0.683(5) 5(1)
C(12) 0.669(6) 0.634(2) 0.619(6) 5(1)
C(13) 0.739(5) 0.571(3) 0.367(4) 2(1)
C(14) 0.803(3) 0.550(3) 0.297(6) 2(1)
C(15) 0.760(4) 0.505(3) 0.195(5) 2(1)
C(16) 0.653(4) 0.479(3) 0.163(4) 2(1)
C(17) 0.589(3) 0.499(3) 0.233(5) 2(1)
C(18) 0.632(4) 0.545(3) 0.335(4) 2(1)
C(19) 0.888(5) 0.577(3) 0.615(5) 4(1)
C(20) 0.930(5) 0.520(3) 0.574(4) 4(1)
C(21) 0.991(5) 0.480(3) 0.653(5) 4(1)
C(22) 1.010(5) 0.497(3) 0.774(5) 4(1)
C(23) 0.968(5) 0.554(3) 0.816(4) 4(1)
C(24) 0.907(5) 0.594(3) 0.736(5) 4(1)
C(25) 0.167(5) 0.805(3) 0.877(5) 3(1)
C(26) 0.230(5) 0.849(2) 0.829(6) 3(1)
C(27) 0.301(4) 0.822(3) 0.775(5) 3(1)
C(28) 0.309(4) 0.751(3) 0.769(5) 3(1)
C(29) 0.247(5) 0.706(2) 0.817(5) 3(1)
C(30) 0.176(5) 0.733(3) 0.871(5) 3(1)
C(31) 0.015(3) 0.775(2) 0.983(4) 0.9(6)
C(32) 0.030(3) 0.735(2) 1.073(3) 0.9(6)
C(33) 0.034(3) 0.684(2) 1.106(3) 09(6)
C(34) 0.141(3) 0.671(2) 1.049(3) 0.9(6)
C(35) -0.186(3) 0.711(2) 0.959(3) 09(6)

 

 

216

 

 

Table 5.9. (cont'd).

atom x r 2 Bed (AZ)a
C(36) 0.122(3) 0.762(2) 0.925(3) 0.9(6)
C(37) 0.009(4) 0.892(3) 0.845(4) 2(1)
C(38) —0.028(5) 0.858(2) 0.731(5) 2(1)
C(39) —0.087(4) 0.891(3) 0.640(3) 2(1)
C(40) 0.110(4) 0.959(3) 0.662(4) 2(1)
C(41) —0.073(4) 0.994(2) 0.776(5) 2(1)
C(42) 0.013(4) 0.960(3) 0.867(3) 2(1)
C(43) 0.136(6) 0.897(4) 1.068(6) 5(1)
C(44) 0.237(6) 0.929(4) 1.076(5) 5(1)
C(45) 0.293(4) 0.972(4) 1.177(6) 5(1)
C(46) 0.249(6) 0.983(4) 1.270(5) 5(1)
C(47) 0.148(6) 0.951(4) 1.261(6) 5(1)
C(48) 0.091(5) 0.908(4) 1.160(8) 5(1)
C(49) 0.256(6) 0.241(4) 0.765(6) 4(1)
C(50) 0.261(5) 0.229(3) 0.650(6) 4(1)
C(51) 0.230(6) 0.278(4) 0.571(5) 4(1)
C(52) 0.193(5) 0.339(3) 0.607(5) 4(1)
C(53) 0.187(5) 0.350(3) 0.722(6) 4(1)
C(54) 0.219(6) 0.301(4) 0.801(4) 4(1)
C(55) 0.152(2) 0.163(2) 0.907(3) 0.3(5)
C(56) 0.058(3) 0.190(2) 0.855(3) 0.3(5)
C(57) —0.026(2) 0.184(2) 0.905(3) 0.3(5)
C(58) -0.016(2) 0.151(2) 1.007(3) 0.3(5)
C(59) 0.078(3) 0.124(2) 1.060(3) 0.3(5)
C(60) 0.162(2) 0.130(2) 1.010(3) 0.3(5)
C(61) 0.267(5) 0.095(3) 0.766(5) 4(1)
C(62) 0.174(4) 0.052(3) 0.707(5) 4(1)
C(63) 0.176(4) 0.003(3) 0.627(5) 4(1)
C(64) 0.271(5) —0.017(3) 0.605(4) 4(1)
C(65) 0.364(4) 0.026(3) 0.664(5) 4(1)
C(66) 0.362(4) 0.082(3) 0.745(5) 4(1)
C(67) 0.378(3) 0.192(2) 0.969(3) 1.9(6)
C(68) 0.430(4) 0.259(2) 1.008(4) 1.9(6)
C(69) 0.521(3) 0.270(2) 1.102(4) 1.9(6)
C(70) 0.560(3) 0.213(2) 1.158(3) 1.9(6)
C(71) 0.508(4) 0.146(2) 1.120(4) 1.9(6)

 

 

 

217

 

 

Table 5.9. (cont'd).

atom x y z Bea (A03
C(72) 0.417(4) 0.135(2) 1.026(4) 1.9(6)
C(73) 0.656(5) 0.220(3) 0.698(5) 2(1)
C(74) 0.653(5) 0.227(2) 0.815(5) 2(1)
C(75) 0.662(5) 0.169(3) 0.879(4) 2(1)
C(76) 0.674(5) 0.104(2) 0.826(5) 2(1)
C(77) 0.677(5) 0.098(2) 0.710(5) 2(1)
C(78) 0.668(5) 0.156(3) 0.646(4) 2(1)
C(79) 0.720(6) 0.307(5) 055(1) 11(2)
C(80) 0.741(8) 0.333(5) 0.453(8) 11(2)
C(81) 0.84(1) 0.335(4) 0.439(6) 11(2)
C(82) 0.923(6) 0.311(5) 052(1) 11(2)
C(83) 0.902(7) 0.285(4) 0.623(7) 11(2)
C(84) 0.80(1) 0.283(4) 0.637(7) 11(2)
C(85) 0.506(5) 0.275(5) 0.505(6) 8(1)
C(86) 0.460(7) 0.318(3) 0.421(8) 8(1)
C(87) 0.372(7) 0.292(4) 0.328(7) 8(1)
C(88) 0.330(5) 0.222(5) 0.319(6) 8(1)
C(89) 0.375(6) 0.178(3) 0.402(8) 8(1)
C(90) 0.464(6) 0.205(5) 0.495(6) 8(1)
C(91) 0.611(6) 0.364(3) 0.698(5) 5(1)
C(92) 0.514(5) 0.369(3) 0.720(6) 5(1)
C(93) 0.497(4) 0.430(4) 0.781(6) 5(1)
C(94) 0.578(5) 0.485(3) 0.818(5) 5(1)
C(95) 0.675(5) 0.481(3) 0.795(5) 5(1)
C(96) 0.692(5) 0.420(4) 0.735(6) 5(1)

 

 

a Anisotropically refined atoms are given in the form of the isotropic
equivalent displacement parameter defined as Beg: (87r2/3)[a2B11 +
b2B22 + c2B33 + ab(cosy)312 + ac(cos[3)B13 + bc(cosa)B23]. The
anisotropic temperature factor expression is exp[-27r2(B11a*2h2 + +
2312a*b*hk + ...)].

218

XRD (X-ray Powder Diffraction) patterns were obtained on
either a Phillips XRG—3000 computer-controlled powder
diffractometer or a Rigaku-Denki/RW4OOF2 (Rotaflex) rotating anode
powder diffractometer. Ni—filtered, Cu radiation was used at the
condition of 35 KV, 35 mA for the Phillips XRG-3000 and 45 KV, 100
mA for the Rigaku-Denki/RW4OOF2 (Rotaflex). Based on the atomic
coordinates from the X-ray single crystal diffraction study, X—ray
powder patterns for all compounds were calculated using the
software package CERIUS.17 The observed X-ray powder patterns
were in good agreement with those calculated. Calculated and
observed X—ray powder patterns showing d-spacings and intensities

of strong hkl reflections are compiled in Tables 5.10-5.12.

 

219

Table 5.10. Calculated and Observed X—ray Powder Diffraction
Pattern of K4Pt4S22'4H20 (II).

 

 

’1 k l dcalc (A) dobs (A) I/Imax (ObS, %)
1 1 1 8.64 8 57 87
2 0 0 7.48 7 45 30
3 1 1 4.51 4.50 19
2 2 2 4.32 4.33 34
3 3 1 3.43 3 44 39
4 2 2 3.05 3 06 43
5 1 1 2.880 2 893 100
3 3 3 2.880

6 0 0 2 494 2 503 87
4 4 2

6 2 0 2.366 2.375 15
5 3 3 2.282 2.292 31
7 1 1 2.095 2.110 58
5 5 1 2.095

8 2 2 1.764 1.760 46
6 6 0 1.764

7 5 1 1.728 1.732 46
5 5 5 1.728

8 4 2 1.633 1.644 23

 

220

Table 5.11. Calculated and Observed X—ray Powder Diffraction
Pattern of (Ph4P)2[Pt(S4)2]'CH3OH (IV).

 

 

h k 1 defile (A) dobs (A) 1/1mfl (obs, %)
2 0 0 10.69 10.82 22
0 0 2 8.82 8.88 51
0 1 1 8.80

1 1 1 8.37 8.44 12
2 1 0 8.11 8.19 31
3 1 0 6.72 6.79 46
4 0 0 6.72

3 1 1 6.28 6.34 16
2 1 2 5.97 6.02 35
3 1 2 5.35 5.38 100
4 0 2 5.34

4 1 1 5.34

1 2 1 4.80 4.82 30
2 2 1 4.59 4.61 34
5 1 1 4.59

6 0 1 4.34 4.37 65
3 2 1 4.29 4.31 36
2 0 4 4.19 4.21 15
2 2 2 4.18

6 1 0 4.10 4.13 14
6 1 1 3.99 4.02 38
1 2 3 3.81 3.82 10
6 1 2 3.72 3.71 33
2 2 3 3.70

5 2 0 3.69

4 0 4 3.69

4 2 2 3.68

7 1 0 3.59 3.61 20
2 0 5 3.41 3.43 31
5 2 2 3.41

0 1 5 3.33 3.35 28
0 2 4 3.33

7 1 2 3.33

1 2 4 3.30 3.32 29
6 2 1 3.30

 

 

Table 5.11.

(cont'd).

221

 

p—A
HHOOUJUJOLAOOOOr—‘UJOOMUINw-h-POOOOH

3“

N

#Wr—AONWNWNOWWHWNNWNHHOW

N

NUIQUJON-hOUJN-h-bUJWv—thIN-RMHNN

dcalc (A)

3.14

3.14

3.14

2.985
2.984
2.982
2.832
2.831
2.829
2.804
2.789
2.673
2.673
2.671
2.576
2.575
2.573
2.447
2.445
2.445
2.433
2.432

dobs (A)

3.15

2.993

2.842

2.810

2.680

2.584

2.453

I/I11m (obs, %)

25

23

21

24

25

16

22

 

 

Table 5.12.

Calculated and Observed X—ray Powder Diffraction

222

Pattern 0f (Ph4P)4[Pt(S4)(Ss)21[Pt(55)31 (V)-

 

 

h k l dcalc (A) dobs (A) I/Imax (Obs, %)
0 0 1 11.37 11.50 50
1 1 0 10.03 10.00 100
0 2 —1 7.72 7.65 85
1 1 1 6.66 6.65 18
2 -2 0 5.60 5.62 21
1 -1 —2 5.50 5.51 15
2 2 —1 5.14 5.13 13
0 2 —2 5.13

2 0 —2 4.98 4.99 15
0 4 —1 4.58 4.59 18

 

II

 

223

RESULTS AND DISCUSSION

1. Synthesis

As we were encouraged with the successful synthesis of
K2PdSe10, we applied the hydrothermal synthesis technique to the
other members of Group 10. The hydrothermal reaction of K2PtCl4
and K284 in a 1:5 ratio produced K4[Pt4822]'4HzO (II), as shown in eq.
(5.2).

Water

4K2PtCl4 + 20K284 130°C lday

K4[Pt4822]'4H20 + 16KC1 + 14K2Sx ................... eq (5.2)

In the above reaction Pt(II) metal ions were oxidized to Pt(IV) with
the concomitant reduction of S42— ligands to 832‘ and 82', to yield the
[Pt4(S)4(S3)6]4' complex. (II) is quite soluble in water, supporting the
presence of the cocrystallized water molecules. The Re analog,
[Re4822]4' was reported to be prepared by the reaction of ammonium
perrhenate with an aqueous polysulfide solution at ca. 60 °C.18 In
this reaction the reduction of Re(VII) to Re(IV) by 83' shows the
versatile redox ability of polysulfide ligands. Compound (II) might
be also prepared in an open system without using the hydrothermal
technique. The Se analog of (II) was also prepared by a

hydrothermal reaction as shown in eq. (5.3).

KOH > 110°C
4K2PtCl4 + 8K28€4 Water 2 days

K4[Pt48622] + 16KC1 + 2K2$ex ........................ eq' (53)

 

 

 

224

K4[Pt4Se22] (III) is not crystallographically isostructural to (II). It
has no cocrystallized water molecule and it is insoluble in most
solvents. The Ni analog, [Ni4Se4(Se3)5(Se4)]4' was obtained recently
by Ibers et al. in a different synthetic manner.8 It was isolated as a
Et4N+ salt from the reaction in DMF. It is notable, in this reaction,
that a polyselenide solution was added to a Ni(II) metal solution.
When the same reaction was done in the reverse order of addition,
[Ni(Se4)2]2- was isolated as a major product. In most cases, the metal
solution was added to the polychalcogenide with the notion that the
thermodynamically stable binary metal chalcogenide, instead of the
metal polychalcogenide, can be formed in a condition of excess metal
ions. However, if the binary metal chalcogenide is marginally stable
and can dissolve in the polar solvents used, metal rich clusters could
be produced under the conditions of excess metal. As employed
here, another effective approach can be the hydro(solvato)thermal
technique that provides a condition at which the binary metal
chalcogenide can dissolve.

Upon employing organic cations to explore new platinum
polychalcogenide compounds with the hydro(solvato)therma1
technique, (Ph4P)2[Pt(S4)2]'CH3OH (IV) was obtained by the
methanothermal reaction of K2PtCl4, K284, and Ph4PBr in a 13532 ratio,

as shown in eq. (5.4).

MeOH
K2PtCl4 + 5K284 + 2Ph4PBr 80°C 1 day >

(Ph4P)2[Pt(S4)2]'CH3OH + 4KC1 + 2KBr + 31(st ------ eq. (5.4)

 

 

 

225

When the similar reaction was done hydrothermally, the same
product of (IV) was obtained, but in poor yield and as a
microcrystalline material. (Ph4P)2[Pd(S4)2] could be also readily
prepared by a methanothermal reaction.

(Ph4P)4[Pt(S4)(Ss)2][Pt(S5)3] (V) was prepared by the treatment
of (NH4)2[Pt(S5)3] with KCN (7 equiv) in water at 60 °C, followed by
the addition of Ph4PCl. It is well known that the cyanide ion can
easily abstract S atoms from polysulfide chains with the formation of
the thiocyanate. We used seven equivalents of KCN, in order to form
[Pt(S4)2]2- of (IV) by removing seven zerovalent S atoms from
[Pt(S5)3]2'. The microcrystalline material obtained from the above
reaction was recrystallized in DMF to give single crystals of
(Ph4P)4[Pt(S4)(Ss)2][Pt(Ss)3] (V). The major material before
recrystallization is virtually the same as (V), based on spectroscopic
and elemental analyses, but their XRD powder patterns differ. To
ensure the chalcogen—abstracting reactivity of CN', the reaction with
seventeen equivalents of CN' was also carried out. In this case all the
[Pt(Ss)3]2' reacted to give a colorless solution without forming a
precipitate upon addition of Ph4P+. [Pt(CN)4]2' was proposed to be a

final product from the complete S abstraction reaction (see eq. (5.5)).

[Pt(ss)312- + 17CN- —> [Pt(CN)4]2- + 13SCN- + 282- ------ eq. (5.5)

Based on the work reported here, it is clear that we could not obtain
the previously claimed [Pt(S5)2]2' complex.3(a),14 At this point, there
is not enough evidence to either confirm or deny the existence of

[Pt(Ss)2]2‘ and more work is needed to address this interesting issue.

5.. --' -..—- —. ‘—w-r—.—T—‘-“

226

The recent report of [Pd(Se5)2]7~wll raises a possibility that the
homoleptic M(Ss) (M=Ni(II), Pd(II), and Pt(II)) ring containing
species such as [Pt(85)2]2' might be also stabilized. However, metal
polysulfide and polyselenide chemistry have not been always
parallel; indeed they have proven to be much different in a number
of cases. The five-membered ring M(S4) (M=Ni(II), Pd(II), and
Pt(II)) is predominant in the known Group 10 metal poysulfide
complexes, though there is one exceptional example of [Pd(S3N)(Ss)]'
.19

Interestingly, when Ph3P was used as a S abstracting reagent,
neutral (Ph3P)2Pt(S4) was reported to be obtained by the reaction as
shown in eq (5.6).20

[Pt(85)3]2- + 12Ph3P —> (Ph3P)2Pt(S4) + 10Ph3PS + sZ- eq. (5.6)

The (Ph3P)2Pt(S4) is stable upon treatment with additional Ph3P. It
can not be reduced to (Ph3P)4Pt by further S abstraction as the
reverse reaction is more favorable. The reaction between (Ph3P)4Pt
and elemental sulfur was reported to yield (Ph3P)2Pt(S4).21 The
mechanism of the chalcogen-abstraction reaction is still obscure and
would be acutely dependent on the nature of metal polychalcogenide
complexes and abstracting reagents used. Further detailed

mechanistic studies are required to better understand the chalcogen—

abstraction reaction.

 

 

227

2. Physicochemical Studies

2.1 UV/Vis spectroscopy

DMF or CH3CN solutions of (II) and (IV) are reddish brown and
give featureless UV/Vis spectra. The orange—brown CH3CN solution
of (V) shows broad peaks at 480 nm (e=5.1x103 cm‘lM'l), 320 nm
(a=15x103), and 275 nm (8:36X103) in its spectrum (see Figure 5.11).
For comparison, two peaks were found at 390 and 310 nm in the

UV/Vis spectrum of (Ph4P)2[Pt(Ss)3].3(e)

2.2 Far-IR spectroscopy

In the far-IR spectra of polysufide complexes (II), (IV), and
(V) (see Figure 5.12), the peaks in the range of 492—437 cm'1 could
be attributed to S—S vibration modes. In the previously
characterized metal polysulfide complexes, the S—S vibration modes
occur in the similar energy region. Some representative examples
are as follows: [Re4S22]4' (465 cm'l),18(a) [Pd2S28]4' (482 and 453
cm'l),10 [M(S6)2]2~ (M=Zn, Cd, Hg) (~495 and 455 cm'l),22 [Ni(S4)2]2'
(480 and 430 cm'l),4(a) [Cu3S12]3' (468, 455, and 437 cm‘l),23
[Cu2820]4' (484 and 456 cm‘l),23 and [Fe2S12]2' (474 cm'l).24 The
rest of the peaks in the lower energy region seem to be associated
with Pt—S vibration modes. In the far~IR spectrum of (Ph3P)2Pt(S4),
for comparison, 315 and 326 cm‘1 peaks were assigned to the Pt—S
vibration modes.19(a) The far—IR spectrum of (V) is a little different
from that of (Ph4P)2[Pt(Ss)3]3(e) (see Table 5.13), supporting the

existence of the different anion [Pt(S4)(Ss)212‘ in (V)-

228

 

 

 

 

 

 

 

a)
u
c
m
E
o 275
U)
.Q
<
320
4,89
W W
l
200 400 600 800
Wavelength (nm)

Figure 5.11. UV/Vis spectrum of (Ph4P)4[Pt(S4)(Ss)2][Pt(Ss)3]
(V) in CH3CN. '

 

TRANSMITTANCE

229

(A)

(B)

(C)

 

 

 

 

 

 

 

800 516 432 348 2611 180
WAVENUMBER
Figure 5.12. Far-IR spectra (CsI pellet) of K4[Pt4822]-4H20 (II),

(Ph4P)2[Pt(S4)2]'CH30H (1V), and (Ph4P)4[Pt(S4)(SS)21[Pt(35)3] (V)-

336

 

 

230

There is only one broad peak at 470 cm'1 without apparent Se—
Se vibration modes in the far—IR spectrum of (III) (see Figure 5.13).
Table 5.13 shows the detailed spectral data of the compound, (II),
(III). (IV), (V), and (Ph4P)2[Pt(Ss)3]-

Table 5.13. Far—IR Spectral Data for K4[Pt4522]-4H20 (II),
K4[Pt456221 (111), (Ph4P)2[Pt(S4)2]'CH30H (1V).
(Ph4P)4[Pt(S4)(Ss)2][Pt(55)3l (V), and (Ph4P)2[Pt(Ss)3l*-

 

Compound Vibration Frequency (cm-1)

K4[Pt4822]-4H20 537 (w, sh)**, 491 (m, hr), 464 (s, hr), 355
(w), 327 (m), 301 (w), 250 (m), 236 (m),
207(s), 151 (s)

K4[Pt4Se22] 470 (m, br)

(Ph4P)2[Pt(S4)2]'CH3OH 462 (m), 442 (S), 338 (m), 303 (m), 270 (m),
200 (w)

(Ph4P)4[Pt(S4)(Ss)2]- 492 (W), 455 (m), 437 (w, sh), 356 (m), 325

[Pt(Ss)3] (m), 301 (m), 257 (m), 223 (m), 202 (w)

(Ph4P)2[Pt(Ss)3]* 455 (m), 440 (w), 410 (w), 400 (m), 385

(m), 370 (w)

 

*ref. 3(e). **s: strong, m: medium, w: weak, sh: shoulder, br: broad.

2.3 Thermal Gravimetric Analysis

TGA results for all compounds are summarized in Table 5.14
and shown in Figures 5.14 and 5.15. K4[Pt4Szz]-4H20 (II) loses 4.5 %
of its weight in the temperature range of 125—200 °C, which
corresponds to the loss of four H20 molecules (calc. 4.2 %). In the

next step it loses elemental S to give a residue with a formula of

TRANSMFITANCE

 

800 516

Figure 5.13.

932 348 264 160
mmeNUMBER

Far—IR spectrum (CsI pellet) of K4[Pt4Se22] (III).

 

44—98

 

VV(%)

VV(%)

 

 

 

232

 

 

 

 

 

 

 

 

 

(A)
1 1 O r I l l l I I
90 ~ _
7O - _
SO - _
30 I I I I I I I I
O 200 400 600 800
TmanID
(B)
1 1 O I I I I I I I I
90 -
70 ~
50 -
30 -
1 O I I I 1 I I I I
O 200 400 600 800

Temp. (C)

Figure 5.14. TGA diagrams of (A) K4[Pt4822]-4H20 (II) and (B)
(Ph4P)2[Pt(S4)2l'CH3OH (IV)-

 

 

233

 

 

 

 

105
95 -
8: 85 _
3
75 —
65
0

Figure 5.15.

200 400 600 800
Temp. (C)

TGA diagram of (Ph4P)4[Pt(S4)(Ss)2][Pt(SS)3] (V)-

 

234

4(K2PtS3). For the (Ph4P)2[Pt(S4)2]-CH3OH (IV) 2.6 % of weight loss in
the temperature range of 90-200 oC could be due to the loss of one
methanol molecule (calc. 2.8 %). It loses 55.5 % of its weight in the
second step of weight loss, probably as Ph3PS, other organic species
and elemental S. (Ph4P)4[Pt(S4)(S5)2][Pt(Ss)3] (V) loses 4.8 % weight
in the temperature range of 150—185 °C, possibly due to two
cocrystallized DMF molecules (calc. 5.2 %). However, these DMF
molecules could not be identified in the structure as the data set was
not of good enough quality to allow their location. It is quite
probable that they might be disordered. In the next step of weight
loss, (V) loses 62.2 % of its weight, as in the case of (IV). In both
(IV) and (V), weight loss continues above 700 °C. The final residue
appears by SEM/EDS analysis to be elemental Pt.

Table 5.14. TGA Data for K4[Pt4Szz]-4H20 (II),
(Ph4P)2[Pt(S4)2]-CH3OH (IV). and (Ph4P)4lPt(S4)(Ss)2][Pt(Ss)3] (V).

 

 

Compound Temperature range (°C) Weight loss (%)
K4[Pt4322]'4H20 125 - 200 4.5

350 — 590 23.7
(Ph4P)21Pt<s4)21-CH30H 90 - 200 2-6

290 — 545 55.5
(Ph4P)4[Pt(S4)(Ss)2]- 150 — 185 4.8
[Pt(Ss)3] 285 — 520 62.2

 

235

3. Description of Structures

3.1 Structure of [Pt4522]4' in (II)

The structure of [Pt4Szz]4' is similar to that of the [Re4822]4'
complex.16 [Pt4Szg]4' features a cubane [Pt4S4]4+ core surrounded by
six S32' ligands as shown in Figure 5.16. Four Pt4+ metal centers and
four SZ‘ ions are combined to form a Pt—S cube with six 832' ligands
connecting diagonal pairs of Pt metal ions in the six faces of the cube.
Thus a more descriptive formula would be [Pt4S4(S3)6]4'. The S(3)
atoms of the S32" ligands are disordered at two positions, 0.59 A
above and below the Pt—S(2)—S(2')—Pt' plane. The center of the
[Pt4S22]4- cluster is sitting on the crystallographic special position (0,
0, 0) of 43m symmetry. A crystallographic 3—fold axis passes
through Pt and 8(1) atoms. [Pt4822]4' possesses Td symmetry if the
disordered S(3) atoms are considered to be located on the Pt-S(2)—
S(2')—Pt' plane. The Pt—Pt distance of 3.478(4) A suggests no bonding
between the Pt metal atoms. In the Re analog [Re4822]4' there is
considerable metal—metal bonding between Re atoms (Re—Re distance,
2.76 A), which causes severe distortions in the [Re4S4] cubane core.16
Electronically, the closest analog of [Pt4S22]4‘ is [Ni4Se4(Se3)5(Se4)]4', a
remarkable N14+ compound. In this molecule the [Ni4Se4] cubane
core is distorted due to the presence of a Se42‘ chain.8 In contrast,
little distortion is observed in the Pt—S cubane of [Pt4822]4', as
evidenced from the bond angles around Pt and 8(1) atoms (Sl—Pt—Sl,
84.4(6)°; Pt—Sl—Pt, 95.3(6)°). Selected bond distances and angles in
the [Pt4822]4‘ cluster are summarized in Table 5.15. The distance

between S atoms in the Pt4S4 cubane core is 3.l6(3) A.

 

Figure 5.16. ORTEP representation and labeling scheme of
[Pt4822]4'. S(3) atoms are located at the midpoint between two
disordered positions.

 

237

Table 5.15. Selected Bond Distances (A) and Bond Angles (deg) in

the [Pt4822]4‘ Anion of (11). Standard Deviations Are Given in
Parenthesesa

 

Pt-S(1) 2.35(1) S(2)—S(3) 1.98(2)
Pt-S(2) 2.33(2)

Pt-S (mean) 2.34(1)

S(l)-Pt-S(1) 84.4(6) Pt—S(1)-Pt 95.3(6)
S(l)-Pt-S(2) 92.6(6) Pt-S(2)-S(3) 113(1)
S(1)-Pt-S(2) 175.9(6) S(2)-S(3)—S(2) 122(2)

 

a The estimated standard deviation in the mean bond distance was
calculated by the equation 01 = {in(ln-l)2/n(n-I)}1/2, where In is the
distance of the nth bond, 1 is the mean bond distance, and n is the

number of bonds.

 

 

 

 

 

 

 

 

 

238

The distances between K+ ions and S atoms are in the range of 3.22
to 3.88 A. Two of four K+ ions in (II) are disordered together with
four water molecules at 2mm symmetry positions. It was modeled
that the two K+ ions are located on a pair of opposite vertices of an
octahedron whose center is a 43m symmetry position, and four H—
bonded water molecules (O-O distance, 2.86(5) A) in a square planar
arrangement coordinate to the two K“ ions above and below them.
In the (NH4)4[Re4Szz]-2H2018 which is isostructural to (II), two NH4+
ions are similarly disordered with two water molecules at the same
position. The model of these disordered K” ions and water molecules
is shown in the packing diagram of (II) (see Figure 5.17). In this
model the distance between K+ ions is 4.04(8) A. The presence and
quantity of water in the structure was confirmed by thermal

gravimetric analysis (TGA) measurements (vide supra).

3.2 Structure of [Pt(S4)2]2' in (IV)

(Ph4P)2[Pt(S4)2]-CH3OH (IV) is composed of [Pt(S4)2]7-' anions
with non-interacting Ph4P’r cations. Pt(S4)2]2‘ is a new member of
the well known metal octachalcogenide family. The other two
members in the Ni triad, [Ni(S4)2]2‘ 4 and [Pd(S4)2]2‘ 4a are known as
Et4N+ and Ph4P+ salts and the Sc analog, [Pt(Se4)2]2',6 is also known.
Two different views of [Pt(S4)2]2' are shown in Figure 5.18 and the
packing diagram of (IV) in the unit cell is shown in Figure 5.19. The
Pt metal center has a square-planar coordination geometry. The
average Pt—S and S-S distances are 2.31(6) and 2.05(8) A,

respectively. Selected bond distances and angles in the [Pt(S4)2]2'

 

 

239

 

 

1P t482214-
€{s (K3, H20) 7
(f \A‘...
4K 1’- I
g: .41 '
mew-'44:; .
1‘. VII
" ‘I

9°.

 

 

 

 

 

 

 

 

Figure 5.17. The packing diagram of K4[Pt4822]‘4H20 (II).
[Pt4S22]2' clusters are simplified as large open circles for a clear view.

240

S4 .3
s. (e (9‘

/%<5Ҥ32

81

S7

 

Figure 5.18. ORTEP representation and labeling scheme of
[Pt(S4)2]2' in two views.

 

 

241

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

of

(stereo-view)

diagran1

packing

The

Figure 5.19.

(Ph4P)2[Pt(S4)2]'CH30H (1V)-

 

242

Table 5.16. Selected Bond Distances (A) and Bond Angles (deg) in
the [Pt(S4)2]2‘ Anion of (IV). Standard Deviations Are Given in

Parentheses.a

 

 

Pt-S(1) 2.40(2) 8(1)-S(2) l.97(3)
Pt-S(4) 2.29(2) S(2)—S(3) 2.03(3)
Pt-S(5) 2.25(2) S(3)-8(4) 2.14(3)
Pt-S(8) 2.31(2) S(5)—S(6) 2.09(3)
S(6)-S(7) l.96(3)
Pt—S (mean) 2.31(6) S(7)-8(8) 2.12(3)
S-S (mean) 2.05(8)
S(1)-Pt-S(5) 88.1(8) Pt—S(1)-S(2) 105(1)
S(1)-Pt-S(4) 94.9(7) Pt-S(5)-S(6) 108(1)
S(1)-Pt-S(8) 172.1(7) Pt-S(4)-S(3) 102(1)
S(5)—Pt-S(4) 175.9(7) Pt-S(8)-S(7) 104(1)
S(5)-Pt-S(8) 91.8(7) S(1)-S(2)-S(3) 100(1)
S(4)-Pt-S(8) 85.7(7) S(4)-S(3)-S(2) 100(1)
S(5)-S(6)-S(7) 93(1)
S(8)—S(7)-S(6) 99(1)

 

a The estimated standard deviation in the mean bond distance was
calculated by the equation a] = {in(ln-l)2/n(n-I)}1/2, where In is the
distance of the nth bond, 1 is the mean bond distance, and n is the
number of bonds.

 

f

243

are summarized in Table 5.16. The Pt(S4) five membered ring in
[Pt(S4)2]2‘ has been found previously in neutral compounds such as
(R3P)2Pt(S4).20,21(a) In the Pt(S4) ring the alternating behavior of S-S
bonds can be recognized, though it is not very pronounced. The
average internal and external S-S bond distances are 200(5) and
2.08(8) A, respectively. This behavior is also seen in the other Pt(S4)
ring containing compounds, (Ph2PCH2CH2PPh2)Pt(S4)21(a) and
(Ph3P)2Pt(S4)20 (see Table 5.17).

Table 5.17. Comparison of S-S Bond Distances (A) in the Pt(S4)
Ring Containing Compounds with Estimated Standard Deviations in

 

 

 

Parentheses.
S 1
Pt 1d2
S(4){35(3)
Compound d1 & d3 d2
(Ph4P)2[Pt(S4)2]'CH3OHa 197(3), 2.14(3) 203(3)
209(3), 2.12(3) 1.96(3)
(thPCHzCHzPPh2)Pt(Sa)b 2.069(5), 2.047(5) 2.012(6)
(Ph3P)2Pt(S4)C 2.024(8), 2.081(10) 2.022(10)

 

a: this work, b: ref. 19(c), c: ref. 18.

The alternation in Q-Q (Q=S, Se, Te) bonds of the M(Q4) ring has been
previously observed, especially in d2 and d3 metal complexes, and

can be explained in terms of strong M(dn)—Q(dn) interactions which

 

 

244

result in weakening the Q(dn)—Q(dn) interactions involving terminal Q
atoms.21(a)a25

The stabilization of the [Pt4S2214‘ and [Pt(S4)2]2' ions marks the
most significant development in platinum polysulfide chemistry
since the structural determination of K2[Pt(85)3]. The effectiveness of
the hydro(solvato)thermal synthetic technique for the preparation of

new metal polychalcogenide complexes is proven once again here.

3.3 Structure of [Pt(Ss)2(S4)]2“ and [Pt(85)3]2‘ in (V)

In the non-centrosymmetric structure of (V) two independent
molecular anions, [Pt(S5)2(S4)]2‘ and [Pt(85)3]2‘, are stabilized with
non-interacting Ph4P+ cations. The [Pt(85)3]2' complex was
previously known as K+,3(b) NH4+,3(d) and Ph4P+ salts,3(e) but the
other [Pt(Ss)2(S4)]2' complex is hitherto unknown. The coordination
environment for Pt in both complexes is octahedral as shown in
Figure 5.20. Figure 5.21 shows the packing diagram of (V) in the
unit cell. The PtIV(S4) five—membered ring is seen here for the first
time in the [Pt(S5)2(S4)]2' complex, though the PtH(S4) ring is known.
The structure of (V) is not quite well defined as some S-S distances,
ranging from 1.80(6) to 2.23(5) A, are in the limit of the normal S—S
bond distance. The 85 ligands might be disordered with S4 ligands to
some degree and it could be responsible for the large variations in
the S-S bond distances. The poor data set prevented us from
revealing the disordered structure in detail. The average Pt—S and S—
S distances are 2.40(7) and 2.04(11) A, respectively, which are in the
normal range. Selected bond distances and angles in the

[Pt(85)2(S4)]2' and [Pt(Ss)3]2' complexes of (V) are summarized in

 

 

—i—

245

Tables 5.18 and 5.19. At this stage, a question can be raised whether
or not [Pt(S4)3]2' could be stabilized, though there is no obvious
reason against it. One synthetic approach would be the employment
of the milder S abstracting reagent such as R3P instead of CN' in the

stoichiometric amount needed to remove three S atoms from

[Pt(Ss)3]2'.

 

 

 

 

246

32

83 g! 84

 

818

 

Figure 5.20. ORTEP representation and labeling scheme of
[Pt(55)312' and [Pt(Ss)2(S4)12' in (Ph4P)4lPt(S4)(Ss)2l[Pt(Ss)3] (V).

 

 

 

 

 

 

 

 

247

 

 

 

Figure 5.21. The packing diagram (stereo-view) of
(Ph4P)4[Pt(S4)(Ss)21[Pt(35)31 (V).

 

 

 

—i—

248

Table 5.18. Selected Bond Distances (A) in the [Pt(S4)(Ss)2]2- and
[Pt(Ss)3]2‘ Anions of (V). Standard Deviations Are Given in
Parentheses.a

 

 

Pt(l)-S(l) 2.43(4) 3(1)-S(2) l.91(5)
Pt(l)-S(5) 240(3) S(2)-S(3) 211(3)
Pt(1)-S(6) 251(3) S(3)-8(4) 205(3)
Pt(l)-S(10) 229(4) S(4)-S(5) 2.07(4)
Pt(l)*S(11) 242(2) S(6)-S(7) 1.80(6)
Pt(l)-S(15) 2.44(3) S(7)-8(8) 1.535(6)
Pt(2)-S(16) 229(4) S(8)-S(9) 2.02(6)
Pt(2)-S(20) 2.40(3) S(9)-S(10) 209(6)
Pt(2)—S(21) 2.44(2) S(ll)-S(12) 2.04(4)
Pt(2)-S(25) 235(3) S(12)-S(13) 107(5)
Pt(2)-S(26) 235(3) S(13)-S(14) 1.98(5)
Pt(2)-S(29) 2.43(3) S(14)-S(15) 190(4)
S(16)-S(17) 2.23(5)
S(17)-S(18) 2.09(6)
S(18)-S(l9) 209(6)
Pt-S (mean) 2.40(7) S(l9)-S(20) 1.98(4)
S(21)-S(22) 196(5)
S(22)-S(23) 2.16(6)
S(23)-S(24) 222(4)
S(24)-S(25) 2.06(3)
S(26)-S(27) 213(4)
S(27)—S(28) 2.01(4)
S(28)—S(29) 220(5)
S-S (mean) 2.04(ll)
a The estimated standard deviation in the mean bond distance was
calculated by the equation at = {in(ln-l)2/n(n-I)}1/2, where In is the

 

distance of the nth bond, 1 is the mean bond distance, and n is the
number of bonds.

 

i

249

Table 5.19. Selected Bond Angles (deg) in the [Pt(S4)(S5)2]2- and
[Pt(85)3]7~' Anions of (V). Standard Deviations Are Given in

 

Parentheses.

S(1)—Pt(l)—S(5) 98(1) Pt(l)—S(1)-S(2) 108(2)
S(1)—Pt(1)-S(6) 175(1) Pt(1)—S(5)—S(4) 106(1)
S(1)—Pt(1)-S(10) 85(1) Pt(l)-S(6)—S(7) 113(2)
S(1)-Pt(1)—S(ll) 101(1) Pt(1)—S(10)—S(9) 113(2)
S(1)—Pt(l)-S(15) 85(1) Pt(1)-S(11)—S(12) 110(1)
S(5)-Pt(1)—S(6) 83(1) Pt(1)—S(15)—S(14) 111(2)
S(5)—Pt(1)—S(10) 100(1) Pt(2)—S(16)—S(17) 104(2)
S(5)—Pt(1)—S(11) 78.6(9) Pt(2)—S(20)—S(19) 113(2)
S(5)-Pt(1)—S(15) 169(1) Pt(2)-S(21)—S(22) 110(2)
S(6)—Pt(l)—S(10) 90(1) Pt(2)—S(25)—S(24) 111(1)
S(6)—Pt(1)—S(ll) 84.1(9) Pt(2)—S(26)—S(27) 106(1)
S(6)—Pt(l)—S(15) 95(1) Pt(2)-S(29)-S(28) 104(1)
S(10)—Pt(1)—S(ll) 174(1) S(1)—S(2)-S(3) 116(2)
S(10)—Pt(l)-S(15) 90(1) S(2)-S(3)—S(4) 100(1)
S(11)-Pt(1)—S(15) 91(1) S(3)—S(4)—S(5) 105(1)
S(16)—Pt(2)—S(20) 95(1) S(6)—S(7)—S(8) 116(4)
S(16)—Pt(2)—S(2l) 94(1) S(7)—S(8)-S(9) 108(3)
S(16)—Pt(2)-S(25) 86(1) S(8)—S(9)—S(10) 114(3)
S(16)—Pt(2)-S(26) 97(1) S(11)—S(12)—S(13) 103(2)
S(16)—Pt(2)—S(29) 172(1) S(12)—S(13)—S(14) 105(2)
S(20)-Pt(2)—S(2l) 171(1) S(13)—S(14)—S(15) 110(2)
S(20)—Pt(2)—S(25) 87(1) S(16)—S(17)—S(18) 105(2)
S(20)—Pt(2)—S(26) 86(1) S(17)—S(18)-S(19) 95(2)
S(20)—Pt(2)—S(29) 90(1) S(18)—S(19)—S(20) 107(2)
S(21)-Pt(2)—S(25) 93.8(8) S(21)—S(22)—S(23) 102(2)
S(21)-Pt(2)—S(26) 93(1) S(22)-S(23)-S(24) 95(2)
S(21)—Pt(2)—S(29) 81.1(9) S(23)—S(24)-S(25) 108(2)
S(25)—Pt(2)—S(26) 172.3(8) S(26)—S(27)—S(28) 92(2)
S(25)-Pt(2)—S(29) 88(1) S(27)—S(28)—S(29) 101(2)

S(26)—Pt(2)—S(29) 90(1)

 

 

 

i

(1)

(2)

(3)

(4)

(5)

(6)

(7)

 

250

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Haradem, P. S.; Cronin, J. L.; Krause, R. A.; Katz, L. Inorg. Chim.
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(a) Banda, R. M. H.; Cusick, J.; Scudder, M. L.; Craig, D. C.; Dance, I.
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Krauter, G.; Dehnicke, K.; Fenske, D. Chem—Ztg. 1990, 114, 7-9.

(a) Adams, R. D.; Wolfe, T. A.; Eichhorn, B. W.; Haushalter, R. C.
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Crystallogr. 1991, 47C, 1193—1196. (c) Wolkers, H.; Dehnicke,
K.; Fenske, D.; Khassanov, A.; Hafner, S. S. Acta Crystallogr.
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McConnachie, J. M.; Ansari, M. A.; Ibers, J. A. J. Am. Chem. Soc.
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McConnachie, J. M.; Ansari, M. A.; Ibers, J. A. Inorg. Chim. Acta
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Miiller, A.; Schmitz, K.; Krickemeyer, E.; Penk, M.; Bégge, H.
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McConnachie, J. M.; Ansari, M. A.; Ibers, J. A. Inorg. Chem.
1993, 32, 3250—3255.

Sillanpaa, R.; Cartwright, P. S.; Gillard, R. D.; Valkonen, J.
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Ansari, M. A.; Ibers, J. A. Inorg. Chem. 1989, 28, 4068—4069,

Schmidt, V. M.; Hoffman, G. G. Z. Anorg. Allg. Chem. 1979, 452,
1 12—122.

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CHAPTER 6

THE USE OF SOLUBLE METAL POLYCHALCOGENIDES AS LOW
TEMPERATURE PRECURSORS TO NANOCRYSTALLINE
BINARY AND TERNARY METAL CHALCOGENIDES

253

 

 

 

254

ABSTRACT

The molecular polychalcogenide complexes [M(Se4)2]2‘ (M: Cd,
Hg, Mn), [Sn(Se4)3]2', and [Hg(Te4)2]2' can be converted to the
corresponding binary semiconductor compounds. DMF solutions of
these complexes react with chalcogen—abstracting reagents such as
CN' and (n—Bu)3P to yield the corresponding binary metal
chalcogenide compounds at 155 °C or less. Depending on the metal
precursor complexes, chalcogen—abstracting reagents, and the
reaction conditions, the particle size of the binary metal chalcogenide
varies from nanometer—size to the bulk regime. Quantum confined
CdSe, bulk or nanometer-sized HgSe, SnSe, and HgTe were prepared
and characterized by XRD, TEM, SEM, and UV/Vis spectroscopy. This
chalcogen—abstracting method produces pure metastable y—MnSe.
When appropriate stoichiometric mixtures of [Cd(Se4)2]2' and
[Mn(Se4)2]2' were employed, solid solutions of Cd1_anxSe (0<x<l)
were obtained over the whole range of x. The Cd1_anxSe solid
solutions, including y—MnSe, have hexagonal wurtzite type structures.
Their unit cell parameters show a linear relation to composition,
obeying Vegard’s law. The particle sizes of Cd1-anxSe depend on
composition (i.e. x) and range from 60 to 450 A. These nanometer—
sized Cd1_anxSe solid solutions exhibit paramagnetic behavior at
temperatures over 40 K. A magnetic transition to a spin-glass state
occurs at various temperatures below 40 K, depending on x.
Interestingly, the pure y—MnSe “as produced” shows a paramagnetic
behavior without a magnetic transition. The y—MnSe converts to the

more stable a—form when annealed above 300 °C.

 

 

 

INTRODUCTION

A molecular approach for the syntheses of solid state
compounds is currently a field of intense investigation.1 The main
impetus in this field is driven by the demand for either new
materials with novel properties or existing materials fabricated in
special forms such as thin film and extremely small particles.

Solid state binary or ternary metal chalcogenides enjoy such
wide practical applications as IR detection and imaging (e.g. Hg1-x-
Cdee),2 electroluminescent devices (e.g. ZnS, CdSe),3 optoelectronics
(e.g. Tl3AsSe3),4 solar cells (e.g. CuInSe2),5 and high energy density
rechargeable batteries.6 Up to now most of these materials were
prepared in bulk at high temperatures.

A sizable number of molecular metal polychalcogenide
complexes are now available largely due to the extensive synthetic
efforts of our group and elsewhere during the last decade.7 While
the properties of these complexes are beginning to be probed, their
potential as precursors for the low temperature syntheses of
corresponding binary metal chalcogenides has not been explored.
We demonstrate here that the soluble metal polychalcogenide
complexes (e.g. [M(Se4)2]2' (M: Cd, Hg, Mn), [Sn(Se4)3]2', and
[Hg(Te4)2]2' ) can be excellent non—pyrolytic, low temperature
precursors to important binary and ternary solid state
semiconductors in a nanocrystalline form. This method is proven to
be a convenient route for the preparation of y-MnSe with the
wurtzite structure and DMS (dilute magnetic semiconductor)

materials of Cd1_anxSe solid solutions. The latter are of both

 

 

 

 

”—

256

scientific and technological interest because their electronic, optical,
and magnetic properties vary widely depending on the concentration
of x.8 The study of these properties and their possible applications
have been limited by the fact that pure single phase materials can be
produced in only a rather limited range of x by the conventional high

temperature direct synthesis.

EXPERIMENTAL SECTION

Reagents

The chemicals in this research were used as obtained without
further purification. Mercuric chloride, analyzed reagent, J. T. Baker
Inc., Phillipsburg, New Jersey; Cadmium(II) chloride (99%),
Tetraethylammonium bromide (98%), n—Tributylphosphine (98%),
and KCN (97%) were from Aldrich Chemical Company Inc.,
Milwaukee, Wisconsin. K28e4 and K2Te4 were prepared by dissolving
the stoichiometric amounts of the elements in liquid ammonia, as
described in Chapter 2. Methyl iodide (98% purity) was from J. T.
Baker Inc., Phillipsburg, New Jersey. DMF (A.C.S. grade, EM Science,
Gibbstown, New Jersey) was distilled under reduced pressure after
being stored over KOH for more than a week and over 4A Linde
molecular sieves for several days. CH3CN (A.C.S. grade, EM Science,
Gibbstown, New Jersey) was distilled after refluxing over CaH2 for
several hours. Diethyl ether (A.C.S. anhydrous, Columbus Chemical

Industries Inc., Columbus, Wisconsin) was distilled after refluxing

 

257

over potassium metal in the presence of benzophenone and

triethylene-glycol-dimethyl ether for several hours.

Physicochemical Methods

XRD (X—ray Powder Diffraction) patterns were obtained on
either a Phillips XRG—3000 computer—controlled powder
diffractometer or a Rigaku—Denki/RW400F2 (Rotaflex) rotating anode
powder diffractometer. Ni—filtered, Cu radiation was used at the
condition of 35 KV, 35 mA for the Phillips XRG—3000 and 45 KV, 100
mA for the Rigaku—Denki/RW400F2 (Rotaflex). The sample was put
on a glass slide using a double—sided sticky tape. The observed X-ray
powder patterns were in good agreement with those given in the
JCPDS Powder Diffraction File.9 The crystallite particle size was
determined from the half width of peaks in the XRD patterns, using

the Scherrer formula:

_ K x
6172 c036

where D is the average particle size (A), K is a constant related to the
crystallite shape (0.9 was used here on the assumption that the
crystallites are in perfect spherical shape), A is the wavelength of
radiation (Cu Ka=l.542 A), [51/2 is the half width of peak (radian),
and 0 is the Bragg angle (deg). A quartz standard was used to correct
for instrumental peak broadening.

Magnetic susceptibility measurements were performed on a
MPMS Quantum Design SQUID (Superconducting QUantum

Interference Device) magneto—susceptometer over the temperature

 

 

 

258

range 2-300 K. Powder and pressed pellet samples of Cd1_anxSe
were placed, under N2 atmosphere, in plastic bags which were sealed
thereafter with a thermal press. For the extremely air-sensitive
powder samples of y—MnSe and Cdo,2Mno,3Se, quartz tubes were used
and sealed with a flame. In each case the sample was cooled first
from 300 to 2 K in a zero magnetic field, and then after applying a
field of 100 G the magnetic susceptibility was measured, as the
temperature was increased to 300 K. The measurement was
repeated after cooling with an applied field of 100 G, to yield another
data set. These two runs measure the zero field cooled (ZFC) and the
field cooled (FC) dc magnetic susceptibility.

UV/Vis/Near—IR diffuse reflectance spectra were obtained as
described in Chapter 4. The reflectance data were converted to

absorbance data with the Kubelka—Munk equation:10

a/S = (I—R)2/2R

where a is the absorption coefficient, S is the scattering coefficient,
and R is the reflectance at a given wavelength. The bandgap energy
value of Cd1_anxSe was considered the value where the Energy axis
meets the line extrapolated from the linear portion of the absorption
edge in a (oz/S)2 vs Energy plot. Here (oz/S)2 was used instead of
(or/S), since Cd1_anxSe samples are well known direct bandgap
materials.

Scanning electron microscopy (SEM) and semi—quantitative
microprobe analysis were performed on a JEOL JSM—35C equipped
with a Tracor Northern TN 5500 X—ray microanalysis attachment.

Detailed experimental procedures and conditions are described in

 

 

259

Chapter 2. The calibration factor for a Cd/Mn elemental ratio was
determined to be 1.38 by using a homogeneous 1:1 stoichiometric
mixture of CdClz and Mn(CH3COO)2 which was obtained by
evaporating the solvent from an aqueous solution of the mixture.

Transmission electron microscopy (TEM) and selected area
electron diffraction (SAED) studies were performed on a JEOL—100
CX(II). Samples were dispersed in ether and sonicated for about 2
min. These samples were deposited on holey film-coated copper
grids by dipping the grids into the sample containing solution for a
few seconds. D-spacings obtained from the SAED diffraction pattern
were further calibrated with an aluminum standard.

UV/Vis spectra for the CdSe particle growth monitoring
experiment were recorded on a Varian Cary-2300 spectrometer. A
DMSO solution of [Cd(Se4)2]2‘ and (n—Bu)3P in a stoichiometric ratio of
1:6 was put in a quartz UVNis cell. The concentration of [Cd(Se4)2]2'
in the solution was 5.0x10'3 M. The quartz cell was placed in the
preheated oil bath for specified time periods. The reported

temperature is that of the oil bath.

Synthesis

All experiments and manipulations were performed under an
atmosphere of dry nitrogen by using either a Vacuum Atmosphere
Dri—Lab glovebox or a Schlenk line. Precursor metal
polychalcogenide complexes were prepared by following the
procedure reported previously.11 The Et4N+ salts could be obtained

just by using Et4NBr instead of Ph4PBr in the reported procedure.

260

Preparation of CdSe, using KCN To a 100 ml DMF
solution of 0.10 g (0.10 mmol) (Et4N)2[Cd(Se4)2], 0.040 g (0.61 mmol)
KCN was added. This solution was stirred and refluxed under N2 for
6 hrs. The reddish brown solution became green, then light yellow,
and finally dark brown upon reflux. A dark brown precipitate was
observed one hour after the solution began to reflux. The brownish
black powder was isolated by filtration with a frit of fine pore size.
This product was washed with DMF and ether and dried in vacuo.
The yield was 90%. A semiquantitative analysis on the product by
using the SEM/EDS technique gave the Cd:Se atomic ratio as
1.00:1.05.

Preparation of CdSe, using (n-Bu)3P To a stirred 120
ml DMF solution of 0.20 g (0.20 mmol) (Et4N)2[Cd(Se4)2], 0.30 ml
(0.24 g, 1.20 mmol) (n—Bu)3P was added dropwise with a syringe.
Upon addition of (n—Bu)3P, the reddish brown solution turned to
greenish brown, green thereafter, and finally light yellow. This
solution was refluxed under N2 for 6 hrs. A dark brown colloidal
precipitate was observed within 30 min after the solution began to
reflux. The dark brown powder was isolated by centrifuging and
filtering with a frit of fine pore size. This product was washed with a
minimum amount of DMF and ether and dried in vacuo. The yield
was 85%. A semiquantitative analysis on the product by using the

SEM/EDS technique gave the Cd:Se atomic ratio as 1.00:1.04.

Preparation of HgSe, using KCN To a 100 ml DMF
solution of 0.20 g (0.18 mmol) (Et4N)2[Hg(Se4)2], 0.075 g (1.15 mmol)

 

261

KCN was added. This solution was stirred and refluxed under N2 for
6 hrs. The reddish brown solution became light brown, then grey,
and finally greyish black upon reflux. A greyish black precipitate
was observed one hour after reflux started. The precipitate was
isolated by filtration with a frit of fine pore-size, washed with DMF
and ether, and dried in vacuo. The yield was 80%. A
semiquantitative analysis accomplished by the SEM/EDS technique

gave the Hg:Se atomic ratio as 1.00:1.08.

Preparation of HgSe, using (n-Bu)3P To a 50 ml DMF
solution of 0.100 g (0.092 mmol) (Et4N)2[Hg(Se4)2], 0.14 ml (0.11 g,
0.56 mmol) (n—Bu)3P was added. Upon addition of (n—Bu)3P, the
color change was similar to that observed in the preparation of CdSe.
To the above solution 0.012 ml (0.027 g, 0.019 mmol) CH3I was
added. As soon as the CH3I was added, black colloidal precipitates
formed. The black powder was isolated by filtration through a frit of
fine pore size. This product was washed with DMF and ether and
dried in vacuo. The yield was 85%. A semiquantitative analysis on
the product was accomplished by using the SEM/EDS technique and

gave the Hg:Se atomic ratio as 1.00:1.05.

Preparation of SnSe, using KCN To a 100 m1 DMF
solution of 0.12 g (0.068 mmol) (Ph4P)2[Sn(Se4)3], 0.044 g (0.68
mmol) KCN was added. This solution was stirred and refluxed under
N2 for 10 hours. A black precipitate was observed one hour after
reflux started. The greyish black powder was isolated by filtration

through a frit of fine pore—size. This product was washed with DMF

 

 

262

and ether and dried in vacuo. The yield was 80%. A
semiquantitative analysis on the product by using the SEM/EDS

technique gave the Sn:Se atomic ratio as 1.00:1.07.

Preparation of HgTe, using (n-Bu)3P To a 150 ml DMF
solution of 0.30 g (0.16 mmol) (Ph4P)2[Hg(Te4)2], 0.28 ml (0.23 g,
1.12 mmol) (n—Bu)3P was added. This solution was stirred and
refluxed under N2 for 10 hours. The dark brown color of the solution
became lighter upon addition of (n—Bu)3P. A black precipitate was
observed one hour after the solution began to reflux. The black
powder was isolated by filtration through a frit of fine pore size,
washed with DMF and ether, and dried in vacuo. The yield was 60%.
A semiquantitative analysis on the product was accomplished by
using the SEM/EDS technique and gave the Hg:Te atomic ratio as
1.00:0.95.

Preparation of Cd0,5Mn0,5Se, using (n-Bu)3P To a 120
ml DMF solution of 0.300 g (0.30 mmol) (Et4N)2[Cd(Se4)2] and 0.284 g
(0.30 mmol) (Et4N)2[Mn(Se4)2], 0.95 ml (0.77 g, 3.81 mmol) (n—Bu)3P
was added with a syringe. This solution was stirred and refluxed
under N2 for 6 hours. A light orange precipitate was observed one
hour after the solution began to reflux. The light orange powder was
isolated by filtration through a frit of fine pore—size, washed with
DMF and ether, and dried in vacuo. The yield was almost
quantitative. A semiquantitative analysis on the product by using
the SEM/EDS technique gave the Cd:Mn:Se atomic ratio as
l.00:1.06:2.11.

 

 

 

’1—

263

The same procedure was used for the preparation of

Cd0_gMno,2Se and Cdo.2Mn0.3Se.

Preparation of y-MnSe, using (n-Bu)3P To a 120 ml DMF
solution of 0.501 g (0.53 mmol) (Et4N)2[Mn(Se4)2], 0.81 ml (0.66 g,
3.25 mmol) (n—Bu)3P was added with a syringe. Upon addition of (n-
Bu)3P, the reddish brown solution turned to green, pink orange
thereafter, and finally light pink. The final solution was colloidal.
This solution was stirred and refluxed under N2 for 6 hours. A milky
yellow precipitate was observed within an hour after the solution
began to reflux. The milky yellow powder was isolated by filtration
through a frit of fine pore-size, washed with DMF and ether, and
dried in vacuo. The yield was 78%. A semiquantitative analysis on
the product by using the SEM/EDS technique gave the Mn:Se atomic
ratio as 1.00:0.94.

 

 

 

 

264

RESULTS AND DISCUSSION

The molecular approach to the synthesis of metal chalcogenide
semiconductors mainly involves the pyrolysis and thermolysis of
organometallic precursors, or solution synthesis through metathesis
reactions that utilize appropriate metal and chalcogenide reagents.12
In comparison to these methods, our synthetic approach involves the
exhaustive depletion of the excess chalcogen atoms from the
chalcogen-rich metal polychalcogenide complexes. The structures of
the complexes used in this study are shown in Figure 6.1. It is well
known that CN' and R3P can easily abstract chalcogen atoms from
polychalcogenide chains with the formation of QCN' and R3PQ (Q=S,
Se, Te), respectively.13 The removal of all zero-valent chalcogen
atoms could result in the formation of coordinatively unsaturated
intermediates which are extremely unstable and thus polymerize
themselves in three dimensions to build up an extended lattice, as
illustrated in Scheme (1). The by—products, QCN‘ and R3PQ (Q=S, Se,
Te), are soluble in a number of solvents and can be readily removed.
Polar organic solvents such as DMF, CH3CN and DMSO were chosen in
this reaction, largely due to the solubility of metal polychalcogenide
precursors. In most cases, reflux conditions were applied to produce
the crystalline semiconductors which can be easily characterized by
XRD. However, the reaction temperature and time could be varied to

arrest the growth of the crystallite at a certain size.

 

 

265

’o/Q\MM,..(Q\Q- 2‘

6 / \Q,C$

. \Q ..

 

 

(M = Cd, Mn, Hg, Zn; Q=S, Se, Te)

 

 

 

Figure 6.1. Schematic representation for the structures of
[M(Q4)]2' and [Sn(Se4)3]2' precursor complexes.

 

 

 

 

266
F O ' 2 ' 2 -
/ _ o
(\3 \M...«~\“‘Q\lo 6(n-Bu)3P (or scN) ’ M/ + 6(n-Bu)3PQ
o\Q/ \o—o Q’ (or BQCN')
L _

 

 

reacfive
intermediate

.1 + 02'

semiconductor
crystallites

Scheme (I)

CdSe crxstallites
CdSe was prepared from [Cd(Se4)2]2', by using CN‘ and (n-Bu)3P

as Se abstracting reagents, as shown in eq. (6.1).

[Cd(Se4)2]2- + 6KCN (or 6(n—Bu)3P) %>

CdSe + 6KSeCN (or 6(n-Bu)3PSe) + 8e2- -------- eq. (6.1)

Both reagents gave the hexagonal, wurtzite structure type of CdSe, as
evidenced by the XRD patterns (see Figures 6.2 and 6.3).
Interestingly, the average particle size of CdSe is 150 A when CN-
was used, but only 60 A when (n—Bu)3P was used. The particle sizes
were determined by applying the Scherrer formula to the (110)
peaks in the XRD patterns. Similar particle sizes resulted when other

hkl peaks were used. TEM micrographs of the CdSe particles,

 

267

 

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produced by using (n—Bu)3P, confirms their 60 A size, see Figure 6.4.
SAED (Selected Area Electron Diffraction) patterns on these particles
verify the hexagonal wurtzite structure type (see Figure 6.5). Here it
is noteworthy that the particle size of a certain compound can be
varied by employing different chalcogen abstracting reagents. In
general, (n-Bu)3P yields smaller particles than CN'. This could be
ascribed to the better mineralizer effect of KCN than (n—Bu)3P.

The growth of CdSe crystallites can be monitored by UV/Vis
spectroscopy as shown in Figure 6.6. The UV/Vis spectra were
measured on the DMSO solution of [Cd(Se4)2]2' treated with (n—Bu)3P,
at intervals while increasing the temperature. The final light brown
solution still remained clear and no precipitates formed, unlike the
reaction in DMF where precipitates formed under reflux condition.
The shift of the absorption edge toward lower energies upon
increasing temperature and reaction time can be explained with a
quantum size effect and it is similar to the one observed for the
quantum—confined CdSe particles prepared via other methods”,15
The absorption edge in the spectrum of the final solution occurs near
610 nm (2.0 eV), a slightly higher value than the bandgap energy of
bulk CdSe (1.7 eV). This suggests that the final product remaining
soluble in DMSO would be still quantum—confined CdSe particles,
whose size might be less than 60 A. For comparison, the 60 A size
CdSe particles obtained from the reaction in DMF are not soluble in
DMSO. There are three absorption peaks at 377, 410, and 430 nm in
the spectra of the early stage solutions. At this point they can not be

assigned for sure, but are possibly due to exciton transitions

 

270

 

Figure 6.4. TEM micrograph of the CdSe particles obtained
using (n-Bu)3P as a chalcogen abstracting reagent.

 

 

 

271

 

Figure 6.5. SAED (Selected Area Electron Diffraction) pattern of
the CdSe particles obtained using (n-Bu)3P as a chalcogen abstracting
reagent.

 

Absorbance

 

 

 

 

 

 

377 nm
(410 nm
lst 25 °C
2nd 80 °C
3rd 100 °C
- . 4th 120 °C
\M 5th 140 °C
§'\ 6th 160 °C
N o
\ 430 ,m 7th 170 C
\, / 8th 170 0C
"4} 9th 170 0C
\
p9th
lst
400 500 600 700
Wavelength (nm)
Figure 6.6. Evolution of the CdSe particle growth in DMSO

solution monitored by UV/Vis spectroscopy.

 

ll'i

273

in very small CdSe particles. The UV/Vis spectra of the quantum
confined CdSe particles, which were prepared by the reaction of Cd2+
and Se(SiMe3)2 in the inverse micellar medium, do not show such

absorption peaks.14(d),(e)

HgSe crystallites

The HgSe crystallites also could be prepared using CN' or (n-
Bu)3P from [Hg(Se4)2]2' complexes. Under the reflux condition
micrometer—sized bulk HgSe was obtained when CN' was used. The
XRD pattern shows that it is the cubic, zinc blende structure type of
HgSe (see Figure 6.7). The sizes of the bulk HgSe crystallites are in
the micrometer range, as shown in its TEM micrograph (see Figure
6.8). Interestingly, under the similar reflux condition with (n-Bu)3P,
no precipitate was produced. The small "embryo" HgSe particles,
formed upon addition of (n—Bu)3P, did not grow to large crystallites
while the temperature was being increased to reflux. It came to our
attention that if we passivate the surface of the "embryo" HgSe
particles which might have some dangling Se atoms and thus are
negatively charged, the neutral HgSe particles will form and
precipitate out from solution. We employed CH3I to passivate the
negative charge on the surface of the "embryo" HgSe particles. This
process is shown in Scheme (11). Upon addition of CH3I to the clear
light yellow solution, after treatment with (n—Bu)3P at r.t., a black
precipitate was immediately produced. Eq (6.2) shows the balanced

equation for this reaction.

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KCN as a chalcogen abstracting reagent.

276

Et4N+ CH3
- +
Se _Et4N Se /CH3
Et N+_ Se CH3 Se
4 s \s-
- - CH 1
151410+ Se Se [51410+ ‘53—» CH3—Se Se—CH3
Se- Se
-e+ Et4N+ 19 \CH
Et4N CH3 3
Scheme (II)
[Hg(Se4)2]2‘ + 6(n—Bu)3P +2CH3I ?—tMF>
HgSe + 6(n—Bu)3PSe + (CH3)2Se + 21' ------ eq. (6.2)

As shown from the XRD pattern in Figure 6.9, these HgSe particles
are also a cubic, zinc blende type phase, but in much smaller size (ca.
80 A), compared to those obtained by using CN'. The similar surface
passivation of quantum—confined CdSe particles was recently
reported by Steigerwald et al.14(d),(e) When RSeSiMe3 was added to
the micelle—encapsulated, Cd—rich "embryo" CdSe particles, the RSe
group coordinated to the particles and yielded the species capped
with the R group. These particles were readily isolated as
precipitates from the inverse micellar medium and found to be
soluble in organic donor solvents such as pyridine. Our methyl group
capped HgSe particles are not soluble in such solvents including
ethylenediamine, probably due to their relatively large particle size

and the small size of capping methyl groups.

 

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SnSe and HgTe crystallites

In a search for other accessible binary metal chalcogenides
applying the chalcogen abstracting method, we found that SnSe and
HgTe could be also produced from their polychalcogenide precursors,

as shown in eq. (6.3) and (6.4), respectively.

[Sn(Se4)3]2' + 10KCN ng—UME> SnSe + lOKSeCN + 862- ------- eq. (6.3)

[Hg(Te4)2]2- + 6(n—Bu)3P %

reflux

HgTe + 6(n-Bu)3PSe + Sez‘ -------- eq. (6.4)

The SnSe crystallite was characterized by its XRD pattern to be the
GeS structure type, as shown in Figure 6.10. We also attempted to
stabilize SnSe2 using 9 equivalents of CN' or (n-Bu)3P, without
success. In addition, the SnSe crystallite could not be prepared when
(n-Bu)3P was used as a chalcogen abstracting reagent.

As characterized from the XRD pattern in Figure 6.11, the HgTe
represents the cubic zinc blende structure type. The preparation of
HgTe crystallites might be an good indication that the chalcogen
abstracting method for the synthesis of metal chalcogenide
compound semiconductors would not be limited to Se, but could be
expanded to S and Te. Table 6.1 shows the summary of all the
binary and ternary metal chalcogenides prepared so far by the

chalcogen abstracting method. It includes CuSe and CuInSe2 which

were also prepared in our lab.16

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Table 6.1 Binary and Ternary Metal Chalcogenides Prepared by

Using the Chalcogen Abstraction Method.

 

 

Compound Structure Precursor Reagent Particle
type size (A)
CdSe Wurtzite [Cd(Se4)2]2‘ (n-Bu)3P 6 0
KCN 150
HgSe Sphalerite [Hg(Se4)2]2‘ (n—Bu)3P 100
KCN 10,000(a)
CuSe(b) CuS type [CU4(Se4)3]2‘ (n-Bu)3P 240
KCN 450
SnSe GeS type [Sn(Se4)3]2' KCN 1,000(a)
MnSe Wurtzite [Mn(Se4)2]2' (n-Bu)3P 450
HgTe Sphalerite [Hg(Te4)2]2' (n-Bu)3P 5,000(a)
CuInSe2(b) Chalcopyrite [CU4(SC4)3]2’ (n-Bu)3P 100
& [In38e1513-
KCN 5,000(3)
Cd1_anxSe Wurtzite [Cd(Se4)2]2' (n-Bu)3P 220—450

& [Mn(Se4)2]2‘

 

All particle sizes were determined using the Scherrer formula, except
where indicated. (a) determined by TEM or SEM study; (b) ref. 16.

Cd1-anxSe and y-MnSe crystallites

 

according to the eq. (6.5).

(1-X)[Cd(Se4)2]2' + (X)[Mn(Se4)2]2‘ + 6(n-BU)3P

 

L___

precursors were used, Cd1_anxSe solid solutions

DMF.

reflux

When the appropriate mixtures of [Cd(Se4)2]2' and [Mn(Se4)2]2-

were prepared

Cd1-anxSe + 6(n-Bu)3PSe + Sez‘ ------ eq. (6.5)

As an end-member of the Cd1-anxSe solid solutions, MnSe was also

obtained from the above reaction. The XRD pattern of this MnSe

 

 

 

 

282

corresponds to that of the wurtzite structure type y-MnSe in a single
phase (see Fig 6.12).

There] are four phases of MnSe reported in the literature: a-
MnSe with the NaCl structure type (most stable form),17 fi-MnSe with
the zinc blende structure type,18 y-MnSe with the wurtzite structure
type,13(a) and o-MnSe with the NiAs structure type (high pressure
form).19 The y-MnSe phase was first prepared by the reaction of
HgSe and MnC12 in aqueous ammonia solution.18(a) However, other
groups reported that this synthetic approach could not be
reproduced and yielded the y—MnSe only as a minor constituent with
the major product fi-MnSe.18(b) As a result little is known about this
material. The magnetic properties of all MnSe phases are of
particular interest due to the various Mn2+ spin-spin interactions and
their magnetic structures.18(b),20

The known high temperature direct synthesis method can only
yield Cd1_anxSe solid solutions in the hexagonal, wurtzite structure
type where 0<x<0.5, and in the cubic, NaCl structure type where
0.95<x<1.8 In the intermediate composition regime (O.5<x<0.95),
phase separation occurred between the wurtzite and NaCl structure
type phases. Figure 6.13 shows the phase diagram of Cd1_anxSe
solid solutions.“ Our molecular polychalcogenide—based synthetic
approach produced Cd1-anxSe solid solutions with the wurtzite
structure type over the whole range of x, unlike those prepared by
the high temperature method. These Cd1_anxSe are nanometer—
sized particles with a mean diameter of 220—350 A, where the
nominal values of x=0.2, 0.5, and 0.8. Structure and particle size

determinations were accomplished by powder XRD while the nominal

 

 

 

 

283

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. "Roch.300
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0
dl200 "
‘1’
«1100 2
_ Wurtznte and 2
Wurtzute rock solt “'000 g
— . 900 S
.—
" -‘ 800
L- O -+ 700
m 1 n 1 L 1 1 1
1.0 0.8 0.6 0.4 0.2 0.0
CdSe Mole Fraction x MnSe
Figure 6.13. The phase diagram of the CdSe—MnSe system

(adopted from ref. 21).

 

 

 

285

Mn concentration was verified by using the SEM/EDS technique.
Figure 6.14 shows a series of the XRD patterns of Cd1_anxSe,
demonstrating the retention of the wurtzite structure up to x=1 and
the increase of average crystallite size upon increasing Mn content.
The latter property was unexpected and is consistent with our other
observations that the particle sizes achievable under identical
reaction conditions strongly depend on the metals involved. Among
the end-members, CdSe and MnSe, the latter grows into larger
crystallites.

The a- and c— lattice parameters of Cd1-anxSe were plotted as
a function of x in Figure 6.15. The straight line confirms that this
solid solution follows Vegard's law and it is in complete agreement
with literature values reported for bulk samples where x<0.5. Upon
compacting the nanometer-sized particles into pellets and annealing
them at 600 °C, the crystallite sizes became comparable to those of
bulk materials. Where x>0.5, in addition to the growth of crystallite,
a-MnSe appeared as a separate phase. Even without being
compacted to pellets, pure y-MnSe particles converted completely to
the or phase upon heating at 300 °C. The y-MnSe is extremely air—
sensitive and its milky yellow color turns to black immediately upon
exposure to air. TGA results for the y—MnSe are shown in Figure 6.16.
The weight gain (ca. 18%), occurred in the temperature range 150-
380 °C, was caused by the uptake of oxygen to give an intermediate
with a composition of MnSeO1,5. This intermediate might be a
mixture of elemental Se and amorphous Mn203, as its XRD pattern
shows only a crystalline phase of elemental Se. The elemental Se

was lost in the temperature range of 450—590 °C to yield y-Mn203 as

 

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ti

 

 

250 A

x=0.2 W/L' 220A
x=0.0 60A

V I V

40.0 451.0 50.0 55.0
26 (deg)

 

 

«t

Figure 6.14. X—ray powder diffraction patterns for a series of
Cd1-anxSe solid solutions. Their particle sizes, as determined using
Scherrer formula, are shown next to each pattern.

 

 

287

 

7.00

O

c axis (A)

6.95

6.90

6.85

 

 

 

 

l
0.0 0.2 0.4 0.6 0.8 1.0

composition (x)

   
 

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a axis (A)

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lel

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0.4 0.6 0.8 1.0

composition (x)

O
O
O
N

Figure 6.15. Plot of (A) a- and (B) c- lattice parameters of cm.
anxSe solid solutions as a function of x.

 

Weight Loss (%)

 

288

 

130
120—1
110—.
1005
90-1
80-4
70-

60-

 

50

 

 

 

Figure 6.16.

i l l
2 0 O 4 O O 6 0 0
Temperature(0 C)

TGA diagram of y-MnSe.

i
800

1000

*7:

289

the final decomposition product.

The bandgap energies of the nanometer—sized Cd1_anxSe solid
solutions were determined by diffuse reflectance spectroscopy.
Figure 6.17 shows the optical absorption spectra of these solid
solutions at various compositions. Upon increasing the Mn content
the absorption edge moves to higher energies. As shown in Figure
6.18, the bandgap energies of Cd1_anxSe solid solutions vary
linearly with the composition. The linear equation, fitted by the least
squares method, is Eg(eV)=1.68+0.92x, which is comparable to the
reported value of 1.70+1.08x.22 This is the first time the bandgap
energy has been measured over the whole range of x in this system.
The previously reported values are extrapolated from those
measured on the Cd1_anxSe where x<0.5.

The study on the nanocrystalline Cd1_anxSe was motivated by
two different but related aims: (a) the production of pure wurtzite
phase material over the whole range of Mn concentration and the
study of magnetic (and other) properties of this new material, (b) the
need to know how the magnetic properties of these nanometer—sized
DMS materials depend on particle size. In View of the latter goal, of
particular interest is how the critical temperature, at which the
system goes from a paramagnetic to a spin glass state (Tf), or to an
antiferromagnetic state (Tn), depends on the particle size. Bulk Cd1_
anxSe (0<x<0.5) materials in the wurtzite structure type show a
magnetic phase transition from a paramagnetic to a spin glass state
in the temperature range 0< T <20 K,8 while pure a—MnSe shows an
antiferromagnetic transition between 145 and 170 K.20

It has been reported that in bulk samples of Cd1_anxSe

 

 

 

 

 

 

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Energy (eV)

Figure 6.17. Optical absorption spectra of Cd1_anxSe solid
solutions.

 

 

291

 

28 LIIL_LllLi_L_JlL#_LlJJI

 

 

 

 

Figure 6.18. Plot of bandgap energies of Cd1-anxSe solid
solutions as a function of x.

 

292

(0<x<0.5) the ZFC (zero field cooled) susceptibility exhibits a peak at
(or very near) the spin glass freezing temperature (Tf). The behavior
of the FC (field cooled) susceptibility is more complex, but normally
shows an inflection point at the Tf temperature. The Tf values for
the nanometer-sized ("as produced") and annealed samples of Cd1_
anxSe (x=0.2, 0.5, 0.8, and 1.0), as obtained from the ZFC and FC
susceptibility measurements, are summarized and compared with
those for bulk samples in Table 6.2. The magnetic behavior of the
annealed samples of Cd1-anxSe (x=0.2, 0.5) approaches that of bulk
samples. One important qualitative observation is that the Tf of

nanocrystallites are smaller than those of the bulk samples.

Table 6.2 Magnetic Freezing Temperatures for Various Cd1_anxSe.

 

 

Compound Fresh Annealed Bulk
nanocrystallites pellets samples(a)

Cd0.3Mn0.2Se(b) Tf < 2 K Tf < 2 K Tf = 2 K

Cdo.79Mno.2ISe(C)

Cd0,5Mn0,5Se(b) 5 < Tf < 14 K Tf = 17 K Tf = 20 K

Cd0.48MnO.5256(C)

Cd0.2Mno,8Se(b) 8 < Tf < 35 K NA NA

Cd0.21Mn0.79Se(C)

y—MnSe Tf ~40 K(d) NA NA

 

NA: Not Available; (a) reference 8; (b) nominal stoichiometry; (c)
observed stoichiometry; (d) after annealing up to 110 °C.

Figure 6.19 shows ZFC (Zero Field Cooled) and FC (Field Cooled)
magnetic susceptibility data of y-MnSe. Before y—MnSe is annealed, it
exhibits a paramagnetic behavior without a transition to a spin-glass

state. Upon annealing at 110 °C for several hours, it becomes a spin—

 

 

 

293

EN
E
110°C
)-

I-
» 130 °c

A 150 °c

._ w ‘ 300 °c-

L . 1 L L L A 1 . L 1

o 100 200 30.0

f 3 rfiTVT'If"

Magnetization (Arbitrary unit)

r‘fi'l'l T Y

VfYT ‘T

 

W

Temperature (K)

Figure 6.19. Variable temperature magnetic susceptibility data
for y-MnSe annealed at various temperatures. In each case with the

annealing temperature shown, a top graph represents the FC (Field
Cooled) susceptibility and a bottom one the ZFC (Zero Field Cooled)
susceptibility.

 

 

 

—7—

294

glass with a freezing temperature (Tf) of ~ 40 K. Upon further
annealing at 300 °C it transforms to aeMnSe and shows an
antiferromagnetic transition with a Neel temperature at ~120 K,
which is close to the value reported for bulk a-MnSe. The annealed
product, a-MnSe, was confirmed by XRD. Interestingly, y—MnS, which
possesses the same wurtzite structure type as y-MnSe, is reported to
be antiferromagnetic with a Neel temparature of ~100 K. Considering
this, the spin-glass behavior of our y—MnSe is unique. It is probably
due to its small crystallite size and/or defects in the crystal lattice.
To better understand the magnetic properties of y-MnSe and to
determine its magnetic structure, a neutron diffraction study would

be needed. Based on these results, it is clear that the magnetic

 

properties of Cd1-anxSe (x=0.2, 0.5, 0.8, and 1.0) are interesting but
also complicated and thus, a great deal of careful work is necessary

for further insight.

[I

 

—»—

(1)

(2)

(3)

(4)

(5)

(6)

(7)

 

295

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