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This is to certify that the

thesis entitled

A Vibrational Analysis of Sodium Tetrazolate:
Tetrazole Complexes of Nickel (II) and Copper (II).

presented by

Lawrence L Barber

has been accepted towards fulfillment
of the requirements for

£13.D. degree inLhemiaDgL

W.
”3 "7&5

Major professor

Date August 2, 1967

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ABSTRACT
A VIBRATIONAL ANALYSIS OF
SODIUM TETRAZOLATE: TETRAZOLE

COMPLEXES OF NICKEL(II) AND COPPER(II)

by Lawrence Lee Garber

The vibrational analysis of sodium tetrazolate was made by means
of a normal coordinate analysis calculation on the tetrazolate ion.
The symmetry of the tetrazolate anion is sz. The calculated A1 modes
are 3124, 1461, 1243, 1138 and 962 cm'l, and may be attributed to the
C-H stretch, two symmetric ring deformations, a symmetric ring breathing,
and a symmetric ring deformation, respectively. The calculated 31 modes
are 1453, 1063, 1013, and 730 cm-1, and are attributed to the C-H bend
and asymmetric ring deformations, respectively. The calculated Bz modes
and A2 mode are 910 and 456 cm-1, and 537 cm-1, respectively and are
attributed to the C-H out-of-plane wag, a ring out-of-plane bend which is
asymmetric with respect to the C2 axis and a ring out-of-plane bend which
is symmetric with reSpect to the C2 axis, respectively. The observed A1
vibrational fundamentals, determined from the measurement of the depolar-
ization ratios are 3120, 1290, 1161, and 1065 em'l. The fifth A1 mode,
1455 cm-1, was not observed in the Raman spectrum because of masking by
the asymmetric 1445 cm-1 peak...The observed B1 modes are 1445, 1023, 1015
and 702 cm-1, while, the observed B2 modes are 910 and 454 cm-1. The A2 mode

which is Raman active only was not observed experimentally.

Lawrence Lee Garber

The pale-blue complex, bis(tetrazolato)copper(II)monohydrate, is

insoluble in all common solvents. The insolubility indicates polymer
3

formation. The complex.decomposes when heated and appears from the reflectance
spectrum to octahedral and thus six coordinate.. Two bands at 328 and
315 cm”1 are attributed to CueN bonds. .The magnetic moment of 1.76 B.M.
indicates one unpaired electron.

The complexes.bis(lemethyleSetetrazolyl)nickel(II) and bis(l-cyclo-
hexyl-S—tetrazolyl)nickel(II),.are insoluble in all common solvents
(thus suggesting a polymeric structure),.decompose when heated and are

sensitive to the atmosphere.. The reflectance spectra indicate that nickel

is in an octahedral environment. -The observed d-d transitions are 8.06 x 103 cm.-1

and 14.7x'103 cm-l, and 8.33 x7103.cm-l and 14.7 x103 cm-l, respectively.

3 3
The transition, A28 3.

for-bis(lemethyl-S—tetrazo)nickel(II) and.at approximately 26.6 x 103 cm-

T1g(P),.was observed at approximately 25.0 x 103 cm"1

1

for bis(lecyclohexyle—tetrazolyl)nickel(II).. Charge transfer bands were observed
at.30.9.xi103.cm-l.for.bis(lemethyleSetetrazolyl)nickel(II) and at 35.1 x 103 cm-1
and 42.9.x7103,cm—1.for.bis(lecyclohexyl-Setetrazolyl)nickel(II). Bands were
.obaerved at 595, 456, and'298.cmfl.which may be attributed to.the Ni-C bend,

Ni-C stretch and.the.Ni—N bond,-respectively,.for bis(l-methyleS-tetrazolyl)nickel(II
The Ni—C bend at’581.cm-1 and a-band.at 316 cmf1 which may be attributed to a Ni-N
bond were observed.for.bis(l-cyclohexyl-S—tetrazolyl)nickel(II).' The observed
magnetic moments, 2.90 and 2.98.B.M., fOr bis(l-methyl-S-tetrazolyl)nickel(II) and

bis(1-cyclohexy1-5-tetrazolyl)nickel(II), respectively indicate two unpaired

electrons.

A VIBRATIONAL ANALYSIS OF
SODIUM TETRAZOLATE: TETRAZOLE

COMPLEXES OF NICKEL(II) AND COPPER(II)

By

Lawrence Lee Garber

A THESIS

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

'DOCTOR OF PHILOSOPHY
Department of Chemistry

1967

Acknowledgment

The author gratefully acknowledges Professor Carl H. Brubaker, Jr.
for his guidance, patience and encouragement; and to his wife, Carolyn,
whose understanding, assistance and reassurance made this dissertation
possible.

The author wishes to express thanks to Dr. L. B. Sims for his
aid in supplying the vibrational analysis program and for his assistance
in regards to the interpretation of the vibrational analysis data;
to Mr. Hans Sachse, who improved the original version of the vibrational
analysis program.

Appreciation is extended to Professor Robert C. Taylor and
Mr. Harlen Clark, University of Michigan, for the Raman spectra,
and to Dr. C. Van Hall, Dow Chemical Company, for the reflectance
spectra.

Financial assistance from the National Institutes of Health is

gratefully acknowledged.

ii

II.

III.

Table of Contents

Historical. O O C O O O ....... O ..... O O O O O O O ..... O ....... .
Theoretical O C O C O ..... O O O O O O O O O O O O C ...... O O O ..... O O C
A. Basic Principles of Infrared and Raman
Spectroscopy. O O O ..... O O O I O O O O O O O O O O C O ..... O O O O O
B. Vibrational Analysis (Normal Coordinate
Analysis)... ..... . ..... . ........ . ........ ......
Experimental ....... ... ..... . .......................
A. Purification Of SCI-vents I O O O O O O O C O O O O O O O O O O O O O O

B.

Preparation of Tetrazoles and Related
compoundSOO..........OOOOOOOOOOOOOOOOO00......O

Hydrazoic Acid.................................
N—cyclohexylformamide..........................
1-methyltetrazole.......... ...... ..............
l-phenyltetrazole............... ..... ..........
1—cyclohexy1tetrazole..........................
Tetrazole......................................

Sodium Tetrazolate Monohydrate.................

Preparation of Metal Compounds Reactants.......
Nicke1(II) chloride............................
Iron(II) chloride..............................
Dichlorobis(triethylphosphine)nickel(II).......

Preparation of Compounds............ ......... ..
Bis(tetrazolato)copper(II) monohydrate.........
l-methyl-S-tetrazolyllithium~1/2THF............
Bis(l-methyl-S-tetrazolyl)nicke1(II)...........
Bis(1-cyclohexy1-5-tetrazoly1)nicke1(II).......

Attempted Preparation of
bis(1-pheny1-5-tetraZOJ-y1)n1Cke1(II) o o o o o o o o o O O

Attempted Preparation of
bis(1-methy1~5-tetrazoly1)iron(II). o o o o o o o o o o o 0

iii

9

14

23
23

23
23
23
24
26
26
28
28

33
33
33
34

34
34
34
36
37

37

37

E. Analytical Methods.............................

Nickel Determination.. ............

Iron Determination.............................

Copper Determination.... ....... ................

cyanide Determination.....OOOOQOO......00......

Carbon, Hydrogen and Nitrogen Analyses... ..... .

F. Purification of Nitrogen Gas......

G. Spectroscopic Techniques..........

H. Magnetic Susceptibility Measurements.. ..... ....

IV. Vibrational Analysis Calculation

(Normal Coordinate Analysis)..........

V. Results and Disc0881onocooooooooocooooooooooooooooo

A. Normal Coordinate Analysis Calculation for
sadim TetraZOIateOOOO......OOOOOOOOOOIOOOOO...

B. syntheseBOOOOOOOOO.........OOOOOOOOOOOOO0......

Bis(tetrazolato)c0pper(II) monohydrate.........
l-methyl-S-tetrazolyllithium-l/2THF............
Bis(l-methyl-S-tetrazolyl)nickel(II)...........
Bis(l-cyclohexyl—S-tetrazolyl)nicke1(II).......

References.................OOOIOOOOOOOOOOO

iv

page
38
38
39
39
39
40

4O

40

42

43

63

63
73
73
78
83

96

Table

II.

III.

IV.

VI.

VII.

VIII.

IX.

XI.

XII.

XIII.

XIV.

XVII.

List of Tables

page
Infrared Spectrum of l-methyltetrazole from 100 to
5000 cm—IOOO ..... 000 0000000000000 00000 OOOOOOOOOOOOOOOOOOOOO 25
Infrared Spectrum of l-phenyltetrazole from 100 to
5000 cm—1000000000 ...... 0 ........ 0 OOOOOOOOOOOOOOOOOOOO 00000 27
Infrared Spectrum of l-cyclohexyltetrazole from 100—
5000 CHI—1 ........ 0 000000000000 00000 ..... 0000000000 000000000 29
Infrared Spectrum of Tetrazole from 300-5000 cm"1 ...... .... 30
Infrared Spectrum of Sodium Tetrazolate Monohydrate
from 300-5000 cm_10.0000..000000.0000000000000000000. 000000 3].

Raman Spectrum of Sodium Tetrazolate Monohydrate from
150-5000 cm-10000000000000000000000000000000000000000000000 32

Infrared Spectrum of Dichlorobis(triethylphosphine)nicke1(II)
from 650-5000 cm-100000000000000000000000000000000000000000 35

Formulae for the Computation of 2,8........................ 45
Structure Of SOdi‘m‘ TetraZOIate0000000000000000000000000000 49
Relationship between Subscripts and Internal Coordinates... 53

Representations Generated by the Internal Coordinate Sets.. 55

Symmetry Coordinates for the Tetrazolate Ion
(sz symetry)00000000000000000000.000000000000000.0.000... 56

Expressions for the Symmetrized Force Constants............ 59
values for Force Constants000000000000000000000000000000000 64

Results of the Normal Coordinate Analysis Calculation
for Sodium Tetrazolate..................................... 65

Infrared Spectrum for Sodium Tetrazolate Monohydrate
with A8818nment80000000000000000000000000000000000000000000 67

Raman Spectrum and Depolarization Ratios for
sadim TetraZOIate000000000.0000000000000000.0.0.0.00000000 68

List of Tables (continued)
Table page

XVIII. Distribution of Each Vibration Among the Cartesian
Normal coordinates000000000000000000000.0000000000000000000 70

XIX. Infrared Spectrum for Bis(tetrazolato)copper(II)
Monohydrate and Vibrational Assignment....... .............. 76

XX. Infrared Spectra of l-methyl-S—tetrazolyllithium-l/2THF
and 1-methy1tetraZOIeoooo000.00.... 000000 00000000000 0000000 80

XXI. The Electronic Absorption Spectra for Some Tetrazole
Complexes.... ....... . ...................................... 85

XXII. The Magnetic Moments of Some Tetrazole Complexes ..... ...... 86
XXIII. Infrared Spectrum for Bis(l-methyl-S-tetrazolyl)nicke1(II). 87

XXIV. Infrared Spectra for bis(l-cyclohexyl-S-tetrazolyl)-
nicke1(II) and l-cyclohexyltetrazole....................... 92

vi

1. Historical
A. General
Tetrazoles are five membered, heterocyclic ring compounds which contain
four nitrogen atoms and one carbon atom. For the structure of the parent

compound, tetrazole, with the proper numbering of the atoms refer to I.

 

Substituents on the tetrazole ring may be present at the 1 and/or the
5 positions. An extensive review of tetrazoles will not be discussed

since thorough reviews are presented elsewhere (1,2).

B. Coordination Compounds

Coordination compounds of various tetrazoles have been formed with
both nonmetals and various transition metals. Popov, B181, and Craft (3)
determined, spectrophotometrically, the formation constants of the 1:1
pentamethylenetetrazole (hereafter abbreviated PMT) complexes of iodine
monobromide, iodine monochloride, and iodine in carbon tetrachloride solution.
Only the PMT-ICI complex could be isolated in a crystalline form. Papov,
Wehman, and Vaughn (4) extended this work by investigating, spectrophoto—

metrically, the complexes of iodine monochloride with 7-methyl-,8-sec-butyl-and

BegrbutylPMT. Attempts to isolate these complexes in a crystalline

form were unsuccessful. The formation constants indicate that the above
complexes are slightly stronger than the corresponding parent PMT-1C1
complex. From infrared studies of the I-Cl stretching vibrations by
Person, Humphrey, Deskin and Popov (5) it was concluded that PMT is a
moderately strong donorand forms complexes with iodine and the inter-
halogens'investigated.

A large number of metal tetrazole coordination compounds have been
formed. Bladin (6) prepared the first silver tetrazolate complex and
silver complexes of 5-substitutedtetrazolate anions by adding hot silver
nitrate to an aqueous solution of the respective tetrazole. Olivera-
Mandala and Alagna (7) prepared a canary—yellow tetrachlorobis(l-ethyl—
tetrazole)p1atinum(IV) complex by adding platinum(IV) chloride to an
alcoholic hydrogen chloride mixture of the ligand. Herbst and Garbrecht
(8) prepared the silver complexes of 5-substitutedtetrazoles by adding
equimolar amounts of silver nitrate to solutions of sodium 5-substituted-
tetrazolates. Herbst and Mihina (9) have used silver complexes to aid
in the characterization of 5-substitutedtetrazoles. Rheinboldt and
Stelliner (10), Dister (11) and Zwikker (12) have reported the prepara-
tion of PMT-silver complexes. The stabilities of the complexes in
water were not determined. Popov and Holm (13) prepared the silver
complexes of PHI, substitutedPMTs and l-cyclohexyl-S-methy1tetrazole in
acetonitrile. The complexes were found to be unstable in water and a
large excess of ligand was needed to complex even a portion of the silver
ion present. The approximate formation constants, determined potentio-

metrically, were of the order of 102. Popov and Holm (13) determined,

polarographically, that cobalt(II), thallium(I) and cadmium ion form
extremely weak complexes (if any) with PMT, in contrast to the strong
tendency of PMT to form complexes with the interhalogens (3,4).

D'Itri and Popov (14,15) have prepared anhydrous complexes of
PMT with manganese(II), iron(II), iron(III), coba1t(II), nicke1(II),
copper(II), cepper(I), and zinc(II) perchlorates. The hydrated metal
perchlorates were dehydrated with 2,2'-dimethoxypr0pane. In all
cases except copper(I) six moles of PMT were coordinated to the
central metal ion. Six coordination was quite unexpected since all
previous metal tetrazole complexes have had only two tetrazoles per
metal ion (16,17,18,19,20,21) and since PMT is rather bhlky.
Cu(PMT)2C104 and Cu(PMT)4(ClO4)2 were also isolated. Xeray powder
patterns indicate that all six coordinated metal complexes are iso-
morphous. Magnetic susceptibility measurements indicate that the
complexes are high spin and hence that PMT is not a strong ligand,

a weakness confirmed by the visible absorption spectra. Compared
with the free ligand the infrared spectra of the complexes were
essentially unchanged.

Kuska, D'Itri and Popov (22) have observed the electron spin
resonance spectra for Mn(PMT)6(C104)2, Cu(PMT)6(C104)2 and
Cu(PMT)4(C104)2. For the M'n(PM.T)6(C104)2 complex, dispersed in
Zn(PMT)6(ClO4)2, the data indicate that the metal-ligand bonds are
91 per cent ionic with essentially octahedral symmetry. For the
copper complexes it was possible to resolve the copper nuclear
hyperfine splittings in the undiluted samples, which is unusual

since interactions between neighboring paramagnets are expected to

cause significant broadening of the lines so that only g" and gJ_
absorptions are resolvable. The symmetry for Cu(PMT)6(C104)2 is
tetragonal with the distortion from octahedral symmetry influenced
both by a local Jahn-Teller effect and lattice distortion. As would
be expected, Cu(PMT)4(C104)2 exhibits a definite tetragonal symmetry.
The capper-ligand bonds are more covalent than the manganese-ligand
bonds, an expected difference.

Brubaker (16) prepared and characterized two crystalline forms
of bis(S-aminotetrazolato)copper(II). The visible and ultraviolet
Spectra suggest coordination rather than simple salt formation. The
infrared spectrum indicates that coordination does not involve the
amino group. Spectrophotometric studies in aqueous solution gave a
formation constant of 1012. Further studies showed similar behavior
with tetrazole, S-phenyltetrazole and 1-ethy1tetrazole. A very weak
complex is formed between copper(II) ion and 1,5-dimethyltetrazole
which, together with relative instability of the silver PMT complex
(13), indicates that a replaceable ring hydrogen is necessary for
stable complex formation.

Daugherty and Brubaker (17,18) prepared various bis(5-substi-
tutedtetrazolato)copper(II) and nickel(II) complexes by mixing aqueous
or alcoholic solutions of the reactants. The nickel(II) forms only
impure and poorly characterized complexes in contrast to the copper(II)
complexes. In dimethylformamide complexation between nickel(II)
and the 5-substitutedtetrazolate anion is clearly indicated from the
absorption spectrum. The visible spectrum in solution also indicates

that nickel(II) is octahedrally coordinated. The nickel(II) and

capper(II) complexes are insoluble in both polar and nonpolar solvents,
which suggests polymer formation. When heated, the complexes decompose
without melting and cannot be sublimed. When Cu(NO3)2 was used as a
reactant with the 5-aryltetrazoles, no precipitate formed. With

CuSO4 or CuCl2 an immediate precipitation ensued. From turbidity
studies it was concluded that sulfate or chloride ion is necessary to
produce precipitation of the copper complexes.

Jonassen 3; 31., (19,23) have also investigated bis(5-sub-
stitutedtetrazolato)iron(II), coba1t(II), nickel(II) and copper(II)
'dihydrate complexes. The substituent in their studies was strongly
electronegative. These complexes also are totally insoluble in polar
and nonpolar solvents. The Mgssbauer spectra were observed for bis(5-
nitro—, 5-chloro- and 5-trifluoromethyltetrazolato)iron(II) complexes.
From the absence of observable quadrupole splittings it is concluded
that the environment of the metal ion is highly symmetrical, and
reflectance spectra indicate that it is octahedral. The magnetic sus-
ceptibility for bis(5-trifluoromethyltetrazolato)iron(II) is 1.1 B.M.
The reflectance spectrum for this complex indicates that the S-tri—
fluoromethyltetrazolate anion lies between 2,2'rbipyridine and
1,10-phenanthroline in the spectrochemical series. This, together
with the observed low magnetic moment, indicates that the paramag-
netic state lies close to the spin-paired ground state. Jonassen,
Terry and Harris (20) showed that 5-trifluoromethyltetrazolate anion
is a weakly coordinating ligand contrasted with the 5-aminotetrazolate
anion (16). Jonassen and Smith (24) have investigated the thermal
decomposition of sodium S-trifluoromethyltetrazolate dihydrate and

bis(5-trif1uoromethyltetrazolato)iron(II), cobalt(II), nickel(II),

and capper(Il) dihydrate complexes. These compounds were allowed to
pyrolize in a Bendix Time of Flight Mass Spectrometer. The pyrolysis

components for each complex are H20, CF3CN, CF3CN2, N2 and (CN)2, and

the residues are CoF3, and NiFZ, FeF3 and (NH

enthalpy of decomposition was calculated from DTA for the complexes.

4)2CuF4(H20)x. The

Brubaker and Gilbert (21) have prepared various dichlorobis(1-
substitutedtetrazole)coba1t(II), nickel(II), platinum(II) and zinc(II)
complexes. The nickel, cobalt and platinum complexes are insoluble
and all decompose without melting. The zinc complexes are slightly sol-
uble in ethanol and tetrahydrofuran. The stability constants were det—
ermined, spectrophotometrically, for nickel(II) complexes with l-
methyltetrazole and l-cyclohexyltetrazole in absolute ethanol and for
cobalt(II) with l-methyltetrazole and l-cyclohexyltetrazole in tet-
rahydrofuran. l-methyl- and l-cyclohexyltetrazole complexes of each
metal are of comparable strength. For the nickel complexes and the
cobalt complexes the overall formation constants are 102 and 105,
respectively. These formation constants are much lower than observed
for the bis(S-aminotetrazolato)copper(II) complex (16). The lower
formation constants substantiate the idea that a replaceable ring
hydrogen is necessary to form stable complexes with substituted
tetrazoles. No appreciable difference was observed in the infrared
spectra of the complex between the free ligand and the complexed
ligand.

Stolle, g; 31., (25) have reported the preparation of the Grignard
reagent of 1-phenyltetrazole(l-phenyl-5-tetrazolylmagnesium iodide).

Gilbert (26) attempted to prepare a bis(1-phenyl-5-tetrazolyl)-

nickel(II) complex by reacting the Grignard reagent with anhydrous
nickel(II) chloride. The preparation yielded a black solid in all
cases. Attempts were made to prove the existence of l-phenyl-S-
tetrazolylmagnesium iodide but were unsuccessful. Attempts to remove
the hydrogen ion from the 5-carbon with lithium and sodium amide in
liquid ammonia were unsuccessful. The hydrogen bonded to the 5
position is not very acidic.

Beck and Fehlhammer (27), with a novel synthesis, have prepared
bis(5-trifluoromethyltetrazolato)bis(triphenylphosphine)palladium(II)
by reacting bis(triphenylphosphine)palladium(II) azide with trifluoro-
acetonitrile in dichloromethane at 0°C. A tetraphenylarsenium tet-
rakis(l-cyclohexyl-S-tetrazolyl)gold(III) complex was also prepared
by the reaction of tetraphenylarsenium tetraazidogold(III) with cyclo-
hexylisonitrile under the same conditions. The proton NMR spectrum
(in DCC13) showed three signals at‘Y-2.4, 5.2 and 8.3 corresponding
to the 20 phenyl protons, the 4 tertiary hydrogen atoms on the cyclo-
hexyl ring and the 40 methylene protons on the cyclohexyl ring,
respectively, with the ratios of the intensities, 5:1:10, respectively.
The infrared spectrum of the l-cyclohexyl-S-tetrazolyl ligand is
essentially the same as it is for l-cyclohexyltetrazole.

Holm and Donnelly (28) prepared tetrazolate complexes of iron(II),
nickel(II), cadmium(II) and coba1t(II) by the reaction of the corr-
esponding metal salt with tetrazole in water. The iron(II) tetrazolate
complex is very poorly defined and is very sensitive to air oxidation.
In most cases the complexes are hydrated. From stability constant

studies nickel(II) in dimethylformamide forms a very weak complex with

the tetrazolate anion. Infrared studies indicate that the effect of
complexation of the tetrazolate anion does not greatly shift the

vibrational frequencies.

II. Theoretical

A. Basic Principles 9; Infrared and Raman Spectroscopy.

Infrared and Raman spectra of molecules are of great importance
to chemists for understanding molecular bonding and molecular
structural properties. The principles of infrared and Raman spect-
roscopy have been set forth in detail by a number of authors
(29,30,31,32,33,34,35,36,37). Molecules which are absorbing or
emitting a quantum of vibrational energy show absorption bands in
the region from about 100 to 3500 cm—1. Infrared spectra originate
in transitions between two vibrational levels of a molecule in the
electronic ground state, whereas, Raman spectra originate in the
electronic polarization of a molecule caused by ultraviolet or
visible light. If the permanent dipole, h, of a molecule changes as

a particular vibration at frequency v occurs, the molecule will

I
interact with the infrared radiation of v . The intensity of absorp-

1
tion will depend upon (an/3Q)2 where Q is the displacement from the
equilibrium configuration. Thus infrared absorption occurs as a
result of a changing dipole moment. In order for Raman absorption to
occur, the molecular polarizability, 3, must change during the vibra-
tion and the intensity will depend upon the (3a/3Q)2.

Group theory is an invaluable aid in the determination of Raman
and/or infrared activity or inactivity of a particular normal vibra-
tional mode of a molecule. Excellent descriptions of the application
of group theory to molecular vibrations are presented by Cotton (38),

Wilson, ggngl., (30) and Nakamoto (29).

From Raman spectra it is possible to distinguish between

10

symmetric and asymmetric normal vibrational modes by measuring the
depolarization ratio. The basis for the depolarization ratio can be

explained by examination of the molecular polarizability tensor, 3.

a a o
xx xy xz
Z = a a a (2.1)
yx YY yz
a o a

 

 

zx zy zz

Physically, the various tensor elements of the molecular polar-
izability will define an ellipsoid. For a totally symmetrical vibra-
tion only the diagonal elements of the polarizability tensor change
with time, whereas, for an asymmetrical vibration the off diagonal
elements change with time and both are associated with the Raman
scattering.

If unpolarized light is used to excite a Raman spectrum, the
scattering at 90’ to the incident light will be found to be at
least partially polarized. The extent of polarization depends upon
the way in which the polarizability ellipsoid varies during the
vibration.

The intensity of an oscillating induced-dipole is
I I Kuz (2 2)
o 0

where "o is the amplitude of the induced-dipole moment given by

u - pocosvat (2.3)
4 4
16w v

and K I -?§;r- (2.4)

11

in which v is the frequency of oscillation and c is the velocity of
light.
The polarizability tensor, 3, is related to the induced-dipole

moment, a, by
E = E E (2.5)

where E is the electric field vector. Combining equations (2.2) and

(2.4) the intensity is

I =- KaZEz (2.6)

If one introduces a nonrotating axes, the total radiation

emitted per unit solid angle in the x direction is

3 4
2
I - 45‘;— <u§y + 513,2) (2.7)

For an anisotrOpic molecule, ux+ uy+ uz and are expressed as
u I a E + a E + a E (2.8)
x xx x xy y xz z
u I a E + a E + a E
Y 73 x YY Y yz z

u I a E + a + a E
z zx x zyEy 22 2

If the direction of propagation of light is coincident with
the y axis and if the incident light is plane-polarized with E
parallel to the direction of observation, i.e., along the x axis,
the total intensity observed [IT(obs." )] is from equations (2.6),

(2.7) and (2.8),

2n3v‘ 2 2 2
IT(obs." ) I -—Eg-(ayx + azx)Eo (2.9)

12

where Ebis the amplitude of E. If the electric field vector is
parallel to the z axis (perpendicular to the axis of observation),
the intensity, IT(obs.J_), is

2n3v4 2 2 2

IT(obs.J_) = “23-(a + a )E (2.10)

yz 22 o

The intensity, I"(obs._L), of that part of light which is polarized

parallel to B when R is parallel to the z axis is

2153\)4 2 2
I"(obs.J_) ='—Eg—— azon (2.11)

From electromagnetic theory the intensity, 10, of the incident

light is related to the amplitude of the electric field by

I .——— E (2.12)

0 8n 0

Upon substitution for E02, equations (2.9), (2.10), (2.11) become

4 4
l6n v 2 2
IT(obs." ) I c Io(ayx + azx) (2.13)
4 4
16h v 2 2
IT(obs.J_) = c 10(01yz + azz) (2.14)
4 4
I"(obs._L) ..légrx_ Iooiz (2.15)

For N molecules which are freely orientated in space (e.g., a
powder or liquid), equations (2.13), (2.14), and (2.15) become

16n4v4 282
C i

IT(obs." ) I o 15

NI

13

 

4 4 2 2
16V v 451_ + 78
IT(obs.| ) I'-Ez-—:NIO( 45 ) (2.17)
16fl4V4 4512 + 432)

 

I"(obs._L) = ——;z——-N10( (2.18)

where y I l/3(oxx + ayy + azz)

2 2

and 3‘: 1/2[(axx - ayy) + (o - 022) + (ozz - axx)2]

yy

7 is the spherical part of the polarizability and B is the anisotropic
part.

The depolarization ratio, p, is defined as the ratio of the
intensity polarized perpendicular to B to the intensity parallel to
E. If plane polarized light is used, the ratios of the intensities

are given by

. IT(obs._L) - Iu(obs._L) . 3B2

 

o

For an asymmetric vibration y equals zero. Therefore pp equals 3/4.
For a symmetric vibration y and B are both non-zero. Therefore pp
has the range O<pp<3/4.

If unpolarized incident light is used, the intensities observed
parallel and perpendicular to the incident light must be considered.
The intensity observed parallel to the incident light contributes

one-half of its intensity to the parallel and perpendicular components,

respectively. The depolarization ratio, 6“, becomes

9 .. IT(obs-L) - Iniost.) + 1/2 IT(obs..,) 632

u I"(obs. )'+ 1/2 IT(obs.") -45Y2+782 (2.20)

14

Thus for an asymmetric vibration pu equals 6/7 and for a symmetric

vibration pu has the range O<pu<6/7.

B. Vibrational Analysis (Normal Coordinate Analysis).
The theoretical analysis of a vibrational absorption spectrum is
known as vibrational analysis. The method used to perform the vibra—

tional analysis is known as Normal Coordinate Analysis. The principles

 

of Normal Coordinate Analysis are discussed eloquently by a number of
authors (29,30,39,40,4l,42).

The purpose of performing a normal coordinate analysis is either
to calculate force constants from observed eigenvalues (maxima for
the vibrational modes) or to predict theoretically the vibrational
spectrum from a suitable set of force constants. A normal coordinate
analysis also permits one to make vibrational assignments for a
particular molecule.

A molecule possesses 3N (N I number of atoms) degrees of freedom
of which, for a nonlinear molecule, three are rotational modes and
three are translational modes. Thus, there are 3N-6 normal vibrational
modes.

The total vibrational energy is a sum of the kinetic energy and
the potential energy. To calculate the vibrational frequencies, it
is necessary to formulate the potential and kinetic energies in terms
of suitable coordinates. Internal coordinates are usually chosen
rather than Cartesian displacement coordinates since the force constants
in terms of internal coordinates have a clearer physical meaning and

a set of internal coordinates does not involve the translational and

15

rotational motion of the molecule.

A relationship between the internal coordinates and Cartesian
coordiantes is needed. If Rt represents one of the 3N-6 internal
coordinates and xi one of the 3N displacement coordinates, the relation—
ship will have the form

N

3
Rt= z Btixi (t = 1,2,..., 3N-6) (2.21)
i=1

where the coefficients Bt are constants determined by the geometry

1

of the molecule. Equation (2.21) is expressed in matrix form as
_R_= BX (2.22)

where 3 and X are column matrices of the internal and displacement
coordinates, respectively.
The potential energy, V, expressed in terms of internal coor-

dinates is

n n
2
2v = 2 f (A ) + x f (AR )(AR ) (2.23)
1‘1 11 R1 1+3'1 ij 1 j

where, n=n' is the number of internal coordinates, fii is the force

constant of the ith internal coordinate, fij is the interaction force
constant, and R1 and R.j are the internal coordinates, or
3N-6
I 0‘ n _
2V 2 finiRj (j 1,2,..., 3N 6) (2.24)

iIl

16

Expressed In matrix form

2v = 3' £3 (2.25)

where 3 is a column matrix, R' is its transpose and E is the force
constant'matrix.

Since the kinetic energy, T, of a particle of mass M and velocity
V is given by 2T = MVZ, the total kinetic energy of a molecule is

given by

(2.26)

where m1 is the mass associated with the displacement coordinate x

and x1 is the time derivative of xi. The kinetic energy is not

easily expressed in terms of internal coordinates. By defining a set

i

of quantities le as
3N
le 31:1 Bk1 Eli/mi (k, 1 = 1, 2,..., 3N-6) (2.27)

it can be shown (41) that the kinetic energy can be expressed as

3N-6 ,

. -1 -
3,: z (c ) R (2.28)
1.1-1 13 1 3

N = i's’l
where R_is the internal coordinate velocities and Q71 is the reciprocal

of the §_matrix.

The §_matrix is defined as

9:15.! 15. (2.29)

‘where §_is defined in equation (2.22) and M71 is a diagonal matrix whose
components are “1’ where 111 is the reduced mass.

If normal coordinates Qk (k = l, 2,..., 3N) are introduced, the
kinetic and potential energies achieve a simplier form. The normal
coordinates are defined as linear combinations of mass—weighted

Cartesian coordinates, qi =Tmixi, as

3N
Qk =.X likqi (2.30)
i=1

The coefficients, lik’ are chosen so that the kinetic and potential

energies have the form

3N ,
c 3N
2T = 2 0i 2v = z Ain (2.31)
k=1 k=l

where Ak are constants, i.e., the potential energy has no cross terms.
A further prOperty of normal coordinates is that the transformation

from Cartesian coordinates to normal coordinates is orthogonal, i.e.,

:n1.2 3N '2
E qi I Z Qk (2.32)
181 k

D.
a:
..3
c)
<

32' —e—- + ——- . o (k - 1, 2,..., 3N) (2.33)

18

If equations (2.31) are substituted into equation (2.33) the

equations of motion are given by

Qk + Aka = 0 (2.34)

Equation (2.34) has the solutions:
_ ° 1/2 :-
Qk - Qk (108(Ak t + 8k) (2.3))

where Qfi and e are the amplitude and phase constants, respectively,

k

and Ak is related to the frequency of the ith vibration by

= (Ak)1/2

2nc

where i = k (2.36)

The normal coordinates are linearly related

to the internal coordinates by the transformation L, which diagonalizes

Q and E, by 3N-6
R1 - 2 Lika (R = 1, 2,..., 3N) (2.37)
i=1
-1
or R=LgorQ=L3 (2.38)

From equations (2.28) and (2.25) the kinetic and potential energies
are expressed by

LQ=TEQ as”

and 251-911: 219-9: .119. (2.40)

19

where A_is a diagonal matrix, with A ii

Therefore from equations (2.39) and (2.40)

1'6'11-2

and

yum

Solving for L} in equation (2.41) (Lf I Lil g) and substituting for

L' in equation (2.42)

QEL'LA
or lea-age-o
3N-6 3N-6
or Z 2 G F - 6 1 L I 0
< 1p p: 11 1831.
J p
where Gij is the Kronecker delta symbol., For equation (2.45) to be
true
3N-6
Z G F - 6 A I 0
12133 13k
P
m lat-Jg- 0

From equation (2.47) the eigenvalues for a particular molecule can
be calculated. Equation (2.47) has 3N-6 nonzero roots.
The secular equation (2.47) may be further simplified by intro-

ducing the symmetry properties of the molecule.

I 11, while §.is a unit matrix.

(2.41)

(2.42)

(2.43)

(2.44)

(2.45)

(2.46)

(2.47)

20

The internal coordinates, R1, can be transformed to symmetry

coordinates, S by use of an orthogonal matrix, Q:

1’

§_=_g_g (2.48)
Recalling equation (2.38)
s=219=189 (2.49)
and g_= L"1 _1 U R = L-1 (2.50)
._ _. .... -s _.

where_I-_.s ‘.Q.L- The kinetic and potential energies, expressed in

symmetry coordinates, are

2v-i" 8'12 3-23 12's (2.51)

and 2T - 31"1 s' 9:1 (1'1 s = gé' 9'1 Q's (2.52)
wherefl-1 IIQ' for an orthogonal matrix.
Equations (2.39) and (2.40) become

zi-é'isa'ligé-é'aé <2-53)

2v-9'L13gg'9'i9. (2.54)

'1! a . ’1 t .
£56.15 1:1. 1.9.3.1. <2 55)

21

 

and L F L' = A I L F L' (2.56)
-s -'-s - —“_8‘—

where 0'1 = U (3'1 U' (2.57)
-s .... ._

and F = U F U' (2.58)

—s ._._..

Thus equation (2.43) becomes
G F L = L A (2.59)
-s —s - -—'-

or G F - EA I = O (2.60)

-s -s 5— k'

The §_and 2 matrices are symmetrized and the secular equation is
reduced to block form which simplifies the solution for the vibrational
frequencies of the normal modes of vibration.

To make vibrational assignments one must examine the extent

of displacement of the coordinates, x1, yi, and 2 Once the solutions

10
of the secular equation are obtained, the transformation matrix, L,
can be calculated from equation (2.44). The transformation matrix,

.L: is related to the normal coordinates matrix, Q, by

Q a 1:1 3 (2.38)

From equation (2.22)

.0.=(£

luv
v
IN

(2.61)

where‘g is a column matrix containing the displacement coordinates

-1
x1, y1, 21, x2, y2, 22, ..., xn, yn, 2n and I: is defined as the

22

eigenvector inverse matrix. By plotting the displacements for each
eigenvalue, 1k, it is possible to determine which atom or atoms are

changing for a particular vibration.

III. EXperimental
Reagent grade chemicals were used throughout this investigation.

A. Purification g: Solvents

Reagent grade diethylether (Et20) and tetrahydrofuran (THF) were
purified by being refluxed with lithium aluminum hydride under pre-
purified nitrogen and were distilled. The fractions boiling at
34.5°C. and 65°C., respectively, were collected and stored under
nitrogen and over sodium metal in sealed vessels.

Reagent grade acetone was purified by allowing the solvent to
stand over anhydrous calcium chloride for at least three weeks. The
acetone was subsequently refluxed with Drierite and distilled under

nitrogen directly into the filtration flask.
B. Preparation 9;.Tetrazoles and Related Chemicals

Hydrazoic Acid: The method of Garbrecht (43) was used. To a sludge

 

of 520 g. of sodium azide and 500 m1. of water in 1500 ml. of toluene
were added dropwise with stirring 250 m1. of concentrated sulfuric
acid at 0°C. The toluene layer was decanted into a tightly stoppered
bottle. Anhydrous sodium sulfate was used to dry the hydrazoic acid.
The concentration of hydrazoic acid in toluene was determined by
titration with standard sodium hydroxide and phenolthalein as the

indicator.

N-cyclohexylformamigg; The method of preparation described Ugi g£.§l,,

(44) was used. Ethyl formate was added dropwise to a slight excess of

23

24

freshly distilled cyclohexylamine immersed in an ice bath. After the
exothermic reaction ceased, the solution was refluxed for two hours
and distilled to remove water, ethanol and unreacted cyclohexylamine.
The N-cyclohexylformamide fraction was collected at 145—146°C. and

29 torr.

l-methyltetrazole: The preparation of methyl isocyanide of Ugi and

 

Meyr (45) was utilized with a modification by Gilbert (26). To 0.6
moles of reagent grade N-methylformamide in 100 m1. of pyridine and

200 ml. of chloroform were added dropwise with stirring 0.3 moles of
phosphorous oxytrichloride at 0°C. The reaction was allowed to proceed
at 0°C. for one-half hour after the addition of phOSphorous oxytrichlor-
ide. The methyl isocyanide, chloroform mixture was distilled with

a minimum pot temperature (in order to prevent polymerization of methyl
isocyanide) into a solution of excess hydrazoic acid in toluene.
Separation of pyridine from the methyl isocyanide, chloroform fraction
was best obtained by distillation through a 24 inch fractionating
column packed with glass helices. The distillate and hydrazoic acid

in toluene were allowed to reflux for twenty-four hours under anhydrous
conditions. Evaporation to dryness with an air jet gave a crude
product of approximately twenty to thirty per cent yield. Sublimation
of the crude product under reduced pressure gave a white, crystalline
product whose melting point was 37-38°C. The infrared spectrum of
l-methyltetrazole is given in Table I. If large quantities of the
reactants are used, the per cent yield of 1-methyltetrazole decreases

because of the increased methyl isocyanide polymerization which is

25

Table I. Infrared Spectruma of l-methyltetrazole from
100 to 5000 tm-l.

 

3400
3135
2980
1639
1496
1471
1422
1402
1279
1225
1174
1113
1058
1040
973
928
881
719
678
658
534
476

357

(vw) broad
(s)
(m)
(vw)
(s)
(VW)
(m)
(w)
(s)
(m)
(vs)
(a)
(m)
(w)
(vs)
(m)
(vs)
(8)
(vs)
(a)
(s)
(s)
(s)

aIntensities in parenthesis (vs-very strong, s-strong,
mImedium, wIweak, vavery weak, shIshoulder).

26

catalyzed by pyridine and heat. Even with the use of a glass helices
column, the separation of the pyrdine and methyl isocyanide is not
complete. Since pyridine appears to prevent the initial precipitation
of ldmethyltetrazole, quinoline and aniline were substituted for
pyridine as bases in the preparation of methyl isocyanide. Quinoline
and aniline are of comparable basicity to pyridine, but have higher
boiling points. With quinoline and aniline no methyl isocyanide could

be produced.

lephenyltetrazole: The method of Herbst and Fallon (46) was used.

To 0.25 moles of formanilide in toluene were added dropwise with
stirring 0.25 moles of phosphorous pentachloride at 0°C. Upon complete
reaction excess hydrazoic acid in toluene was added to the solution.
After being refluxed for twenty-four hours, the solution was poured
over ice, made alkaline with sodium hydroxide and filtered. The
residue was washed first with a 4% sodium hydroxide solution and then
with water. A further quantity was obtained by separating the toluene
layer from the initial filtrate and evaporating it to dryness.
Sublimation of the crude product at reduced pressure gave a white
crystalline solid which melted at 65—66°C. The infrared spectrum of

l-phenyltetrazole is presented in Table II.

l-cyclohexyltetrazole: The preparation by Ugi g£_§l,, (440 of cyclohexyl

 

isocyanide was utilized. To a solution consisting of 0.5 moles of
N-cyclohexylformamide, 250 ml. of pyridine and 200 ml. of petroleum

ether (b.p. 30-60'C.), 0.3 moles of POCl were added dropwise with

3

27

Table II. Infrared Spectrum3 of l-phenyltetrazole
from 100-5000 cm-l.

 

3125 (vs) 1100 (s)
1618 (vs) 1085 (m)
1510 (vs) 1058 (m)
1471 (s) 1000 (s)
1400 (s) 967 (s)
1380 (sh) 916 (s)
1340 (w) 888 (s)
1310 (w) 765 (vs)
1284 (w) 718 (s)
1240 (vw) 688 (vs)
1218 (vs) 504 (s)
1198 (w) 441 (s)
1180 (w) 355 (S)
1170 (vw) 295 (s)
177 (s)

 

8As defined in Table I.

28

stirring at 0°C. After the addition of POCl was complete, 300 ml.

3
of ice water was added with stirring until all of the solid material
had dissolved. The organic layer was separated from the aqueous

layer. The aqueous layer was extracted with three-20 m1. portions of
petroleum ether and the extract was added to the organic layer which

was extracted with three-25 m1. portions of water and dried over

magnesium sulfate. The crude product in petroleum ether was added

.1 1 r -‘jtlA-"?

to an excess of hydrazoic acid in toluene. The mixture was allowed

 

to reflux for twenty-four hours after which the solvent was removed '
by evaporation in an air jet. An oily solution remained. To this if
solution was added about 20 ml. of acetone. Immediately, crude,

pale-yellow l-cyclohexyltetrazole precipitated and was sublimed at

reduced pressure to yield a white, very fluffy crystalline compound

which melted at 46—47°C. The infrared spectrum is given in Table III.

Tetrazole: Tetrazole was donated by Dr. N. A. Daugherty and was

 

prepared by diazotization of S-aminotetrazole. The infrared spectrum

.of tetrazole is presented in Table IV.

Sodigm Tetggzolate Monohydrate: Equimolar amounts of sodium hydroxide
and tetrazole were mixed in water. Sodium tetrazolate monohydrate

was crystallized by slow evaporation of the aqueous solution. To
remove unreacted tetrazole, ethyl acetate was added to the sodium
tetrazolate monohydrate crystals and filtered. Sodium tetrazolate
monohydrate was recrystallized from water. The infrared and Raman

Spectra are presented in Tables V and VI.

29

Table III. Infrared Spectruma of l-cyclohexyltetrazole
from 100-5000 cm'l.

 

3125 (s) 1101 (vs)
2930 (vs) 1054 (m)
2850 (s) 1032 (m)
2650 (w) 1001 (s)
1740 (vw) 970 (s)
1610 (vw) 920 (vw)
1470 (s) 897 (vs)
1450 (vs) 881 (vs)
1424 (m) 820 (s)
1404 (w) 746 (s)
1366 (m) 718 (vw)
1344 (w) 675 (vs)
1310 (m) 659 (vs)
1266 (m) 554 (m)
1242 (w) 468 (m)
1180 (sh) 439 (8)
1167 (vs) 337 (m)
1138 (s) 242 (m)

 

8As defined in Table I.

30

Table IV. Infrared Spectrum8 of Tetrazole from
300-5000 em-l.

 

,3140
2930
2350
1800
1665
1522
1455
1445
1258
1152
1082
1052
1018
980
950
920
780
665
659

557

451

(m)
(m)
(W)
(m)
(m)
(m)
(m)
(m)
(vs)
(8)
(m)
(m)
(m)
(w)
(W)
(V)
(W)
(vs)
(a)
(s)
(s)

 

8As defined in Table I.

F...

31

Table V. Infrared Spectrum8 of Sodium Tetrazolate Monohydrate
from 300—5000 em'l.

 

3300
3120
2930
2370
1785
1685
1640
1455
1445
1290
1210
1161
1132
1065
1023
1015

910

702

660

454

(vs)
(sh)
(m)
(m)
(m)

01
\.

(sh)
(s)
(s)
(s)
(s)
(vs)
(m)
(vs)
(vs)
(vs)
(vs)
(vs)
(w)
(w)

 

8As defined in Table I.

32

Table VI. Raman Spectrum8 of Sodium Tetrazolate Monohydrate
from 150-5000 cm-l.

 

3128 (m)
1780 (vw)
1696 (sh)
1647 (s)
1438 (s)
1287 (vs)
1189 (vs)
1130 (w)
1079 (w)
1025 (w)
1009 (w)

702 (w)

 

8As defined in Table I.

33

C. Preparation of Metal Compound Reactants

 

 

Nicke1(Il) chloride: To hydrated nickel(II) chloride was added an

 

excess of thionyl chloride (47). The mixture was stirred until the
effervescence of sulfur dioxide and hydrogen chloride ceased and was

left to stand for one—half hour under nitrogen. The excess thionyl

 

N‘

chloride was removed by distillation under reduced pressure. H
Addition of nitrogen to the reaction vessel permitted the system

to attain atmospheric pressure under anhydrous conditions. The yellow,

scale-like nickel(II) chloride was stored under anhydrous conditions. i

Iron(II) chloride: Anhydrous iron(III) chloride was prepared by the
same method as described for anhydrous nickel(II) chloride with the
exception that the mixture was refluxed for two hours after the
addition of excess thionyl chloride.

Anhydrous iron (II) chloride was prepared with the method
described by Kovacic and Brace (48). To 1 mole of anhydrous
iron(III) chloride under anhydrous conditions was added 2 moles of
chlorobenzene. The mixture was stirred at a rapid rate and heated for
thirty minutes to 126°C., whereupon the black slurry thickened. The
reaction was allowed to proceed for two hours at 128° to 139°C. In
the course of the reaction the mixture became light tan, less viscous
and hydrogen chloride gas was evolved. The tan solid was filtered
under anhydrous conditions, washed repeatedly with chloroform, and
dried ighygggg. The iron(II) chloride was stored under anhydrous

conditions.

34

Dichlorobis(triethylphosphine)nickel(II): The method described by
Jensen g£_§l,, (49) was used. Triethylphosphine (prepared by the
reaction of an equimolar amount of phosphorous trichloride and ethyl
magnesium bromide) was added to an equimolar amount of a cold ethanolic
solution of hydrated nickel chloride. Wine-red, crystalline dichloro-
bis(triethylphosphine)nicke1(II) precipitated and was immediately
filtered. The compound was purified by dissolving the complex in
benzene and was recrystallized by the addition of pentane. The infrared
spectrum is given in Table VII and was used to identify the dichloro-

bis(triethylphOSphine)nickel(II).

D. Preparation of Compounds

 

Bis(tetrazolato)copper(ll)monohydrate: To 0.02 moles of tetrazole

in 50 m1. of water were added drOpwise with stirring 0.0095 moles of
capper(II) nitrate trihydrate in 50 ml. of water. Immediately a pale-
blue solid precipitated. The solution was stirred for four hours,
filtered and washed repeatedly with water, ethylacetate, ethanol and
ether to remove any remaining reactants. A yield of eighty—two per

cent was obtained. Anal. Calculated for Cu(CHN 'H20: Cu, 28.93;

4)2
C, 10.94; H, 1.84; N, 51.02. Found: Cu, 28.95; C, 11.04; H, 1.83;

N, 51.15.

l-methyl-S-tetrazolyllithium'1/2 THF: To an excess of nfbutyllithium

 

(prepared by the reaction of equimolar amounts of lithium and
Brbutylchloride at -35°C. under nitrogen) in 300 m1. of freshly distilled,

anhydrous THF were added 0.02 moles of 1-methy1tetrazole under anhydrous

35

 

Table VII. Infrared Spectrum of Dichlorobis—
(triethylphosphine)nickel(II) from
650-5000 tm-l.
a

3390 (m) 1138 (sh)
2910 (vs) 1085 (m)
2880 (s) 1068 (m)
2820 (m) 1036 (vs)
2450 (w) 1030 (sh)
1665 (m) 1009 (w)
1595 (m) 999 (m)
1560 (vs) 985 (vw)
1482 (m) 890 (vw)
1462 (m) 857 (s)
1445 (m) 813 (vs)
1408 (s) 790 (vw)
1380 (vs) 760 (vs)
51375 (sh) 718 (vs)
1281 (vs) 702 (s)
1147 (sh) 689 (s)
1142 (m)

 

8As defined in Table I.

36

conditions at -50°C. The solution was stirred continuously for one
hour at -50°C. after which a white solid precipitated. If the solution
was warmed, butane was evolved, as verified by mass spectrography.

The solid was filtered under anhydrous conditions and washed repeat-

edly with anhydrous THF and Et 0 to remove unreacted l-methyltetrazcle.

2

Anal. Calculated for LiC2H3N4°l/2 THF: C, 38.11; H, 5.60; N, 44.44.

Found: C, 38.62; H, 4.92; N, 45.06.

Bis(1-methyl-5-tetrazolyl)nickel(II): 1-methy1-5-tetrazoly1—
lithium'1/2THF was prepared as above but was used in situ. To about
0.02 moles of a THF suspension of the tetrazolyllithium at about -50°C.
were added about 0.01 moles of dichlorobis(triethylphosphine)nicke1(II).
The mixture was stirred for two hours under nitrogen and was allowed

to come to room temperature under nitrogen and stand for about four
hours. A finely divided green solid was separated either by
centrifugation or by filtration under anhydrous and anaeorobic condi—
tions, washed repeatedly with anhydrous acetone, THF, and Et 0,

allowed to dry in and stored under an inert atmosphere. A yield of
eighty per cent (based on the amount of dichlorobis(triethylphosphine)-
nickel(II)) was obtained. A very low yield was obtained when anhydrous
nickel(II) chloride was used in place of the triethylphosphine complex
even after being stirred at room temperature for one week. Extreme
care must be exercised to insure that the complex is not exposed to air
or moisture when wet. When wet the complex decomposes to give a
yellow complex, whereas, when dry the decomposition rate appears to be

much slower and without the formation of the yellow compound. No

..[J

L

*’ ‘.. 'IN\‘ CHM '- {
‘1‘ " ’ I'

 

37

attempt was made to identify the yellow compound. Anal. Calculated

for Ni(C Ni, 26.11; CN, 23.14. Found: Ni, 26.00; CN, 22.97.

2H3N4)2‘
Satisfactory commercial C, H, and N analyses could not be obtained.
If the complex is treated with nitromethane, a new green substance

forms which appears to be a disolvate. Anal. Calculated for

Ni(C -2cn NO : Ni, 16.9- Found: Ni. 17.1. F‘a

H3N4)2 3 2 .

2

Bis(1-cyclohexyl-5-tetrazolyl)nickel(II): The same procedure was

“)2 except that the solution and suspended

solid were allowed to stand for 1 to 2 days before filtration of the V

used as described for Ni(C2H3N

light green complex. When wet and exposed to air, the compound

decomposes to give a yellow compound. As was observed for Ni(C2H3N4)2

the decomposition is much slower when the sample is dry. Anal.

Calculated for Ni(C7H Ni, 16.26; CN, 14.41; C, 46.57; H, 6.14.

11N4)2‘
Found: Ni, 16.23; CN, 14.29; C, 46.18; H, 6.81. The commercial

nitrogen analysis was not satisfactory.

Attempted Preparation 2:.bis(ltphenyl-S-tetrazolyl)nickel(II): When

 

the same conditions and method as described for bis(l-methyl-S-
tetrazolyl)nicke1(II) were used no reaction occurred between l-phenyl-
5-tetrazolyllithium and dichlorobis(triethylphosphine)nickel(II)

even when the THF solution and suspension of 1—phenyl-5—tetra-
zolyllithium were heated for one week. Filtration of the solution and

suspension left only the white 1-phenyl-5-tetrazolyllithium.

Attempted Preparation 2f.bis(l—methyl-S-tetrazolyl)iron(II): To a
0.02 moles suspension of l-methyl—S-tetrazolyllithium was added 0.01

moles of anhydrous iron(II) chloride. After letting the suspension

 

38

stand for 6 weeks a very poorly defined orange compound was isolated.

Anal. Calculated for Fe(C Fe, 25.17. Found: 26.50. Because

2H3N4)2‘
of the length of time required for preparation and lack of purity,

this attempted preparation was abandoned.
E. Analytical Methods

Nickel Determination

 

The following two methods were used.
Volumetric: Since cyanide ion is formed from the decomposition of
bis(l-substituted-S-tetrazolyl)nickel(II) complexes with ammonia
(see Results), the standard volumetric technique for the determina-
tion of nickel with cyanide ion (50) could not be used. To a weighed
sample of the complex (about 50-80 mg.) was added 30 ml. of 6 M
hydrochloric acid and 50 ml. of water. The solution was heated to
boiling to expel hydrogen cyanide and was evaporated to partial dryness.
To the residue (nickel(II) chloride) was added 20 ml. of l M sulfuric
acid. The solution was neutralized with concentrated ammonium
hydroxide to which were added 5 ml. of concentrated ammonium hydroxide,
30 ml. of water, 20 ml. of a standard cyanide ion solution and 1 ml.
of potassium iodide (l g. per 100 ml.) as the indicator. The uncomplexed
cyanide ion was titrated with a standard silver ion solution.
Gravimetric: A weighed amount of sample was placed in a tared crucible
and heated slowly to decompose the complex to nickel(II) oxide and the

crucible was heated to constant weight.

39

Iron Determination

To approximately 100 mg. of sample was added 20 m1. of concentrated
nitric acid. The mixture was diluted to 75 m1. after dissolution of
the sample. Two to three drOps of methyl orange and 6 M aqueous ammonia

were added until the solution was basic. After coagulation the iron(III)

 

r”a
hydroxide was filtered with No. 540 filter paper, washed several times E E
and placed in a tared crucible which was heated to constant weight. i I
The iron in the sample was determined as iron(li3) oxide.
l
Copper Determination f

 

The percentage of copper was determined spectrophotometrically.
To duplicate samples of 20 to 40 mg. of sample 5 ml. of concentrated
nitric acid was added. After the complex dissolved, 30 m1. of water
was added and most of the nitric acid was fumed away. The solutions
were cooled, diluted with a small amount of water and quantitatively

transferred to 25 ml. volumetric flasks. Ten ml. of a buffer which was

 

5.0 M with respect to both ammonia and ammonium chloride was added to
the flasks. The samples were diluted to volume with water and their
absorbencies were measured at 620 mu with a Beckmann model DU spectro-
photometer.

Each time that a capper analysis was made, two or more samples

of known composition were also run.

Cyanide Determination

Since cyanide ion is formed quantitatively by the decomposition

 

40

of bis(l-substituted-S-tetrazolyl)nickel(II) complexes with ammonia

(see Results), it is possible to determine the amount of tetrazole

present once the percentage of nickel is known. To 40-60 mg. of sample

were added 5 m1. of concentrated ammonium hydroxide, 30 ml. of water,
1 m1. of potassium iodide solution and 20 ml. of standard cyanide ion
solution. The uncomplexed cyanide ion was titrated with standard
silver ion from which the amount of cyanide ion, which is present as

a result of decomposition of the complex, can be calculated.

Carbon, Hydrpgen and Nitrogen Analyses

The Spang Microanalytical Laboratory, Ann Arbor, Michigan

determined carbon, hydrogen and nitrogen.

F. Purification pf Nitrogen Gas

 

 

Matheson prepurified nitrogen was passed through a train of

sulfuric acid, barium oxide and phosphorous pentoxide to remove any

water vapor and through a column of copper wire at 500°C. and a column

of Kieselguhr at 170°C. to remove any oxygen.
G. Spectroscopic Techniques

Infrared spectra were recorded on Unicam, S.P. 200 spectrometer
with potassium bromide discs or with Nujol and Fluorolube mulls
between sodium chloride plates for the 650—5000 cm"1 region. For the
100—650 cm.1 region a Perkin-Elmer Model 301 spectrometer was used.

Spectra were obtained with Nujol mulls between cesium bromide or

ijmj

Th' ..
l

 

41

polyethylene plates. Below 300 cm.1 polyethylene plates were used
exclusively. Care was taken to avoid contact with water vapor.

The unpolarized and polarized Raman spectra for a l M and a
3 M aqueous solutions of sodium tetrazolate monohydrate were obtained,
respectively, with a helical Toronto are as the source of exciting
radiation. The spectrograph was a Gaertner two-prism spectrograph
with a f3.5 camera lens. The 22938 cm.1 line of mercury was effective-
ly isolated from the mercury emission spectrum by a saturated aqueous
solution of potassium nitrite to absorb the ultraviolet lines and an
ethyl violet-ethanol solution to filter out light of longer wavelength
than the blue exciting line. The spectrograph was adjusted to give a
dispersion of about 200 cm.1 per mm on the plate with a resolution of
~about 10-15 cm-l. The spectra were recorded on Eastmann Kodak Ila-o
spectrosc0pic plates preheated in vacuum for twelve hours.

The spectral lines on the photographic plates were measured
directly with a Mann comparator and indirectly from tracingstwrusing a
traveling scale. The tracings were obtained with a Joyce-Lockel
microdensitometer. The values of the peaks in cm.1 were calculated by
a computer program with an interpolation from a quartic equation.

The reflectance electronic absorption spectra were measured with
a DKZ spectrometer and diffuse reflectance attachment and a Cary Model
15 spectrometer with reflectance attachment. For the measurements
with the Cary 15 finely divided undiluted samples were placed between
quartz plates with one of the plates covered with electrical tape.

A 2" x 2" aluminum plate with a cylindrical bore (1" x 1/16") was used

42

as a sample holder for the DK2 measurements. All samples were prepared
with two parts of magnesium oxide or silica to one part of sample.

The samples were packed with force into the sample holder so that

none of the sample would fall into the reflectance cavity. For the
water sensitive complexes the samples were loaded in a dry box and

kept under anhydrous conditions until the spectra were obtained.

During scanning the samples were eXposed to the atmosphere. Each
spectrum was repeated to determine whether or not decomposition had

taken place. In all cases no observable decomposition occurred.

H. ,Magnetig,$nsggptibility Measurements

 

The Gouy method was used to obtain the magnetic moments for the
paramagnetic compounds. An Alpha Scientific Laboratories AL 7500 M
Electromagnet and AL 7500 PS Power Supply equipped with a Mettler
single pan balance was used and an inert atmosphere was used for

moisture sensitive compounds.

IV. Vibrational Analysis Calculation
(Normal Coordinate Analysis)

The normal coordinate analysis calculation was performed on the
Control Data 3600 Computer of the Michigan State University Computer
Laboratory. The Fortran program, SD-90321, written by Schachtschneider
(51,52) and modified by Dr. L. B. Sims and Mr. Hans Sachse, was used ’*
to calculate the eigenvalues for the genuine normal modes of vibration
for sodium tetrazolate.

The program SD-90321 requires the following input data:

(a) The atomic positions (polar coordinates).

(b) The internal coordinates (bond stretching,

valence angle bending, out-of—plane wagging,
torsional, linear valence angle bending, and

in-plane wagging).

(c) A potential field of the generalized valence
force field type (GVFF).

(d) Masses of the atoms.

(e) The y_matrix (symmetry properties of the
molecule).

The §_matrix is calculated from the equation

p . p' M'1 p (4.1)

where‘M'.1 is the diagonal matrix of the reciprocal atomic masses,
and §_is the transformation from Cartesian displacement coordinates

X to the internal coordinates R:

3'23 (mm
The matrix elements are computed by the Wilson ;;vector technique

(30). The displacements of the atoms are described by a vector,

43

 

44

pa, one for each atom, so that the internal coordinates are expressed

W
N '_ ‘_ 3N
Rt = 2 Sta ' 08 I Z Btixi (t=l,2,...,3N—6) (4.3)
a=1 i=1

where;ta is the vector which describes the displacement of atom a
and a; is the unit displacement vector of atom a. The three Bti's
which belong to atom a are the components of the vector Eka.

The gevectors are computed by use of Wilson's formulae (30)

 

which are given in Table VIII for the various internal coordinates. ’

The unit vector, 2 is given by

u’
213 = [(xj—xifi-i- (yj-yi)‘; + (zj-zi)k]/rij (4.4)

where r11 is the bond distance between atoms 1 and j and i; 3; and k

are the unit vectors in the x, y, and 2 directions.

The solution of the secular equation (see Section II—B):

EEL'E

k>

(4.5)

is obtained by diagonalizing the product 9 §_by use of the Jacobi
G

method for symmetric matrices (53). Although is not symmetric,

the solution may be accomplished by solving two symmetric problems (50).
The Q 2 problem is solved in two stages. First, consider the

solution of

ER'RL (mm

where 2 is the eigenvector matrix and £_is the diagonal eigenvalue

Table VIII. Formulae for the Computation of Eka.

45

 

Bond Stretch

 

8ti ' “613
3:?

t3 1;)

 

Valence Angle Bend for Angle a J

 

C08 (1 e

 

 

 

 

 

 

 

 

- ijleli ‘ 11
5ti 2 r sin
11 ijl
cosoijlelj - e11
stj r sina
13 ijl
;_ - (rli - rljcosaiilh11 + (r11 + rlicosaijl e11
tk
rurljsindi.11
Out-of—plane Wag Ymijl’ For Coplanar Atoms
8 - " "'1';- " 81110111 Ella—El— n 3:
t1 rmi r sino r sine apex atom
ij mil il 1ij
stj I Binamil "anchor atom"
rijsina311
st1 I Sinamij "anchor atom"
rflsind‘111
8 - .1.
tm r "end atom"

im

Table VIII.

46

(continued).

 

 

 

 

 

 

 

 

Torsion 6ijlm
;- = -eiix e11
t1 r sinzo
ij ijl
_- . (r11 - riicosaij1)eiix eil cosqjlmeml x eli
stj rjlrijSinaileinakjl rjlsinajlmsinajlm
331 = (r11 - rmlcosajlm)em1 x elj cosaiileij x ejl
rlj-- rmlsinajlm - rljsinaijlsinaijl
- ‘ -em1 x elj
tm r sin 0
m1 jl

 

47

matrix of Q, If there are redundancies present, 2 will contain a row
and column with elements of zero for each redundancy. Thus §_will
give a zero root for each redundancy. Since §_is real and symmetric,

.2 is orthogonal and the roots are real and positive; thus;

§_=,2_L,Q' (4.7)
Let W_be a matrix defined as

11 = 1m .11 (4.8)
Then:

9-22' (mm
By defining a matrix Bias

H I 31' 331 (4.10)

the secular equation (4.5) can be written as
EE'EA «an

where Q is the orthogonal eigenvector matrix of §_and A_is the diagonal
eigenvalue matrix of H, The elements of A_are the 11, which are related

to the vibrational frequencies, v1, by:

vi . ( 1,)1/2 (4.12)

2st
The eigenvector matrix L (see Section II-B) is given by

L'EE (4.13)

[.1
.1
' ‘Ww

 

48

and its inverse by

a c W (4.14)

The Cartesian displacement coordinates from which it is possible
to make the vibrational assignments are formulated by a transformation,

T, from normal coordinate space to Cartesian space.

22= 19. (4.15)

For each normal vibration, u there are associated three

1’
Cartesian displacements xn, yn, and zn with each atom, a. The elements

of column 1 of I, taken three at a time, may be considered to be the

elements of a vector T:

the direction of the straightline motions of the a atoms in normal mode

with its origin at atom a. These vectors give

1 and the lengths show the relative amplitudes for each atom.

The transformation matrix, I, is computed from the equation (50).

.T. = M'1 11' .E 1.. 1’1 (4.16)

where all of the matrices have already been defined.
The structure of sodium tetrazolate has been determined by
Palenik (54) and is given in Table IX. The system contains nineteen

internal coordinates: 6 bond stretching coordinates (Arlz, Ar23,

Ar34, Ar45’ Ar51, Ar56), 7 angle bending coordinates (A0156, A3456’

A0123, Ac234, Aa345, Aa451, Aa512), l out-of—plane wag (AY6SI4)’

and 5 torsions (A61234, A62345, A63451, A04512, A65123).

Table IX. Structure

49

of Sodium Tetrazolate.

 

a

r12 = r34 = 1.348 A°
r23 = 1.310 A°

r15 = r45 = 1.329 A°
r56 = 0.911 A°

)456 = E156 é 123.8°
)154 = 112.4°

1512 = )345 = 104.3°
)123 = 3234 I 109.5°

 

aThe subscripts refer to the position of the atoms in the
ring. See Historical Section for correct numbering of the
ring. The number 6 refers to the hydrogen bonded to the
carbon atom.

50

In Figure 11 the four atoms, 1,5,4, and 6, define a plane. For
an out-of—plane wagging motion of the bond which is defined by atoms

5 and 6 the bond 5-6 is displaced out of the original plane (Figure III),

where + in Figure III

 

 

 

II III

designates the out-of—plane motion.

In Figure IV the fours atoms, 1,2,3, and 4, define a plane.
For a torsional motion (Figure V) the bond defined by atoms 1 and 2
moves out of the original plane and the bond defined by atoms 3 and 4

moves out of the original plane but in the opposite direction.

IV V

The potential field is of the GVFF type and contains both diagonal

and off diagonal force constants.

 

‘5.“- “a

 

51

2 2
2V - f1’1(Arl) + f2,2(Ar2) + f2’3(Ar2)(Ar3)

...

+

f3’5(Ar3)(Ar5) + f

£5,6(Ar5)(Ar6) + f
£6,9(Ar6)(Aa9) + f

2
£8,9(Aa8)(A09) + f9,9(Aa9) + f

f9,11

f10,12(°°‘10

£15,16(A°15

2
£16,16(A516) + f17,17

f2 4(Ar2)(Ar4) + f2’5(Ar2)(Ar5) + £2,6(Ar2)(Ar6)

(Ar2 )(Aa7 ) + f Ar2)(Aa8) + f (Ar2)(Aa9)

f2 ,7 2 ,8( 2,9

f2 10(Ar2)(A0110) + f3 3(Ar 3)2 +f3’4(Ar3)(Ar4)

(Ar3)(Aalo) + f (Ar3)(Aa )

3,10 3,11 11

2
f4’4(Ar4) + f4,5(Ar4)(Ar5) + £4,6(1r4)(Ar6) +

11(Ar4)(Aa11) + f (Ar4)(Aa

2
12) + £5,5(Ar5)

4,12

(Ar5)(Aolz) + f (Ar5)(Aal3)

5,12 5,13

f6’6(Ar6)2 + f6’7(Ar6)(Aa7) + f6’8(Ar6)(Aa8)

2
6,13(A‘6)(A“13) I £7,7(Aa7)

2
f7’8(Aa7)(Aa8) + £7,9(Aa7)(Ao9) + £8,8(Aa8)

(Aa9)(Aa

9,10 10)

(Aa9)(Aa11) + f (A09)(Aa12) + f (4a9)(Aa )

9,12 9,13 13

2
(Aalo) + f (Ao10)(Ac11)

10,10 10,11

)(Ach) + f (Aalo)(Aa

10,13 13)

2

2
(ball) + f (Ao11)(A012) + £12,12(Aa12)

11,11 11,12

2 2
£13,13(A“13) I £14,14(AY14) + £15,15(A515)

)(A616) + £15,19(A515)(A519)

2 2
(A617) + f (A618)

18,18

(A6

f19,19 19)2

(4.17)

.i"

l

V‘- "W4;E.m tun-5.1
'l

52

The relationship between the subscripts and the internal coordinates
is given in Table X.

The initial stretching force constants were approximated with
Badger's rule (55,56,57) which has been improved by Herschbach (58)

to give ”a

a .. d 3
F a .11..._Ll (4.18)

re ' dij

where re is the equilibrium bond length, and aij and dij are constants (g
which are fixed for bonds between atoms from rows i and j of the
periodic table. The initial in-plane angle force constants were
transferred from those for the cyclopentadienide ion (59) and those for
the out-of—plane modes from benzene (60). These force constants were
adjusted by trial and error until a reasonable fit was obtained between
the calculated eigenvalues and the observed eigenvalues. The inter—
action force constants were added one at a time and varied over a
reasonable range from negative to positive. The interaction constants
which gave a closer convergence to the observed eigenvalues were
retained in the potential field.

The symmetry of the tetrazolate ion is C The set of

2v'

eighteen Cartesian displacement vectors for the tetrazolate ion

reduces to 6A1 + 2A. + 6B + 4B2. Removal of the translational and

2 l
rotational representations (A1 + A2 + 231 + 282) leaves 5A1 + A2
+ 481 + 2B2 representations for the genuine vibrational modes. The

nature of the twelve vibrational modes may be further specified in

terms of the contribution made by the internal coordinates, and are

53

Table X. Relationship between Subscripts and Internal

 

 

Coordinates
Subscript Internal Coordinate

l Ar56

2 Ar15

3 Arl2

4 Ar23

S Ar34

6 Ark5

7 A“1:56
8 AOL456
9 A"‘154
10 Aa512
11 Aa123
12 M1234
13 Ao345
1“ AY6514
15 A65123
16 A61234
17 A62345
18 A63451
l9

A64512

 

54

given in Table XI and give a total of 8A + 3A2 + SB + 38 representa-

l 1 2
tions. Thus, there are 3A + 2A + B + B redundancies. The seven

1 2 l 2

redundancies were left in the calculation. Two obvious redundancies
are: (a) all ring angles cannot increase and (b) the three angles
around the carbon atom cannot increase. The other five redundancies
are not obvious.

The symmetry coordinates, 81’ are given in Table XII and were
constructed by using the following technique. The sets of symmetri-
cally equivalent internal coordinates were determined by examining

the effects of the operations for C v symmetry upon each internal

2
coordinate. For example, the operations E and ov(y,z) each transform
each internal coordinate into itself (the y and z axes define the
plane of the tetrazolate ring with the z axis coincident with the C-H
bond, and the x axis is perpendicular to the plane of the ring).

For an internal coordinate such as Ar the Operations C2 and

15
O;(xz) each transform Ar15 to AréS’ whereas, for Ar23 the Operations

C2 and o;(xz) transform Ar23 into itself. Examination of the character
for each Operation for each irreducible representation determines the
proper combination for all equivalent internal coordinates. All
symmetry coordinates must be orthogonal and normalized. Thus, the
symmetry coordination for the set Ar15 and Ar45 for the A1 representa-
tion is

1
S2 =- HArlS + M45) (4.19)

representation

1
S9 " V‘T‘Arls ' “45) (“'20)

whereas, for the B1

55

Table XI. Representations Generated by the Internal Coordinate Sets.

 

Bond Stretching

 

 

Set Representation
Arss A1

Ar12 and Ar3A A1 + B1
Ar23 A1

Ar15 and Ar45 A1 + Bl

 

Valence Angle Bending

 

 

Set Representation
AG 456 and Aa156 A1 + B1
AOL1:54 A1
A0512 and Aa345 Al + Bl
A0123 and Aa234 A1 + B1

 

Out of Plane Nagging

 

 

 

 

 

Set Representation
AY6514 B2
Torsional

Set Representation
A61234 A2
A5 3123 and A5231.5 A2 + B2
A6v.51 and A51.512 A2 + B2

 

56

Table XII. Symmetry Coordinates for The Tetrazolate Ion

(sz symmetry).

 

Species Svmmetry
Coordinate

Expression

 

 

1 1 56
s 1
2 {'2’ (“15 + “45)
1
S3 «'2’ (“12 + “34)
S4 Ar23
S ‘—l- (Au + Ad )
5 f2" 156 456
S6 AOL154
S "L- (Au + An )
7 4'2- 512 345
s J— (Au + Au )
8 «'2' 123 234
B S -l- (Ar - Ar )
1 9 {'2' 15 45
S -l- (Ar - Ar )
10 «T 12 34
S '-l— (Au - Au )
11 4'2" 156 456
S -l- (Au - Au )
12 «'2' 512 , 345
S '-l- (Ao - Au )
13 31'2" 123 234

Table XII. (continued).

57

 

 

 

Species Symmetry Expression
Coordinate
B2 S14 AY6514
s --1—- (A6 — A6 )
15 4 2 5123 2345
S 1 (A6 - A6 )
16 J 5 3451 4512
A s 4— (A6 A6 )
2 17 ‘1 2 5123 2345
S18 A61234
s ~1— (A6 A6 )
19 4 2 3451 4512

58

The y_matrix (see Section II) is Obtained from the coefficients of
the internal coordinates in the expressions for the symmetry coordinates.

The A 81’ and B species shown in Table XII are Raman active,

1. A2.
whereas, the A1, Bl’ and 82 are infrared active.

The in-plane modes can be separated from the out-Of-plane modes.

2

The 5A1 + 4B1 representations are the in-plane vibrational modes,

whereas, the A2 + 282 representations are the out-of—plane modes.

The symmetrized force constants, given in Table XIII, were
constructed by placing the force constants in tabular (or matrix)
form where the internal coordinates label each row and column in an
ordered fashion and by using the following rules (30). For a diagonal
symmetrized force constant, F11, which corresponds to a particular

symmetry coordinate, S the force constant, in the first row

1’ £1,3’

and in the column labeled by a given internal coordinate, AR , was

1:!
appeared in the

multiplied by the coefficient, c, with which ARij

symmetry coordinate, S The product cf was divided by the coeffi-

1' 1,1

cient, c; of the first internal coordinate (row label). This process
was repeated for each column and the results were added. All other
diagonal symmetrized force constants were obtained for each symmetry
coordinate with the same method. For the off-diagonal force constants,

F two different symmetry coordinates must be considered. For each

13’

representation the force constant, in the first row and in the

fij’
column labeled by a given internal coordinate was multiplied by the

coefficient, c, with which that internal coordinate appeared in the

symmetry coordinate, S The product cf was divided by the

i' ij

59

Table XIII. Expressions for the Symmetrized Force Constants.a

 

T

Species Symmetrized Expression
Force Constant

 

A1 F1,1 f1,1
F2,2 f2,2 + f2,6
F2,3 f2,3 + f2,5
F2,4 v7 f2,4
F2,5 f2,7 + f2,8
F2,6 Vi f2,9
F2,7 f2,10 + f2,13
F2,8 f2,11 + f2,12
F3,3 f3,3 + f3,5
F3,4 v7'f3,4
F3,5 f3,7 + f3,8
F3,6 V7.f3,9
F3,7 f3,10 + f3,12
F3,8 f3,11 + f3,12
F4,4 f4,4
F4,5 vz‘l' f4,7 +11% f4,8
F4,6 f4,9
F4,7 é. f4,10 2% f4,13
F4,8 é f4,11 2%. f4,12
F5,5 f7,7 + f7,8
F ff’f

5,6 7,9

6O

 

 

 

Table XIII. (continued)
Species ' Symmetrized Expression
Force Constant
A1 (cont.) F5’7 £7,10 + f7,13
F5,8 f7,11+ f7,12
F6,6 f9,9
F6,7 639,10 +6-— f9,13
F6,8 ¢%-f9,11 +v%.f9,12
F7,7 f10,10 + f10,13
F7,8 f10,11 + f10,12
F8,8 f11,11 + f11,12
B1 F9,9 f2,2 ' f2,6

F9,10 f2,3 ‘ f2,5
F9,11 f2,7 ‘ f2,8
F9,12 f2,10 ‘ f2,13
F9,13 f2,11 ‘ f2,12
F10,10 f3,3 ' f3,5
F10,11 f3,7 f3,8
F10,12 f3,10 ’ f3,13
F10,13 f3,11 f3,12
F11,11 f7,7 f7,8
F11,12 f7,10 f7,13
F11,13 f7,11 ' f7,12

61

Table XIII. (continued)

 

Species Symmetrized Expression
Force Constant

 

 

 

Bl (c°“t') F12,12 t10,10 ‘ f10,13
F12,13 f10,11 ’ f10,12
F13,13 f11,11 ‘ f11,12

B2 F14,14 f14,14
F14,15 {If—£14,15 “é: f14,17
F14,16 5% f14,18 ‘¢%.f14,19
F15,15 f15,15 ’ f15,17
F15,16 f15,18 ’ f15,19
F16,16 f18,18 ' f18,19

A2 F17,17 f15,15 + f15,17
F17,18 “2 f15,16
F17,19 f15,18 + f15,19
F18,18 f16,16
F18,19 é. f16,18 +61- f16,19
F19,19 f18,18 + f18,19

 

aThe subscripts for the symmetrized force constants correspond
to the subscripts for the symmetry coordinates.

62

coefficient, c', of the first internal coordinate (row label) which
appears in the symmetry coordinate Sj' This was done for each column
and the results were added. This process was repeated for all other

symmetry coordinate combinations for each particular representation.

V. Results and Discussion

A. Normal Coordinate Analysis Calculation for Sodium Tetrazolate

The normal coordinate analysis calculation was done with the
aim of making assignments of the normal modes of vibration (such as
bond stretch, ring breathing, etc.) for the tetrazolate anion. Much
controversy exists in the literature about the vibrational assignments
for tetrazoles. Previous authors have attempted to make vibrational
assignments strictly from experimental evidence and by analogy with

compounds which contain portions (or subgroups) of the tetrazole ring.

 

In this calculation the effects of hydrogen bonding due to the
water of hydration were neglected. This neglect is a good approxima-
tion since all vibrational modes due to hydrogen bonding occur below
200 cm-1. Thus any interactions between those modes and the genuine
modes for tetrazole are quite small and would affect the calculated
frequencies by only a few cm-l.

The tetrazolate ion vibrations were analyzed by obtaining an
initial set Of force constants for the internal coordinates and by
adjusting these constants so that the Observed spectrum was reproduced.
The final set of diagonal and interaction constants are listed in
Table XIV. Only those interaction constants which caused a significant
difference in the calculated frequencies were retained. The inter-
action force constants, whose difference upon construction of the
symmetrized force constants is very small, were neglected. The

vibrational frequencies for sodium tetrazolate, calculated by use Of

the force constants in Table XIV, are given in Table XV. Comparison

63

 

Table XIV.

a
Values for Force Constants .

 

f1,1 I 5.268

f2,2 I 5.36

f2,3 I 1.05

f2’4 I 0.50

f2,5 I 0.35

f 1.45

2,6

192’7 I -0.12

f2,8. -0.009

f2’9 I 0.13

f2,10 I 0.13

f3,3 I 5.21

f3,“ I 0.57

f3,5 I 1.05

£3,10 I 0.30

f3’11 I 0.35

f4,“ I 5.56

f4,5 I 0.57

f4,6 I 0.50

f4’11 I 0.25

£4.12 I 0.25

f5,5 I 5.21

f5,6 I 1.05

f5,12

f5’13 I 0.30

f6,6 I 5.36

f6,7 I -0.09

0.35

f I -0.22
f I 0.58
f I -0.22
f I 1.44

f9,10 I 0.28

f9,11

f9,12

f9,13

f10,10

f10,11

f10,12

f10,13

f11,11

f11,12

f12,12

f13,13

f14,14

f15,15

f15,16

f15,19

f16,16

f17,17

f18,18

f19,19

0.15

0.15

0.28

1.34

0.28

0.15

0.40

1.39

0.50

1.39

1.34

0.297

0.201

-0.006

I -0.006

I 0.201

I 0.201

I 0.201

I 0.201

 

0
8Units are mdyne/A .

65

Table XV. Results of the Normal Coordinate Analysis
Calculation for Sodium Tetrazolate.

 

 

 

 

 

Species Vibrational Calculateda %Eb

Modes Frequency

Al VI 3125 +0.16%
v2 1461 +0.41%
v3 1243 -3.78%
v4 1138 -1.98%
vs 962 -9.86%

B1 v6 1453 +0.56%
v7 1063 +3.91%
vs 1013 -0.20%
v9 730 +3.99%

82 VIC 910 0.00%
v11 456 +0.44%

A2 v12 537 -----

 

8Units are in cm-l.

bzz - (”calc. ' ”obs.) 100
V
obs.

66

of the data given in Table XV with the spectral data for sodium
tetrazolate monohydrate (Tables XVI and XVII) show that the pattern
is reproduced for most frequencies.

From the measured depolarization ratios (Table XVII) for sodium
tetrazolate monohydrate the vibrational modes at 3128, 1287, 1189, and
1079 cm‘1 are symmetric, whereas, the 1438, 1130, 1025, 1009 and 702
cm—% modes are asymmetric. The out-of—plane bands (910, 454 and 537
cm-1) were not observed in the Raman spectrum, which indicates that
the polarizability, Z, is quite small for these modes. Thus, the
A2 vibrational mode was not detected. However, since the calculated
frequencies for the 32 modes are in close agreement with the observed
frequencies, and since the symmetrized force constants, F

17,17’ F18,18 and
(A.2 mode) (Table XIII) differ only in sign from the symmetrized

F19,19
force constants for the 82 mode which describes the torsional motion,
the calculated value is fairly accurate. The observed eigenvalue
should not differ from the calculated eigenvalue by more than 5-10 cm-1.
The band Observed at 1130 cm"1 in the Raman, which is Observed at 1132
cm.1 in the infrared, must be a combination since no calculated
asymmetric band has a corresponding energy. Also a band approximately
equal to 1130 cm.1 is not found for tetrazole (Table IV) or for
bis(tetrazolato)c0pper(II) (Table XIX). 0f the five expected A1
vibrational modes, four are observed in the Raman. The fifth band,

1 in the infrared spectrum) is probably masked

by the asymmetric band found at 1437 cm-1. Two other bands, 1696 and

v2, (v2 equals 1455 cm-

1647 cm-1, are Observed in the Raman spectrum. The 1647 cm”1 band

Table XVI.

67

Infrared Spectrum for Sodium Tetrazolate Monohydrate

with Assignmentsa.

 

Vibrational Observed

Frequency,icm

3300
VI 3120
2930
2370
1785
1685
1640
v2 1455
v6 1445
v3 1290
1210
v4 1161
1132
vs 1065
v7 1023
vs 1015
v10 910
v9 702
660
v11 454

Assignment

O-H stretch
C—H stretch

v2 + v6

v2 + v10

8+"9

O-H bend

\J

sym. ring deformation
C—H in-plane bend
sym. ring deformation
v9 + v12(a)

sym. ring breathing
v9 + v11
sym. ring deformation
asym. ring deformation
asym. ring deformation
C-H out—of—plane bend
asym. ring deformation
1640-v8

out-of-plane ring bend
asym. with respect to
C2 axis

 

V

12

is taken as the calculated value.

 

68

Table XVII. Raman Spectrum and Depolarization Ratios for
Sodium Tetrazolate

 

 

Vibrational Raman Depolarization

Mode Spectruma Ratio
v1 3128(m) 0.331
1696(sh) . -----

1647(m) -----

v6 1438(8) 0.862
v3 1287(vs) 0.432
v4 1189(vs) 0.417
1130(w) 0.858

vs 1079(w) 0.242
v7 1025(w) - 0.897
vs 1009(w) 0.875
v9 702(w) 0.800

 

aUnits are in cm-l.

bIntensities were measured with a planimeter.

69

is due to water, whereas, the 1696 cm“1 band is a combination. If
areasonable set of force constants is used, it is impossible to
reproduce the observed spectrum within acceptable error so that one
of the genuine modes is located at 1696 cm-1. Depolarization ratios
could not be measured for the 1647 and 1696 cm-1 bands because of
fluorescence, which was present from 1500 to 2800 cm“1. Attempts

to remove the fluorescendng material by passing the aqueous solution
of sodium tetrazolate through activated carbon were unsuccessful.

The difference between the calculated frequencies and observed
frequencies is quite small except for us which was calculated to be
962 cm”1 versus an observed value of 1065 cm-1. This indicates that
the final set of force constants are not completely accurate, however,
one can still make the vibrational assignments.

The distribution of each particular vibration among the Cartesian
normal coordinates is given in Table XVIII. From the distributions the
vibrational assignments were made. Each coefficient was multiplied by
the square of the atomic mass, which better describes the relative
motion of the atoms with respect to each other. The frequencies,
v1, v6 and v10 (Table XVI) are a C-H stretch, a C-H in-plane bend,
and a C-H out-of—plane, respectively. For all other vibrations the
ring vibrates as a whole, i.e., there are no particular C-N, N-N,
stretching, etc. modes. v2, v3, and v5 are symmetric in-plane-ring
deformations, where, VA is a symmetric ring breathing mode. v7, v8,

v are asymmetric ring deformations. v11 is an out-of—plane ring

9

bend asymmetric with respect to the C2 axis, whereas, v12 is an out-

of-plane ring bend symmetric with respect to the C2 axis. The

70

Table XVIII. Distribution of Each Vibration Among the Cartesian
Normal Coordinates.

 

 

Vibrational Distributiona
Mode
l -0.094zS + 0.94126
2 -0.061y1 + 0.11121 + 0.082y2
-0.038z2 - 0.082y3 - 0.03823 + 0.061y4
+0.11124 - 0.1522S - 0.20026
3 0.127yl + 0.02421 - 0.058y2 + 0.05322

+0.058y3 + 0.0532 - 0.12.7}!A + 0.0242

3 4

-0.1622 - 0.1972

5 6
4 -0.o42y1 + 0.07121 - 0.151y2
-o.07822 + 0.151y3 - 0.07823 + 0.042y4
+0.07224 + 0.01425
5 0.118y1 + 0.05721 + 0.052y2 - 0.10522
-0.052y3 - 0.10523 - 0.118y4 + 0.05724
+0.1o1z5
6 0.182y5 - 0.678y6
7 ‘ 0.058y1 + 0.09921 - 0.12722
+0.127z3 + 0.058y4 - 0.09924

-o.075y5 - 0.332y6

8 -0.092y1 + 0.0382 + 0.034Y2 - 0.0942

1 2

+0.034y3 + 0.0942 - 0.092y4 - 0.0382

3 4

+0.086y5 + 0.596y6

71

Table XVIII. (continued)

 

 

Vibrational Distributiona
Mode
9 0,058yl - 0.1062:l - 0.103y3 + 0.07823

-0.103y3 + 0.07823 + 0.058y4 + 0.10624
+0.098y5

10 -0.l79x5 + 0.7O7x6

11 0.12x1 - 0.054x2 - 0.54x3 + 0.12x4
-0.101x5 - 0.623x6

12 0.096x1 - 0.163x2 + 0.163x3 - 0.096x4

 

aThe subscripts refer to the position of the atoms in
the ring. The number 6 refers to hydrogen.

72

remaining bands observed in the infrared Spectrum, (Table XVI), are
combination bands except the band at 3300 cm.1 which is the O-H
stretch for water. In all cases for the combinations the direct
product of the representation of the two frequencies which form the
combination yields a representation which is infrared active and
Raman active. The sum of the frequencies which form each combination
is in close agreement with the observed frequency. This further
substantiates the correct identification of the genuine vibrational
modes.

The magnitude Of the interaction constants are quite large
in most cases. Nakamoto (29) predicts that an interaction constant
should have a value of approximately 1/10 the value of the corres-
ponding diagonal force constant. The presence of an unshared pair
of electrons on each nitrogen explains the large magnitude.
Speculation about the significance of the magnitude of the diagonal
force constants is not warranted since the force constants are not
of sufficient accuracy. To Obtain sufficiently accurate force
constants one would have to observe the infrared and/or the Raman
spectrum for isotOpically substituted sodium tetrazolate.

For the most part the vibrational assignments made by previous
authors are not correct. For example, Holm (28) has attributed the
band at 664 cm"1 to the C-H out-of—plane bend, which would require
the force constant, £14,14, to be unreasonably low. As it is,
£14,14 is much smaller than the value calculated é~0.40 mdyn/A ) for
the C-H out-of-plane bend in benzene and the cyclopentadienide ion.

Jonassen (l9), Holm (28), and LeFebre and Werner (61) have assigned

73

the bands at 1430-60 cm“1 to be the N2N3 bond. From this investigation
all bands in the 1430—60 cm”1 region and all other bands, except those

associated with C—H, involve complete ring motion rather than just

a part of the ring.

B. Synthesis.

Bis(tetrazolato)copper(II) Monohydrate
The pale-blue compound, bis(tetrazolato)c0pper(II) monohydrate,
was prepared by reacting equimolar amounts of aqueous tetrazole and
aqueous copper(II) nitrate. The compound decomposes upon heating
and is insoluble in all solvents which indicates a polymeric structure.
The reflectance electronic absorption Spectrum is given in
Table XXI. Fallon ((2) has recorded the ultraviolet spectrum of
tetrazole. Tetrazole shows no absorption bands below 45.5 x 103cm-1.
The band at 37.5 x 103 cm.1 in the complex probably arises from a
transfer of a n electron from the ligand to the de-yz orbital of the
c0pper atom and not a ligand n to n*e1ectron transfer. A single
asymmetric absorption band due to a d-d transition is observed at
14.9 x 103cm-1. The COpper(II) ion usually exists in octahedral
configuration with a tetragonal distortion because of the Jahn-Teller
effect, a square planar configuration or a tetrahedral configuration.
Of these three possibilities for bis(tetrazolato)c0pper(II) mono-
hydrate the tetrahedral configuration is not likely because of the

magnitude of the Dq value. Ditri gg‘al., (15) observed a splitting

of 13.5 x 103 cm“1 and 16.0 x 103 cm.1 for Cu(PMT)6(C104)2 and

 

74

Cu(PMT)4(C104)2, respectively. The reflectance spectrum for
bis(S-trifluoromethyltetrazolato)copper(II) monohydrate (23) is very
similar to that observed for distorted octahedral complexes of
copper(II) with strong nitrogen donors (63), and the spectrum is
almost identical with the spectra for Cu(bipy)§+ and Cu(o—phen)§f

The principle and most intense band was observed at 14.7 x 103cm”1

with a shoulder at 17.9 x 103 cm-l. A much weaker band was observed

at 9.0 x 103 cm—l. Since the trifluoromethyl group is an electron
withdrawing substituent, the tetrazolato ligand should be a stronger
ligand than the 5-trif1uoromethyltetrazolato ligand, because of the
increased electron density on each nitrogen atom. From Ditri's
results the energy Splitting is larger for the square planar complex
than for the six coordinate complex. Thus the coordination of the
copper atom in bis(tetrazolato)copper(II) monohydrate complex is
probably six-fold with a tetragonal symmetry. The band at

2

14.7 x 103 cm“1 is probably the zBlg-——+ B28 transition. The

2 2 2 2
higher and lower energy transitions, Blg_—_+ E8 and Blg-——+ Alg’

respectively, could not be resolved. A band was observed at
6.9 x 103 cm.1 but is probably an overtone of an infrared band
(2 x 3450cmu1) and is not associated with the electronic properties
of the complex. 4

The magnetic moment is given in Table XXII for bis(tetrazolato)-
copper(II) monohydrate. The value 1.76 B.M. compares quite closely

to the spin-only value of 1.73 B.M. which indicates little spin-orbit

coupling. Corrections for the diamagnetism of the ligands and of the

III. 1.7 A7 I.

75

ligands of following compounds were made by use of Pascal's constants
(64). Mercury (tetrathiocyanato)cobaltate(II) was used as the standard.
The infrared spectrum for bis(tetrazolato)COpper(II) is given in
Table XIX. The assignments for the tetrazolate anion were made by
analogy from the results for sodium tetrazolate monohydrate. The
presence of a band at 544 cm-1 substantiates the correctness of the
calculated value for the A mode. Ditri and POpov (65) Observed

2

two unique bands at 300 cm-1 and 276 cm.1 for Cu(PMT)6(C10 which

4)2
they assigned as Cu-N vibrational modes. The two bands at 328 cm"1 ,
and 315 cm.1 are, by comparison, distinct Cu-N stretches. This
observation could indicate two different Cu—N bond distances and would
be in accord with the prOposed tetragonal symmetry of the complex.
Since the copper-nitrogen bond possesses some degree of covalency,
the symmetry of the tetrazole ring is at most Cs’ and, as a result,
only the in-plane and out-of—plane modes are separable. Thus it
is not relevant to discuss the ring modes as being symmetrical or
asymmetrical. The genuine vibrational modes for the tetrazolate
ring are shifted very little as a result Of coordination by the copper
atom. In all cases the sum of the genuine modes for each combination
agrees with the Observed band.
Since copper(II) ion is 3d9 the electron spin resonance spectrum
of bis(tetrazolato)copper(II) would aid in the elucidation of the
bonding and structure of the compound. The ESR spectrum for the
undiluted powder exhibits a very broad absorption band with a line

width of approximately 500 gauss, which indicates that neighboring

unpaired electrons interact strongly. The hyperfine splittings were

 

76

Table XIX. Infrared Spectrum for Bis(tetrazolato)copper(II)
Monohydrate and Vibrational Assignment

 

 

Genuine
Vibrational Absorption Assignment
Modes Maxims

v14 3450 (vs)8 O—H stretch

v1 3100 (m) C-H stretch
2920 (m) 02 + V6
2350 (w) V6 + 010

v13 1640 (sh) O-H bend
1620 (m) v5 + 012

v2 ' 1470 (3) ring deformation

v6 1450 (s) C-H in-plane bend
1390 (m) v8 + v15
1340 (m) v7 + v16

v3 1240 (m) ring deformation
1220 (m) v9 + v12

v4 1160 (3) ring breathing

vs 1060 (8) ring deformation
1045 (sh) v9 + v15

v7 1020 (a) ring deformation

v8 980 (w) ring deformation

v10 900 (vs) C-H out-of—plane bend
835 (w) v12 + v16

09 690 (vs) ring deformation

v 544 (s) out—of—plane ring bend

12

77

 

 

Table XIX. (continued)
Genuine
Vibrational, Absorption Assignment
Modes Maxima
v11 450 (m) out-of—plane ring bend
v15 328 (s) Cu-N stretch
016 315 (s) Cu-N stretch

 

3As defined in Table I.

78

not detected. Attempts to prepare bis(tetrazolato)zinc(II) with copper(II)
as an impurity with both water and ethanol as solvents were unsuccessful.
Bis(tetrazolato)COpper(II) precipitated immediately, whereas, {ht zinc

complex precipitated only after one day.

l-methyl-S-tetrazolyllithium‘1/2THF

 

‘ ‘4“:

Since the tetrazolyl anion is isoelectronic with the cyclo-
pentadienyl ion, reactions between various metal ions and the tetra-
zolyl anion were attempted with the aim of preparing I'sandwich-type"
compounds. In order to prepare the tetrazolyl anion the reaction
between 1-methyl-tetrazole and n—butyllithium was attempted. Gilman
__£.§1., (66) observed that gfbutyllithium when compared with other
gfalkyl lithium compounds and phenyllithium is the most reactive.
0f the three common solvents (dioxane, ether and tetrahydrofuran)
used in organolithium reactions, organolithium compounds are the most
reactive in tetrahydrofuran (67).

The white compound, 1-methy1-5-tetrazolyllithium°1/2 tetra-
hydrofuran was prepared by reacting 1-methy1tetrazole with excess
Igfbutyllithium in anhydrous tetrahydrofuran at -50°C. The temperature
must be kept below -35°C. in order to prevent the lithiumation of the
a positions of tetrahydrofuran.(68). A reaction time of one-half to
one hour was sufficient for complete reaction. l-methyl-S—tetrazolyl-
lithium'1/2tetrahydrofuran is insoluble in tetrahydrofuran and ether.
From the C, H, and N analyses one-half of a mole of tetrahydrofuran

is solvated with the lithium compound.

 

79

The infrared spectrum for l—methyl-S-tetrazolyllithium-1/2THF
is presented in Table XX. The bands for 1-methy1tetrazole at 3135,
1471, and 881 cm-1 by analogy with the normal coordinate analysis
results for sodium tetrazolate, are the ring C-H stretch, C-H
in-plane bend and the C-H out—of-plane bend, respectively. These
bands are absent in LiCH3N4°1l2THF which indicates that the proton
at the 5 position was removed. The Li-C stretch for organolithium
compounds is found at approximately 880 cm—1 (68). Thus the band
at 855 cm.1 is assigned as the Li-C stretch. No such band is observed
for l-methyltetrazole (Table XX) and bis(l-methyl-S—tetrazolyl)-
nicke1(II) (Table XXIII). The band at 605 cm.1 is very strong and
is assigned as the Li-C bend since no such band is observed for
l-methyltetrazole and bis(l-methyl-S-tetrazolyl)nickel(II). The
results from the normal coordinate analysis for sodium tetrazolate
(Table XVI) were used to determine the ring vibrations for l-methyl-
tetrazole and 1-methyl-S-tetrazolyllithium'l/ZTHF. Thus the bands
1496 and 1482, 1279 and 1284, 1174 and 1170, 1113 and 1130, 973 and
970, 928 and 935, and 678 and 673 cm'1 should be the in-plane ring
vibrations for l-methyltetrazole and l-methyl-S-tetrazolyllithium-1/2THF,
respectively. The out-of-plane ring modes are 534 and 556, and 476
and 437, respectively. These bands compare favorably with the ring
modes assigned for sodium tetrazolate monohydrate. The asymmetric
CH3 and symmetric CH3 stretches may be assigned as the 2930 and 2880 cm"1

bands, respectively, and the asymmetric CH3 bend and symmetricCH:3

bend may be assigned as 1425 and 1350 cm"1 bands, respectively (34).

80

 

 

Table XX.- Infrared Spectra-Of1lemethyl—Setetrazolyllithium°1/2 THF
and lemethyltetrazole.
Genuine l-methyl- LiC2H3N4°1/2THF Assignment
Vibrational tetrazole
Mode
3400 (vw), 3400 (m), 07 + v9 + v17
broad broad
V1 3135 (5) ring C-H stretch
02 2980 (m) 2930 (vs) asym. CH3 stretch
v3 2880 (sh) sym. CH3 stretch
2830 (w) 2v7
2250 (vw) v9 + 013
v4 2150 (vs) CEN stretch
1639 (vw) 1610 (w) v11 + v20
vs 1496 (s) 1482 (m) ring vibration
06 1471 (vw) ring C-H bend
1460 (3) due to THE
v7 1422 (m) 1425 (s) asym. CH3 bend
1402 (w) 1382 (vw) 014 + v20
V8 1350 (s) sym. CH3 bend
09 1279 (s) 1284 (vs) ring vibration
v10 1225 (m) 1220 (w) CH3-N stretch
V11 1174 (vs) 1170 (w) ring vibration
1155 vw
. ( ) v18 + v19
v12 1113 (s) 1130 (w) ring vibration
1058 (m) 2v19
1040 (w) v + v

17 21

’l ‘1”?

VII-.11.; v..rnm.mmar

L.

 

81

 

 

Table XX. (continued)
Genuine 1—methyl- LiC2H3N4-1/2 THF Assignment
Vibrational tetrazole
Mode
v13 973 (vs) 970 (sh) ring vibration
v14 928 (m) 935 (vs) ring vibration
v15 881 (vs) ring C-H out-of-plane
wag
V16 855 (w) Li-C stretch
719 (s) 2v21
v17 678 (vs) 673 (a) ring vibration
658 (s) v13 - v21
V18 605 (s) _ Li-C bend
v19 534 (s) 556 (m) out-of—plane ring bend
v20 476 (s) 437 (m) out-of—plane ring bend
357 (m) 354 (sh) CH -N skeletal vibratio

3

 

 

.- “Ta-...;

 

82

The CH3—N stretch may be assigned as the 1220 cm"1 band and the CH3-N

skeletal vibration as the 354 cm.1 band (34). The band at 1460 cm-1

is probably the CH deformation for tetrahydrofuran (34). The band at

2

2150 cm-1 is very intense and occurs in the infrared spectrum for
bis(l-methyl-S-tetrazolyl)nickel(II) (Table XXIII) and bis(l-cyclo-
hexyl-S-tetrazolyl)nickel(II) (Table XXIV). Because of the intensity
this band cannot be a combination. The cyanide stretch for sodium
and potassium cyanide occurs at 2080 cm“1 while the band for COpper(I)
cyanide occurs at 2178 cm-1. In copper(I) cyanide the Cu-CN bond
is essentially covalent, but in potassium and sodium cyanide the bond
is ionic. Since the CIN stretching band of the free ion is shifted to
a higher frequency by coordination, the resonance form (A) is quite
important.

:0 I N? +——-I':E§N:

(A) (B)

The band at 2150 cm"1 suggests that the delocalization of the electrons
is similar in l-methyl-S-tetrazolyllithium'l/2THF. Thus this compound

is probably a polymer with the proposed structure as follows:

+ _ 4
Li N Li

 

 

 

 

/' \
CH3--—-N\\\\S:?///,N
K h\\\C’//IO\\\\ I”’l{/’

.4 \H

2 2

CH3—-—-‘N

 

0—0

H

 

”\"N
\9/

BB
3

‘L'fl-fir D ' 175—” raga-3

.‘L‘

 

1.1--

 

83

This structure would explain the insolubility of the lithium compound
in tetrahydrofuran, ether and benzene. The infrared spectrum for

the lithium compound, except for the missing C-H bands, is essentially
the same as for 1-methyltetrazole which indicates that the tetrazole

ring is intact.

Bis(1-methyl-5-tetra2o1y1)nickel(II)
Bis(1-methy1—5—tetrazolyl)nickel(II) was prepared by reacting
equimolar amounts of 1-methyl-5-tetrazolyllithium and dichlorobis-
(triethylphosphine)nickel(II). This compound when wet is extremely
sensitive to air and moisture but is much more stable when dry. The
compound decomposes when heated and exhibits no detectable solubility

in any common solvents which may indicate polymer formation. The nickel
complex reacts with the polar, non-donor solvent dinitromethane to

form Ni(C2H3N4)2°2CH3NO2 which decomposes explosively when heated.

The Ni(C2H3N4)2 complex decomposes in ammonia to give CN-,
3.

Methanol and HN3 were identified by means of vapor phase

CH3OH, and N
chromatograms. Methanol was also identified by means Of the nmr
spectrum. The cyanide ion was identified by the addition of a saturated
solution of iron(II) sulfate to an ammonical solution of the complex.

To this solution was added aqueous iron(III) chloride. Immediately,

a deep blue precipitate formed which indicates the formation of
Fe[Fe(CN)6]-. The close agreement between the calculated and found
analysis for cyanide indicates that cyanide ion is formed quantitatively.

The compound also dissolves in acidic solutions but not quantitatively.

84

Only about 55% of the ring decomposes as determined by the analysis
for cyanide ion.

From the reflectance spectrum (Table XXI) the symmetry of the
nickel ion is octahedral. The bands observed at 8.06 x 103 cm-1

and 14.7 x 103 cm"1 are the two d-d transitions which correspond to

3 3 . 3 3
1‘ —.——> .
Azg-—+ T2g( ) and A28 Tlg(F). The Dq value for Ni(C2

is 806 cm.1 which compares with a Dq value Of 850 cm_1 and 1070 cm-

H3N4)2
1

for Ni(H20)§+ and Ni(NH3)62+, respectively (69,70). Thus the
1-methyl-5—tetrazo1yl ligand forms a weaker complex than does

water. The shoulder at approximately 25.0 x 103 cm.1 would be the

3Azgu—mr 3T18(P) transition. From the energy-level diagram for (3d)8

computed by Liehr and Ballhausen (71), the transitions for a regular

octahedron should appear at 12.5 x 103 cm.1 to 14 x 103 cm-1 for

3 3 3 -1 3 3
T18(F) and at 23 to 24 x 10 cm , for A28-—-+ T18(P).

A large charge transfer band was observed at 30.9 x 103 cm-l. Fallon

A28(F)-——>

(62) observed no absorption below 43.4 x 103 cm-1 for large number
l-alkyltetrazoles. Thus the charge transfer band should be a result
of a transfer of a w electron from the tetrazole ring to an eg orbital
of the nickel.

The magnetic moment for bis(1-methy1-5-tetrazolyl)nickel(II)
is 2.90 B.M. (Table XXII), and agrees quite well with the spin-only
value of 2.83 B.M. The complex has two unpaired electrons and is
consistent with the electronic absorption spectrum.

The infrared spectrum is given in Table XXIII. In the main,

the features of l-methyltetrazole are retained but with changes in

 

85

Table XXI. The Electronic Absorption Spectra for Some Tetrazole Complexes.

 

bis(tetrazolato)COpper(II) monohydrate

 

14.9 x 103 cm'1

37.5 x 103 cm—1

 

bis(l—methyl-S—tetrazolyl)nickel(II)

. use}

 

8.06 x 103 cm.”1

14.7 x 103 cm‘1

 

=25.0 x 103 cm"1 - shoulder

30.9 x 103 cm”1

 

bis(1-cyclohexyl-5-tetrazolyl)nickel(II)

 

8.33 x 103 cm-1

14.7 x 103 cm-1

=26.6 x 103 cm"1

=35.1 x 103 cm”1

=42.9 x 103 em'1

 

 

 

 

86

amcwm xxHH. are 3mmdmnwn xosm=nm mom moan Hmnnmnowm noavwmxmm

 

 

 

noapOcsa amaomnmncnm Somamnwnm mxvonuamsnmw mpn=105Hw espoused
mcmnmvnwcwwunw Zoamsn. w.z. :oBOSn mHmnnnonm
oeAanev~.:~o MN.m.o. ewes x Ho-e H.oo e.oo H
ZHAnNmoZevN Ne.o.o. wane x Hone ~.eo ~.mo N
ZHAncmHHzev~ -.m.o. OVHN x Houa ~.em ~.mo N

 

eczema om x3 mam won sown.

 

87

Table XXIII. Infrared Spectrum.for.Bis(lemethyl-S-tetrazoly1)-
nickel(II).withlAssignments.-

 

 

Genuine Ni(C2H3Nh)2 Assignment
Vibrational
Mode
3400 (m), v7 +09 +v17
broad
3180 (m) 4 v5 + 010 + v22 fl?
v2 2930(vs) asym. CH3 stretch I_F
v3 2890 (s) sym. CH3 stretch
2830 (s) 267 'r g
2250 (vw) V9 + v13
vh 2150(vs) CEN stretch
1610 (s) V11 + V20
vs 1496 (5) ring vibration
v7 1425 (s) asym. CH3 bend
V8 1348 (vs) sym. CH3 bend
V9 1284 (vs) ring vibration
010 1223 (w) CH -N stretch
011 1182 (m) ring vibration
012 1125 (w) ring vibration
1055 (m) 2019
y13 955 (vs) ring vibration
V14 925 (vs) ring vibration
755 (W) V20 + V20:
v17 675 (vs) ring vibration
660 (s) V13‘ V21
021 595 (w) Ni-C bend

 

019 521 (m) out-of—plane ring vibration

Table XXIII. (continued)

88

 

Genuine Ni(C2H3N4)2 Assignment
Vibrational
Mode
v22 456 (w) Ni-C stretch
v20 437 (m) out—of—plane ring bend
v2h 337 (m) CH3-N skeletal vibration
v 298 (s) Ni-N stretch

23

 

 

fi~

a.
a!
J-

h
F

inhuman-4 ‘ m n“

Afi‘

 

 

89

intensities and slight shifts in position of the absorptions.
Absorptions occur at 595 and 456 cm"1 which are not present for
l-methyltetrazole, and may be attributed to the Ni-C bend and Ni-C
stretch, respectively. The Ni-C stretch in Ni(CN)i-(72) is found at
543 cm-1 and the bend at 433 and 421 cm-1, and the Fe~C stretch (73)

in Fe(CN)2-is found at 416 cm-1. and the bend at 583 cm-1. A band

5'
I
1

occurs at 298 cm"1 which can probably be attributed to an Ni-N bond

(65,74) by analogy to nickel PMT and pyridine complexes. The absence

 

of the bands at 3135, 1471, and 861 cm-1 confirms the formation of “‘
the Ni-C bond. All other vibrational modes were assigned by analogy
with lumethyltetrazole and l-methyl-S-tetrazolyllithium-1/2THF.

The presence of the band at 2150 cm-1 indicates considerable electron
delocalization around theijnrpart of the ring.

Because of the low solubility of the complex in all solvents, the
octahedral configuration of Ni and the presence of the Ni-C bonds and
Ni-N bonds, the structure is probably polymeric. The tetrazole ring
seems to be intact in the complex, if the over-all infrared spectrum is
considered and since at least a part of l-methyltetrazole is recovered,
when the complex is decomposed in acid. Since the ring is broken in
concentrated ammonia between the 1 and 5 positions and the 3 and 4
positions, it appears that the 1-5 N-C and the 3-4 N-N bonds may be

rather ionic.

 

Because nickel is six coordinate, each ligand must provide three
bonds. Two of the six bonds to each nickel are Ni-C bonds, while, the

other four are Ni-N bonds. If the resonance form :C-if’is aprOpos, the

 

90

bond between the 4 nitrogen and Ni would be essentially ionic. The
remaining two bonds are probably covalent bonds formed between the 2
or 3 nitrogen of an adjacent ring and the nickel of the original unit.
By working with Framework Milecular H1dels it was not possible to form

a unit where the Ni-C bond is from one ring, the Ni-N bond from

4

Eu

1

‘

another ring and the Ni—N bond from a third ring. Also, it is

2 or 3

not possible sterically to form a unit where the Ni-C and Ni—N2 or 3

bonds are formed from the same ring and the Ni-N from a second ring.

4
If the Ni-N bond is covalent rather than ionic, the Ni-C and Ni-N

4 4
bonds possess considerable strain because of the formation of a three
membered ring. If the Ni-C and each set of Ni-N bonds are cis, the
simplest unit formed is a hexamer. This is not likely since the
hexamer should be soluble in non-polar solvents. If the Ni-C and
each set of Ni-N bonds are trans, an infinite array is formed, which
is compatible with the insolubilities of the complex.

Crystal structures have been determined for pentamethylene iodine
monochloride and dichlorobis(l-methyltetrazole)zinc(II (75,76). In
both cases coordination involved the 4 position of the tetrazole ring.
Even though PMT-1C1 and Zn(C2H4N4)Clé are not analogous with Ni(C2H3N4)2
the crystal-structural results tend to indicate that the 4 position of

the tetrazole ring is unique and, thus, probably is involved in the

coordination of Ni(C2H3N4)2.

Bis(ltgyclohexyl-S-tetrazolyl)nickel(II)
The reaction between l-cyclohexyl-S-tetrazolyllithium (prepared

ig_situ) and dichlorobis(triethylphosphine)nickel(II) yielded pale-green

a ‘r"

Warm-um...”
.
4

 

 

91

bis(l-cyclohexyl-S-tetrazolyl)nickel(II) after a period of one to two
days. The compound decomposes with heating, is insoluble in all solvents
and is sensitive to the atmosphere.

The compound decomposes in ammonia to give CN-, N3 and cyclohexyl

alcohol similar to what was observed for bis(1-methy1-5-tetrazolyl)-

 

“a.
nickel(II). , E
The reflectance spectrum (Table XXI) shows two distinct bands at
8.33 x 103 cm.1 and 14.7 x 103 cmfl, d-d transitions, which correspond ‘
to 3Azg———+ 3T28(F) and 3AZg———+ 3T18(F), respectively. The Dq value 7“

for the compound is 833 cm-1. The data indicate that the l-cyclohexyl-

S-tetrazolyl ligand forms a slightly stronger complex than does the

l-methyl-S-tetrazolyl anion. A broad band was observed at approximately

26.6 x 103 cm.1 which is the 3A28-——+3T1g(P) transition. If the

3 3 3 3
transitions A28-—+ T18(F) and A28-——+ T18(P) were observed at

14 to 15 x 103 cm"1 and 24 to 25 x 103 cm.1 the symmetry would corres-
pond to that of a regular octahedron. Two broad charge transfer bands
were observed at approximately 35.1 x 103 cm.1 and 42.9 x 103 cm-1
which are probably due to a ligand w electron transfer to the eg orbital
and a ligand n to n* transfer, respectively.

The magnetic moment (Table XXII) is 2.98 B.M. versus a spin-only

value of 2.83 B.M. The presence of two unpaired electrons is in agree-

ment with the reflectance spectra.

 

The infrared spectrum, presented in Table XXIV, shows several

interesting features. The Ni-C bend was Observed at 581 cm-1. This

absorption is slightly lower than that observed for Ni(C2H3N4)2,

92

Table XXIV. Infrared Spectra for Bis(l-cyclohexyl-S-tetrazoly1)—

nickel(II) and 1-cyclohexyltetrazole.

 

 

Genuine 1-cyclohexy1—
Vibrational tetrazole Ni(C7H11N4)2 Assignmenta
Mode
3420 (s) 1370 + 1350 + v7
v1 3125 (3) ring C-H stretch
2930 (vs) 2930 (vs) Rb C-H stretch
2850 (s) 2850 (s) R C-H stretch
2650 (w) 2650 (w) 1338 + 1302
2520 (w) 1370 + 1146
2130 (vs) CEN stretch
1740 (vw) 1710 (a) v3 + v9
1610 (vw) 1622 (8) v3 + v10
v2 1470 (3) ring C-H bend
1450 (vs) 1450 (vs) *
1424 (m) v4 + 337
1404 (w) 1054 + 337
1366 (m) 1370 (m) *
1350 (m) 900 + v10
1344 (w) 1338 (w) *
1310 (m) 1302 (m) *
1266 (m) 1262 (s) *
1242 (w) 1241 (w) *
1215 (s) 900 + v11
v 1180 (sh) 1185 (w) ring vibration

 

93

 

 

 

Table XXIV. (continued)
Genuine 1-cyclohexyl- Ni(C7H11N4)2 Assignment
Vibrational tetrazole
Mode
1167 (vs) 1163 (w) *
1138 (s) 1146 (w) * “f“
04 1101 (vs) 1095 (w) ring vibration :
1078 (w) 69 + 466 ‘*
1054 (m) 1044 (vw) * E
1032 (m) 1031 (m) *
vs 1001 (s) 1000 (vw) ring vibration
970 (s) 955 (vs) *
920 (vw) 900 (vs) *
897 (vs) 895 (V8) *
v6 881 (vs) ring C-H out-of—plane bend
858 (8) v9 + 337
820 (s) 802 (sh) *
790 (s) 466 + v11
746 (a) v3 - v10
718 (vw) 1266 - v10
v7 675 (vs) 695 (8) ring vibration
659 (vs) 2(337)
v8 581 (m) Ni-C bend
v9 554 (m) 523 (m) out-of-plane-ring
vibration
468 (m) 466 (m) *

 

. V - “‘—

 

 

 

 

94
Table XXIV. (continued)
Genuine l-cyclohexyl- Ni(C7H11N4)2 Assignmenta
Vibrational tetrazole
Mode
v10 439 (s) 444 (m) out-of—plane-ring
vibration 1
366 (m) 1262 - 900
337 (m) 337 (m) * i
011 316 (sh) Ni-N stretch g
242 (m) 1344 - 1101 or

1138 - 897

 

3* implies a vibration due to the cyclohexyl group.

bR indicates cyclohexyl.

95

which indicates that the Ni-C bond is slightly weaker. No frequency
which could be attributed to the Ni-C stretch was observed. The Ni-C
stretch is probably masked by the 466 and/or 444 cm-1 bands. A
shoulder was Observed at 316 cm,-1 which has been attributed to the
Ni-N bond and this band is absent in the l-cyclohexyltetrazole infrared
spectrum. The band at 2130 cm71, CN bond, indicates that the bonding
in Ni(C7H11N4)2 is approximately the same as in Ni(C2H3N4)2. The
proton has been removed from the 5 position in the complex because the
absorption bands due to the C-H ring vibrations are missing. The
vibrational modes due to the cyclohexyl substituent were determined by
comparing the infrared spectrum of 1-cyclohexy1tetrazole with those
for cyclohexanol and cyclohexyl amine. Not all of the ring vibrational
modes were observed because of masking by the cyclohexyl modes.

In general the results for bis(1~methy1-5-tetrazoly1)nickel(II)
and bis(l-cyclohexyl-S—tetrazolyl)nickel(II) are the same. Thus the bonding

characteristics should be identical.

 

3+

4
.5
ji

1

 

 

11.
12.
13.
14.
15.
16.
17.

18.

19.

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v. ‘1"!

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‘1'
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