PART ONE DIMETHYL PHOSPHITE SUBSTITUTION ON THE OXOPENTABROMOMOLYBDATE (V) COMPLEX PART TWO A NEW METHOD FOR PREPARATION AND SOME PROPERTIES OF TRIS (ACETYLACETONATO) TITANIUM. (III) Thesis for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY GRACE Y-S. L0 1971 This is to certify that the thesis entitled Part One: Dimethyl Phosphite Substitution on the Oxopentabromomolybdate(V) Complex Part Two: A New Method for Preparation and Some Properties of Tris(Acetylacetonato)Titanium(III) presented by Grace Y-S. Lo has been accepted towards fulfillment of the requirements for Ph.D. degree mihem’sjm Major professor Date September 10. 1921 y “Ema av ‘7' : nuns & saIS' Iaonx NNDERYINU ii LIBRARY BINDEns SPRINGPORT Mlfllfllfl ABSTRACT PART ONE DIMETHYL PHOSPHITE SUBSTITUTION ON THE OXOPENTABROMOMOLYBDATE (v) COMPLEX PART TWO A NEW METHOD FORPREPARATION AND SOME PROPERTIES OF TRIS (ACETYLACETONATO )TITANIUM(III ) By Grace Y-S. Lo PART ONE A study of the chemical behavior of dimethyl phosphite, (CH3O)2PO(H), with the ammonium salt of the oxopentabromo- molybdate(V) anion, (NH4)2MoOBr5, in tetrahydrofuran was carried out. The stepwise substitution of the bromo ligand by dimethyl phosphite was observed by analysis of esr spec- tral changes. The relative concentration of each species in solutions of this reaction mixture was obtained as a function of time with the assistance of computer simulated esr spectra by using a curvefitting program. rFrom these data, rate constants and activation parameters of each individual substitution step of this reaction were obtained. This appears to be a valuable technique for determining reaction dynamics for this type of system. Grace Y-S. Lo PART TWO A new method for preparing tris(acetylacetonato)titan- ium(III), Ti(acac)3, was found that is more convenient than the reported methods. A preliminary study showed that the oxidation of Ti(acac)3 to a Ti(IV) complex in methylene chlbride solution occurs gia_a paramagnetic intermediate species which gives an axially symmetrical esr signal. PART ONE DIMETHYL PHOSPHITE SUBSTITUTION ON THE oxo PENTABROMOMO LYBDATE (v) COMPLEX PART TWO A NEW METHOD FOR PREPARATION AND SOME PROPERTIES OF TRIS(ACETYLACETONATO)TITANIUM(III) BY Grace Y-S. Lo A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1971 To My Parents ii ACKNOWLEDGMENT I would like to express my appreciation to Professor Carl H. Brubaker, Jr. for his guidance and encouragement throughout this investigation. I am also grateful to Dr. John C. Evans, my supervisor at the Chemical Physics Research Laboratory of the Dow Chemical Company, for his help and encouragement to initiate this study. Many helpful discussions with Professor James L. Dye and.Dr. Theodore J. Williams are greatly appreciated. Financial support from the National Science Foundation and the Dow Chemical Company is also acknowledged. iii TABLE OF CONTENTS PART ONE DIMETHYL PHOSPHITE SUBSTITUTION ON THE OXOPENTABROMOMOLYBDATE(V) COMPLEX ’INTRODUCTION . . . . . . . . . . . . . . . . . . . . EXPERIMENTAL SECTION . . . . . . . . . . . . . . . . A. B. C. D. E. F. G. .H. RESULTS A. B. C. CD. Materials . . . . . . . . . . . . . . . . . Analytical Method . . . . . . . . . . . . . Spectroscopic Measurements . . . . . . . . ‘Preparation of Ammonium Oxopentabromo- molybdate(v) . . . . . . . . . . . . . . ' Rate Studies 0 O O O O I I O O O O O O O 0 Determination of Line-shape and Line Widths from Esr Spectra . . . . . . . . . . . . Computer Simulation of Esr Spectra Containing Several Overlapping Lines . . . . . . . . Determination of 9 Values from Esr Spectra AND DISCUSSION 0 O O O O O O O O O O O O O The Substitution Reaction . . . . . . . . . Determination of Relative Concentrations . -Analysis of Kinetics . . . . . . . . . . . The First Step of the Substitution Reaction CONCLUSIONS . . . . . . . . ... . . . . . . . . . . iv Page Ulrhthth 0'30! 18 18 23 24 37 44 TABLE OF CONTENTS (Cont.) A NEW METHOD FOR PREPARATION AND SOME PROPERTIES OF TRIS(ACETYLACETONATO)TITANIUM(III) PART TWO INTRODUCTION . . . . . . . . . . . . . . . . . EXPERIMENTAL SECTION . . . . . . . . . . . . . A. B. C. D. E. F. RESULTS A. B. Materials . . . . . . . . . . . . . . Analytical Methods . . . . . . . . . .Experimental Apparatus and Technique Preparation of Compounds . . . . . . Preparation of Solutions for Esr Study Esr Measurements . . . . . . . . . . AND DISCUSSION . . . . . . . . . . . Preparation of Compounds . . . . . . Esr Spectra . . . . . . . . . . . . . CONCLUSIONS . . . . . . . . . . . . . . . . . BIBLIOGRAPHY . . . . . . . . . . . . . . . . . APPENDIX 1 C I O O O O O O O C D O O O C O O O Page 46 47 47 48 48 49 51 51 52 52 53 61 62 64 TABLE 11'. III. IV. LIST OF TABLES Line widths and g values for complexes of molybdenum(v) . . . . . . . . . . . . Rate constants for the first substitution Step , MOOBr4 t0 MOOBr3 L o o o o o o o 0 Rate constants for the substitution step, MOOBrsL to MOOBr2L2 o o o o o o o o o o 0 -Rate constants for the substitution step, MOOBrsz to MOOBrL3 o o o o o o o o o o 0 Rate constants for the last substitution Step ’ MOOBrLa to MOOL4 o o o o o o o o 0 Values of activation parameters for the_sub- stitution steps, Mi + L __;_, Mi+1'+ Br , i = 1-4 . . . . . . . . . . . . . . . . . g values for Ti(acac)3 and Ti(hfac)3 in CH2C12 and toluenei . .'. . . . . . . . . vi 0 Page 13 33 34 35 36 42 57 FIGURE 1a. 1b. 10. 11. 12. LIST OF FIGURES Absorption first derivative line-shape . . . Lorentzian (-—--) and Gaussian ( tion first derivative curves with the same parameters . . . . . . . . . . . . . . . . . ES]: SpeCtra Of M00154 0 o o o o o o o o o o o Esr apectra of MoOL4 . . . . . . . . . . . . ,Esr spectra of MoOBr4- . . . . . . . . . . . Observed and simulated esr spectra of oxobromo- (dimethyl phosphito)molybdate(v) complexes . First derivative esr spectra of bromo(dimethyl phosphito)complexes of molybdenyl recorded at various time intervals . . . . . . . . . . . 2km of fractions versus time for the reaction of MoOEr4 with (CH3052P0(H) in THF at 29.60 Plot of X1 versus time (min.) for the first substitution step, MoOBr4 to MoOBr3L . . . . Plot of —lnX2 versus time (min.) for the sub- stitution step, MoOBr3L to MoOBrsz . . . . . Plot of -lnX3 versus time (min.) for the sub- stitution step, MoOBr2L2 to MoOBrL3 . . . . . Plot of —lnx4 versus time (min.) for the last Pkn:of -ln k; (l-mole-I-sec-l) versus IZT OK for the first substitution step, MOOBr4 to MOOBI 3 L o o o o o o o o o o o o o o o o o o 0 vii ) absorp- Page 10 11 12 15 19 25 28 29 3O 31 38 LIST OF FIGURES (Cont.) FIGURE 13. 14. 15. 16. 17. 18. Page Plot of -1n k; (l-mole-l-sec-l) versus 1/T OK for the substitution step, MoOBraL to MOOBr2L2 ,39 - -1 Plot of -ln k; (l-mole 1°sec ) versus l/T 0K for the substitution step, MoOBrsz to MOOBrL3 40 .Plot of -ln k; (l-mole-l-sec_1) versus l/T 0K for the last substitution step, MoOBrL3 to MOOL4 41 Esr speCtra of a) Ti(acac)3; b) Ti(hfac)3 in toluene at 77°K . . . . . . . . . . . . . 54 Esr spectra of Ti(acac)3 and Ti(hfac)3 in CH C12 solutions with different Ti(hfac)3/ Ti acac)3 mole ratios at 770K . . . . . . . . 55 Esr spectra of Ti(acac)3 in CH2C12 (a) and on oxidation of this solution by air (b and c) at 770K . . . . . . . . . . . . . . . . . . . 59 viii PART ONE DIMETHYL PHOSPHITE SUBSTITUTION ON THE OXOPENTABROMOMOLYBDATE (v) COMPLEX INTRODUCTION Recently, Marov and coworkersl.2 have reported a sequence of investigations of ligand substitution equi- libria on molybdenyl complexes. Their studies showed that the stepwise complex formation of molybdenyl complexes can be investigated by use of electron spin resonance (esr) spectroscopy. ‘Similarly, preliminary studies of diethyl phosphite,.(EtO)2PO(H), substitution on molybdenum penta- chloride by means of esr spectral changes were performed by Dalton3 in this laboratory. These studies indicated that esr spectroscopy could be applied to study reaction dynamics of suitable paramagnetic transition metal complex systems. A number of complexes in various solvents were investi- gated in an effort to find a chemical system in which sub- stitution of ligands on the complex gave distinct successive species (as reflected by their esr spectra) and in which the reaction(s) occurred with convenient rates. Of those considered the most thoroughly, the substitution of C1- in MoOClsz- by dimethyl phosphite, (CH3O)2PO(H), was too slow to be conveniently studied. The reaction of the oxopenta- bromomolybdate(v) compleX, MOOBr52-, with dimethyl phosphite 2 3 had the required properties giving nearly separate esr lines for the stepwise substitution products and they formed at reasonable rates. For this system the reaction dynamics were studied as completely as possible by using computer assisted esr spectral curve fitting to find the fractions of the various species present as a function of time. The general theories and mechanisms of substitution reactions on transition metal complexes have been extensively reviewed by Basolo and Pearson.4 Several other sources were also consulted for the general expressions of kinetic rate laws5"7 and esr spectroscopy.3-9 EXPERIMENTAL SECTION A. Materials Molybdenum pentabromide, ammonium bromide, hydrogen bromide (lecture bottle), and thionyl bromide (SOBrZ) were used as obtained from Alfa Inorganics, Matheson Coleman and Bell, Matheson Gas Products, and Research Organic/Inorganic Chemical Corporation respectively. Hydrobromic acid (48%) and phosphorous acid were obtained from Fisher Scientific Company and used without further purification. Dimethylyphosphite ((CH3O)2PO(H)) was used as obtained from Stauffer Chemical Company. Its nmr spectrum showed no impurities. Diethylamine was obtained from Mallinckrodt Chemical Works and dried with calcium sulfate. Tetrahydrofuran (THF) was refluxed in the presence of lithium aluminum hydride and distilled immediately before use. B. Analytical Method Bromide Analysis. About 45 mg of ammonium oxopentabromo- molybdate(v), (NH4)2[MoOBr5], was dissolved in 50.0 ml 4 5 distilled water. Ten ml aliquots of this solution were with- drawn and diluted with ca. 20 ml distilled water. Bromide was then determined by potentiometric titration with a standardized silver nitrate solution. C. Spectroscopic Measurements Infrared Spectra. The infrared spectra were recorded by use of a Perkin-Elmer 237B grating spectrometer. The Nujol mull sample was prepared in a dry box and placed be- tween rock salt plates. Nuclear Magnetic Resonance Spectra. The nuclear mag- netic resonance spectra were recorded by use of a Varian A56/60D instrument. Electron Spin Resonance Spectra. The electron spin resonance spectra were recorded by use of a Varian E-4 EPR spectrometer. The temperature of the sample compartment was kept constant through use of a Varian variable tempera- ture controller. The instrument was calibrated with a pitch sample. D. Preparation of Ammonium Oxopentabromomolybdate(V).10 The anhydrous hydrogen bromide was bubbled into a round-bottom flask containing a mixture of about 8 g of MoBr5 (0.02 mole) and 100 ml of 48% hydrobromic acid. -When most of the solid was dissolved the mixture was filtered, and a solution of 4 g NH4Br in 10 ml distilled water was added to the filtrate. The resultant solution was saturated 6 with HBr gas at 0°, and the (NH4)2[MoOBr5] precipitated as golden brown solid. .This solid was filtered under a nitro- gen athSphere, washed with 30 ml of ether containing 10% thionyl bromide, washed again with 70 ml dry ether, and finally vacuum dried. The washing with thionyl bromide was essential to avoid hydrolysis of the solid product. The infrared spectrum of the solid product showed a strong ab- sorption band at 975 cm-1, which is consistent with the Mo-O stretching frequency. No absorption band in the region of the OH stretching frequency was observed in the spectrum. Bromide Analysis. Calcd for (NH4)3MOOBI5: 72.97; Found: 72.90. E. ;Rate Studies All solutions for the rate study were prepared in a nitrogen glove bag. For a typical run, 4.50 ml of dimethyl phosphite (ligand) and 3.00 ml of THF were mixed well (the final di- methyl phosphite concentration was 6.80M) and brought to about 26°. Then 1.62 ml of this solution was added to 0.0732 g of (NH4)2[MOOBr5] to give a final complex concen- tration, 0.083M, The esr sample tube was filled with the complex solution and sealed under nitrogen. The sealed tube was placed in a water bath at 26° for about ten minutes and then transferred to the sample compartment (maintained at 26°) of the esr instrument. The actual tem- perature was measured by use of a thermocouple before and 7 after the kinetic experiment and was found to be 25.9 i 0.1°. Es; spectra of the reaction solution were recorded at con- venient time intervals until the reaction was about 90% complete. Conditions that were varied were complex concentration (0.059 - 0.083M), dimethyl phosphite concentration (6.80 - 9.74M), and temperature (22.2 — 33.3°). F. Determination of Line-shape and Line Widths from Esr Spectra The theory and technique of esr spectroscopy has been fully described},9 A typical first derivative esr spectrum in arbitrary scale is shown in Figure 1a. The ordinate is amplitude, y', in arbitrary units and the abscissa is field strength, H, in gauss. The line-shape parameters are de- fined as fOllows: Apr is the peak-to-peak width; H0 is the center of the line; and Y'm is the maximum amplitude which occurs at H—Ho = 1 1/2 Apr. There are two common line—shapes used to describe an esr line. The Gaussian first derivative line-shape has the form given by the equation GY' = .1/2 YI<¥7§—%H°—>expt- ESTA—3H2] ' PP PP the Lorentzian first derivative line-shape has the form given by the equation 8 HTS-{7%) 131'(H) = H - 59 2 2 . PP The difference in line-shapes between Lorentzian and Gaussian first derivative lines with the same parameters is shown in Figure 1b. The theoretical esr spectra of MoOBr4- (> 90% pure), and pure MOOL4 were synthesized by a simple computer pro- gram (See Appendix 1) which employed the equations of both line-shapes. The three parameters (AH , Ho, and y$) were PP measured from the experimental spectra and inserted into the program to produce theoretical esr spectra. It was found that the experimental esr spectra were most consistent with the theoretical Lorentzian line-shape as shown by a comparison of Figures 2 and 4 with Figure 3. The measured line widths of MoOBr4- and MOOL4 were 14.8 and 10.8 gauss respectively. The line.widths of the three mixed ligand complexes, MoOBr3L, MoOBrsz, and MoOBrL3, were estimated by assuming a linear change between the line widths of MoOBr4- and.MoOL4. Their values are given in Table I. G. Computer Simulation of Esr Spectra Containing Several OverlappipgfLines For the case of several overlapping lines, the total amplitude (Y') of the first derivative lines at the magnetic field (H) is the summation of the amplitudes (z yi) of the units) |*< Amplitude (arbitrary O Figure la. Absorption first derivative line-shape. >8}? HJJ m-H H c 11” - e y I m ,/ V x '3 I” u x’ j / m E fl H(gauss) Figure 1b. Lorentzian (—--) and Gaussian (-——O absorption first deriva- tive curves with the same parameters. m H Y ' -v-'l C‘. 5 O ___ >1 H (U H u -:-l .0 H m (D 'U :1 u «4 FI Q. E n: Figure 2. 10 O T hyperfine hyperfine l I I L l I l 3410 3430 3450 3470 H (gauss) Esr spectra of MoOL4. The solid line is the experimental spectrum and the circles are computer synthesized data with the Lorentzian line-shape including the hyperfine structure. Arbitrary "0" selected. 11 ’a? 4.) -H r: Y‘ s >‘ O —— H m H .1.) -H n H o O o s .U -r-I ... E I I l I I I I 3410 3430 3450 3470 H (gauss) Figure 3. Esr spectra* of MoOL4. The solid line is the experimental spectra and the circles are computer synthesized data with the Gaussian line-shape including no hyperfine structure. Arbitrary "0" selected. Amplitude (arbitrary units) Figure 4. 12 _ ' I 0 MOOBr3L + hyperfine T hyperfine | I | -3270 3300 3330 H (gauss) Esr spectra of MoOBr4- (>90% pure). The solid line is the experimental spectrum and the circles are computer synthesized data with the Lorentzian line-shape including MoOBrsL (small amount) and hyperfine struc- ture. Arbitrary "0" selected. 13 Table 1. Line widths and g values for complexes of molybdenum(V). Complexa Apr b 9 Value (gauss) MOOBr4- 14.8 1.990 : o.oo1C *MoOBrsL 13.8 1.972 r 0.001c MoOBrsz 12.8 1.955;1.948(i o.oo1)c'd MoOErL3 11.8 1.932 r 0.001c Moor,4 10.8 1.912 i o.oo1C MoOBr; e --- 1.993e MoOBr3(H2PO4)’ e --- 1.974e MoOBr2(H2PO4); e l --- 1.958;1.950e’d MoOBr(H3PO4); e --- 1.934e MOO (H3Po4g e --- 1 .91463 aL is the abbreviation of dimethyl phosphite. Where the charges of the complexes are uncertain, they are not given. bEstimated as described in Section F. CCalculated as described in Section H. dSlight differences were observed for cis and trans isomers; however, since the association of isomers with the different values is uncertain, they are reported together as given in the table. eReference 15. 14 individual lines at that field. The Lorentzian first deri- vative overlapping line—shape has the form represented by the following equations: 16Y$(i)(1/: gH:0(i;) B(i '<. u ubdz ‘< *< u l i H "110(1) 2 1 3 + . 2 I (1/2 Aprjl)) The theoretical esr spectra containing several over- lapping lines were simulated by a computer to give a best fit with the experimental spectrum by adjusting the two sets of parameters, Ho's and y$'s, with a curve—fitting computer program.11 The values of line widths, Apr's, were obtained as described in Section F and used as con— stants. vFigure 5 shows a typical computer output plot. H. Determination of 9 Values from Esr Spectra The values of g were calculated from the klystron frequency (v in MHz) and the magnetic field strength of the center of the line (H0 in gauss) according to the following equation. 9: ll—--"-—=o.71442¢39x1- “O Ho Ho where h is Planck's constant and U0 is the Bohr magneton. The 9 .value of MoOL4 was calculated from the Ho value which was measured from the experimental spectrum of pure MOOL4 and the klystron frequency which was directly read off the dial. The instrument was calibrated by 15 ..w muses an m muses OEmm osu CH mum mucflom Umumasoamu paw Hmucoefluomxm momma .ucHOQ pwumHDOHmo m mcmOE .ucflom Hmucweflnomxo cm mcmwe . .mmxmamaoo A>VODOUQHHOE IAODH£QMOLQ HHLDOEHUVOEOHQOxO mo muvoomm HMO UmumHDEHm ppm UO>HOmQO O N .m Ousmflm 16 .m Onsmflm ATIII. Ammsmmvm O xo 0 xx o x o 0 xx x x xoo o x 3 o ox o xo ox o o o xo x x ox x x o x x o o o ox o no ox x x o o ox x x x o o I x o oco x x o oxxxo ox - ox x .1. x use x x x on o x o a oux - o x o oox xx x o x o x uooo x o x o x o xxxx 00 x x o o o x a o x x x a I xu 00x 0 xx o x o o .N (sqrun Krexqrqxe) epnarIdmv 17 measuring the combined spectrum of MOOL4 and a standard pitch sample. This spectrum was recorded by placing the two sample tubes together in the sample compartment. The spectra of MoOL4 and pitch were also recorded’separately. The calibrated 9 value of MOOL4 was the same from both methods. The 9 value of each of the other complexes was calculated by using the corresponding value of Ho. In each case, the Ho value was averaged from a set of ten Ho values which gave the best data fit in the computer outputs in which the Ho value of MOOL4 was used as a constant value. The uncertainty of the g values were estimated from the standard deviation of the corresponding Ho values given by the computer outputs. The 9 values of the complexes thus obtained are given in Table I. RESULTS AND DIS CUSS ION A. The Substitution Reaction VThe esr Spectral changes during the dimethyl phosphite substitution of Br- in MoOBr4- showed five distinct lines which were assigned to MoOBr4-, VOE Hmuou OLE .om.mm um mme ca AmvommAOmmov res; vumooz wo COHDOOOH on» How OEflu msmnm> mCOHuomHm mo DOHm .h Ousmflm 26 com A GHEV OEAE one ooH .b OHDmHm In C 'suoraoexa 'X 27 reactions are insignificant. The first step has an apparent zero-order rate law and the remaining steps have apparent first-order rate laws. Their mathematical forms are given in the following simultaneous equations. d[M1]/dt = - R1 (1) dtmal/dt = k1 - k2IM2] (2) dIMal/dt = k2IM2] - k3IM3] (3) dIM4I/dt = k3IM3] - k4IM4I (4) d[M5]/dt = k4[M4] (5) where k; - kl/[Mo(V)][L], [MQ(V)] is the initial concentra- tion of MooBr4-: k; = ki/[L]' i = 2 - 4. Equation (2) became d[M2]/dt = -k2[M2] after all of M1 had been con- sumed. Exhibiting zero-order behavior, a plot of X1 (X1 is the mole fraction of M1) versus time gave a straight line as shown in Figure 8. After all of M1 had been consumed a plot of ln X2 (X2 is the mole fraction of M2) versus time (Figure 9) gave good linearity indicating a change to a first—order reaction. The last two reaction steps also showed first-order behavior with respect to complex concen- tration since, after all of the preceding species had been consumed, straight lines were obtained from plots of ln X3 and ln-X4 versus time as shown in Figureslo and 11. Un- certainties of the mole fractions were calculated from the y; standard deviations which were estimated statistically .by the computer program used to simulate the esr spectra. 28 120... I I 0 50 100 Time (min ) Figure 8. Plot of X1 (X1 is the mole fraction of MoOBr4-) versus time (min ) for the first substitution step, MOOBr47 to MOOBraL. 29 C) 2.8 F- 2.4 r" C) -1n X2 2.0 r- I I I I 120 130 I 140 150 Time (min.) Figure 9. Plot of -lnx (x2 is the mole fraction of MoOBr3L) sversus time min.) for the substitution step, MOOBr3L to MOOBrsz. 30 2 .7 ._ O I 2.4 —— C) ‘lnX3 C) 2.1 e— l I I I I 160 170 Time (min ) Figure 10. Plot of -1nx3 (X3_is the mole fraction of MooBrsz) versus time (min.) for the substitu- tion step,-MOOBr2L2 to MoOBrLa. 31 "lnX4 | I I 180 200 . 220 Time (min.) Figure 11. Plot of -lnx (X4 is the mole fraction of MOOBrL3) versus time min ) for the last substitution Step, MOOBrLa t0 M00114. 32 It was found that the uncertainties for x1 are less than 10%, for X2 and X4 are less than 7%, and for X3 are less than 20%. Apparent rate constants of each step of this reaction were determined graphically and by a least-squares treat- ment with good agreement by using a small portion of the fraction values as shown in Figures 8—11. They were also found by using a computer program11 which adjusts the four rate constants in the five simultaneous rate law equations to give a best fit with all the experimental fraction values. The observed and calculated rate constants, ki and ki, ob- tained from both methods for each substitution step are given in Tables II-V. Values of k1 obtained from the two methods are in good agreement, as shown in Table II; whereas values of k2, k3, and k4 obtained from the treat- ment of the five simultaneous equations are systematically higher than those obtained by least-squares treatment as given in Tables III-V. The rate constants obtained from the treatment of five simultaneous equations should be more realistic than those obtained by a least-squares treatment of partial data, since all values of Xi were used. The rather high uncertainties are not surprising for such a complex system considering the difficulties described for the experimental measurements and data treatment. The results showed that the.first substitution step has first—order behavior with reSpect to L and zero-order behavior with respect to MOOBr4-, yet the rate does depend 33 .Ieumooz mo soflumuhsmosoo HmDDAsD 0:0 uA HA>VoSL ._3L_A>voz_\xx u ”so .Emumoum HODDQEOU O£D an maamoHDmHDmDm oODmEHDmO OHO3 MOHDGHODHOOGD HHOna .Emumoum HODDQEOO m 00 On: an chHDODUO 3OH.ODOH ODOOCODHDEHO O>Hm OLD mo DCOEDOOHD OLD Eoum COGHODQO .xx .DcmDchO HOCHOIOHON UO>HOOQOQ .mammm xx u DO\HIvaOOSHUI BOA ODOR OHQEHO OHOQB DGOEDOODD OOHODUOIDOOOH an OOCHODQO .xx .chmDmcoo HOOHOIOHON 0O>HOOQOO 0H.o H H0.H NH.0 H NN.H v0.0 H 00.H 00.0 H 00.H 05.0 000.0 0.00 0 HH.0 H b¢.H 00.0 H H0.H v0.0 H 00.H 00.0 H 00.0 00.0 000.0 0.00 h VN.0.H b0.H 0H.0 H 50.0 00.0 H 00.H 00.0 H H0.0 00.0 000.0 0.00 0 00.0 H 00.0 00.0 H 00.0 00.0 H o0.H 00.0 H 0b.0 00.0 0b0.0 0.00 0 NH.0 H N0.H 50.0 H 00.0 00.0 H.bm.H 00.0 H 00.0 00.0 000.0 0.00 0 0H.0 H 00.H 00.0 H 00.0 00.0 H H0.H Ho.0 H 00.0 00.0 000.0 N.NN 0 00.0 H hv.N 0H.0 H 00.H 00.0 H 00.0 00.0 H H0.H 00.0 000.0 0.00 N 50.0 H 00.0 0H.o H 00.0 00.0 H 00.0 v0.0 H 00.0 00.0 000.0 0.00 H ADIOOO AH OOm H OOm Ax OOm .xIOHOE.HV .HLHHOHOEV .HMOHOE.HV .HIHMOHOEV .mv dflv AUov .Oz. 0.:sex x «A These x As onhmos x “A Ihnox x As .Amvom Acnmov_ HA>VozL .deme .ssom .qmumooz OD vnmooz .mODm COHDDDHDOQDO DmnHm OED Dom chmDmCOO ODmm .HH OHQOB .Hq_\sx u «x . .HQLHNSme n De\0szaeu .380 some we» 2000 enemasusmou I .Emumoum HODSQEOO OED 0n MAHOOHDmHDmDm oODmEHDmO OHO3 OOHDCHODDOOCD HHOQB .Emumoum HODDQEOO m 00 Om: an OCOHDOOUO 30H ODOH ODOOEODHDEHO O>Hw OLD mo DCOEDOODD OQD EODM oOaHmDQO .«x .chmDmCOO HOoHOIDmHHH UO>HOOQOQ .mammm HSSLNM u ue\_e:.eu sea moms OHQEHO ODO£3 DEOEDOOHD mOHmsvaDOOOH an oOchDQO .«x .chODmcoo HOoHOIDmHHm oO>HOmnom 34 00.0 0.H H v.0 0.H H 0.0 00.0 H 00.0 H 00.0 ¢b.0 000.0 0.00 0 0.H H 0.0 0.H H 0.v 00.0 H 08.0 0H.0 H 00.0 00.0 000.0 0.00 b 0.H H H.h 0.H H 0.0 00.H H Wm.0 00.0 H 00.0 00.0 000.0 0.00 0 0.H H 0.0 00.0 H 08.0 Hv.0 H 00.0 00.0 H 00.0 00.0 000.0 0.00 0 H.H H 0.0 00.0 H 0H.0 0H.0 H 00.0 00.0 H 00.0 00.0 000.0 0.00 v 00.0 H 0H.v 0v.0 H 00.0 0H.0 H 0H.0 80.0 H 0H.0 00.0 000.0 0.00 0 0.0 H 0.HH H.0 H 0.5 00.0 H 0v.» 0H.0 H 00.0 00.0 000.0 0.00 0 0.0 H 5.0H 0.H H b.0H Hb.0 H 00.0H 00.0 H 00.0 00.0 000.0 0.00 H memwmflv A783 .umwmmmflv A783 ME . 3.0 muse .oz 08.2 x 0. er: x ... as: x ...... hr: x .r :58 8.5: 23.8 . Se .50.... .uquumooz OD Anamooz .mODm EOHDDDHDmQDM OED How chmDmaoo ODmm .HHH OHQOB ._q_\ex u ms .flqaanzamx n De\0nzueu "38H some use scum emomasosmoo .Emumoum HODDQEOO ODD an adamOHDmHDmDm oODmEHDmO OHO3 MOHDCHODHOOCD HHOSB .Emnmoum HODDQEOO m mszd an OGOHDOOUO 30H ODOH ODOOGODHSEHO O>Hm OLD HO DCOEDOOHD OSD Eoum oOchDQO .mx .chmDmcoo HOUHOIDOHHH UO>HOOQOQ .H GOHDDHOO How .mammm HnEme u Do\mm2001 30H ODOR mp OOGHODQO .mx .chmDmcoo HOoHOIDmHHm CO>HOOQOO ax GHODQO OD chHom ODmo £050CO Doc Onm OHOEB. OHQEHO OHO£3 DGOEDOOHD mOumsvaDmmOH 35 0.x A H.e o.m s o.e sn.o u me.n mn.o s mm.h ee.m mme.o o.em m e.H A e.n N.H A m.e em.o s Hm.e ms.o R me.m mm.m mmo.o m.nm_ s s.H A e.e ~.H A n.e se.o A nw.e om.o A om.m om.e mno.o 0.8m m 8.0 a m.u m.H « o.n Hs.o A He.n m~.o a mm.m om.o oso.o m.mu n es.o A mo.e mn.o A mx.e N.H A «.9 om.o H mw.m ow.m mmo.o m.hm e me.o n oe.m mn.o A me.m «H.o A mm.m mo.o 0 ea.“ om.e mmo.o «.mm m e.m A n.m w.H n m.n me.o s ee.e me.o D mm.m om.e mmo.o u.mm m H.N A m.mH n.fi u m.m III. III om.e mmo.o «.mm H Imam: 3-0.3 Imam: $-33 we 8 3.0 as 0.0noH x mx neoH x ex 0.mnoH 8 ms meofl x ex "Amvom AeanVL _A>Voz_ .msme .sHom .mqnmooz OD «Aaumooz .mODm GOHDDDHDOQTO ODD Dom ODcmDmCOO ODmm .>H OHQOB amqnu\vv_.. " VX. . .ERLEeszR u De\Eszeu "SOR 00mm 0:0 scum OODmRsoRmoo .EORmoRm RODDQEOO OED.>E mHHOOHDmHDODm UODOEHDOO OROB OOHDCHODROOED RHOEB. .EORmoRm RODOQEOO O 0ch5 an OOOHDOOUO BOH ODOR OOOOOODHOEHO O>Hm OED mo DOOEDOORD OED EORm OOEHODEO .vE .ODEODOEOO ROOROIDORHM OO>ROOEOE .mammO Hvzavx u DO\Hv=HoI BOA ODOR OHQEHO OROEB DEOEDOORD OOROSUOIDOOOH 0E OOEHODEO .vx .chODchO ROOROIDORHM OO>ROOEOO 36 H¢.0 H 00.0 ov.0 H 0040 00.0 H 00.0 00.0 H 00.H $0.0 000.0 0.00 0 00.0 H 00.0 00.0 H 0H.0 00.0 H H0.H 00.0 H 00.H 00.0 000.0 0.00 b 00.0 H 00.0 00.0 H 00.H 00.0 H 00.0 00.0 H 00.H 00.0 000.0 0.00 0 00.0 H $0.0 00.0 H 00.0 00.0 H 00.0 v0.0 H 00.H 00.0 000.0 0.00 0 0H.0 H 00.0 0H.0 H 00.H 00.0 H 00.0 00.0 H 00.H 00.0 000.0 0.00 v 00.0 H 00.H 0H.0 H 0H.H 00.0 H 00.H H0.o H H0.o 00.0 000.0 0.00 0 H0.0 H 00.0 00.0 H 00.0 00.0 H Ho.0 00.0 H 00.0 00.0 000.0 0.00 0 00.0 H 00.0 00.0 H 00.0 00.0 H H0.v 00.0 H v0.0 00.0 000.0 0.00 H ARIOOm . ARIOOO II .RIOHOE.HV ARIOOOV .RIOHOE.HV ARIOOO .fiv . dmv MOOV .Oz. . OOH x ”E vow x «E 00H x ”M vofi x x EAmvom AOmmUVH HA>VOSH . SOB .cHom O E E O.O O .vqooz OD qumoOz .QODm OOHDODHDOEOO DmOH OED Rom ODOODOEOO ODOm .> OHEOB 37 on the initial concentration of MoOBr4-. More work was done in an effort to find evidence which would be helpful in understanding this puzzling point. This will be discussed in the next section. Unlike the first substitution step, the remaining substitution steps have mixed second-order’ behavior (i433 first-order with respect to the corresponding complex and first-order with respect to L) which is reason- able for ligand substitution reaction. Plots of -lnki, i = 1 - 4 versus l/T 9K for the four individual substitution steps were made from six ki values (solns. 1-6) in the last column of Tables II-V reSpectively. The graphs were linear within experimental error as shown in Figures 12-15. Solutions 7 and 8 were studied with much higher (CH30)2PO(H) concentration which amounts to a signifi— cant solvent change. Therefore they are not included in Arrhenius plots. The activation energy,.Ea, and its uncer- tainty were obtained from a least-squares treatment of these six points. From this, the other activation parameters, 1 i I o 298. and A8298, were calculated. They are given In log A, AH Table VI. D. The First Step of the Substitution Reaction Studies were made to find the effect of light, glass surface area, acid, or base on the rate of this reaction in an effort to gain some understanding of the behavior of the first substitution step as described in Section C. All ex- periments were carried out at 25.90, the initial concentration 38 11.4 11.0 —ln k; 10 .6 10.2 l 3.26 3.;0 3E§4 5438 1/T 0K x 103 Figure 12. Plot of -ln k; (l-mole-1-sec-1) versus L/TQK for the first substitution step, MoOBr4‘ to 39 9. 9 5F. C) -ln k; 9.1 ~— 0 8.7 r- l l l l 3.26 3.30 3.34 3.38 l/T 0K x 103 .Figure 13. Plot of -ln k; (l‘mole-1-sec-1).versus 1/T0x for the substitution step, MoOBr3L to MoOBrsz. 40 10.2— 0 9.8—- I ‘1!) ka 0 O 9.4— O 9.0_.. l ' l l l 3 .26 3.30 3.34 3.38 1/T °K x103 Figure 14. Plot of -ln k; (l-mole—losec-l) versus l/T OK for the substitution step, MoOBraLz to MOORrLa. 41 10.9 10.5 I -ln k4 10.1 9.7 I I l J 3.26 3.30 3.34 3.38 1/T 0K x 103 I _ .- Figure 15. ,Plot of -ln k4 (l°mole 1~sec ;) versus l/T 9K for the last substitution step, MoOBrL3 to M00L4. 42 .sOHDmaommanm Eoum wagon emu Dm DcmDmcou meH m mchs 00 UmeHsUHmo mmB Autumn. ImHOE.H CH HODomm HMHDcmcomxmem mH «v < camoqm H m.m H H.HH . H.H H v.mH m.H H o.oH s.H H o.om .400: 0» Hquooz m.o H o.>H u o.m H H.wH m.H H m.m ¢.u H >.mH Hquooz 0D «amumooz sum «.m.m,,- H.H H m.om m.o H m.HH H.H H N.H~ «gaumooz op HHHmooz m.th m.mH u m.H H v.mH m.H H H.m w.H H o.mH qHHmooz ou IHHmooz ,AHumDOEwmmmmv.Hmov AHImeMmeoxv « moD AHIwHOEmHmoxV mmum coHDsDHDszm m< mq m m H H .¢ I H n H . Hm + H+H2. A A.+ H2 I a .x .mmmDm COHDSDHDmQSm 00D How mHmeEMHmm coHDm>HDomtmo mmsam> .H> magma 43 of MOOBr4- was 0.082g_and the concentration of (CH30)2PO(H) was 6.80!, The solution of the reaction mixture was pre- pared and handled in the dark for the study of light effect. For the study of glass surface area effect, an increase in the glass surface area was accomplished by the addition of three capillary tubes (with both ends open) to the reaction solution. The surface area was estimated from the diameters and the lengths of the tubes added and the approximate sur- face area in contact with the solution was increased about three-fold. Phosphorous aCid,H3P03, and diethylamine, EtzNH, were used for studies of the acid or base effect on this reaction. The concentration of added H3P03 was 0.008§_ and 0.045ngor two separate solutions and the concentration of EtzNH was 0.0085, The results demonstrate that light, glass surface area, H3PO3, and EtzNH have no significant catalytic effect on the rate of this reaction. Attempts to derive a complex rate law from various forms to fit the observed behavior were made without success. At this time, no reasonable explanation for the apparent contradiction of zero—order behavior and dependency on initial concentration for the first stubstitution step can be given. CONCLUSIONS The results of this research indicate that esr spec- troscopy is a good method for giving valuable qualitative information about the successive ligand substitution on paramagnetic transition metal complexes. The determination of the relative concentration of each species in the solu- tion of the reaction mixture as a function of time is also possible with the assistance of computer simulated esr spectra, and from these the reaction rates and rate con- stants can be determined whereas other spectroscopic methods may not observe the differences for such similar species. .In this research, there are two remaining problems. The charges on the substituted complexes are uncertain, and there is a lack of reasonable explanation for the behavior of the first substitution step as described in the text. -More work with similar systems such as the substitution of different ligands on MoOBr: may be helpful in solving these problems. 44 PART TWO A NEW METHOD FOR PREPARATION AND SOME PROPERTIES OF TRIS (ACETYLACETONATO )TITANIUM(III ) 45 INTRODUCTION Tris(acetylactonato)titanium(III), Ti(acac)3, has been preparedlsv'17 and a study of its esr spectrum reported by MCG'arvey.18 _The preparation of tris(hexafluoroacetyl- acetonato)titanium(III), Ti(hfac)3, also was reported recently.19 However, the mixed ligand complexes,,: Ti(acac)2(hfac) and Ti(acac)(hfac)2, have not been reported. ,In this research, studies were made in an effort to find evidence of the existence and the ligand exchange behavior of these mixed ligand complexes by following esr spectral changes. 46 EXPERIMENTAL SECTION A. Materials Titanium trichloride was used as obtained from Research Organic/Inorganic Chemical Corporation. Acetylacetone and hexafluoroacetylacetone were Obtained from Columbia Organic Chemicals, Co., Inc., They were fur- ther purified by fractional distillation and stored under a nitrogen atmosphere. Toluene was purified by refluxing over phosphorus pentoxide followed by fractional distillation. .It was then stored under a nitrogen atmosphere. Methylene chloride was allowed to reflux continuously over calcium hydride and distilled immediately before use. gages, -Ammonia (lecture bottle) was obtained from the Matheson Company and used without further purification. Prepurified nitrogen from Liquid Carbonics was further purified by passing it through an activated copper catalyst (BTS catalyst -- BASF R 3-11 from Badische Anilin-Soda- Fabric AG) and subsequently through Aquasorb (containing phosphorus pentoxide from Mallinckrodt Chemical.WOrks) when needed. 47 48 B. Analytical Methods Carbon and Hydrogen Analysis. These analyses were per- formed by Spang Microanalytical Laboratories. Samples were stored in sealed tubes under vacuum and handled under a dry nitrogen atmosphere. Titanium Analysis. The solid Ti(III) complex was oxidized to Ti(IV) complex in 1.8g sulfuric acid solution containing 0.3% H202. The titanium content was then deter— mined Spectrophotometrically.20 Spectra were recorded by use of a Cary Model 14 spectrometer. ,Duplicate analyses showed reproducible results (within 1.1%). C. ”Experimental Apparatus and Technique The Ti(III) complexes were extremely sensitive to oxygen and the hexafluoroacetylacetone ligand was sensitive to water vapor. .All reactions and manipulations were per- formed under a dry nitrogen atmosphere. A dry nitrogen atmosphere box was used to transfer all air sensitive materials. A vacuum manifold in connection with the nitro- gen line and Schlenk tube techniques, similar to those re- ported by Herzog,21 were used during the preparation of compounds. The sublimed final products were stored in sealed tubes under vacuum. 49 D. .Preparation of Compounds Tris(hexafluoroacetylacetonato)titanium(III).19 A solution containing 11.0 g (52.9 mmole) hexafluoroacetylace- tone (ligand) in 10 ml of toluene was added dropwise to a stirred mixture of 2.84 g (18.4 mmole) TiC13 suspended in 12 ml of toluene. There was a slow evolution of HCl gas and a gradual color change from purple to blue accompanying the addition of ligand. After all the solution of ligand had been added, the mixture was allowed to reflux until the evolution of HCl ceased and then refluxed for two more hours. The small amount of solid residue was removed by filtration While the mixture was hot. HDark blue needle—shaped crystals precipitated from the filtrate when it was cooled to room temperature. This product was filtered and vacuum dried. It was purified by sublimation at 70-800 under vacuum. ~Analysis Calcd for C15H3F1806Ti: C, 26.93; H, 0.45; Ti, 7.16. -F0und: C, 27.06; H, 0.77; Ti, 7.18. Tris(acetylacetonato)titanium(III). Ti(acac)3 was prepared according to the reported procedure:17 A solution of 20 ml of 6§_ammonium hydroxide was added dropwise into a stirred mixture of 10.0 g (98.9 mmole) aceQflacetone in 40 ml of oxygen—free water. (This solution was then added dropwise to a Stirred solution of 5.2 g (33.7 mmole) TiCl3 in 50 m1 of oxygen-free water. The solution first changed to red then blue and finally a blue solid formed. The 50 solid product was filtered, washed with oxygen-free water and vacuum dried. However, it was found that Ti(acac)3 can be prepared more conveniently by the following method: The ammonium salt of aceQdacetonate was prepared by passing dry NH3 into 5.26 g (52.5 mmole) of stirred acetylacetone under a nitro- gen atmosphere. The flask containing this freshly prepared salt and a Schlenk tube containing 2.72 g (17.6 mmole) TiCl3 were quickly connected,by use of bent adapters with attached ground joints,to each Side of a 250 ml three-necked flask that contained 50 ml of toluene. The whole system was evacuated immediately, and the TiCl3 and NH4acac were added to the toluene by turning the bent tubes. The adapters were disconnected from the three-necked flask and both sides of the flask were stoppered while dry nitrogen was passed through the system. The system was then evacuated immedi— ately. This mixture was stirred under vacuum at room temper- ature for four hours. During this time, the mixture changed gradually from purple to blue in color with the formation of white NH4C1 which is insoluble in toluene. The NH4C1 was removed by vacuum filtration. A dark blue solid residue was obtained when the toluene solvent in the filtrate was evaporated in vacuo. The product was purified by sublima- tion at 140-1500 under vacuum. Analysis Calcd for C15H2106Ti: C, 52119; H, 6.13; Ti, 13.87,'HFound: C, 51.95; H, 6.06; Ti, 13.90. 51 E. Preparation of Solutions for Esr Study Solutions for the esr study were prepared in a nitro- gen glove bag. The stock solutions of 0.441 g Ti(hfac)3 in 40 ml CH2C12 (the Ti(hfac)3 concentration was 0.01Qg) and 0.266 g Ti(acac)3 in 40 ml CH2C12 (the Ti(acac)3 con- centration was 0.019fl) were prepared, and solutions contain- ing a mixture of these two complexes in CH2C12 with differ- ent Ti(hfac)3/Ti(acac)3 mole ratios were then prepared from these two stock solutions. The esr tubes were filled with these solutions and sealed under nitrogen. »F. Es; Measurements Most of the first derivative esr spectra were recorded by use of a Varian V 4502 x-band spectrometer (the Varian E—4 EPR Spectrometer as described in Part One was used also) at 779K. Values of g were calculated from the klystron frequency and the field strength of the center of the line as described in Part One of this thesis. The klystron frequency was determined by use of a spectrum analyzer and the field strength was measured according to the markers from the measured known proton frequencies of a water sample. The instrument was calibrated with a pitch sample. RESULTS AND DISCUSSION A. Preparation of Compounds Ti(hfac)3 was prepared according to the reported pro- cedure as described in the experimental section. A problem of obtaining an oily product instead of crystals was en- countered, which was overcome by using a slight excess of TiCla. This probably indicates that the Oily product was due to the presence of excess ligand. Ti(acac)3 was prepared by both the reported and a new method as described in the Experimental Section. For the reported method the filtration was very slow (5 hours) even when a coarse fritted glass disc was used for the vacuum filtration. -During this long filtration time air may leak in and oxidize the product. There was an apparent color change from blue to brown after washing. .A very low yield resulted. (An advantage of the new method is that no washing is required and the filtration of NH4Cl was ac- complished in two minutes. Attempts to prepare the mixed ligand complexes, .Ti(acac)2(hfac) and Ti(acac)(hfac)2, with methods similar to those for preparing Ti(acac)3 and Ti(hfac)3 were made without success. It was found that Ti(hfac)3 cannot be 52 53 prepared from TiCl3 and NH4hfac in toluene even when the mixture was refluxed at elevated temperature for 20 hours. This probably implies that NH4hfac is completely insoluble in toluene. No effort was made to use other solvents. It was found that Ti(hfac)3 was much more stable than Ti(acac)3 toward oxidation as judged from the apparent color change of the solid samples on exposure to air. The mixed ligand complexes (if they exist) should be less stable than Ti(acac)3 toward oxidation as indicated by the ear spectral changes which will be discussed in the following section. B. Esr Spectra Esr spectra of Ti(acac)3 and Ti(hfac)3 in both CH2C12 and toluene were obtained at 779K. For both complexes, ax- ially symmxrical spectra were resolved from toluene solu- tions as shown in Figure 16 whereas single lines were ob— tained‘from CH2C12 solutions as shown in Figure 17a and h. Their g values are given in Table VII. Attempts to study the ligand exchange behavior between Ti(acac)3 and Ti(hfac)3 in CH2C12 by following esr spectral changes were made without success. -Figure 17 shows a series ofVesr spectra of a mixture of Ti(acac)3 and Ti(hfac)3 in CH3C12 solutions with different Ti(hfaé)3/Ti(acac)3 mole ratios. The spectral change seems to indicate the existence of mixed ligands complexes. .However, it was found later that the solution of Ti(acac)3 in CH2C12 on exposure to air 54 100 gauss L l Figure 16. Esr spectra of a) Ti(acac)3; b) Ti(hfac)3 in toluene at 779K. ~ Figure 17. 55 Esr spectra of Ti(acac)3 and Ti(hfac)3 in CH2C12 solutions with different Ti(hfac)3/Ti(acac)3 mole ratios at 770K. a) pure Ti(acac)3; b) ratio = 0.10; c) ratio = 0.15; d) ratio - 0.37; e) ratio - 0.57; f) ratio = 0.86; 9) ratio - 1.29; h) pure Ti(hfac)3. These spectral changes were probably caused by the oxidation intermedi— ate as described in the text. 56 h 100 gauss Figure 17. 57 Table VII. 9 values fog Ti(acac)3 and Ti(hfac)3 in CH2C12 and toluene. Complex Solvent 9 g". QL Ti(acac 3 toluene . 2.00310.001' 1.934i0.001 Ti(hfac 3 toluene 2.004i0.001 1.947i0.001 Ti(hfac 3 CH2C12 1.967I0.001 ) ) Ti(acac)3 cnzcl2 1.954i0.001 ) ) b b Ti(acac 3b CH2C12 2.00210.001 1.93410.001 aSpectra were recorded at 770K. The uncertainties were estimated from the reproducibility of g values of several spectra of the same solutions recorded at different times. bSolution was exposed to air (spectrum is shown in Figure 18c). 58 gave the same result as shown in Figure 18. Spectrum a was recorded for the unexposed solution. After spectrum a was obtained, the blue solution of Ti(acac)3 was transferred from the original sealed sample tube into an empty sample tube exposing the solution to room atmosphere and this tube was sealed immediately. The color of the solution then changed from blue to brownish blue. The esr spectrum of this solution is shown in Figure 18b. This procedure was repeated once more. The solution color changed further to brown and Spectrum c resulted. On recording these spectra, an increase in the gain setting of the esr instru- ment was required in order to retain a similar intensity of the signals from spectra a to b to c. The solution became yellow in color on further oxidation and the esr Signal was completely lost. These results indicate that the oxidation of Ti(III) to Ti(IV) occurs gig a paramag- netic intermediate species which may be a dimer, (acac)2Ti-O-Ti(acac)2, that would give an axially symetri- cal esr signal to account for spectrum c. Spectrum b showed that the solution contained a mixture of Ti(acac)3 and the intermediate species. From this evidence, the spec- tral changes of the mixed solutions of Ti(acac)3 and Ti(hfac)3 shown in Figure 17 were probably caused by the oxidation intermediate, since apparent color changes from blue to brownish blue and greenish blue were observed when the two stock solutions of pure complexes were mixed. This also suggests that the mixed solutions of Ti(acac)3 and 59 L 100 gauss [— I Figure 18. .Esr spectra of Ti(acac)3 in CH3C12 (a) and on oxidation of this solution by air (b and c) at 770K. . 60 Ti(hfac)3 were much more unstable than the solution of Ti(acac)3 toward oxidation. CONCLUSIONS There is no definite evidence for the existence or non- existence of the mixed ligand compleXes, Ti(acac)2(hfac) and Ti(acac)(hfac)2, resulting from this research because of the oxidation problem. It would be interesting to carry out this work under extremely inert atmospheric conditions such as byzuse of a high vacuum line or a highly inert atmosphere box to prevent the oxidation problem. The possibility of oxidation of Ti(acac)3 to a Ti(IV)- complex 212.3 paramagnetic intermediate species is very interesting. More work such as studies Of the oxidation of Ti(acac)3 or Ti(hfac)3 using known amounts of oxygen or rate studies Of the oxidation process could reveal more de- tails of this process. The success of the preparation of Ti(acac)3 by use of NH4acac and TiCl3 in toluene suggests that the mixed ligand complexes may be prepared similarly if a suitable solvent can be found. 61 BIBLIOGRAPHY 1. 10. 11. 12. 13. BIBLIOGRAPHY I. N. Marov, Yu. N. Dubrov, V. K. Belyaeva, A. N. _Ermakov, and D. I. Ryabchikov, Russ. J. Inorg, Chem., '12, 1311 (1966). I. N. Marov, V. K. Belyaeva, A. N. Ermakov, and Yu. N.-Dubrov, Russ. J. Inorg. Chem., 14” 1391 (1969). L. A. Dalton, M. S. Thesis, Michigan State University, .East Lansing, Michigan, 1967. -F. Basolo and R. G. Pearson, "Mechanisms of Inorganic ReactiOns," New York: John Wiley and Sons, Inc., Second Edition (1967). S. W. Benson, "The Foundations of Chemical Kinetics," New York: McGraw-Hill Book Company, Inc., 1960. -J. P. Hunt, "Metal Ions in Aqueous Solution,” New York: W. A. Benjamin, Inc., 1965. C. H. Bamford and C. F. H. Tipper, Editors, "Compre- hensive Chemical Kinetics," Vol. 2, New York: Elsevier Publishing Company, 1969. M. Bersohn and J. C. Baird, "An Introduction to Election Paramagnetic Resonance," New York: W. A. Benjamin, Inc. 1966. C. P. Poole, Jr., "Electron Spin Resonance,“ New York: Interscience Publishers, 1967. E. A. Allen, B. J. Brisdon, D. A. Edwards, G. W. A. ~Fowles, and R. G. Williams, J. Chem. Soc., 4649 (1963). J. L. Dye and v. A. Nicely,-J. Chem. Ed., 2’8", 443 (1971). P. T. Manoharan and M. T. Rogers, J. Chem. PhyL, 42, 5510 (1968). J.-C. Sheldon, Proceedings of the XII International Conference of Coordination Chemistry, Sydney, 1969. 62 14. 15. 16. 17. 18. 19. 20. 21. 63 J. G.-Scane, Acta Cryst., 23, 85 (1967). I. N. Marov, Yu. N. Dubrov, V. K. Belyaeva, and A. N. .Ermakov, Russ. J. Inorg. Chem., 13, 1107 (1968). B. N. Chakravarti, NaturwisSenschaften, 42, 286 (1958). -D. W. Barnum, J. Inorg. Nucl. Chem., 21, 221 (1961). B. R. McGarvey, J. Chem. Phya, 38, 388 (1963). .F. H. Fry and W. R. Watt, J. Inorg..Nucl..Chem., 32, 3115 (1968). International Union of Pure Applied Chemistry, Commis- sion on Spectroscopy and Other Optical Procedures for Analysis, "Tables of Spectrophotometric Absorption Data of Compounds Used for the Colorimetric Determination of Elements," London: Butterworths, 1963. S. Herzog, J. Dehnert, and K..Luhder in-"Technique. of ‘Inorganic Chemistry," V61; VII, H. B. Jonassen and A. ”Weissberger,.Eds. New York: Interscience Publishers, 1968. APPENDIX 1 . A List of a‘ Simple Fortran- Program for the Calcu- lation of Theoretical Esr Spectra.a aThis program was written by Mr. Liping Woo. 64 902000 0.0H0 00020 2% 00 2 02H09200 I 0 0000 902000 0.0H0 00020 000 00 2 02H09200 I v 0000 902000 0.0H0 00020 00 00 2 02H09200 I 0 0000 >00>H9 l000000 902000 OHH 00HOH9000 920H0 020 0.0H00 00020 902 000092H 020 02.H0 0000 02H09200 I 0 0000 000>H9000000 902000 0H0 00HOH9 I000 900H0 00020 0 020 9202 000092H 02H09200 l H 0000 "902000 00000 0900 mODBquE¢ eqam u z» meoHs xmmsz mus zH mezHom «EEO mo mmmzsz u emz 29020090 000H0 002H0 I 02 09020090 000H0 00H9H2H I H2 20HN920000 020 20HO0D00 0900 92H00 I 0>H9H000 20HN920000 M0 00000I02HA 0090000000 92H00 I 02000 20HO0D00 20 00000I02HA 0090000000 92H00 I 0>H90002 A09HOH0 ¢ 09 0D 000092H W20V u N002H 20H900 900900 I 0 0900 0900 00 000202 I 92 0090000 009 2H 00000 00 000202 I 2 «0009020000 9D02H 00 20H90H00000 0090000 009202H000X0 009 2000 00000002 0003 20H90000000 2H 0000 0009020000 029 .00000 I02H0 0>H90>H000 900H0 20HN9200QH 020 20HO0D00 0900 02H00 00 0090000 000 000H9000009 009 090000000 09 0000 0H 2000000 0H09 OUUUUUUUUOUUUUUOUUUUUUUUU000000 mm00n50 m.mHDUm0m Hmm HOUHDmHowFH. mo COHDMHDOHOU 00D Dom Emumoum cmuDuom 0H0EH0 m 00 D30 0 .H NH020000 65 .oqume .o u wwme - 0.sz uh on on emzm\:mum5 "mama emz namzm .Am.ovmxm9uhm Hmum 20HN920000 020 20HO0D00 00 00000 02H0 0900 090000000 Am.HHmoa .umH wa