THE TiCh-uTiF‘ SYSTEM I. TETANIUMUV) CHLORlDE FLUORIDES 11. FLUORENE-IQ NMR STUDY IN TETRAHYDROFURAN Thesis for the Degree of Ph. D. MICHIGAN STATE UNiVERSlTY ROBERT SCRANTON BORDEN 1967 LIBRARY Michigan State University THES‘S This is to certify that the thesis entitled The TiCl4--TiF4 System I. Titanium(IV) Chloride Fluorides H. F luorine- 1‘) NMR Study in Tetrahydrofuran presented by Robert S. Borden has been accepted towards fulfillment of the requirements for Ph. D. degree in Chemistry Major professor Date October 27, 1967 0-169 Z: amome av 1‘ HUME & SUNS' etggmnm mc. 'NDERS MCIIIGII ABSTRACT THE TiC14--TiF4 SYSTEM I. TITANIUM(IV) CHLORIDE FLUORIDES II. FLUORINE-19 NMR STUDY IN TETRAHYDROFURAN by Robert Scranton Borden I. The TiCl4--TiF4 system was studied to determine if halogen exchange takes place and, if possible, to develop methods for the isolation of titanium(IV) chloride fluorides. Halogen exchange and the existence of TiF3Cl, TiFgClg, and TiFCla were confirmed in the vapor phase by mass spectral studies. TiCl4 and TiF4 react at 90°C in the absence of solvent to give an apparent equilibrium mixture of starting compounds and mixed halides. Halogen exchange is postulated to proceed through a five-coordinate bridged intermediate. TiFaClg, a yellow solid, can be conveniently isolated in high yield but yellow solid TiF3Cl was isolated only with difficulty and in low yield. TiFCla was not isolated but is probably an un- stable liquid which diSproportionates at room temperature into TiFaClg and TiC14. The thermal stabilities of the mixed halides are believed to be in the order TiF3Cl > TiF2C12 > TiFCla. Neither TiF3Cl nor TiF2C12 gave an X—ray diffraction pattern. A polymeric six—coordinate structure is suggested to account for the observed properties of these compounds. Robert Scranton Borden II. The TiCl4--TiF4—-tetrahydrofuran (THF) system was studied by 19F magnetic resonance techniques to confirm that halogen exchange takes place, to identify the titanium(IV) chloride fluoride THF complexes, and to determine the stereo- chemistry of the isomers involved. At room temperature spectral detail was lacking because of rapid THF and halide exchange, but at —60°C a well resolved spectrum was obtained which showed the presence of the titanium(IV) chloride fluoride THF complexes as well as the titanium tetrafluoride THF complex. Approximate equilibrium constants were calculated for the formation of each mixed halide complex from the starting compounds. The difference in the free energy values calcu- lated from experimental equilibrium constants and free energy values calculated from statistical equilibrium constants expected for random distribution were +220, +180, and -180 cal/mole for TiF3Cl-2THF, TiFgClg-ZTHF, and TiFC13°2THF. A detailed analysis of the low temperature 19F magnetic resonance spectra gives the following information about each of the observed isomers. TiF5°2THFz The gi§_isomer strongly predominates with a gig to ££§g§_ratio of approximately 35 to 1. Two equal intensity triplets are observed for the gig isomer with (SFF = 60 ppm and JFF = 57.7 Hz. The Eggpg isomer gives a singlet approximately 12 ppm upfield from the high field triplet of the cis isomer. Robert Scranton Borden TiF3Cl-2THF: Only one isomer is observed for this compound. The 19F NMR data strongly suggest that this isomer contains THF groups gig to each other and two fluorine atoms Erggg to each other. This isomer gives rise to a low field triplet and a higher field doublet in 1 to 2 intensity ratio with (SPF = 67 ppm and JFF = 35.1 Hz. TiFaCl232THF: Two isomers are observed for this com- pound. The presence of an enantiomorph isomer with similar ligands gig to each other is conclusively established by virtue of its unique splitting pattern. Two equal intensity doublets are observed for this isomer with (SFF = 76 ppm and JFF = 45 Hz. The second isomer, with an approximate ratio to the enantiomorph. isomer of 5 to 1, appears as a singlet about 6 ppm downfield from the high field doublet of the enantiomorph isomer. The position of this peak sug- gests that it arises from an isomer with gig fluorine and either gig chlorine and EgggquHF or gig THF and Egggg chlorine. The former is somewhat more consistent with the observed data and, therefore, is slightly favored. TiFCla'ZTHF: A single 19F resonance observed for this compound indicates the presence of only one isomer. Assign- ment of this resonance to a specific isomer is tenuous. The most consistent data are obtained by ascfibing'this Robert Scranton Borden resonance to the isomer containing trans THF groups. A close second and third choice would be the isomer having cis THF and trans chlorine and the isomer having cis THF and cis chlorine. THE TiCl4--TiF4 SYSTEM I. TITANIUM(IV) CHLORIDE FLUORIDES II. FLUORINE-19 NMR STUDY IN TETRAHYDROFURAN BY Robert Scranton Borden A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1967 Stigd' 3~3r 4. LA I‘ y‘ by ACKNOWLEDGMENTS The author wishes to express his appreciation to Dr. Robert N. Hammer, under whose direction this investiga- tion was undertaken, for his encouragement during this research, for his help and guidance in the preparation of this manuscript, and for his contribution toward the author's intellectual enrichment. The author is indebted to the Dow Chemical Company for Opening their research facilities to him and for a summer research fellowship in 1964. Grateful appreciation is extended to Dr. R. F. Rolf and Dr. J. E. Heeschen for making available neutron activation and 19F magnetic resonance spectroscopy facilities. Thanks also go to Mr. James Anderson, who recorded most of the 19F magnetic resonance spectra presented in this dissertation. The assistance of Philip Pilato in obtaining the mass Spectra and of Michael Gross in obtaining several 19F magnetic resonance spectra is gratefully acknowledged. Mass spectroscopy facilities were made available through the generosity of Dr. H. A. Eick. Receipt of the 1965-66 DuPont Teaching Fellowship is gratefully acknowledged and appreciation is given to the E. I. duPont deNemours and Company, Inc., for making this fellowship possible. A great deal of gratitude is expressed for the help, advice, and moral support of my colleagues and friends. Particular thanks go to Nelson Hsi, John Stezowski, and Richard Anderson. The appreciation felt for the encouragement given to the author by his parents is beyond his ability to express in words. Final acknowledgment is made to the authorfs wife, Barbara, whose confidence, encouragement, and love.during the darkest hours and deepest depths of depression gave him the strength and ability to succeed. ii TABLE OF CONTENTS Page PART I TITANIUM(IV) CHLORIDE FLUORIDES INTRODUCTION . . . . . . . . . . . . . . . . . . . . 2 EXPERIMENTAL . . . . . . . . . . . . . . . . . . . . 5 Purification of Reagents . . . . . . . . . . . . 5 A. Titanium Tetrachloride. . . . . . . . . . 5 B. Titanium Tetrafluoride. . . . . . . . . 5 Preparation of Titanium(IV) Chloride Fluoride. . 6 A. General Procedure . . . . . . . . . . . . 6 B. Titanium Chloride Trifluoride . . . . . . 7 C. Titanium Dichloride Difluoride. . . . . . 8 D. Titanium Trichloride Fluoride . . . . . . 15 B. Other Possible Compounds. . . . . . . . . 16 F. Physical Properties . . . . . . . . . . . 18 Mass Spectroscopy. . . . . . . . . . . . . . . . 20 A. Instrumentation . . . . . . . . . . . . . 20 B. Titanium Tetrachloride. . . . . . . . . . 20 C. Titanium(IV) Chloride Fluorides . . . . . 24 Analytical Methods . . . . . . . . . . . . . . . 30 A. Titanium Analysis . . . . . . . . . . . . 50 i. Gravimetric determination . . . . . 50 ii. Neutron activation analysis . . . 57 iii. Titration of titanium(III) with standard iron(III) solution . . . . 57 B. Chlorine Analysis . . . . . . . . . . . . 58 C. Fluorine Analysis . . . . . . . . . . . . 39 D. X-Ray Diffraction . . . . . . . . . . . . 59 DISCUSSION . . . . . . . . . . . . . . . . . . . . . 41 Mass Spectroscopy. . . . . . . . . . . . . . . . 41 Theoretical Considerations . . . . . . . . . . . 45 Interpretation of Experimental Results . . . . . 46 A. Heterogeneous Reaction. . . . . . . . . . 46 B. Gas Phase Reaction. . . . . . . . . . . . 48 Solid State Structure. . . . . . . . . . . . . . 49 iii TABLE OF CONTENTS -- continued CONCLUS ION . C O O O O O O O O O O O O O O O O O O SIGNIFICANCE . . . . . . . . . . . . . . . . . . . RECOMMENDATIONS FOR FUTURE WORK. . . . . . . . . . PART II FLUORINE-19 NMR STUDY IN TETRAHYDROFURAN INTRODUCTION . . . . . . . . . . . . . . . . . . . MER IMENTAI’ O O O O O O O O O O O O O O C O O O O Instrumentation. . . . . . . . . . . . . . . Preparation of the 19F NMR Samples . . . . . . A. Purification of Reagents. . . . . . . . B. Preparation of THF Solutions. . . . . . C. Preparation of NMR Samples. . . . . . . D. Decomposition . . . . . . . . . . . . . E. Complex Formation . . . . . . . . . . . Magnetic Resonance of TiF4 2THF. . . . . . Magnetic Resonance of TinCl4-x 2THF Solu- tions. . . . . . . . . . . . . . . 19F Magnetic Resonance of TiCl4- -TiF4/THF Solu- tions. . . . . . . . . . . . . . . . . . . 19F 19F DISCUSSION . . . . . . . . . . . . . . . . . . . . Halogen Exchange . . . . . . . . . . . . . . . 18F Magnetic Resonance--Stereochemical Considera- tions. . . . . . . . . . . . . . . . . . . 19F Magnetic Resonance--TiF4-2THF. . . . . . . A. Prior Studies . . . . . . . . . . . . . B. Theoretical Interpretation. . . . . . . C. Supporting Evidence . . . . . . . . . . D. Interpretation of Spectra . . . . . . . 18F Magnetic Resonance--TiF2C12’2THF, Isomer J A. Interpretation of Spectra . . . . . . . B. Theoretical Considerations for a w Bond? ing Order F > THF > C1. . . . . . . . . C. Theoretical Considerations for a w Bond- ing Order F > Cl > THF. . . . . . . . . Interpretation of Spectra. . . . . . . . . . . A. Temperature Effects . . . . . . . . . . iv Page 54 55 57 60 61 61 61 61 62 63 64 64 64 68 73 84 84 85 88 88 89 89 9O 92 92 92 93 94 94 TABLE OF CONTENTS -- Continued Page B. Observed 19F Resonances. . . . . . . . . . 94 C. W Bonding Order F > THF > C1 . . . . . . . 95 i. TiF3C1-2THF. . . . . . . . . . . . . 95 ii. TiFgClg'ZTHF . . . . . . . . . . . . 96 iii. TiFC13-2THF. . . . . . . . . . . . . 96 D. n Bonding Order F > C1 > THF . . . . . . . 97 i. TiF3Cl'2THF. . . . . . . . . . . . . 100 ii. TiFZCla-ZTHF . . . . . . . . . . . . 100 iii. TiFC13°2THF. . . . . . . . . . . . . 100 E. Summary. . . . . . . . . . . . . . . . . 100 Stereochemistry . . . . . . . . . . . . . . . . 102 ' A. Influencing Factors. . . . . . . . . . . . 102 B. TiF4'2THF. . . . . . . . . . . . . . . . . 102 C. TiF3Cl-2THF. . . . . . . . . . . . . . . . 105 D. TiFgClg'ZTHF . . . . . . . . . . . . . . . 103 E. TiFClg-ZTHF. . . . . . . . . . . . . . . . 105 EQUILIBRIUM CONSTANTS . . . . . . . . . . . . . . . . 105 Experimental Data . . . . . . . . . . . . . . . . 105 Equilibrium Considerations. . . . . . . . . . . . 105 Method of Calculation . . . . . . . . . . . . . . 106 Equilibrium Concentrations. . . . . . . . . . . . 107 Equilibrium Constants . . . . . . . . . . . . . . 109 A. Experimental Equilibrium Constants . . . . 109 B. Statistical Equilibrium Constants. . . . . 114 Discussion. . . . . . . . . . . . . . . . . . . . 117 Investigations of Other Workers . . . . . . . . . 119 Conclusion. . . . . . . . . . . . . . . . . . . . 120 CONCLUSION. . . . . . . . . . . . . . . . . . . . . . 121 SIGNIFICANCE. . . . . . . . . . . . . . . . . . . . . 124 RECOMMENDATIONS FOR FUTURE WORK . . . . . . . . . . . 127 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . 129 APPENDICES. . . . . . . . . . . . . . . . . . . . . . 152 LIST OF TABLES TABLE 1. 2. 10. 11. 12. 15. 14. 15. X-ray powder diffraction data for the hydroly- sis product of TiFSCl and TiFgClg. . . . . . . Mass spectral data. TiCl4 at 25 ev ionizing potential. . . . . . . . . . . . . . . . . . . Mass spectral data. TiCl4 and TiFCla at 25 ev ionizing potential . . . . . . . . . . . . . . .Mass spectral data.«TiCl4 and TiFCla, selected peaks. . . . . . . . . . . . . . . . . . . . . Mass spectral data-TinCl4.x compounds at 50 ev ionizing potential. . . . . . . . . . . . . Isotopic abundance . . . . . . . . . . . . . . 19F chemical shigt and coupling constants for TiF4. ZTI-IFI at -60 C o o o o o o o o o o o o o o 19F chemical shifts for TinCl4_x samples at -60°c...........'.'..—....... Peak assignment and 19F coupling constants for TinCl4-x samples. 0 o o o o o o o o o o o o o Intensity data for TinCl4-x samples . . . . . 19F chemical shifts and coupliBg constants for TiCl4-eTiF4/THF samples at 460 C Equilibrium mole per cent values for TiCl4-- TiF4/THF samples 0 o o o o o o o o o o o o o o Isomers of titanium(IV) chloride fluoride THF compounds. . . . . . . . . . . . . . . . . . . 19F chemical shifts for selected compounds where w bonding is postulated. . . . . . . . . 19F chemical shifts and coupling constants for the TinCl4_ ~2THF isomers proposed from a w bonding-Order F > THF > C1 . . . . . . . . . . vi Page 19 25 27 29 55 41 67 7O 71 72 81 85 87 98 99 LIST OF TABLES -- Continued TABLE Page 16. 19F chemical shifts and coupling constants for the TinCl4_X-2THF isomers proposed from a v bonding—Ordef F > C1 > THF. . . . . . . . . . . 101 17. Equilibrium calculations for 1.0 M_TiF2C12-2THF at -70 Co a o o o o o o o o o o o o o o o o o o 108 18. EquiliBrium calculations for 0.5 M_TiF2C12'2THF at -60 C. . . . . . . . . . . . . . . . . . . . 110 19. Equilibrium calculations for 0.52 M TiF2C12° 2THF and 0.17 g TiF3C1-2THF at ~60UC. . . . . . 111 20. Summary of equilibrium constants. . . . . . . . 115 21. Statistical and experimental equilibrium constants C O O O O O O O O O O O C O O O O O O 118 vii LIST OF FIGURES FIGURE 1. 2. 5a. 5b. 4a. 4b. 6a. 6b. 7a. 7b. 7c. 9a. Apparatus for the preparation of TiF2C12. . Gas phase reaction apparatus for the prepara- tion of TinC-l4_X compounds . . . . . . . . . Mass spectrum of TiCl4 at 25 ev ionizing potential. High mass region. Mass spectrum of TiCl4 at 25 ev ionizing potential. Low mass region . Mass spectra of TiCl4 and TiFCla at 25 ev ionizing potential. High mass region . . . Mass spectra of TiCl4 and TiFCla at 25 ev ionizing potential. Mass spectra of TiC14 and TiFCla. species at 25 and 70 ev ionizing potentials . Mass spectra of TinC14-x compounds at 50 ev Low mass region. . . . Selected ionizing potential.—'Higfi'mass region . . . Mass spectra of TinCl4_X compounds at 50 ionizing potential.”’Low—mass region. . . . 19F magnetic resonance of 0.5 -60°C . . . . . . . . . . 19F magnetic resonance of 0.5 -40°c . . . . . . . . . . 19F magnetic resonance of 0.5 25°C. . . . . . . . . . . 19F magnetic resonance of 1.0 at -70 C. . . . . . . . . 19F magnetic resonance of 0.29 M_TiF4 + 0.097 M_TiC14/THF at -60°C. . . viii E. M. '13 fl. TiF4'2THF at TiF4'2THF at TiF4'2THF at TiF2C12/.THF ev Page 10 15 21 22 25 26 51 52 66 66 66 69 75 LIST OF FIGURES - Continued FIGURE - Page 9b. Expanded view of 19F resonances in Figure 9a . 76 10. 19F magnetic resonance of 0.24 M_TiF4 + 0.20 M TiCl4/THF at -60°C - . . . . . . . . . . . . . 77 11. 19F magnetic resonance of 0.16 M TiF4 + 0.16 olz TiC14/THF at -60°C . . . . . . . . . . . . . 78 12. 19F magnetic resonance of 0.56 M TiF4 + 0.72 M TiCl4/THF at -60°C . . . . . . . . . . . . . . 79 15. 19F magnetic resonance of 0.067 M_TiF4 +-0.20 M_TiCl4/THF at -60°C . . . . . . . . . . . . . 80 ix LIST OF APPENDICES APPENDIX Page I. Reaction of TiF4, TiF3Cl, and TiFgClg with (CBHS) asiOHo o o o o o a o o o o o 0 Q o o o 155 II. Automatically Controlled Constant Pressure 0 O 0 O O O O O 155 Dry Box. . . . . . . . PART I TITANIUM(IV) CHLORIDE FLUORIDES I NTRODUC TI ON When this research began in February of 1965, only one mixed chloride fluoride of titanium had been reported. In 1905, Ruff and Ipsen (45) reported the isolation of a yellow solid intermediate from the reaction of TiCl4 with HF or AgF. This material was found to contain a variable ratio of titanium, chlorine, and fluorine. Ruff and Ipsen were unable to obtain a product of constant composition. In 1955, Vorres (48,50) reported the preparation of yellow solid TiF3Cl by the reaction of TiFa with elemental chlorine. Halogen analyses of the product differed from theory by several per cent. During the period between the studies of Ruff and those of Vorres, no additional work was done in this area. In December of 1965, Dehnicke (10) reported the prepa— ration of the yellow solid TiF2C12 by the reaction of chlorine monofluoride with TiC14. His note, however, was very brief and lacked substantiating evidence. Dehnicke (25) has also recently reported the preparation of the yellow—brown solid TiFaBr by the reaction of bromine trifluoride with TiBr4. Again experimental details and substantiating evidence are lacking. The literature contains a number of references to mixed bromide chlorides, bromide iodides, and chloride iodides of titanium(IV). TiClsBr and TiClgBrg were first prepared in 1876 by the action of bromine on TiCla and TiClg, respectively (18,19). The TiCl4-—TiBr4 system was studied in 1945 by Raman spectroscopy (11). The three mixed bromide chlorides were found to be in equilibrium with each other and with the pure halides, but separation of the pure components was not pos- sible. The mixed halides of titanium(IV) are generally made by the oxidation of a lower valent titanium halide with a halogen of higher atomic weight than contained by the titanium halide. A number of patents cover the use of these compounds as polymerization catalysts (47). Halogen exchange is well-known for a number of metal and nonmetal systems. The BF3--BC13--BBr3 system was examined in 1960 by nuclear magnetic resonance (NMR) spectroscopy (9). All the mixed halide compounds were observed but their iso- lation was not possible. Halogen exchange was established in 1964 for the AsF3--A5013 system by both 19F NMR and mass spectroscopy (44). Isolation of the mixed halides was again not possible. Halogen exchange also has been confirmed for the PC13--PBr3 system (17), however exchange in the PF3Clg-- PFaBrg system apparently does not take place (29). The mixed halides of organo-silicon, -germanium, and -antimony also have been identified in mixtures of the pure halides (28,54,55). Halogen exchange reactions between transition metal halides have not been studied extensively. The CrC13-- CrBra (22) and VC13--VBr3 (50) systems have been examined and while solid solution formation was observed, halogen exchange was not conclusively established. The only case where halogen exchange between transition metal halides appears to be well-established is in the TiC14--TiBr4 system (11). A great deal of work on scrambling or redistribution exchange reactions has been done by J. R. Van Wazer, K. Moedritzer, and co-workers. They have published exten— sively in the Journal of the American Chemical Sgciety and in Iggrganic Chemistry from 1959 to the present time. This dissertation reports an investigation of the TiCl4--TiF4 system. It was the intent to determine if halogen exchange takes place and, if so, the suitability of this system for the preparation of the titanium(IV) chloride fluorides. EXPERIMENTAL Purification prReagentg A. Titanium Tetraghloride Purified TiCl4 was obtained from the J. T. Baker Chemi- cal Company. For most reactions this material was used without further purification. When specified as distilled, the above material was distilled under nitrogen from decolor- izing Charcoal through a Vigreaux column into a flamed out receiver or directly into the reaction vessel; only the middle fraction was collected. Since TiCl4 reacts with all stopcock greases tested, these were avoided by using Teflon stopcocks and Teflon sleeves for standard taper connections or by using specially constructed glass and Teflon systems containing no joints. Apiezon type W black wax was found satisfactory for making temporary standard taper glass to glass connections. The distilled material was a perfectly clear, colorless liquid. B. Titanium Tetrafluoride Titanium tetrafluoride as obtained from Alfa Inorganics was a gray-white powdery solid of an advertized minimum 97% purity. While the analysis of this material appeared in good agreement with theory, the physical properties of the sample indicated that further purification was necessary. 5 For example, on sublimation a substantial nonvolatile residue remained. The material was only partially soluble with slow reaction in water and the majority of the sample appeared to be insoluble in tetrahydrofuran. This commercial TiF4 was purified by passing a stream of dry nitrogen over the sample in a flamed out Pyrex tube at ZOO-250°C. Several Teflon baffles were placed in the cold end of the tube to prevent the very finely divided TiF4 from being swept from the system. A series of traps and a drying tower on the exit line prevented water vapor from diffusing back into the system. The pure white finely divided TiF4 was removed from the tube in a dry box and stored in a tightly Closed container. This material reacted vigorously with water or tetrahydrofuranl to give a clear solution. Attempts to vacuum sublime the commercial grade TiF4 proved unsatisfactory. The sublimate formed a glassy solid that could not be con- veniently removed from the cold finger. grepagation of TitaniumLIVLChloride Fluorides A. General Procedure All reactions attempted were direct reactions between TiC14 and TiF4 in the absence of solvent. Two basic tech- niques were employed. The first method involved a hetero- geneous reaction where TiF4 was suspended in TiCl4, the J'The tetrahydrofuran must be cooled to near its freez- ing point and the TiF4 added slowly. If the addition takes place at room temperature a secondary reaction may take place to yield a red solution. sample refluxed, and finally distilled. The second method involved passing a nitrogen stream saturated with TiCl4 over a sample of TiF4 in a heated tube. This gas phase method often produced materials of indefinite and variable composition. In both methods great care was taken to work under an inert atmosphere and to avoid possible contact with stopcock grease, water, or other contaminants. Glassware was flamed out under vacuum and flushed with dry nitrogen prior to use. All glass and Teflon systems were employed. B. Titanium Chloride Trifluoride To a 100 ml distilling flask containing 11 grams (0.058 mole) of TiCl4, 5.61 grams (0.029 mole) of TiF4 was added. There was no initial reaction. Upon heating, the mixture turned yellow and began to boil at Au900C. The temperature of the heating mantle was raised to 160°C and the sample allowed to reflux overnight. A bright yellow solid coated the upper walls of the reaction flask and the distillation column. The distillation column was then heated to permit refluxing liquid to begin distilling into the receiver flask. Yellow solid tended to plug the distillation take-off and made removal of liquid very difficult. The mantle temperature was raised to 200°C and the sample distilled to dryness. The lower half of the distilling flask contained a dark gray solid whereas the upper half and the distilling column con- tained a bright yellow solid. This yellow solid was collected under an inert atmosphere and sublimed onto a cold finger in a short pathlength sublimator at 150°C and 0.1 mm Hg pressure. The sublimate was then resublimed at 1000C and 0.1 mm Hg pressure over a 48 hour period. A significant amount of residue remained after each sublimation. This indicates that part of the sample had decomposed under these conditions. Analysis of the bright yellow sublimate was as follows: Theory for Found Average L TiF3Cl Titanium 155.85, 55.80. 55.85 54.15 Chlorine (26.56, 26.40, 26.55. 26.57 25.26 Fluorine By Difference 59.80 40.61 Several samples having a composition approaching that of TiF3Cl were obtained by passing a nitrogen stream saturated with TiCl4 over a sample of TiF4 in a heated tube. The material nearest the hot zone always had the lowest chlorine analysis, which usually ranged between 20 and 50% (theory for TiF3Cl = 25.5% Cl). As the distance from the hot zone in- creased, the chlorine content of the sample also increased. Since only a small yield of material with variable composition was obtained by this method, no further efforts were made to develop it further for the preparation of TiF3Cl. C. Titanium Dichloride Difluoride Titanium dichloride difluoride can be prepared in good yield by the direct reaction of solid TiF4 and liquid TiCl4 using a very large excess of the latter. The mixture is refluxed and then distilled. Excess TiCl4 is removed from the distillate by vacuum evaporation, leaving TiF2C12 as a yellow solid. The apparatus (Figure 1) is thoroughly flamed out under vacuum and then flushed with dry nitrogen while the reactants are added to the reaction flask. The following procedure is typical for a run using commercial grade reactants. TiF4 (1.9 grams) and 40 ml (69 grams) of TiCl4 were added to reaction flask A against an outward flow of nitro- gen. The reaction flask was then heated to reflux for 15 minutes. The solution turned yellow and a small amount of bright yellow solid began to collect above the liquid level and in the distilling column. The vapor refluxed at 150°C whereas the boiling point for TiCl4 is 156°C. The distil- ling column was heated to allow distillation to begin. The distillate which collected in flask B was a cloudy yellow color. The amount of solid contained in the distillate appeared to increase on standing as if it were precipitating from solution. The distillation was stopped with only a few milliliters of liquid remaining in the reaction flask. The distillation temperature had risen to 155°C and the material distilling over had become a much lighter clear yellow liquid. The distillate was frozen in a dry ice bath and then while the system was flushed with dry nitrogen the joint between flasks A and B was disconnected and closed with a glass cap. 1O is In; , lilc _ l if... f: ' v! «SD‘MW' u._,."‘ )\‘l' tum a...v_} ~ In! Figure 1. Apparatus for the preparation of TiF2C12. (A) Reaction flask, 500 ml (B) Product collection flask, 500 ml (C) TiC14 collection flask, 500 ml (D) Heated Vigreaux column, 8 inch (E) Heating mantle (1) Ring-seal joint for the introduction of reactants-- 50 mm (2) "SolV—Seal" Teflon joint——5 mm (5) Ring-Seal joint for product removal-—5O mm (4) "Solv-Seal" Teflon joint—-15 mm (5) Nitrogen inlet (6) Vacuum connection 11 This allowed flasks B and C to be evacuated without volatil- izing any liquid remaining in flask A. When a good vacuum was achieved, the connection to the vacuum pump was closed and the dry ice bath was moved from flask B to flask C. As flask B warmed to room temperature, TiCl4 was volatilized and collected as a white solid in flask C. In order to achieve a reasonable transfer rate for the TiCl4, it was some- times necessary to refreeze the contents of both)flasks B and C and re-evacuate the system. This provides for the removal of nitrogen that was trapped during the first freez- ing process. Toward the end of the volatilization process, the material which collected in flask C was a light yellow color, indicating that some product or volatile impurity had been carried over. After all the liquid was removed from the bright yellow solid remaining in flask B, the system was swept with dry nitrogen as the joint between flasks B and C was disconnected and capped. Flask B (containing the sample) was then evacuated for 24 hours, after which the flask was moved into a dry box where the product was collected. Its analysis was as follows: Theory for Found Average 'TiF2C12 Titanium 50.56, 50.45 50.40 50.55 Chlorine 46.12, 46.04 46.08 45.22 Fluorine By Difference 25.52 24.25 The analysis of the sample, which was slightly high in chlorine 12 and low in fluorine, indicates slight contamination with TiCl4 or TiFCla. Calculated on the basis that the impurity was TiCl4, the sample would be 97% pure. The product weighed 2.6 grams for a yield of 55%. Using purified reactants a yield approaching 100% can be expected. In some runs where a much larger excess of TiCl4 was used, the distillate collected as a Clear yellow solution. After standing for several minutes the clear solution turned cloudy and TiF2C12 precipitated as a fine yellow solid. When a much smaller excess of TiC14 was used, a great deal of solid formed in the distillation column and condenser; it tended to plug the apparatus. Titaniummdichloride difluoride also can be prepared by passing a nitrogen stream saturated with TiCl4 over a sample of TiF4 in a heated tube. The apparatus is shown in Figure 2. Dry nitrogen was bubbled through purified TiCl4 at 80°C at the rate of 80 ml/minute and then was passed over 5 grams of TiF4 in a horizontal tube at 200°C for 20 hours. Shortly after the process was started, a very finely divided light yellow solid collected along the length of the reaction tube extending from the furnace. Teflon baffles prevented this material from being carried out of the reaction tube. A great deal of care was required to maintain the proper concen- tration of TiCl4 in the reaction tube. Too large an excess of TiCl4 caused its condensation on the cold portion of the reaction tube. Too small an excess of TiCl4 resulted in ., ._ w”; f‘ill: MAIN SMAJWM ‘96-— I“: mrmw a Figure 2. Gas phase reaction apparatus for the preparation of TinCl4-x_compounds. (A) Distilled TiCl4 storage container (B) Tube furnace (C) Reaction tube, 50 mm (D) Ring-seal joint, 50 mm (X) Constriction at the point where the tube is to be sealed off (1) Inlet from TiCl4 distillation apparatus (2) Nitrogen inlet (5) Vacuum connection (4) Connection to cold traps and drying tower All stopcocks are Teflon 14 incomplete reaction and contamination of the product with higher fluorides (TiF4 or TiF3Cl). After the reaction period the TiF4 was allowed to cool to room temperature and dry nitrogen was then passed over the sample for several minutes. Next, the reaction tube was evacuated for approximately 10 minutes before it was sealed off at point ngith a torch and removed from the system. The sample was removed in two portions in the dry box, The portion nearest the hot zone was a heterogeneous mixture of small bright yellow pieces and a fine light yellow powder. Chlorine analyses of 21.09% and 55.88% confirmed the heterogeneous nature of this material. The portion farthest from the hot zone was a very fine light yellow solid which appeared fairly uniform. Its analysis was as follows: Theory for Found Average :TiFgClg Titanium 51.15, 51.10. 51.15 50.55 Chlorine 45.64, 44.65, 45.25 45.17 45.22 Fluorine By Difference 25.80 24.25 The spread in the chlorine analysis indiCates that the sample was not completely homogeneous. During repeated runs the sample farthest from the hot zone always had the highest chlorine analysis, which usually approximated that required for TiF2C12. When a large excess of TiCl4 was used such that the sample was actually wet, the chlorine analysis was quite high: this could be reduced to that required for TiFgClg by vacuum drying. 15 The method just described for the preparation of TiF2C12 is neither as convenient nor is the quality and consistency of the product as good as with the first method described. D. Titanium Tgichloride Fluoride Several unsuccessful attempts were made to isolate TiFCla. Observations made during these attempts tend to indi- cate that, at room temperature, TiFC13 is a liquid which undergoes disproportionation into TiF2C12 and TiCl4. The method previously described for the preparation of TiF2C12, involving the direct reaction of solid TiF; with approximately a 50:1 molar excess of TiCl4, was originally carried out in an attempt to prepare TiFCla. The extremely large excess of TiCl4 would certainly be expected to favor the formation of TiFCla. The small amount of solid formed above the reflux- ing liquid in the reaction flask indicates that the fermation of TiF3Cl and TiFgClg is not favored. In another experiment a 4:1 ratio of TiF4 to TiCl4 was heated at 100°C for 24 hours. The contents of the flask were then filtered to yield a bright yellow liquid--presumably a solution of TiFCla in TiCl4. Analysis of this sample showed 74.2% chlorine, indicating that only 4% could be TiFCla. A portion of this sample was distilled at atmospheric pres- sure. At 154OC a clear, dark yellow distillate was collected. Upon standing, the clear distillate became cloudy and a yellowrsolid (subsequently shown to be TiFgCla) slowly formed. As the distillation was continued, the temperature rose to 16 the boiling point of TiCl4 and the material distilling over became colorless. Distillation of samples at reduced pressure and tempera- ture simply gave distillates that were more dilute solutions of the yellow liquid. At 50 mm Hg pressure and 47°C the distillate was still dark yellow. At 5 mm Hg and 55°C the distillate.was light yellow. At lower pressure.and at_ temperatures below 50°C, the distillate was nearly colorless. Every attempt to separate the yellow solution into its components failed. Each time the solution was concentrated, a yellow solid (TiFgClg) formed. (E. Other PossibleCompggpds Throughout the development of the syntheses of TiF3Cl and TiFgClg, numerous samples were Obtained which had compo- sitions intermediate between these two. Several examples follow: Commercial grade TiFA was ground to a fine powder and 48.2 grams of this was added to 172 ml of commercial grade TiCl4 in a 500 ml flask. The TiCl4 and TiF4 were in a 4:1 molar ratio. The flask was heated to 100°C in an oil bath and stirred with a magnetic stirrer for 24 hours. A heavy yellow coating covered the upper walls of the flask. This sample was collected and found to contain 54% chlorine. Excess liquid was removed from the dirty yellow solid remain- ing in the bottom of the flask. After drying, the sample contained 24.85% chlorine. Sublimation of this material gave 17 a bright yellow solid containing 58.5% chlorine and 51.5% titanium. This corresponds to Ti3F7C15 or 2TiF2Clg-TiF3Cl which requires 58.57% chlorine and 51.74% titanium. Another solid sample was obtained by distilling the liquid removed from the original reaction mixture. In the first fraction distilled from this liquid, a solid formed. This solid was separated by filtration and then dried by passing dry nitrogen over it for five minutes, after which the solid was placed under vacuum for five minutes. The resulting material contained 55.7% chlorine, which corres- ponds to Ti2F3C15 (possibly TiF3Cl‘TiC1¢ or TiFgClg°TiFC13) which requires 55.7% chlorine. However, the correspondence between the analytical results and a fixed stoichiometry is probably fortuitous. It is most likely that this sample was TiF2C12 wet with incompletely removed TiCl4. The occurrence of nonstoichiometric samples and the possibility of addition compounds will be discussed in more ’detail in the discusSion'section., At this point, suffice it to say that mass spectral data which presently will be dis- cussed do not show the presence of any mixed chloride fluoride Species other than TiF3C1, TiF2C12, and TiFCla. Therefore more complex species apparently do not exist in the vapor phase and their existence in distinct molecular form, other than as possible addition compounds, in the solid state is doubtful. 18 F. Physical Properties Both titanium chloride trifluoride and titanium dichloride difluoride are bright yellow solids which are not easily distinguished by physical appearance. They are both insoluble in common nondonor solvents such as benzene, toluene, hexane, and carbon tetrachloride. In donor solvents such as tetra- hydrofuran, fluorine-19 NMR studies have shown that dispropor- tionation takes place to give a solution containing, in equilibrium, all the titanium(IV) chloride fluoride addition complexes of tetrahydrofuran. The results of these studies will be more fully discussed in Part II of this thesis. Both TiF3Cl and TiF2C12 react with donor substances hav- ing an active hydrogen such as water, alcohols, and silanols. The reaction with silanols is discuSSed in more detail in Appendix I. Exposure to the atmosphere causes the samples to hydrolyze to a white powder which is believed to be either TiO(OH)F or TiOFg. The X-ray diffraction pattern corresponds to that reported by Vorres and Donohue (49)”for.Ti0Fg (Table 1). Dehnicke (10), however, reports that the material thought to be TiOFg by Vorres is actually TiO(OH)F. No ad- ditional effort has been made to resolve this variance. Both TiF3Cl and TiF2C12 give no X-ray diffraction pattern and appear to be amorphous. Titanium chloride trifluoride appears to be somewhat more thermally stable than titanium dichloride difluoride. In a sealed melting point tube TiF3Cl showed the first visible sign of decomposition at 215°C whereas TiF2C12 19 Table 1. X-ray powder diffraction data for the hydrolysis product of TiFsCl and TiFgClg. Observed Data Reported by Vorres (49) for TiOFg g g _ Plane 5.80 5.76 100 2.69 2.67 110 2.20 2.18 111 1.90 1.89 200 1.70 1.69 210 1.56 1.54 211 1.55 1.54 220 1.27 1.26 221,500 20 began to decompose at 140°C. At higher temperatures a yellow liquid distilled from the samples leaving a gray residue. The gray residue, which was probably TiF4, sublimes away in an open flame. Mass Spggtroscgpy A. ngtrumentation All mass spectra were obtained with a Bendix time of flight mass Spectrometer. Sample introduction was accom- pliShéd either externally through about one foot of quarter- inch copper tubing which lead to the ionizing beam or internally by adding the sample to a Knudsen effusion cell which was placed inside the mass spectrometer and directly below the ionizing beam. The system was originally designed for high temperature effusion studies and it was not possible to measure the relatively low temperatures at which the effusion cell was operated. The effusion cell was heated very slowly until a pressure rise was observed in the system indicating that the sample was volatilizing. B. Titanium Tetrachlggide Figures 5a and 5b Show the mass spectrum obtained for a sample of distilled titanium tetrachloride that was external- ly introduced into the mass Spectrometer. At an ionizing potential of 25 electron volts the following Species were + . + . + . + + + observed: TiCl4 , T1C13 , T1C12 , T1Cl , HCl , and Cl . 21 .GOHmou mmmE nmflm .Hmflucouom mCHNHGOH >o mm um waves mo Ednuoomm mum: .mm onsmflm Tttt trite. III... 6668 SSE-6.9 ZZII #808 61.98:... ”dawn”? __L_. _ lbw“? _____ 741+ +¢Hoea m m A + flows + HU.B 22 .COflmou mmmE 30A 98 S? : 44 -r38 8 . T . 1 .HMHucouom mGHNHGOH >m mm um eaUHB mo Esuuoomm mmmz -r88 --L€ J-ss 2 +HOHB .Qm onsmflm fiFQZ VH0 Cam +HUE All NZ 25 Table 2. Mass spectral data. TiCl4 at 25 ev ionizing potential. W Mass Abundance gagig Species Mass-to-charge “g. T‘.Tf_'_fT'f ' Abundance Species Ratio Calculated. Observed. Ratio 194 12 11 + 192 51 51 TiCl‘ 190 100 100 54 188 80 85 186 7.6 6.2 159 5.1 4.4 + 157 55 57 TiCla 155 98 96 100 155 100 100 151 9.7 8.9 122 14 14 . + 120 67 68 TlClZ 118 100 100 a 75 116 10 9.0 85 58 57 + 84 10 7.9 TiCl; 85 100 100 »42 82 9-7 7.9 81 10 10 + 58 52 29 HC1 56 100 100 92 + 57 52 20 C1 55 100 100 7‘6 N2 28 -- -- 5.8 24 Table 2 includes the calculated and observed mass-to-charge ratio, mass intensity ratios, and the relative abundance of each Species. The rather intense mass peaks observed for HCl may be due to slight hydrolysis of the sample as it passed through the external inlet system or perhaps to HCl as an impurity in the sample. No mass peaks were observed for any oxygen-containing species. C. Titanium(TV) Chloride gluorides A sample of TiF2C12 was placed in a glass container and connected through the external inlet to the mass spectrometer. At an ionizing potential of 25 electron volts and with the sample at room temperature only the cracking pattern of TiCl4 was observed. The T1014 background disappeared after pumping on the sample for a short period. The sample was then slowly heated and at 550C both TiCl4 and TiFCla were observed in the spectrum. The Species present were TiC14+, TiC13+, TiC12+, TiCl+, TiFCla+, TiFC12+, and TiFCl+. Figures 4a and 4b Show this spectrum and Table 5 contains the enumerated data. By increasing the sample temperature and the ionizing potential, more intense mass peaks were observed. These data are shown in Figure 5 and Table 4. In both these Spectra, the sample pressure was fairly unstable. The relative abundance of the species present is therefore of doubtful Significance except to Show that TiCl4 was present in much higher concentration than TiFCla. 25 .GOHmouxmmmE swam .HMHucouom mcHNAGOH >o mm um maumHB Cam eaUHB mo muuoomm mmmz .mw ousmflm IIII III III II III I 6668 LLL SSS 88 22.... O .7808 9.78 LS8 6!. 808 8 .-P. _P% F__ .. ... F Aqua -qq 4.. uh _4q 4 +Homea savage «Hesse + + . +maoaa «Hoes- n .n . + HULH. ecowmon mmmE 30A .Hmwucouom mcflNSGOH >0 mm um oaomfla was «HOSE mo Esuuommm mum: .Qe musmflm 6 888 L .7 8 88 3 L 58... I. 9 8 9c. 8 p .P- L _ p .. p J .Jd . . a .1 a rim 7. 1% N2 + +HUflB 26 M M +Hom we +Ho 27 Table 5. Mass spectral data. TiCl4 and TiFCla at 25 ev ionig- ’ ing potential. Externally introduced sample at 55 C. ===l== = Mass Abundance Ratio Species MasS-to-charge ._ g.‘.. f; _____ __ff _ Abundance Species Ratio Calculated Observed Ratio 194 12 12 + 192 52 51 TiCl4 190 100 100 62 188 80 81 186 7.6 7.5 + 176 55 521 TiFCla 174 98 98 5.6 172 100 100 159 5.1 5.1 + 157 55 55 TiCla 155 98 97 100 155 100 100 151 9.7 9.5 . + 159 67 66 T1FC12 157 100 100 4'6 122 14 14 . +. 120 67 68 Tlclew 118 100 100 44 116 10 9.5 TiFCl+ 102 -- -- 1.5 + 85 58 55 TiCl 85 100 100 4.5 81 10.4 152 ? + 58 52 29 HC1 56 100 100 11 C1+ 35 -- -- -- N2+ .28 " -‘ " . .mamausouom mCHNHGOH >o On Cam mm um moaoomm pouooaom .mHUmHB 6cm eaoea mo muuoomm mmmz 28 .m onsmflm .211 IIII III.II III 81.9 1111 vv.sss 000 8859 ... 9.780 SI 6.1.6. .788 9993... 555 "x: ITI1+=| It. III+I| I: Dude +H saves ++ n omae + H . m Chas + A . a +HU.B 29 5N 0d am dd >.m mm >o oh Doom 00d 00d mm +Hoaa NH OH em mm mm mm hm OOH m.mh >o Ow Doom OOH mm mn~> ++OHUAB mm mm m.m> 00d 00a N06 >0 mm Doom pd oa moa +HumHa mm mm #06 d.m OH mma ooa OOH end >O OS 0005 mm no and +NHUmHB ma ed fled II II med 0d >.m cud OCH OCH mud n >o mm Coon mm mm «ed + HUhHB mm mm med waucouom OHSUOHOQEOB Cm>uomno pmumHsUHmo oflumm mmflommm meANASOH mamsmm. . k ..- 41m...) .... Dmumzolouummmz owumm OUGOUGSQ< mmmz .oamsmw poosvonucfl waamcumuxm .mxmmm Umuomamm haumfia Cam eaves .mumo Hmuuommm one: .8 OHQOB 50 A sample of mixed titanium(IV) chloride fluoride having a composition corresponding to 2TiF2C12-TiF3Cl was placed in a high nickel content stainless steel effusion cell and placed directly below the ionizing beam in the mass spectrom- eter. At room temperature no mass peaks were observed. The sample was slowly heated until enough sample was volatilized to give a usable spectrum. The spectrum which appears in Figure 6 clearly Shows the existence in the vapor phase of TiC14, TiFClg, TiF2C12, and TiF3Cl. The data calculated from this Spectrum are given in Table 5. Analytical Methods A. Titaglpm AnaTysis Determination of titanium was accomplished in one of three ways: .i. Gravimetric determination. Samples were hydrolyzed and ignited to Tiog. A 0.5 gram sample was accurately weighed into a platinum crucible under nitrogen. The sample was then exposed to the atmosphere and allowed to hydrolyze. Three toffour milliliters of Six molar sulfuric acid were added and the sample was carefully heated to dryness. The sulfuric acid treatment was repeated and the sample was then ignited to constant weight. From the weight of the titanium dioxide thus obtained the per cent titanium in the sample was calculdted. The ignited T102 was not pure white but salmon in color. In a number of cases low results were obtained and 51 I. .coamou mmmE swam .Hmaucouom mcfluflsow >o om um mpcsomEoo.l :Ho has NO muuoomm mmmz .mm ousmflm III II III... IIIIIII IIIIII IIIIII IIIII 666 88 LLLL 8999999 9.7.7668 ZZZZIT 00000 93088 8.780 081.898... BIOS/.9 98 I088 9.7830 ...-b .p.. ...:Lr pPE-. ..bp up I... W«_.u .—._ -_: ... ‘2‘ «q ....Ja ...HJ. « ode m Chas + H . + H . .v #39. . - -..»;4;_; a e : nus : owmae «Sommea. 7 ,+Hu m.e”..:+a an - + 03M ,. ..... USN I : +NU .. N ...... - UHF .- saves + Hum.e . a +. .. ... +Ucm .n +H0m.B 52 I. I. .eoemou name 304 .Hmaucouom mcfluflcoe >o om um mUGDOQEoo xieauxmfla mo mnuoomm mmmz .Qm onsmem .7.7 a... 6 88889 99999 .99 95.77.77 . . 88 89 S 95.78I 681.95 as I069L9 55 BL 98 . ..... F_:P -. —__.p. __ .PP. J unu-d uqduq -— ---44- .a unq- aUHB ++ Um .Gm +H p +aU mee + whee 96.. A + . U +HU.B «a d . ...— n..-.-.h . ...... k/ri «...—...... .A::. ..v s-.~v 4wia~n£ ..Ih an n..P)\ 55 possflusoo 0H 09 0a II >.m II and «OH moa NOH II ooa II mmd moa 90d OOH n.¢ mm m.> mma +OHUHB um um OH em ¢.m ooa mmd can we we mm N.> mm ma emd +Naommwa mm mm II mm II em mmd m.m m.h II m.> II dd OmH +nHUdB +NHUmmflB +flHUHB +NHUmmflB muemeowsH; ; 85m *UDDMHSOHOU. _ , . . mucosa oaumm mmwoomm Consumes. UODMHSOAMU .omumm ooempssn<.mmmz 7. mmumnoloulmmmz. . .mxmmm muse mcflmmmHuo>o oEom o>ms mowoomm mcdzoaaom one we . 5.8 cps 008 009 mud 0 mm mm SSH + Homes «m mm med >.m m.> mma mm om mmd ooa ooa omd +¢Hoae om mm de ma Nd dad p0>ummnb.... >MONCH oaumm mowoomm mmumzoloulmmmz owumm musmpcsnd mmmz hbonuo5_soamswmo cmmwscx .Hmflusouom mcHNACOA >o om um mossomeoo.mreauxmfla .mvmp Hmuuoomm mmmz .m manna .‘I ..N. 54 pmscducoo po>uomnb xwmm ddem Muo> mm ++edUdB o.s o.m o.m II ca II - cod om om om II 00d II Ned ON ON o.m md 0d dd nOd +d0md8 hm mm md dd mm 0d 90d Cam mNdA oed .d and n.~ 00d moa +smda o.m o.m II o.m II N.> 80d InIII Ill lul +domda + m.9 +dohda + Eda m.d >.m h.m II 0d II mdd hm um um II 00d II mdd . mm ed m.e 0d md od add +~Hode dm we mm 0d so 0d ONd cam mOd med m.m 00d m.¢ 00d de +d0~hd9 mm mm II mm II mm mmd d m.m II m.N II m.m mmd IMHOAS HONMMH _IMdde. .IdeMdH + + + + dd dd dd II 0d II mmd med 50d 80d II 00d II end mm we we «.8 no 0d and +maomde on we m.e we m.¢ 00d Odd can mN md md 8.9 .-dd 0d ddd +dommd8 m.md m.md II m.md II on med +maomd +dUuhda +maude +d0nmda hudmcoucd 85m .I woundsodmo mucosa 0dumm mmdowmm Consume: Coumdoodmo Odumm mocmpcsnfl WMOZ omumnoloulmmwz II I I (I) l‘l) Coscdusoo .m Odnme I‘ll. I V-h. 55 poscducoo 00d 00d m.dd mm mm m.me 18HE 0d dd md Nd 0d ed 00d 00d me +d8 m.> «.> me >.m m.> om xmom csoexcs ddmem wuo> dm m 00d 00d mm . - . am em 08 . ++ Needs dd dd mm m.m 0d mm 00d 00d um +mdB d.m «.5 mm m.n «.5 mm Um>uomno mucosa 0dumm medoomm Odumm oucmocsnd mmmz omHM£OIouImmmz mm m.» N.> II 0d II dm me we we II 00d II mm dd dd N.> N.d 0d dd em SHUdB dm dn SN m.m on 0d mm pew 08 Cd m.d .mm m.m 00d mm +mmd9 +Hodm ;s. MMMdI w. Hands . +umdau. hudmsmued 53m .OODDHSOHDU mucosa odumm medoomm Consume: CODDHDOHMU Odumm monopssnd mmmz omHDSOIouImmmz poscducoo .m magma 56 ooumo pdsosm mosdo> pouodsodoo omosu mo Eso osB .modudmsoucd Cousmoofi osu sud3 .Oduou oosopcsso moms dooduouoosu Homonm osu sdoucdoe 0» mm on osmom moms Udmouomd Hosuo osu How wudmcousd pouoomxo osu meduodsodoo cos» cam Unopaoum o no oodoomm sumo How soon mmoE madmmodno>ocos Doomnod osu mo hudmcousd Consoooe osu mcdsmu as posdouso oHoB mosdo> pouodsodoo 00d 00d mm om mm em +Ho 00d 00d mm Hum 3. ...... S . po>uomso huoosa Oduom modoomm 0duom oosopcsnd mmoz omuosolouloooz Oossdusoo .m manna 57 in some cases there was evidence that the sample reacted with the platinum crucible. The method was also very time con- suming. ii. Neutron activatTQnAanalysis. Several samples were sealed in polyethylene containers and sent to the Dow Chemical Company for neutron activation analysis. By this method it was possible to determine chlorine, fluorine, and oxygen in addition to titanium. A very large sample (three to ten grams) was required. The error expected by this method was on the order of two per cent, which is relatively high. Due to the large samples required, this method received little use. Its main advantage was to establish the absence of oxygen in the samples submitted. iii. Titration of t' anium III with standard iron III solggion. This method was developed by Rahm (45) and modified by Scheffer (46) for the determination of titanium in titanium dioxide and in ore samples. With only Slight further modifi- cation this method has been conveniently applied to the determination of titanium in the titanium(IV) éhISEIde fluorides. A 0.1 to 0.2 gram sample was accurately weighed under nitrogen and then added to a 500 ml Erlenmeyer flask contain- ing 20 mls of concentrated sulfuric acid, 10 mls of H20, and 8 grams of ammonium sulfate. The sample dissolved on heating. When fumes of S03 were observed, heating was discontinued and the sample was allowed to cool to room temperature. One hundred twenty grams of water and 20 mls of concentrated 58 hydrochloric acid were then added and the solution brought to a boil. Reduction of titanium(IV) to titanium(III) was then accomplished by adding one gram of high purity aluminum foil. The apparatus was designed so that as the reduction reaction subsided and the solution cooled, saturated sodium bicarbonate solution was pulled back into the reaction flask to provide a non-oxidizing atmOSphere of carbon dioxide. The titration with standardized iron(III) sOlution was carried out under nitrogen after the sample had cooled to room temperature. The iron(III) solution was prepared so that one milliliter was equivalent to approximately three milligrams of titanium. Ammonium thiocyanate was used to determine the equivalence point by indicating the first excess of iron(III). This method was precise and proved to be very convenient for a large number of samples. B. Chlorine Analysis In addition to the neutron activation method previously mentioned, chlorine was determined by a modified Volhard procedure. A 0.1 to 0.2 gram sample was accurately weighed under nitrogen in a one dram glass vial tightly sealed with a poly- ethylene cap. The vial was then cooled to dry ice tempera- ture to retard the hydrolysis reaction. With the cap re- moved, the vial was carefully drOpped into a 125 ml iodine flask containing a known excess of silver nitrate solution and ten milliliters of 6 N HN03. The iodine flask was 59 quickly stoppered and tilted so that the vial would fall over and allow the sample to react with the silver nitrate solution. After digesting the sample for several minutes, it was filtered to remove the AgCl precipitate. The standard Volhard method (51) was then followed. C. TTuorine Analysis Several methods in addition to neutron activation analysis were attempted in order to determine fluorine, but these met without success. Attempts to precipitate the fluoride as lead chloride fluoride failed when it_was found that titanium coprecipitated. The complete removal of titanium prior to the lead chloride fluoride precipitatioanroved to be extremely difficult. In another attempt to determine fluorine, the sample was allowed to hydrolyze in the atmOSphere to remove the chloride as hydrogen chloride. Steam was then passed over the sample to remove the fluoride as hydrofluoric acid. The acid thus obtained was titrated with standard base, but inconsistent results were obtained. Since neutron activation analysis had shown oxygen contamination not to be a problem and since the only other elements present (Chlorine and titanium) could be accurately determined, fluorine was determined by difference. D. X-ray Diffraction Data The crystallographic grspacings for the hydrolysis product of TiF2C12 and TiF3Cl were calculated from film data obtained 40 with a North American Philips powder diffraction unit using copper kc radiation. A Debye--Scherrer powder diffractiOn camera of 114.6 mm diameter was used. DISCUSSION Mass Spectgoscopy Observation of the three titanium(IV) chloride fluorides by mass spectroscopy conclusively establishes that halogen exchange has taken place and that these compounds have inde- pendent existence. Species assignments were made by correlating the ob- served mass-to-charge ratios and their intensity ratios with those calculated from probability theory for the isotopic masses of each compound. The isotopes of titanium, Chlorine, and fluorine are listed in Table 6 along with their relative abundances (26). Table 6. Isotopic abundance. W Titanium Chlorine Fluorine 45Ti - 8.0% 35C1 - 75.5% 19F - 100% 4711 - 7.4% 37CI - 24.5% 4°Ti - 75.8% 5°Ti - 5.5% 41 42 For any given titanium isotope, the probability of forming any of the five possible species Ti35C1n37Cl(4-ny. where g = 0, 1, 2, 5, or 4, is given by the expression P429. = .,4' (75.99215 (g. (413): These values, when multiplied by the isotopic abundance of each titanium isotope, give the relative isotopic abundances for all the possible TiCl4 masses. Summing all the values for the same mass number gives the calculated relative intensities of all the mass-to-charge peaks for this species. Similar calculations were carried out for each species ex- pected. The following species were observed and confirmed to have the expected charge-to-mass and intensity ratios. C55353§d ObserveddeentiTyTng Species TiCl4 TiCl4+, TiC13+, TiC12+, TiCl+ TiFCla TiFC13+, TiFC12+, TiFCl+, TiF+ TiFgCla TiFgC12+, TiF2C1+, TiF2+ TiFgCl TiF3Cl+, TiF3+ TiF4 ‘ Not observed There can be little doubt as to the identification of these species and therefore little doubt about the existence of the parent compounds in the vapor state. This conclusively establishes that halogen exchange has taken place to give all the titanium(IV) chloride fluorides. 45 The Knudsen effusion method (5) was employed to over— come the difficulties encountered in the external introduction of the sample into the mass Spectrometer. It was particularly expected to reduce the chance of intermolecular gas phase collisions and thereby give more explicit information regard— ing the nature of the solid sample. The presence of TiCl4 as well as the titanium(IV) chloride fluorides in the vapor above these samples indicates either that the samples are mixtures of all these species or--more 1ikely--that the sample undergoes incongruous vaporization, diSproportionating to give the observed species. The failure to observe any Species more complex than those listed tends to eliminate Ti2F3C15, TisF7C15 and other bridging type complexes as existing in distinct molecular form. TheggeticaTTConSidegations In considering an idealized reaction between gaseous tetrahedral molecules, the reaction might be expected to proceed through an intermediate addition type "activation complex" as the following reaction suggests: TiCl4 + Tin, —* I Cl I C1 - Ti l Cl ' ‘ C1 F F l Ti -IF I F '—")' TiFC13 "I" TiF3Cl 44 The existence of numerous fiveecoordinate addition complexes of titanium gives some credence to the postulation of this intermediate (8,27,56). As this reaction continues, the concentrations of TiFCls and TiF3Cl increase and they begin to react with the starting material and themselves. Van Wazer (55) pointed out in a study of scrambling reactions of tetrahedral Silicon compounds that at equilibrium there are twelve ways for two pairs of five components (two reactants and three mixed products) to react to form the other components. The twelve reactions for the idealized exchange between TiCl4 and TiF4 follow: (1) TiC14 + TiF4 ——e- TiF3Cl + TiFCla (2) TiCl4 + TiF3Cl -—>- TiFgClg + TiFCla (5) TiE4 + TiECI3 —-> TiFgClg + TiF3Cl (4) TiCl4 + TiFgClg -——>- 2TiFC13 (5) TILE4 + TiE2C12 —> ZTiF3Cl (6) TiF3Cl + TiFCla -—>' 2TiF2C12 (7) TiF3Cl + TiECI3 -—> TiCl4 + TiF4 (8) TiFgClg + TiFCls --> TiC14 + TiF3C1 (9) TiFgCla + TiF3Cl —-7' TiF4 + TiFCla (10) 2TiFC13 ——>- Tic14 + TiFgClg (11) 2TiF3Cl —->- Tin, + TiE2c12 (12) 2TiF2C12 ——>- TiF3Cl + TiFCls Equations seven through twelve are simply the reverse re- actions of the first six. 45 The ideal case for gaseous tetrahedral molecules is far from the actual case. The greatest factor contributing to the nonideality of the system is that TiF4, TiF3Cl, and TiF2C12 are solids and probably are octahedrally coordinated. TiFCla was not isolated, but it is believed to be a liquid at room temperature. TiCl4 is a liquid and known to have tetrahedral coordination. TiF4 is an amorphous Solid and structural details are unknown. Its structure is perhaps best described as containing a disordered array of polymeric six-coordinate titanium chains which have fluorine bridge bonding. Titanium could be eight-coordinate as is ZrF4, however if this were the case, one would expect a more ordered crystalline structure and insolubility in donor solvents. The low sublimation temperature of TiF4 (284°C) indicates that the structure is not ionic as has been suggested by some authors. The effect of solid structures with greater than four coordination for titanium would be to increase the stabilities of these components due to increased molecular bond energies. These energies might be expected to increase with increasing fluorine. The observed decomposition temperatures of TiF3C1 and TiF2C12 of 215°C and 140°C, reapectively, tend to support this contention. The net effect of these deviations from ideality would be to give a larger equilibrium concentration of TiF4, TiF3Cl, and perhaps TiF2C12 than would be predicted for random ordering. 46 Interpretapipn of Experimental Results A. Heterogeneous Reaction The key to interpreting the experimental data probably rests with the only mixed halide not isolated, TiFCla. It is postqlated that this compound is an unstable yellow liquid at room temperature and that it undergoes spontaneous disproportionation to TiF2C12 and TiCl4. In an isolated system under fixed conditions of tempera- ture and pressure, TiF3Cl, TiFgClg, and TiFCls are un— doubtedly in equilibrium with each other and with TiCl4 and TiF4. However, under the actual experimental conditions, the most volatile components TiFCla and TiC14 would volatilize and condense on the walls of the reaction container. In this concentrated form, TiFCla is believed to disproportionate to give the yellow solid TiF2C12. TiFgClg could then under- go further reaction according to equation 8 or equation 12 to produce TiFSCl. The yellow solid observed on the wall of the reaction container probably was a mixture of TiF2C12 and TiF3Cl. TiF3Cl was isolated from a reaction in which the temperatures employed were approximately 80°C higher than for the other reactions. This would certainly hasten con- version of TiF2C12 to TiF3Cl by equation 12. Some TiF4 could also have been formed according to equation 11. Since the sample isolated from this reaction was sublimed twice in a short path sublimator, it is reasonable to expect the 47 isolation of relatively pure TiF3Cl. In many other reactions where lower temperatures were maintained, the yellow solid isolated had an analysis between TiF3Cl and TiFgClg. Titanium dichloride difluoride was isolated from a yellow liquid distilled from a reaction mixture containing TiCl4 and TiF4 in a 50:1 molar ratio (p. 9). The large excess of TiCl4 should favor the formation of TiFCla, which probably was distilled along with TiCl4 into the receiver flask. Upon standing, TiF2C12 forms as a yellow solid and the excess TiCl4 was then pulled off under vacuum. Isolation of solid TiF2C12 from the yellow liquid strongly indicates that some sort of molecular rearrangement takes place. Since TiF2C12 is known from mass spectroscopy Studies to exist in the vapor state at elevated temperatures, it is conceivable for some TiFgClg to have been distilled directly; however, considering the large excess of TiCl4, it is expected that any gaseous TiFgClg would have been converted’to TiFCla according to equation 4. Perhaps the best evidence for the formation of TiFCla as an intermediate in the preparation of TiFgClg comes from the mass spectral results. When a sample of TiF2C12 was connected externally to the mass spectrometer through a one foot length of quarter-inch copper tubing and the sample heated, the only compounds observed were TiCl4 and TiFCls. This conclusively establishes TiFCls as a substance of finite stability and high volatility. TiF2012 was probably condensed 48 on the cool walls of the copper tube. Considering the rela- tively high concentration of TiCl4 in the gas phase it is also possible that any gaseous TiFgClg was converted to TiFCla according to equation 4 before reaching the mass spectrometer. B. Gas Phase Reaction In considering the results from the gas phase reaction, where TiCl4 vapor was passed over TiF4 in a heated tube (p. 12); the twelve reactions previously discussed can again be considered. The predominant reactions in this case prob- ably would be 1 and 2. TiF3Cl initially produced in reaction 1 could undergo further collision with TiCl4 which is in excess in the gas phase to produce TiF2C12 by equation 2. Material closest to the hot zone always had the highest fluorine analysis and probably was a mixture of TiF4, TiF3Cl, and TiF2C12 whereas the sample farthest from the hot zone always had an analysis close to TiF2C12. Under the conditions of this reaction, it is believed that TiFgClg is the major product and that TiF3Cl and TiFC13 are produced in smaller amounts. The material that deposits near the hot zone prob- ably undergoes decomposition according to equations 11 and 12 to produce increased amounts of TiF3Cl and TiF4. No solid sample was ever isolated with a chlorine analysis higher than that expected for TiFgClg. A significant amount of yellow liquid and solid always collected in the cold traps positioned after the reaction 49 tube. Some of the solid was probably carried by the nitro- gen stream past the baffles to the traps. It is also possible that some TiFCls which had been formed initially in the reaction later underwent disprOportionation according to equation 10 to yield solid TiFgClg and TiCl4. The yellow liquid was probably a solution of TiFCls in TiCl4. Failure to obtain any solid with a chlorine concentration higher than expected for TiF2C12 and the observation of the yellow solu- tion in the cold traps further supports the contention that TiFCls is a liquid. Solid State Structugg The solid state structures of TiF4, TiF3Cl, and TiF2C12 are unknown. In a brief note, Dehnicke (10) claimed to have prepared TiF2C12 and reported an X-ray diffraction pattern as well as infrared data for the solid sample. From the infrared spectrum he concluded that TiF2C12 has ga¥_symmetry with tetrahedral halide arrangement around the titanium. He also concluded that the metal-chlorine bond is strengthened and the metal-fluorine bond is weakened in comparison with TiF4 and TiCl4. The reaction employed is represented by the following equation: 0°C ) TiC14 + ZCIF TiFgClg + 2C12 Unfortunately no analysis or further details are given. 50 If a large excess of TiCl4 were employed, formation of TiFCla followed by disproportionation to TiFgClg might be expected. A more nearly stoichiometric ratio of reactants should give mixtures of products as in the case of TiCl4— TiF4 exchange. None of the samples prepared by the TiCl4-TiF4 exchange reaction, including TiFgClg, has shown an X-ray diffraction pattern. TiF3Cl prepared by chlorination of TiFa by Vorres (48) also did not give a diffraction pattern. The existence of an ordered solid state structure for TiF2C12 is doubtful in view of the amorphous nature of TiF4 and TiF3Cl; however under appropriate conditions an ordered structure may well be possible. The existence of a solid state structure for TiF2C12 with gg!_symmetry and tetrahedral halide coordination, either ordered or disordered, is ex- tremely doubtful. Samples of TiF2C12 subjected to pressures as low as 1 x 10‘7 mm Hg in the mass spectrometer showed no significant vapor pressure at room temperature. At elevated temperature TiCl4 was first given off, followed by TiFClg, then TiFgClg, and finally TiF3Cl. This behavior suggests extremely strong intermolecular interactions which would not be expected for the tetrahedral structure. It seems far more reasonable to suspect sixfold octahedral coordination, most probably with fluorine bridge bonding. Fluorine bridge bonding is well- established (36). The example closest to the present case 51 occurs in the complex formed between TiF4 and gfphenylene- bis(dimethylarsine) (diars) which has the formula (TiF4)2diars. On the basis of infrared evidence this complex is believed to have the structure indicated below (7). F F F F I p ! H T1 T1 F diars Chlorine bridge bonding also has been well-established in such complexes as (TiCl4-POC13)2 (4) and (TiCl4-AcOEt)2 (5). Where a choice exists between fluorine and chlorine, it would seem more reasonable to predict fluorine bridge bond- ing on the basis of its greater ionic character. TiFCla is incapable of forming a six-coordinate solid state structure employing only fluorine bridging. TiFCla is also the only titanium(IV) chloride fluoride not isolated in the solid state. There are numerous six-coordinate structures that can be drawn for TiF3Cl and TiF2C12. Some of the possible types for TiF2C12 are listed below. c1 )c1 C1 E I E I E . ‘3' ~ .v ~ .r (A) Chain polymer: T1 T1 T1 , ~uF ,.' ‘V F v' . - F Cl >Cl Cl ( in (B) Helix polymer: This type is not easily drawn but may be visualized by considering gig coordination of the chlorine atoms on each titanium atom. This causes the chain to wind around in the form of a helix. (D) Trimer { Ti (E) Tetramer 1” ‘F . I l b]. c1 c1 c1 [E c1 IE \ c1 I E I c1 I E (E) Polyadduct Ti : : TI : : T1 : Ti / Cl I F l Cl I F c1 E c1 E N ‘n Of the structures shown, A and B would seem to be the most consistent with the observed properties of this compound. Long range disorder is common for polymeric substances and would account for its amorphous nature. A polymeric sample would be expected to have a very low vapor pressure. Heating the sample in a vacuum could cause a rupture anywhere in the chain, resulting in extensive molecular rearrangement and loss of the more volatile species. This is consistent with 55 the mass spectroscopy data. It is interesting to note that the monomeric units composing structure B have 93! symmetry. In addition the Ti-F bonds would be weakened due to bridge bonding. This structure, therefore, correlates nicely with the infrared data presented by Dehnicke (10). Structures C and E are judged less likely than A and B since they would be expected to contribute to long range order resulting in a sharp diffraction pattern. Structures D and F are considered less likely than A and B since they involve chlorine bridge bonding. CONCLUSION Titanium tetrachloride and titanium tetrafluoride have been found to undergo halogen exchange to produce the titanium(IV) chloride fluorides. Under appropriate condi- tions TiFgClg can conveniently be isolated in good yield as a yellow solid. TiF3Cl was also isolated as a yellow solid but only in low yield. TiFCla was not isolated but is be- lieved to be an unstable yellow liquid at room temperature which undergoes disproportionation to TiF2C12 and TiCl4. The thermal stabilities of the titanium(IV) chloride fluorides appear to be in the order TiF3Cl > TiFgClg > TiFCls. Titanium chloride trifluoride and titanium dichloride di- fluoride give no X-ray diffraction pattern. A polymeric six-coordinate structure involving fluorine bridge bonding is suggested to account for the observed properties of these compounds. TiF3Cl, TiFgClg, and TiFCla also have been con- clusively identified in the gas phase by mass spectrometric techniques. 54 SIGNIFICANCE Previous difficulties encountered in attempts to prepare titanium(IV) chloride fluorides can now be understood in 'termscxfthe halogen exchange equilibrium process established for the TiCl4--TiF4 system. The observation of a yellow solid containing titanium, chlorine, and fluorine in a varia- ble nonstoichiometric ratio by Ruff and Ipsen (45) and the isolation of TiFSCl which had an analysis 2.3% higher than theory in chlorine and 5.2% lower than theory in fluorine by Vorres (48) can now be attributed to this halogen exchange equilibrium process. The isolation of TiF3Cl and TiFaClg indicates that under certain conditions halogen exchange processes are useful for preparing mixed halide compounds. It is possible that the methods develOped for the isolation of TiF3Cl and TiF2C12 could be applied to the TiF4--TiBr4 system and the Ting- TiI4 system to allow for the isolation of titanium(IV) bromide fluorides and titanium(IV) fluoride iodides. The method developed for the convenient and economical production of TiF2C12 will allow this compound to be examined for catalytic activity and as a potentially useful synthetic intermediate. TiCl4, TiBr4, T114 and the mixed halides of these compounds have been patented as polymerization catalysts. 55 56 TiF2Cla is therefore a potentially useful catalyst. As a synthetic intermediate, TiF2C12 might be valuable in the preparation of a variety of compounds containing a TiFg- group. RECOMMENDATIONS FOR FUTURE WORK 1. The TiCl4-—TiF4 system should be examined in non- donor solvents such as chloroform, benzene, and trifluoro- acetic acid. 2. Attempts should be made to isolate TiFCla by low temperature vacuum line techniques. 5. Solutions of titanium(IV) chloride fluorides in TiCl4 or in trifluoroacetic acid should be examined by 19F magnetic resonance . 4. Attempts should be made to obtain crystalline samples of TiF4, TiF3Cl, and TiF2Clg, perhaps by recrystallization from trifluoroacetic acid. 5. A more detailed study should be made of the hydrolytic and thermal stability of TiF3Cl and TiFaClg. The composition of the hydrolysis product should be determined. 6. Methods for preparing the mixed halides by the re- action of TiCl4 with other metal and nonmetal fluorides should be investigated. 7. The use of TiFgClg as a synthetic intermediate should be studied. 57 58 8. The TiF4--TiBr4 system and similar systems should be examined by employing the methods and techniques developed for the TiCl4-—TiF4 system. PART II FLUORINE-19 NMR STUDY IN TETRAHYDROFURAN 59 INTRODUCTION Fluorine-19 magnetic resonance studies were originally undertaken in an attempt to characterize more fully the titanium(IV) chloride fluoride compounds previously discussed. Titanium tetrachloride and titanium tetrafluoride as well as the mixed halide compounds should form addition complexes with tetrahydrofuran (THF) and other fairly small monodentate coordinating agents, where two donor molecules are bonded to the titanium(IV) halide. It should be possible to distinguish between these complexes by differences in their 19F nuclear magnetic resonance (NMR) spectra. These studies show that the mixed halide compounds under- go disproportionation in THF solution to give an equilibrium mixture of TiF4'2THF, TiF3Cl-2THF, TIE2c12-2THE, TiFC13-2THF. and TiCl4-2THF. The nature of the TiCl4-2THF--TiF4-2THF system is the subject of the following investigation. 60 EXPER IMENTAL Instrumentation Fluorine-19 magnetic resonance spectra were obtained with a Varian Associates HA-1OO high-resolution spectrometer operating at 94.1 mc/sec. The Michigan State University spectrometer was used for recording some spectra, but most were obtained with the instrument at the Dow Chemical Company. Their spectrometer had been modified to permit an unlimited sweep frequency offset (51) and a means for conveniently positioning or eliminating side bands. Trifluoroacetic acid (TFA) and trichlorofluoromethane, CFCla, were employed both as internal and external reference standards. The fluorine-19 magnetic resonance region from -450 ppm to +560 ppm from CFC13 was investigated. All ob- served 19F magnetic resonances were downfield from CFCla in the region between -305 ppm and -165 ppm. The conversion factor (14) relating the two standards employed is given by the expression 6TFA = 6CFC13 - 76.54. Eggparationpgf the 19F NMR Samples A. Purification of Reagents All reagents were carefully purified for use in the preparation of the NMR samples. Purification of TiCl‘ and 61 62 TiF4 has been previously discussed in Part I (p-.S). Reagent grade THF was distilled from lithium aluminum hydride into a flamed out glass ampoule which was sealed by means of a Teflon stopcock. The ampoule was then moved into a dry box where NMR samples were prepared. B. grepagation of THF Solgtions Solutions for NMR study were prepared in a dry box under dry nitrogen. Titanium tetrachloride could be handled in this atmosphere without any observable hydrolysis. Solutions were prepared both from titanium(IV) chloride fluorides and from mixtures of TiCl4 and TiF4. When THF complexes were formed by direct addition at room temperature, a vigorous reaction took place producing a great deal of heat. To pre- vent decomposition of the samples (see footnote page 6) or loss of volatile material, it was necessary to cool the re- agents to the freezing point of THF (-65°C) and then mix the reagents slowly. Cooling was accomplished by circulating liquid nitrogen between the walls of a double-walled beaker which contained sample vials holding the reagents. Titanium(IY) chloride fluoride solutions were prepared by adding a known volume of THF at -65°C to a known weight of mixed halide. Thus for the preparation of 1.0 M TiF2C12. solution, 1.45 ml of THF at -65°C was added by means of a hypodermic syringe to 0.25 gram of TiF2C12. A yellow liquid and solid were instantly formed with the evolution THF vapor as a white fog. As the mixture warmed to room temperature 65 the yellow solid dissolved to give a clear yellow solution. Some solutions were prepared directly from TiCl4 and TiF4. Separate THF solutions of TiCl4 and TiF4 of known concentration were prepared by the same procedure used for mixed halides. These were then mixed to give solutions of the desired TiCl4 to TiF4 ratio. Low solubility of the TiCl4-2THF complex in excess THF necessitated such dilute final solutions that the 19F resonance for some components could not be observed for large TiCl4:TiF4 ratios. Solutions of sufficient concentration were prepared by first isolating the TiCl4-2THF complex and then adding it directly to solu- tions of TiF4-2THF. The various difficulties encountered in preparing solutions directly from TiCl4 and TiF4 resulted in concentration values that were only approximate. Solu- tions of more accurately known concentrations could probably have been prepared from TiCl4-2THF and TiF4-2THF had these complexes both been isolated. C. Preparation of NMR Samples After the preparation of a solution, it was carefully added through a glass dropper with a long narrow tip to a flamed out 5 mm thin walled NMR sample tube. The upper neck of the NMR tube was inserted through a one-hole rubber stopper which was then inserted into the neck of an inverted 50 ml filter flask which had a stopcock side arm. This arrangement allowed the sample to be removed from the dry box while an inert atmosphere was maintained over the sample. The sample 64 tube was then immersed in liquid nitrogen to freeze the sample. After evacuation through the side arm on the 50 ml flask, the tube was sealed off with a hand torch. D. Decomposition Samples prepared under less than rigorously anhydrous conditions decomposed slowly to produce a brown-black solid residue, whereas those obtained under absolutely anhydrous conditions appeared to be indefinitely stable at room tempera— ture. The NMR samples were stored at -78°C to retard possible decomposition. Identical samples stored at room temperature, however, showed no difference in their 19F magnetic resonance spectra. E. Complex Formation Addition of bright yellow TiCl4-2THF solution to an excess of colorless TiF4-2THF solution produced a colorless solution. A noticeable yellow color was not observed until nearly equivalent amounts of the two solutions had been mixed. This indicates that TiF3Cl°2THF, probably TiFgClg-ZTHF, and possibly TiFCla-ZTHF are colorless in THF solution. ingagnetic Resonance of TiF5'2THF A 0.5 M sample of TiF4 in THF was prepared as previously described. At room temperature a single broad 19F magnetic resonance peak was observed at about -18600 Hz (-197 ppm) downfield from the external reference CFCls. As the sample 65 temperature was reduced, the peak first broadened and then separated into two singlets at -40°C. At -50°C the singlets began to split into triplets and at -600C these were well resolved. A very small singlet was also observed upfield from these two triplets. The spectra obtained for this sample are shown in Figures 7a-c. Table 7 summarizes the data obtained from these spectra at -60°C. The equal intensity triplets t4” and t4+ arise from the gig-TiF4°2THF isomer. It is likely that the singlet S4 arises from the trans isomer. The intensity of S4 indicated that the species producing this resonance was present in very low concentration. Assuming that S4 represents the ££§g§_isomer of TiF4'2THF, the equilibrium constant for the following reaction can be determined. - o . —-¥ 0 - o . trans T1F4 2THF C18 T1F4 2THF K [Cls-TiFf’ZTHF] = 196 = 55 at -60°C [trans-T1F4°2THF] 6 Since these are the only data available and since S4 was so small that accurate determination of the intensity ratio was not possible, the value of K is only approximate. 66 ..— 7a:. -6OOC If I I I -225 -197 -165 -155 Figure 7. 19F magnetic rssonance of 0.5 M_TiF4°2THF at -60 (a), -40 (b) and 25 C (c). (External reference: CFClg) 67 .QUGGHOMQH HMGHTUNT QHUWU EOHH UTHSWMQE mflwflnm HMUflEUSU hm." * I- I- m.om- omen- +¢uII¢u m I- mma- ooaaa- «m ooa an mma- comma: +¢u mm an mwmu oomamu I4» owumm um Emm Nm coHumsmHme suflmcmufi mun macaromV maumoo xmmm .ooomu um mmam.¢mfle now mucmumsoo msflamsoo pom *DMHSm HMOflEmso had .5 manna 68 19E Magnetic Resonance of TiFXCl4_x°2THF Solutions Fluorine-19 magnetic resonance spectra were obtained for the following samples. Sample Descpiption 1. 1.0 M_TiF2Clg In THE at -7o°c 2. 0.5 M_TiF2Clg In THE at -60°c 5. 0.32 p TIE2c12 and 0.17 p TiF3Cl In THE at -60°C 4. 0.35 p TiF3Cl In THE at -60°c At room temperature these samples showed only a rough base line. At —60°C all samples showed a nicely resolved spectrum which indicated the presence of the titanium(IV) chloride fluoride THF complexes as well as TiF4'2THF. The spectrum obtained for 1.0 M TiF2Clg (sample 1) is shown in Figure 8. It is typical of the other samples except for the intensity of the various resonance peaks. Tables 8 and 9 summarize the 19F chemical shift and coupling constant data for these samples. Assignment of the specific 19]? magnetic resonances to the species from which they arise is also indicated in Table 9. The justification for these assignments is given in detail in the discussion section. Table 10 lists the measured intensities for the observed resonance peaks and the relative intensities for each com- pound or isomer. Amaumo "mocmummmu Hmcumuxmv .0007 um maimaommfla a 04 mo moemeommu Someone mod .m 9.252 cow- 4mm- mmmummmu mmw- mwm- . U H a . q u 69 Tu mp NU no It NU NU 7O .Uoohl um Toma mosmnwmmu Hmsuouxm naomo Eoum UTHSmmmE mDMHnm m HGQEOHDmMTE ** HMUHETSU mma* mmaI oommHI moaI commaI mmHI oommHI mmaI oommaI +Iu ooml oommHI ooml comma: oomn commaI oomI commal +no NNNI oomomI mmmI oomomI HNNI oomomI HmmI oomomI IIu ommI oomHmI ommI oomHmI ANNI ooeamI mmmI oomamI +mo mmmI oomamI mnmI oomHmI mmmI oomHmI mnmI oomHmI mm mmmn oommml NmmI OOSmNI mmms oommml mmml oommml Hm nmmn ooamml mmNI ooommu mmml ooomml mmml oomemI Imp II II II II II II momI ookmmI Inn A 8mm um Ema Mm 5mm Nm Ema um Blahonmfle In 3.0 mms>oom3 a 3.0 ...EanUmmHH. In. m.o mmmeHommE m 04 coaumcmflmmo @NAUNmHB NI mman . xmmm e oaoemm m madman, m mamamm *Ie maosmm .Uoowl um mmamEMm mmBN.mT¢HumeB How *TDMHSm HMUHETSU mod .m magma .Ampcoomm Hum mmaohuv uuumm CH sm>Hm mum mucmumcoo mcwamsoo mlm * IIII IIII IIII IIII IIII IIII IIII Hm pram.naomna .som an +me no me me m.me a +mo mmam.maommaa um comp me IIII IIII IIII we a Imo . IIII IIII IIII IIII IIII IIII IIII mm mme~.-ommee eon mo +mn no an em enImm N +no n e um oomo +mm e.mm em m.mm emImm a Imp amen no m.e son on +km em IIII m.em IIII a +Iu ,I am ooom +am m.om m.em m.em emIom a II» poem was mm mmmum>¢ d mHmEmm m mamemm N mHmEmm a mamfimm muflmsmucH coaumsmfimmn pasomfiou 0 .mhh. mucmumCOU UCflHQflOU him T>HHMH 0m xmwm .2. * l) l .mmamEMm mrwaumwfle How mucoumcoo mcflamsoo m pom ucmficmflmmm xmmm .m THQMB m." 72 d HH ma ¢a Hm mmBN.0HUmHB me A o om A ca 3 fl m we fl o +3 .55 «Emma. m oa m o Imo ow as no 0e mm mmam.maommaa we Am woe A S A em +no . n me A «N ooa mm mm an an In» mmam Ho man 0.“ @N m A ..V ...-aw“ 0* om fl on on A «N oa A m m 4 I3 meow m3 mmehonmaezmmu. o mmukaonmaa 2:. o magmLommasz. o mma\maommaaz0. :oflmemammo oesomsoo fl (THQEmLmI E\NHUN&.«B ZNm. o N 0% m 0Am§ (I (ll) .mmHmEmm mmsN.xI a oflmamm xmmm I (II) eaumwfla How mump >ufimcmusH .OH THQMB 75 i3§_Magnetic Resonance of TiCl4--Ti§A/TH§Solutions The following samples involving mixtures of TiCl4 and TiF. in THF were prepared as previously described. Sample Qescription 5. 0.29 M_TiF4 + 0.097 H_TIC1. In THE/TEA* 6. 0.24 M_TiF4 + 0.20 pTICl4 In THF/TFA* 7. 0.16 M_TiF4 + 0.16 M_TiCl4 In THF/CFC13** 8. 0.56 M_TiF4 + 0.72 M_TiCl4 In THE/TEA* 9. 0.067 pTIE4 + 0.20 pTICl4 In THF/TFA* * Trifluoroacetic acid (TEA) as internal reference ** Trichlorofluoromethane (CFCls) as internal reference These samples were used to establish that an equilibrium exists between TiF4°2THF and TiCl4-2THF involving all the titanium(IV) chloride fluoride THF complexes. It was also expected that 19F magnetic resonance intensity data would confirm the assignment of the two singlets, S; to TiFCls-ZTHF and S; to TIE2012-2THE. The spectra obtained for these samples showed the same 19F magnetic resonance peaks observed for the samples prepared from the titanium(IV) chloride fluorides. The samples 74 containing a high ratio of TiF4 to TiCl4 showed very strong 19F magnetic resonance peaks for TiF4-2THF (t4' and t4+) and TiF3C1-2THF (t3‘ and d3+) and progressively weaker peaks for TiF2C12-2THF ($2) and TiFC13'2THF ($1). In sample 5 where the ratio of TiF4 to TiCl4 was 5:1 the S; resonance for TiFClg-ZTHF was not observed. As the ratio of TiCl4 to TiF4 increased, the 19F resonance peaks for TiF4-2THF disappeared and the S; 19F resonance for TiFCls-ZTHF became the most predominant. To establish that TFA was not catalyzing the halogen exchange reaction between TiF4-2THF and TiCl4-2THF, sample 7 was prepared with CFCla as the internal reference. Every effort was made to prevent hydrolysis or contamination with HCl. Since this sample gave essentially the same Spectrum as the other samples in this series, it appears that TFA is not responsible for the exchange process. Because of the extreme sensitivity of the TiCl4 toward hydrolysis and the resulting formation of HCl, acid catalysis of the reaction cannot, however, be ruled out. The fact that no 19F resonance was observed for HF indicates only that this substance was not present in sufficient concentration to be observed. The spectra obtained for these samples are presented in Figures 9 through 15. The use of an internal reference per- mitted more accurate measurement of chemical shifts and coupling constants than had previously been achieved. These data are presented in Table 11. Intensity data have been 75 t4+ t4‘ d3+ t3‘ 52 L l l + —345 —508 -209 -259 Figure 9a. 19F magnetic resonance of 0.29g1TiF4 + 0.097 g TiCl4/THF at —60°C. (Internal reference: TEA) 76 1. L -_(_ I ' I ‘ I -345 -508 -299 -276 -239 Figure 9b. Expanded view of 19F resonances in Figure 9a. (Internal reference: TFA) 77 ANNE “mucoummmu chumuch .0000: um .mmHKeHUHB IIImONd + «.39 “.4.de mo mucosommn UHumcmmE mm." .oauusmfih . _ _ . mmmI osmI mmmI moMI.momI mmmI nenI ammI I ... I I 4)- * N H N #U lu+mu ......m lmu mu no mm 78 d3 I . WW 1 1 I T -545 —529 -508 -276 ' Figure 11. 19F magnetic res8nance of 0.16.’__M_TiF4 + 0.1611 TiCl4/THF of -60 C. (Internal reference: CFCla, values converted to TFA scale) 79 32 Si d3+ t3” I I g 1 I T I l 1 -343 -529 -508 7276 Figure 12. J'E’F magnetic resonance of 0.56;l*_’l_TiF4 + 0.72M TiCl4/THF at -60°C. (Internal reference: TFA) 80 Si 1 l l I - I -529 -508 .-276 Figure 15. 19}: magnetic resgnance of 0.067391 TiF4 + 0.20111 TiCl4/THF at -60 C. (Internal reference: TFA) .va-OI-t N O v41... 1‘1‘ h usuh 81 .moamfimm 00:00 mnu mo 0:0 How c0>flm msHm> 080m 030 adamaucmmmm um pm>u0mno 0H03 mxmmm TUGMGOTTH vaumsmmfi hoax I00>H0mno on on xm03 oou 0H03 mxmmm mosmsommu Daumcmmfi mmd¢ “pumpcmum Hmcumucw map so MUCH ou >uHHHQMGH 0:» Cu 050 manmwamn mmwa mum mosam> 0m0£B* “mocmummou Hmcnmuca fine 809m UTHSmMTE muwflnn HMUHETQU mma** .III.. I--- ---- .m IssN.IIoIIs mm N s on *3. a + o mmamhaomfis um come In“. 0 Ian IIII IIII I III mm pram . ~8me o m . see so a no N + o mmem.aoomne um OONQ «.mn a In» . v sum om e an a + u mmem.vaH um comm III H II» mm mm, huwmswusH coaumsmwmwn pcsomfioo 0 who 0>wum~0m xmom s . 5 SI 0 o o \ oom .mmI I...» inn mEI \I \I \I \. ooo.omI +96 IIII mmmI o o o \I 80 SI I...» *3. ..monI o o o .85 .mmI o +~o IIII monI \I \I \I \. ooo .mmI «n IIII mmmI \I ooo .enI \. x 0 an a . no we? 0 x x \ oom .mmI In» In... *HmmI o o o .08 .mnI 0 ..mo «m sea . or mm um um um sowumsmemmo who 55% m mamfimm m magnum b magnum m Tame—mm m 0.353 xmom .uoomI on $353 .mevarIvHoE mom mucmumeoo msfimsoo pom ImumEm Handsoso mos .3 manna 82 treated quantitatively and the equilibrium mole per cent values for each component are given in Table 12. These values are not precise because of uncertainty in the initial concentrations of these samples. It is entirely possible that the concentrations of TiCl4 in samples 5, 7, and 9 were significantly less than that indicated. This error could have arisen from the lower than expected solubility of TiCl4°2THF in excess THF. Samples 6 and 8 were prepared by a different method and are probably more accurate. Table 12 is presented only to indicate the relative change in the equilibrium concentrations of the species present as the initial concentration ratio of TiF4 to TiCl4 changes. This table clearly shows that the maximum concentration of TiF2Clg-2THF is observed for a 1:1 ratio. The concentration of TiFCla-ZTHF is insignificant with a large ratio of TiF4 to TiCl4 but it becomes the predominant species as the ratio of TiF4 to TiCl4 becomes small. These equilibrium mole per cent values were calculated from the intensity of the 19F magnetic resonance peaks as previously assigned Lsee Table 9) for each component. The relative concentration trend agrees very well with that expected for such an equilibrium system and, therefore, adds justification for the fluorine—19 magnetic resonance peak assignments previously made. The method of calculating mole per cent values from 19F magnetic resonance intensity data will be presented in the section dealing with equilibrium constants (p. 105). 85 003300004000 $.02. 0300.0 0 0031030000 $02. 0000.0 0 805:0? 0.00.0 $.02. 003.0 I. 00530304000 $030000 0 00.3083 0300.0 $030000 0 I GOHDQHW000Q Mflmamw IIII 0.00 0.00 0.00 0.0 . mmam.+floaa H0 0.00 0.00 0.0 0.0 0 0 0090.000009 +00 .I00 .00 0.00 p.00 0.00 0.00 0.0 0090.0000009 +00 .Imu 0.0 a.» 0.00 0.00 0.00 0090.000009 +00 .I+u IIII IIII IIII 0.0 0.00 mmem.+0aa xmumI 0000:0000 m m h m m pssomfioo 0000smmz mad 0amfimm 0amfimm 0Hm50m 0HmEmm 0amfimm .m0amfimm mm9\0wflBIIvHUHB How 005H0> us00 H00 0HoE ESHHQHHHsvm .NH 0HQMB DISCUSSION Hglggenfigxchange There are a number of possible mechanisms by which halogen exchange can take place in octahedral titanium(IV) chloride fluoride tetrahydrofuran complexes. Muetterties (56) has found rapid (K 210"3 sec‘l) donor molecule exchange for TiF4 complexes dissolved in excess complexing agent at -25 to +25°C. This suggests the possibility of the follow- ing bridging mechanism. TiF4°2THF ——:$§§—*I TiF4'THF +THE F THF . | I TiF4-THF + TiC14'2THF __EL1F_5. F‘Ti' F V Ti‘Cl 4"‘1‘HF3 F" V Cl' ' Vcl T— +THF THF C1 THF TiF3C1°2THF + TiFC13°THF TiFCla'THF -13§EA- TiFC13°2THF -THF Six equilibrium equations describe all the ways that two components can react by the above mechanism to produce new components. These reactions are analogous to those previously presented to describe the halogen exchange between TiF4 and TiCl4. 84 85 (1) 1/2(TiC14-2THF) + 1/2(TIE4-2THE);——> 1/2(TIE3c1-2THE) + 1/2(TiFC13-2THF) (2) 1/2(TiCl4-2THF) + 1/2(TIE3c1-2THE);;::- 1/2(TiF2C12-2THF) + 1/2(TiE013-2THE) (3) 1/2(TiF4-2THF) + 1/2(TIE013-2THE);;:3- I/2(TIE2c12-2THE) + 1/2(TiF3Cl-2THF) (4) 1/2(TiCl4'2THF) + 1/2(TiF2C12-2THF) ——*' TiFC13°2THF (5) 1/2(TiF4-2THF) + 1/2(TiF2C12'2THF) -*~ TiF3Cl'2THF (6) 1/2(TiF3Cl-2THF) + 1/2(TiEC13°2THF) -—4- TiFgClg'ZTHF A second plausible mechanism involves acid catalyzed halide exchange. Attempts were made to exclude this possibil- ity, but because of the nature of the reactants, elimination of catalytic amounts of acid would be nearly impossible. The presence of HF was not observed by 19F magnetic resonance for any of the samples investigated, but the observation of very small amountstould not be expected. Muetterties (57) has suggested that acid catalyzed fluoride exchange may be responsible for the line broadening of the 19F resonance ob- served for some fluoroanions. lsF Magnetic Resonance—-Stereochemical Considerations TiF3Cl°2THF and TiFC13°2THF each have three possible geometrical isomers whereas TiFQClg-ZTHF has six stereoisomers (five geometrical isomers and one pair of enantiomorphs) (24). 86 TiF4'2THF and TiCl4-2THF each have two possible isomers. Table 15 lists each compound and its possible isomers. A fluorine atom is designated by F0 if it is Eggpp to another fluorine, FB if Eggpp to a THF group, and FY if pp§p§_to a chlorine atom. These three types of fluorine atoms constitute those in any given isomer that can be distinguished from each other by 19F magnetic resonance. Fluorine atoms having the same designation in a given isomer (either a, 8, or 7) cannot be distinguished by 19F NMR. The pig isomer of TiF4-2THF 05) contains two groups of equivalent fluorine, F0 and F6. The first order 19 F magnetic resonance spectrum for this isomer would consist of two equal intensity triplets typical for an A2X2 system. Since all fluorines are equivalent for EggpprTiF4°2THF gg). only a single 19F resonance would be expected . The first order l9F magnetic resonance Spectrum for each TiF3Cl°2THF isomer would consist of a doublet and a triplet of 2:1 intensity ratio typical for an Agx system inasmuch as each isomer contains two equivalent fluorine atoms. Since both fluorines are equivalent in isomers JQISh Eh andAI\of TiF2Clg-2THF, they would give rise to a single 19F resonance. The enantiomorphs g3 and 32 have two dissimilar fluorine atoms. As an AX system, the 19F magnetic resonance would consist of two doublets. 87 Table 15. Isomers of titanium(IV) chloride fluoride THF compounds. Pg 7 THE ’77 TiF4, - 2THF [A] L134] " F5 HE Fa Pa Ti FB HF Fa Fa Fa THE TiFaCl ' 2THF I21 .. [2] .. [a] .. C1 THF F5 THF Fa THF EB THE F5 THE THE Fa Fa c1 c1 TiFaClp'ZTHF I21 .. :1 II III ... III . FE F Cl THF F 1 F Ti c1 HE F7 c1 c1 (1 [‘22.] F7 [32.] F7 F3 THE THE FB C1 THF THF C1 C1 C1 TiFCls ° 2THF I!) ... F7 THE F7 01 TI TI THE 01 01 01 THF 88 The three isomers of TiFCla-ZTHF, each having only one fluorine, would give rise to a single 19F resonance. 19: Magnetic Resonance--TiF,‘2THF A. Epipp Studies Muetterties (56) has examined the 19F magnetic resonance of a number of TiF4'2L complexes, where L is a monodentate ligand, including the TiF4-2THF complex. In all cases, at low temperature, two equal intensity triplets were observed, indicating the existence of only the gigéTiF4°2THF (A) isomer. Ragsdale and Dyer (12) studied cis-trans isomerism for TiF4-2L complexes where L was a substituted pyridine 1-oxide ligand. When L was pyridine 1-oxide, only the gig isomer was observed. When L was 2-methylpyridine 1-oxide, the spectrum showed, in addition to the twp triplets, a small singlet just upfield from the highest field triplet. This singlet accounted for approximately 10% of the spectral in- tensity and was assigned to the Eggpg structure. The 2,6-dimethylpyridine 1—oxide complex of TiF4 gave only a single 19F magnetic resonance in a position just above the high fielstripl t for.the pyridine 1+oxide complex and just below the high field triplet.for the 2,6-dimethylpyridine 1-oxide complex. This singlet was also assigned to the ppgpg structure. From this study it was concluded that the fluorines Eggpg to the ligands(FB)are shifted to lower field than the fluorines trans to each other(Fa). 89 Ragsdale and Stewart (40) prepared a number of [TiFs'ROHJ- complexes for which 19F NMR showed a low field quintuplet and a high field doublet in a 1:4 intensity ratio. The low field quintuplet must arise from the fluorine ppgpg to the ligand, in agreement with the above conclusion. B. Theoretical Inteppretation The chemical shift appears to be dependent upon the degree of fluorine to titanium pW’——>-dv bonding. Titanium(IV) has a 5d0 configuration. In octahedral complexes, the dx I Y d and dxz orbitals are available for waonding along the y2' x, y, and z axes, respectively. Weak W'bonding groups ppgpp to a fluorine would allow for strong pW'-fi>-dw bonding from fluorine to titanium. This should decrease the fluorine shielding constant and cause a downfield shift in the J'9}? magnetic resonance. Fluorines ppgpp to a strong V'bonding donor such as another fluorine should appear at higher field strength. C. Supporting Evidence Ragsdale and Dyer (15) support this reasoning in a study of mixed ligand complexes of titanium tetrafluoride. A series of gingiF4'DD' complexes were studied where D was N,N-di- methylacetamide and D' was a para substituted pyridine 1-oxide. F5 D' 90 This complex contains two equivalent (F0) and two non- equivalent (F‘ and FB') fluorine atoms and gave rise-to a fi spectrum typical of an Ang system. The lowest field reson- ance was a triplet due to F3 which was Eggpp to the weakest w bond donor D. A second triplet due to FB' (ppgpg to D') was slightly further upfield. A doublet of doublets was found at significantly higher fields due to the F0 fluorines which were ppppp to each other. As the papa substituents of D' were varied to weaken the v bonding between the oxygen and the titanium, the triplet due to F6“ moved downfield. The observed coupling constants also seem to indicate the degree of fluorine to titanium W bonding. The coupling constants measured by Ragsdale and Dyer (15) were: J08? : 54-55 Hz, J = 59 Hz, J = 48 H2. This order JBB' >> J06 > JaBI 0E3 66' is also the order expected on the basis of greater coupling for the more strongly w bonded groups. The expected order of w bonding strength is Fa > FB' >> Fa. This reasoning is consistent with the belief that F-F coupling for geminal groups is transmitted both through the bond and through space (16). Increased pW'—€>'dfl bonding would be expected both to increase the bond strength and to reduce the bond length, thereby reducing the distance between fluorine atoms. D. Interpretation of Spectra The observed 19F magnetic resonance spectra for TiF4-2THF are shown on page 66. For cis-TiF4-2THF (isomer‘A), 6303.6 = 60.9 ppm and JF = 57st Hz. .A small singlet S4 is aFB 91 observed 12 ppm upfield from the upfield triplet t4+. The low field triplet t4" is ascribed to Ffi and the high field triplet t4,+ to F0' The S4 singlet most probably arises from the ppppprTiF4°2THF complex (isomer g). This complex contains only Fa fluorine and its 19F resonance should be very near the F0 resonance exihibited for the pig isomer. As Ragsdale and Dyer (12) have shown for the TiF4-2(2-CH3C5H4NO) complex, the p£ap§_isomer gives a single Fa resonance at slightly higher field than the F0 triplet for the gi§_isomer. There is, therefore, little doubt that S4 is due to the ppapg isomer. The equilibrium constant calculated for the con- version of the ppppp_to the cis isomer (pm 65) is equal to 55 at -60°C. Only 5% of the TiF4'2THF isomer exists in the ppgpp form. The enhanced stability of the pig isomer can be attributed mainly to the increased bond strength of the F5 fluorines due to pW'->-dw interactions. On the basis of random ordering, the pig compound also should be preferred over the p£3p§_compound by a 4:1 ratio. The ppppp form would only be preferred if ligands having large steric repulsion were employed. It is interesting to note that both the pig- and ppgpg—SnF4-2C2HSOH isomers are observed in roughly equal proportions at -50°C by 19F NMR (41,42). Tin has a 4dl° configuration which prevents pw'-€>'dw interaction. The chemical shift difference 6FOIFB for the gi_S-SnF4-2C2H50H , isomer was very small, giving rise to a complex multiplet characteristic of an A232 system. The difference in the 92 chemical shift for the cis multiplet and the trans singlet was approximately 5 ppm. :3: Magpetic Resonance-~TiF2C12-2THFI Isomer g A. Iptegpretation of Spectra Of all the possible TiExple-EfZTHF isomers only TiF4-2THF isomer §_and TiFgClg'ZTHF isomer g‘give unique splitting patterns. The presence of two equal intensity doublets having the same coupling constants in the 19F magnetic resonance spectrum for an equilibrium mixture of these complexes con- firms the presence of TiF2C12-2THF isomer‘gs The chemical shift difference and the coupling constant for this isomer are 65'6” = 76 ppm and JF = 45 Hz, respectively. BFV B. Theoretical Considerations for ail Bonding Order F THF C1 The expected pw-%>'dw donation ability of the groups bonded to titanium is F > THF > C1. The low field doublet dg' would then arise from the group Eggpp to the chlorine, F&, and the higher field doublet d2+ would arise from the FB group Eggpp to the THF. The relatively large F-F coupling constant indicates that considerable pn'-a~dw fluorine to titanium bonding is involved, as would be expected from the above assignments. The fairly large 6FBF value indicates 7 that chlorine is a considerably weaker w bond donor than THF. The observed 6F F value of 60.9 ppm for TiF4'2THF isomer A and a B a (SI-”SEW value of 76 ppm for ..TiF2C12--2THF isomer iindicate that 95 THF is slightly closer to fluorine than chlorine in its ability to form v bonds. C. Theoretical Considerations for a v Bonding deer g 2 Cl > THE It is more difficult to account for these observations if the relative w bonding ability of THF and Cl are inverted from that previously suggested. For a F bonding order of F > C1 > THF, the expected (SFBF7 value would be less than or < 60 ppm. The value of 6F ‘5'an - EFT 60 ppm as the W bonding strength of fluorine and chlorine would only approach converge. The belief that (5F F should remain fairly con- stant for the entire series Tigzgl4I§f2THF may, however, be an assumption that grossly oversimplifies the actual situation. As chlorine atoms replace fluorine in this series, steric effects may come into play which could cause a change in the relative H bonding ability of the groups involved. Replace- ment of two fluorine atoms on TiFI‘ZTHF with chlorine atoms might be expected to increase the THF--Ti bond distance; this would deCrease the THF -+'Ti pn'->-d "bonding and allow for greater FB -+-Ti pn'-*'dw bonding. Replacing strong w bonding groups with weaker groups may also allow those remaining fluorines to increase their degree of w bonding. The net effect would be a much larger value of (SF F than 6 I expected on the basis of 6F F for TiF4-2THF isomer A and a a B W bonding order F > C1 > THF. If the H bonding order for this isomer is in fact F > C1 > THF, then the low field 94 doublet d2“ would arise from F0 and the high field doublet d2+ from F . 7 Since both E bonding orders can be justified by the ex- perimental results, both will be used in the spectral interpretation. The more intuitively obvious v bonding order F > THF > C1 will be discussed first. Interpretation ofp§pectra A. Temperature Effects The effect of temperature on the 19F Spectra of addition complexes of TiF4 has been discussed by Muetterties (56) and Ragsdale (12,15,40). Loss of the fine structure and coalescence of the low temperature peaks into a broad singlet at room temperature was attributed to donor molecule exchange. Ligand exchange has also been established for Ti(acac)4 and Ti(tfac)4 (1,2,58). The formation of the mixed halide complexes from TiCl4-2THF and TiF4°2THF clearly establishes that halide ex- change also takes place. The loss of fine structure at temperatures above -50°C and collapse of all 19F resonance peaks at room temperature for the TiF§C14I§f2THF compounds is therefore attributed to both donor molecule exchange and halide exchange. B. Observed 19F Resonances The low temperature 19F magnetic resonance spectrum for the titanium(IV) chloride fluoride THF equilibrium mixture shows, in addition to the peaks t4“ and t4+ for TiF4°2THF 95 isomer Akand d2“ and d2+ for TiF2Clg-2THF isomer 2! a triplet t3- and doublet d3+ in 2:1 ratio--which must arise from an isomer of TiF3C1'2THF--and two singlets with S; at lower field than 82. A study of the intensity of these singlets with regard to the initial ratio of TiCl4 to TiF4 has con- clusively established that $2 arises from TiF2Clg-2THF and S; arises from TiFC13-2THF. C. flpgondipg Order F > THF > C1 i. TiF3Cl-2THF. Assuming the w bonding strength of ligands to be F > THF > C1, the three isomers of TiF3C102THF should each give a low field triplet and a higher field doublet. TiF3Cl-2THF isomer ghwould be expected to have (5 and J values on the order of those observed for FaFB FGFB TiF4-2THF isomer A ((5 = 60 ppm, J = 57.7 Hz). TiF3Cl-2THF isomer 2.with 6- and y-fluorine should give chemical shift and coupling constant values close to those observed for TiFZClg'ZTHF isomer 9; ( 6 = 76 ppm, F FBI JF F = 45 Hz). The third isomer TiF3Cl-2THF isomer §~with B a- and y-fluorine should have a chemical shift approximately equal to the sum of 6F F and 6F F or a 6F F value of a B B v a 7 ““155 ppm. Its coupling constant should be larger than J . and probably smaller than J or 57.7 Hz < J - F F F F06 F57 07 (451-12. The observed chemical shift difference of (5FF = 67 ppm and coupling constant J = 55.1 can only be accounted for by FF 0- and B—fluorine which leads to the selection of TiF3Cl'2THF 96 isomer 2; The low field triplet t3" and the high field doublet d3+ are therefore ascribed respectively to F6 and F0 of TiF3Cl'2THF isomer 9% ii. TiFZClg'ZTHF. The singlet $2 arises from isomer E, g, g, or I. or TiF2C12'2TI-IF. This resonance appears about 6 ppm downfield from the higher field d2* (F6) doublet of TIE2c12-2THE isomer g. The low field doublet d; (F7) is 0’70 ppm downfield from 32. If the singlet Sg arose from an a-fluorine it would be expected /VG0 ppm upfield from d2+. For a B-fluorine, the resonance should be near d2+ and a y-fluorine should be observed near d2”. The observation of 82 very near d2+ indicates that the resonance arises from a 6-fluorine. The only isomer having two equivalent B-fluorines is TiF2C12°2THF isomer g: The 82 peak is assigned to the FB resonance of this isomer. iii. TiFC13°22§§. Isomers of TiFCla-ZTHF give only a single 19F resonance peak. Any Specific isomer assignment must therefore be somewhat tenuous. As fluorine atoms are replaced with chlorine atoms in the series TiFECl4I§f2THF, the chemical shift from the reference moves to lower field strengths. This is contrary to the chemical shift expected on the basis of inductive effects but is justified on the bases of the expected increase in pw’-*'dw bonding. Inductive effects in covalent fluorine compounds are con- sidered to be weak in comparison with the paramagnetic Shield- ing due to pW'-—>-dw interactions (15,59). In systems where «97 w bonding is possible, 19F‘resonances generally shift to low field as fluorine atoms are replaced with less electro- negative atoms. Table 14 clearly illustrates this point for the boron fluoride halides and several other examples. The JBF coupling constants also show the effect of increased w bonding. Table 15 lists the various chemical shifts observed for TiF;_¢_Cl4_3_-2THF compounds. The three isomers of TiFC13-2THF contain only 6- and y-fluorine. Assuming the B-fluorine of isomer E‘to be responsible for the observed 19F resonance 3;, a reasonable decrease of 24 ppm is observed for the chemical shift difference between TiF2C12°2THF and TiFC13°2THF. If S; resulted from a y-fluorine of isomers §~or M: a net in- crease in the chemical shift of 50 ppm would be observed. It seems more reasonable to select TiFCla'ZTHF isomer §*as the isomer reSponsible for S;. A disturbing feature of Table 15 is the discontinuity in the decreasing chemical shift with decreasing fluorine at TiF2C12°2THF. The change in <5FF for each step in the series TiFECl41§°2THF with decreasing fluorine is -55, +58,and -24 ppm. It might be possible to justify a small increase in (SPF because of inductive effects or perhaps steric interactions but an increase of 58 ppm is very difficult to rationalize. D. W Bonding Order F > C1 > THF Reinterpreting the spectra with an assumed w bonding order F > C1 > THF leads to the following conclusions. rfl .|_I1.- pun-«I d0..- .45.. fl;-.b 98. Table 14. 19F chemical shifts for selected compounds where v bonding is postulated. Boron Fluoride Halide System (9) J BF3 BF; Compound ppm Hz BF3 0 15 BF2C1 -51.5 54 BFgBr -68-4 56 BFClg -99.0 74 BFClBr -114.8 92 BFBrg -150.4 108 Carbon Chloride Fluoride System (52) 6CF4 Compound ppm CF; 0 CF3C1 -56.8 CF2C12 —60.4 CFCls -76.7 Phosphorus(V) Chloride Féporide System (6,25) EE*(PPm) Compound F(axial) F(eqpitorial) PFs +66.5 '-- PF4C1 +25.5 -- PF3C12 -67.4 +41.5 PFgCla —125.0 --- pECl. -152 ~-- -)(- CFC13 used as internal reference. .— Y>(m-l-Z." a... . s we“ at r- 99 .0os0u0m0u Hmcn0usw 00 «he Eoum U0usmm0E mumwnm H000E0£0 mma .1. «NI III III III H0 000I III .m 0090.000009 III III III «0 000I III .m. 0090.0000009 00+ .I 00 III I00 s00I +00 000I III 0 0090.0000009 00I III «.00 III In» 000I +00 000I .w 0090.000009 III III III III III ...0 SNNI .m 8090.002. III III 0.00 III I00 000I 0.0 000I .m. 0090.+mfls Ema um am 800 Ema Ema H0500H a a 00 .000 0.00.0 m 0.0 0.0 h. h. .... C .x. Q * Q mn0EomH mmamumrvaomwwe .HO A hue A m H0puo mGwGSOfl h m Eoum v0momonm 0:» 00m musmumsoo mcwamsoo 000 000050 HMUHE0£0 had .00 00009 100 i. TiF3Cl-2THF. Isomers g~and.§.would both give a low field triplet and a high field doublet but because isomer 2. would give an inverted splitting pattern, it can be elimi- nated from consideration. The (SFGF expected for isomer 9* should be larger than that expected for of TiF4'2THF 6.0.3 isomer g~whereas J should be about the same for both I FaFB i compounds. Isomer E should have 6F0Fy and JFaF? values . much smaller than the corresponding values predicted for isomer g~and presumably smaller than those observed for TiF4-2THF isomer 5: The chemical shift and coupling constant values observed for TiF3Cl'2THF appear to be more consistent with isomer SJ but isomer §~is not conclusively ruled out. ii. 1iF2C12°22HF. The low field doublet d2- would arise from the B-fluorine and the high field doublet d2+ from the y-fluorine of isomer g? The strong singlet Sg‘which is very near 03+ is therefore expected to arise from a F7 resonance of isomer Hp iii. TiFCla°2THF. A decrease in the chemical shift with decreasing fluorine for the series TinCl4fl§°2THF can only be maintained if the S; peak arises from a F,y resonance. Both isomers L and ~11 contain v-fluorine, but isomer M is slightly favored on the basis of its structural consistency with TiF2C12-2THF isomer 3;. E. Summary Table 16 lists the expected TiF§C14Ix-2THF isomers, assuming a H bonding order of F > C1 > THF. The assignments 101 .OUCTHQNQH HMGHMHCH mm «he EOHM Umhgmmmfi mUHHSm HMUHEQSU .mmd Ix. 00I III III III 00 000I III 1». 00.00.0302. III III III III 00 000I III :0. 00.00.030.000. 00I .00 III I00 000I +00 000I III m... 00.00.080.000 00I III «.00 I00 000.. III +00 000I :0. 0000.800; III III III III III 00 000I .m. 00.00.0000 III III 0.00 IJ 000I III +3 000I I0. 0000.500. Ema um um Ema Ema Ema H0EowH P Q Q d . Q P d 0.0 0 00. 0 00 .. 0mg .. 0Q .. 00 I. I. .mma A Ho A 0 H0000 mcflvson.0 0 5000 00000000 0008000 hmBN.xI0HUxm09 0£u mom muSMumcoo mafiamsoo paw 000:0 HMUHE0£0 000 .00 0HQMB 102 indicated in this table are preferred over those given in Table 15 because of their greater consistency in the downfield 19F chemical shift with decreasing fluorine. Most of the isomers listed are the same in both tables. The only difference rests in the selection of isomer .11 over isomer g“ for TiF2C12o2THF and isomer §~over isomer 5 for TiFCla'ZTHF. §t§geochemistgy A. gnfluencing Factors This system is too complex to allow accurate stereo- chemical predictions by Gillespie's Valence-Shell Electron— Pair Repulsion (VSEPR¥ theory (20,21). The major factor complicating stereochemical predictions is the effect of pw ——+'dw bonding on the bond energy of the molecule and the degree to which this multiple bonding enhances electronic repulsions. B. TiFg'ZTHF On the basis of VSEPR, isomer g‘ought to be the preferred structure. That isomer 5.13 observed to be the most stable is indicative of increased Ti-F bond energy resulting from enhanced pun-**-dw interaction. In this case it appears that the enhanced stability due to v bonding outweighs the VSEPR effects. :105 c. TiFaCI'ZTHF The most stable structure by virtue of enhanced w bond- ing should be isomer QJ whereas VSEPR theory predicts this isomer to be the least stable. Isomer Q~is observed to be the least consistent with the observed NMR data. In this case, it appears that n bonding stabilization is not the con- trolling factor. Choosing between isomers Q.and §~is diffi- cult on the basis of VSEPR theory. If Cl-Cl repulsion is greater than THF-THF repulsion, then isomer g~would be slight- ly favored. The NMR data suggest that the observed isomer is g“ but it does not eliminate the possible existence of isomer E. m D. TiF2C12°2THF Isomer‘§~would be the energetically most stable for a w bonding order C1 > THF. The inverted N'bonding order would indicate that isomer §~is the most energetically favored. In either case isomeragywould be the second most energetically favored. VSEPR theory suggests isomers §.and ;“as the most stable. The NMR data indicate as the most stable either isomer g; for the 1r bonding order THF > C1 or isomer gfor the inverted w bonding order. The presence of isomer‘gfiin low concentration is also confirmed. There appears to be no agreement among these observations. E. TiFCla'ZTHF If the w bonding order is C1 > THF. then consideration of W'bonding stabilization makes‘§~the isomer of choice, but 104 the inverted 7r bonding order suggests that isomers k and y“ are more stable than 35“. VSEPR theory predicts that isomer ”Ii is the most stable. The NMR data fit With the spectrum anticipated for isomer ‘13“ if the 1r bonding order is THF > C1; for the inverted w bonding order the data fit the pattern expected for either isomer .I-L. or y“. EQUILIBRIUM CONSTANTS Experimental Data Equilibrium concentrations were calculated from fluorine-19 magnetic resonance intensity data obtained for samples 1, 2, and 5 (Table 10). The spectra were recorded without side bands and with a sweep width such that the 19F magnetic resonances appeared as lines (Figure 8). The height of these lines was taken as proportional to the intensity of the 19F magnetic resonance. The spectrum for sample 1 was obtained at -70°C. The spectra for samples 2 and 5 were obtained at -60°C. Equilibrium Considerations In addition to the six equilibrium equations listed in the discussion section (p. 85) , several additional equié- librium expressions can be considered. The following equations represent the formation equilibria of the mixed chloride fluoride complexes from their parent compounds. (7) 1/4(TiC14°2THF) + 5/4(TiF4'2THF) ——‘TiF3Cl'2THF (8) 1/2(TiCl4°2THF) + 1/2(TiF4°2THF) —_"TiF2Clg'2THF (9) 5/4(TiCl4'2THF) + 1/4(TiF4-2THF) —“'TiFC13°2THF .105 106 Equation 10 represents the equilibrium between the two ob- served isomers of TiF2C12-2THF. (10) TiEgClg-ZTHF (J) —- TiF2C12-2THF (F or H) m r- m m The isomers represented in this equation are presumed to be correct on the basis of the observed 19F NMR data (see pp. 96-102). I Since TiCl4-2THF cannot be observed directly by 1"915' NMR, its concentration must be determined by difference. Equi- librium calculations requiring a knowledge of the concen— tration of TiCl4-2THF are therefore subject to large error. A number of equilibria exist in solution which do not directly depend upon TiCl4-2THF. These are represented by equations 3, 5, and 6. The calculated equilibrium constants for equations 5, 5, and 6 should be significantly more accurate than those calculated for equations 1, 2, 4, 7, 8, and 9. Since equilibrium constants calculated for equations 1, 2, and 4 are expected to be of very low accuracy and since they would add little useful knowledge, they will no longer be considered. Method of Calculation Calculation of equilibrium concentrations from intensity data is complicated by the fact that TiCl4'2THF cannot be Observed by J'9F NMR. The total peak intensity observed for each of the other compounds is proportional to the relative amount of fluorine contained in each compound. For all the 107 species but TiCl4-2THF, the relative amount of chlorine con- tained in each was determined by multiplying the relative amount of fluorine by the stoichiometric ratio of chlorine to fluorine for that species. The overall ratio of chlorine to fluorine is determined by the known stoichiometry of the initial sample. The relative amount of chlorine contained in TiCl4-2THF was therefore determined by difference. The relative molar ratio of each Species was then obtained by dividing the relative amount of fluorine by the number of fluorine atoms per molecule or by dividing the relative amount of chlorine by the number of chlorine atoms per mole- cule. Initial molar concentrations were finally arrived at by converting the relative scale to a mole per cent scale and then multiplying by the initial concentration. Since the stoichiometry for the equilibrium equations does not change in going from reactants to products, the total molar concentration at equilibrium equals the initial molar concen- tration. Concentration values therefore are not actually necessary since the mole ratio or mole per cent values could be used in their place in determining the equilibrium constant. Equilibrium Concentrations Sample 1 had an initial concentration of 1.0 g_TiF2Clg in THF. Table 17 gives the measured intensity values obtained from the spectrum of this sample at -70°C (Figure 8) as well as the calculated values leading to the equilibrium concen- trations. 108 .afl 0.00 0000000000000 00008 0000000 000 00 0000 000 0008 000000000 000 000x00 09 00000090 0003 00000000000000 80000000000 .0 .00000> 00000 00008 000 00 000000000000 000 00000> 0000000 0002 .0 .00000008 000 000000000 00 000800 000 an 0000>00 00000000 00 000080 0>000000 000 00 00000008 000 000000000 00 000800 000 00 0000>00 00000000 00 000080 0>000000 000 00000 00000> 00000 00002 .0 .000 00 00000 0003 00000> 00000000 00 000080 0>000000 000 00000 000 .009N.000000B .000800 0000000 000 000 000 003 00000000 00 00000000 00 00000 00000800000000 000 00000 00 00>0000 003 000 008 .000 8000 00000> 00000000.00 000080 0>000000 000 00 800 000 00000000000 an 0000800000 003 0080.00009 000 00000000 00 000080 0>000000 009 .00000800 0000 000 00000000 00 00000000 00 00000 005000 000 0Q 00000> 00000000 00 000080 0>000000 000 m00>0000008 09 00000090 0003 0090.00009 0000 00000 000000800 000 000 000 00000> 00000000 00 000080 0>00000m .0 .000 00 00009 000 00 00000> 000000000 00000008 000 00 000000000000 000 00000> 00000000 00 000080 0>00000m .N .80000000 000000000 00000008 000 000 8000 00000000 0003 00000> 000000000 00000002 .0 00000 00 00000000000 000.0 0.0 0.0 0.0 o o 008N.0000B om0.o 0.00 0.0 0.00 0.0 00 0000.000000 000.0 0.0 0.0 0.0 0.0 00 000 0000.0000000 000.0 0.00 0.00 0.00 0.00 O0 mm.0o.00 0000.0000000 omm.o o.mm 0.00 0.00 m.mm 00 009N.00000B 0No.o 0.N 0.0 o 0.0 0 009N.000B 0&0 .00000 0000 000 00000 00000000 00000000 00000000H 00000800 80000000000 0002 00002 000080 00008< 00000002 murfl “MAG“ 6>HDMH 0m .0000I 00 0000.0000000.m 0.0 000 mao000000000 20000000000 .00 00000 109 Sample 2 had an initial concentration of 0.5 .131 TiFZClg'ZTHF. The data calculated for this sample at —60°C are presented in Table 18. ‘Sample 5 was initially 0.52 g TiF2C12'2THF and 0.17 g TiF3Cl'2THF. The stoichiometric ratio of chlorine to fluorine in this sample was 0.81 to 1.15. The total relative amount of chlorine on the basis of 100 for the relative amount of fluorine must be gf§% x 100 or 70. The data calculated for this sample at —60°C are presented in Table 19. Eguilibrium Constants A. Experimental Equilibrium Constants Equilibrium constants are calculated from the following mass action expressions obtained for each of the seven equa— tions previously discussed (p. 105). 404F2012'ZTHFlélTigacl.ZTHFJé' “3 = 4; I; * [TiF4°2THF] [TiFCla-ZTHF] K _ iTiF3C1‘flIiFL 5 _ . 0' - '0 [T1F4'2THF] [T1F2C12°2THF] TiF C1 'ZTHF K. = [00 3—7—01 a, [TiF3Cl ' 2THF] [T1FC13 ' 2THF] K7 = [giESCl'Zngj [TiC14°2THFJE1T1F4'2THFrg K _ TiF Cl ~2THF] 8 _ ______J___2_§g [TiCl4-2THF] [TiF4-ZTHFI§ 110 mwo.o m.m m.¢ m.ma o o mmam.«aufie mpo.o m.ma m.~ >.nm m.» ma mmam.maomfla m¢o.o «.m N.¢ $.m $.m ma AM¢ mmam.wflommfls mma.o h.mm m.ma ”.mm ~.mm fim Am‘uo.mv mmam.maummfia oma.o m.mm m.¢a m.«a >.¢« mm mmam.aommfle mao.o m.m m.a o m.m oa mmam.+mfle «my .cocoo ucmo Hmm oaumm mcHHOHno wcfluosam huwmamucH UQSOQEOU Edwunflawsvm waoz Hmaoz undead undead vmusmmmz m>flumamm m>Humamm .ooomu um mmam.maommfla.m m.o uom mgoaumasoamo Esaunflawsvm .ma magma 111 mmo.o m.> m.m m.ma o o mmam.+HUfla 0¢o.o m.m m.m m.oa m.m «a mmam.maomfie pmo.o m.> m.m ¢.m «.m om Amy mmam.maommfia fina.o m.mm $.aa m.mm m.mm a“ Am‘uo.m¢ mmem.mflommfla hma.o m.o« a.~a H.5a m.fim omfi mmam.aommfie m¢o.o w.m o.¢ o o.mfi om mmam.¢mfla Amy .coaoo ucmo Hmm Caumm mcwHoHso mcflHOSHm muwmcmucH ocsomfioo Edflnnwawavm maoz HMHOE unscad .unzoE¢ Umnsmmmz 0>flHMH mm 0>HHMHON .0 Om... um mme~.~u«mfia a ha.o wan mmam.maommfla.m mm.o mom mcowumasuHmu asaumaaflsvm .ma manna 112 K9 = [TiFCla’ZTHF] [TiCl4°2THF] ]TiF4'2THFI* [TiFaClg°2THF (g; or m [TiFgClg'ZTHF (gll’ The following experimental equilibrium constants..KE, are calculated for sample 1 (Table 17). E (0.22)§(0.629)§ K = = 5.0 at -70°c 3 (0.026)?-’(o.160)5 K? = (9%?2) %_ = 1 9 at -7o°c (0.026) (0.529) E (0.529) 0 K = L = 2.7 at -70 C 6 (0.22)§(0.16)§ RE = (0'3?) i‘ = 7.5 at -70°c (0.026) (0.046) Kg = (0.3;9) i" = 15 at -7OOC (0.026) (0.046) Kg = (O'i§°) g, = 4.5 at -70°c (0.026) (0.046) E 4 $0.452) _ _ 0 K10- (0.077) 5.9 at 70 C For sample 2 (Table 18) the following values are ob- tained. 115 E (0.160)§(o.214)é (0.015)é(0.07;;E E (0.150) (0.013)%(0.211)é- E (0.211) (0.150) (0.079)“r E (0.150) (0.015)§(0.048)% E (0.211) (0.015)§(0.048)§ 7: m II E (0.079) (0.01:5)‘1‘(0.046)it KE = (0.169) 1° (0.042) Sample 5 (Table 19) gives constant values. E = (0.197)'5'(0.166)'it (0.046)§(o.040) E _ (0.197) (0.046)%(0.1ea)’£ N m I E _ (0.168) (0.197)'l*(0.040)‘3 = 8.5 = 2.5 at at at ’at at at at -60°c -60°c -60°c . . -60°c -60°c ; -60°c -60°c the following equilibrium 4.2 1.9 at 2.2 at at -60°c -60°c -60°c 114 Kg = (0.;97) i’ = 4.4 at -60°c (0.046) (0.056) (0.168) = 4.0 at -60°c K8 ' (0.046)é(0.038;§ E (0.040) 1.0 at -60°C (0.046)1‘(0.058)% E _ (0.131) 0 K10- (0.057) 3.5 at '60 C Table 20 presents a summary of the equilibrium constants calculated for these three samples. As expected, agreement for K2, K2, and RE is much better than for RE, RE, and K3. This illustrates the error introduced because the concentra- tion of TiCl4'2THF could not be determined directly. Direct determination of TiCl4'2THF, perhaps by visible or ultraviolet spectroscopy, would greatly increase the accuracy of K?, K2, and Kg. The low precision of these data makes impossible any firm conclusion regarding the effect of temperature on the equilibrium constant. There does not, however, appear to be any great effect of temperature on the values of the equilibrium constants. B. Statistical Equilibrium Constants Equilibrium constants which consider only the entropy- controlled tendency of a system to achieve random order can be calculated from simple probability theory. These statis- tical equilibrium constants, KS, assume that enthalpy changes and nonrandom entrOpy effects are negligible. 115 0.9 m.» 0.9 0.0 omx 0.0 0.9 0.0 0.9 Ms 9.0 0.9 9.0 09 ms 6.0 9.9 0.0 0.6 ms m.m 0.9 0.9 5m mm m.m m.m 0.0 0.9 ms 0.9 «.9 0.0 0.0 mm E98035 m 3.0 I I mmmum>¢ mmsm.~Hommfle 2 00.0 mmBN.NHommwa z 0.0 mmem.mflommfla z 0.9 0000- 0000- 0006- N 090560 9 mamsmm 0 090660 .mucmumcoo Edflunfiaanvm mo kHMEEdm .ON magma 116 The probability of forming any component containing 2 fluorine atoms, where 11= O, 1, 2, 5, or 4, is given by the expression “.2 = 31; (441W [FJEICnM-fl) where [F] is the mole fraction of total halide that is fluorine and [Cl] equals the mole fraction of the total halide that is chlorine. Solving this expression for the case of equal molar amounts of chlorine and fluorine gives a ratio of components at equilibrium of TiF4‘2THF : TiF3C1°2THF : TiF2Clg°2THF : TiFC13°2THF : TiC14-THF = 1:4:6:4:1. Using these values, statistical equilibrium constants can be calculated for equations 5, 5, 6, 7, 8, and 9. These calculated values follow. i ’5‘ K§= (6)432)er - 2.45 (1) (4) s (4) K = fir = 1.65 5 (1)36)? s (6) K = = 1.50 6 (4)504)? s (4) K = - 4 7 (Mimii 3.. (6) ' K - = e a (1)§(1)§ Kg: (g) = 4 mini 117 ‘iscussion A comparison of the experimental and statistical equi- librium constants is given in Table 21. Free energy values were calculated from the equation -fl3 = -RT In K (T = 2150K). The ratio of the experimental equilibrium constant to the statistical equilibrium constant, KE/KS, indicates stabili- zation of the complex from factors other than random scatter entropy effects. These other factors include changes in the enthalpy of reaction and nonrandom entropy effects. The effect of these factors is clearly indicated by A(AG) which is the difference in the experimental free energy of reaction and the statistical free energy change expected for random ordering. Positive values for A(AG) indicate increased stability and negative values indicate decreased stability per mole of reaction product from that expected for random ordering, negligible nonrandom entropy effects, and no change in the enthalpy of reaction. All AG values are per mole of reaction product. The stability increase appears to be in the order: TiF3C1‘2THF > TiFgClg'ZTHF > TiFClg'ZTHF. It is interesting to note that TiF3Cl'2THF and TiF2Clg-2THF are increased in stability whereas TiFCla-ZTHF is decreased in stability from that expected for random ordering. This may indicate stronger molecular bonding forces as the number of fluorine atoms in the molecule increases and would result in enthalpy changes. The small deviation from randomness 118 omHI mm.o 099 m.m 0mm 9 Amv oma+ m.H 0¢m H.m omw w Amy ONN+ >.H cam 0.m 0mm 9 va omd+ m.H mmm N.N mud m.a Amv o¢d+ 9.H 0mm m.N OHN mm.a Amv oom+ N 0mm m.9 0mm m9.m Amv mHoE\Hmo mx\m& maofi\amo MM mHOEKHmo mm coaumsvm AEGVG mm: Qflfl, 033 50960 903099.40me 900330.30 .mucmumcoo Edflunwafisvm HmucmEHummxm paw HMUHumHumum .HN magma 119 could also.be easily accounted for on the basis of non- random entropy effects. The deviation in the experimentally determined equilibrium constants with temperature is not sufficient, considering the low precision of the data, to allow for any conclusions regarding the importance of enthalpy. It is known that nonrandom entropy changes, such as differences in solvation entropies of reactants and products, could account for significantly greater deviation from the statistically expected values than were observed for this system. gnvestigations of Other Workers Ligand exchange between metal acetylacetonates, M(acac)4. and metal trifluoroacetylacetonates, M(tfac)4, has been studied by both 19F and proton NMR (1,2,58). Pinnavaia and Fay (58) found that formation of the mixed ligand zirconium complexes, Zr(acac)3(tfac), Zr(acac)2(ffac)2, and Zr(acac)(tfac)3 was favored over that expected on the basis of statistical scatter. Equilibrium constants corresponding to XE, K2, and K2 were determined and found to be approximately 1.58 times larger than the statistical equilibrium constants. A study of the temperature dependence of the equilibrium constants lead the authors to conclude that the enthalpy changes for all three reactions are zero. Differences in solvation entropies of reactants and products was suggested to account for the observed nonstatistical distribution. In a study of the same system, Adams and Larsen (1,2) concur with Pinnavaia and Fay 120 and have calculated equilibrium constants corresponding to Kg, RE, and K2 and found these values to be 4.5, 8.5, and 6.0 times larger than the expected statistical equilibrium constants. Conclusion It is clear that either enthalpy or nonrandom entropy changes or a combination of both could account for the deviations from the statistical equilibrium constant values. The question cannot be answered without a more detailed study of the temperature dependence of the equilibrium constants and the determination of more precise experimental values. CONCLUSION The TiCl4-2THF--TiF4-2THF system has been investigated in THF solution by 19F magnetic resonance spectroscopy. At room temperature no spectral detail was observed because of rapid donor molecule and halide exchange. The presence of the three mixed chloride fluoride complexes, as well as the tetrafluoride complex, was confirmed by the well-resolved spectrum at -60°C. Approximate equilibrium constants were calculated for the formation of each mixed halide complex from its parent compounds. The difference in the free energy values calcu- lated from the experimental equilibrium constants and the free energy values calculated from statistical equilibrium constants expected for random distribution were +220, +180, and -180 cal/mole for TiF3Cl-2THF, TiF2C12-2THF, and TiFC13°2THF. This relatively small deviation from random order could be due to either nonrandom entropy effects or small changes in the enthalpy of reaction. The experimental results were not sufficient to determine the magnitude of possible enthalpy changes. A detailed analysis has been made of the low temperature 19F magnetic resonance spectra in an attempt to determine specifically what isomers were present. The following con- clusions are based on spectra that were obtained at -60°C. 121 122 TiFfi'ZTHE: The gi§_isomer strongly predominates with a gi§_to trans ratio of approximately 35 to 1. Two equal intensity triplets are observed for the gi§_isomer with (5FaF8 = 60 ppm and JFaFfi = 57.7 Hz. The Egggg isomer gives a singlet approximately 12 ppm upfield from the high field triplet of the gig isomer. TiF3C1-2THF: Only one isomer is observed for this compound. The 19F NMR data strongly suggest that this isomer contains THF groups gig to each other and two fluorines‘tggng to each other. This isomer gives rise to a low field triplet and a higher field doublet in 2 to 1 intensity ratio with 6FaF5 = 67 ppm and JFaFB = 55.1 Hz. TiFgClg'ZTHF: Two isomers-are observed for this com- pound. The presence of an enantiomorph isomer with similar ligands gig to each other is conclusively established by virtue of its unique splitting pattern. Two equal intensity doublets are observed for this isomer with (SEW...Y = 76 ppm and JFBFV = 45 Hz. The second isomer, with an approximate ratio to the enantiomorph.isomercfi35 to 1, appears as a singlet about 6 ppm downfield from the high field doublet of the enantiomorph isomer. The position of this peak suggests that it arises from an isomer with gi§.fluorine and either gig chlorine and ‘tgggg THF or gig THF and Ergg§_chlorine. The former is some- what more consistent with the observed data and is therefore slightly favored. 125 TiFCla-ZTHF: A single 19F resonance observed for this compound indicates the presence of only one isomer. Assign- ment of this resonance to a specific isomer is very tenuous. The most consistent data is obtained by ascribing this resonance to the isomer containing trans THF groups. A close second and third choice would be the isomer having gi§_THF and trans chlorine and the isomer having gig THF and gig chlorine. SIGNIFICANCE Prior to this investigation it was believed that donor molecule exchange alone was responsible for the observed temperature dependence of the J'9F NMR spectra for TiF4-2L and similar complexes. Halogen exchange between octahedral complexes was unknown. This research has conclusively estab- lished that halogen exchange does take place in the TiC14-2THF-- TiF4°2THF system and it strongly suggests that intermolecular fluoride exchange takes place in TiF4°2L and similar complexes. A mechanism by which halogen exchange can occur has been sug- gested. The accuracy of the equilibrium constants calculated for the TiCl4'2THF--TiF4-2THF system is not precise but it is sufficient to indicate that formation of the mixed halide complexes does not deviate markedly from that expected for random ordering. This indicates that there is nothing un- usual about the bonding or structure for the mixed halide complexes. The qualitative stability order has been found to increase with increasing fluorine as might be expected. The ability to resolve the observed Spectra into their components for each of the six species present indicates that the Ti--F system is ideal for 19F NMR studies. A first order spectrum was observed for each isomer. This is attributed to 124 125 a Sdo configuration which permits strong pW'-—+'dw inter- actions and causes significant differences in the para- magnetic shielding of fluorine atoms in different environ- ments in the complex. The only titanium isotopes with nuclear spin are ‘7Ti (7.4% abundance) with I = 5/2 and ‘9Ti (5.5% abundance) with I = 7/2. The only observed coupling is there- fore between fluorine atoms. The advantages of the Ti--F system over the Sn--F system are clearly evident. This re- search will undoubtedly stimulate other researchers to in- vestigate titanium compounds and complexes by NMR techniques. The greatest significance of this research rests in the ability to determine absolute stereochemical configurations for the octahedral complexes observed. This investigation carries with it theoretical implications that should be of interest to NMR spectroscopists, coordination chemists, and stereochemists. The present study does not provide all the answers, but it does provide a beginning and some interesting theories which can be built on, amplified, and modified during future studies. Confirmatory evidence is added to the theory first prOposed by Ragsdale that groups bonded t£§§§_ to fluorine in an octahedral complex control the tendency toward w bonding for fluorine and therefore strongly affect its shielding constant. The present study suggests that the magnitude of this w bonding is exhibited both by chemical shift and by coupling constant values. Future investigations may allow the NMR spectroscopist to predict accurately the 126 positions of resonance peaks for octahedral complexes as well as the approximate magnitude of chemical shift and coupling constant values. The coordination chemist may then be able to determine quantitatively the w bonding strengths for a large number of ligands. Finally, the stereochemist-dwith knowledge of the configurations of many octahedral complexes-- may be able to develop a theory to account for these observed configurations. RECOMMENDATIONS FOR FUTURE WORK 1. More precise values of the equilibrium constants should be determined. This could be accomplished by first isolating TiCl4-2THF and TiF4-2THF and then combining these in the desired proportions. Alternatively, samples for NMR study could first be prepared by any convenient method and then analyzed for their chlorine to fluorine ratios. 2. Once high precision has been achieved in the calcu- lation of equilibrium constants, a very careful temperature dependence study should be conducted to determine the magni- tude of enthalpy changes. 5. The relative w bonding order of chlorine and tetra- hydrofuran should be determined and the structural assign- ments for the titanium(IV) chloride fluorides should be con- firmed. A study of the TiBr4--TiF4--THF system would result in the replacement of chlorine with a weaker w bonding atom, bromine. The effect of this on the 19F resonance should be clearly evident and should support one of the w bonding orders. Examination of the TiC14--TiF4 system in a bidentate solution should insure gig chelation and would eliminate from consideration a number of structures involving trans coordination, thereby simplifying the system. A number of other systems could be studied which should provide enough 127 128 information for conclusively establishing the structures of all the octahedral complexes observed. The TiCl;--firTiFe-- system could be studied in concentrated hydrochloric acid. It should be possible to establish clearly the w bonding strength of chlorine and THF by comparing the spectrum of TiF4C12--, TiF3C13--, and TiF2Cl4" with those already ob- tained for TiF4°2THF, TiF3Cl'2THF, and TiF2C12'2THF. The addition of methanol to the TiC14--TiF4--THF system should provide for the replacement of chlorine with methoxo- groups and thereby provide additional information. 1. 2. 5. 5. 6. 10. 11. 12. 15. 14. 15. 16. BIBLIOGRAPHY A. C. Adams and E. M. Larsen, Inorg. Chem. 5, 228 (1966). A. C. Adams and E. M. Larsen, J. Am. Chem. Soc. 85, 5508 (1965). J. O'M. Bockris, J. L. White, J. D. MacKenzie, ? Physicgghemigal Measurements at High Temperature, ) Butterworths Scientific Publications, London, 1959, pp. 251-51 259. C. I. Branden and I. Lindqvist, Acta Chem. Scand. _4, 726 (1960). L. Brun, Acta Cryst. 29, 759 (1966). R. P. Carter, Jr., and R. R. Holmes, Inorg. Chem. 4, 758 (1965). R. J. H. Clark, W. Errington, J. Lewis, and R. S. Nyholm, J. Chem. Soc. gg, 989 (1966). F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, Interscience Publishers, New York, Second Edition, 1966. T. D. Coyle and F. G. A. Stone, J. Chem. Phys. 52, 1892 (1960). K. Dehnicke, Naturwissenschaften 52, 660 (1965). M. Delwaulle and F. Francois, Compt. Rend. 220, 175 (1945). -—- D. S. Dyer and R. O. Ragsdale, Chem. Comm. 1966, 601. D. S. Dyer and R. O. Ragsdale, Inorg. Chem. 6, 8 (1967). J. W. Emsley, J. Feeney, and L. H. Sutcliffe, High Resolu- tion Ngclear Magnetic ResonancepSpectroscopy, Pergamon Press, New York, 1966, Vol. 2, p. 875. Ibid., Vol. 2, p. 874. Ibid., Vol. 2, p. 676. 129 17. 18. 19. 20. 21. 22. 25. 24. 25. 26. 27. 28. 29. 50. 51. 52. 55. 54. 150 E. Fluck, J. R. Van Wazer, L. C. D. Groenweghe, J. Am. Chem. Soc. g1, 6565 (1959). C. Friedel and J. Guerin, Ann. Chim. Phys. 5, 24 (1876). C. Friedel and J. Guerin, Compt. Rend. 5;, 889 (1875). R. s. Gillespie, J. Chem. Ed. $9. 295 (1965). R. S. Gillespie and R. S. Nyholm, Quart. Rev. (London) 11, 559 (1957). L. L. Handy and N. W. Gregory, J. Am. Chem. Soc. 14, 891 (1952). R. R. Holmes, R. P. Carter, and G. E. Peterson, Inorg. Chem. 5, 1748 (1964). B. A. Kennedy, D. A. McQuarrie, and C. H. Brubaker, Jr., Inorg. Chem. 5, 265 (1964). G. Lange and K. Dehnicke, Naturwissenschaften, 55, 58 (1966). R. Leighton, Principgls of Modern Physics, McGraw-Hill Book Company, Inc., New York, 1959. I. Lindqvist, inorganic Adduct Molecules of Oxo-Compounds, Academic Press Inc., New York, 1965. G. G. Long, C. G. Moreland, G. O. Doak, and M. Miller, Inorg. Chem. 5, 1558 (1966). W. Mahler and E. L. Muetterties, Inorg. Chem. g, 1520 (1965). R. E. MCCarley, J. W. Roddy, and K. 0. Berry, Inorg. Chem. “5, 50:(1964). M. G. Mellon, Quantitative Analysis, The Macmillan Company, New York, 1956, p. 456. L. H. Meyer and H. S. Gutowsky, J. Phys. Chem. _1, 481 (1955). K. Moedritzer and J. R. Van Wazer, Inorg. Chem. 5, 268 (1964). K. Moedritzer and J. R. Van Wazer, Inorg. Chem. 5, 547 (1966). 151 55. K. Moedritzer and J. R. Van Wazer, Inorg. Chem. 5, 1254 1966). 56. E. L. Muetterties, J. Am. Chem. Soc. _g, 1082 (1960) and references contained therein. 57. E. L. Muetterties and W. D. Phillips, J. Am. Chem. Soc. 81,. 1084 (1959) . 58. T. J. Pinnavaia and R. C. Fay, Inorg. Chem. 5, 255 (1966). 59. J. A. Pople, W. G. Schneider, and H. J. Bernstein, High-resolution Nuclear Magnetic Resonance, McGraw-Hill Book Company, Inc., New York, 1959, p. 172. 40. R. O. Ragsdale and B. B. Stewart, Inorg. Chem. g, 1002 (1965). 41. R. O. Ragsdale and B. B. Stewart, Inorg. Chem. 4, 740 (1965). 42. R. O. Ragsdale and B. B. Stewart, Proc. Chem. Soc. 1964, 194. _" 45. J. A. Rahm, Anal. Chem. 24, 1852 (1952). 44. J. K. Ruff and G. Paulett, Inorg. Chem., 5, 998 (1964). 45. O. Ruff and R. Ipsen, Chem. Ber. 55, 1777 (1905). 46. E. R. Scheffer in Treatise on Analytica; Chemistry, Part II, Vol. 5, pp. 49-50. (Kolthoff and Elving, Editors) 47. G. Vaughan and R. Wragg (to Dunlop Rubber Co.) Brit. 954,040, , Aug. 14, 1965; c. A. Q, P1158_e_ (1964 . 48. K. S. Vorres, M. S. Thesis, Michigan State University, East Lansing, Michigan, 1955. 49. K. S. Vorres and J. Donohue, Acta Cryst.. 5, 25 (1955). 50. K. S. Vorres and F. B. Dutton, J. Am. Chem. Soc., 11, 2019 (1955). 51. A. W. Douglas, 7th Experimental NMR Conference, Mellon Institute, Pittsburgh, 24-26 February 1966. APPENDICES 152 APPENDIX I Reaction of Tim, TiF3Cl, and TiFgClg with (CAEQASiOH A reaction was observed to take plaCe between (C6H5)3SiOH and TiF4, TiF3C1, or TiF2C12 in chloroform. Numerous solid samples were isolated from these reactions, but none in pure form. Most of the solids were insoluble in common solvents and ranged in color from pink to black. Some samples gave fairly simple x—ray diffraction patterns. Filtration of the original reaction mixture usually gave clear yellow to orange filtrates. Addition of pentane or hexane to these solutions caused the formation of solids which couldrufizthen be redissolved. Evaporation of the yellow- orange solution produced a gummy orange material or yellow oil that could not be dried further. Addition of wet solvents to the yellow-orange solutions or exposure of these solutions to the atmosphere caused the formation of a white solid which was identified as tetrakis(triphenyisiloxy)titanium. [(C6H5)3SiO]4Ti, by its infrared spectrum. Infrared evidence indicated that some of the solid samples contained CeHs-Si, Si-O-Ti, and Ti-F bonds. The anticipated reaction products (C6H5)3SiOTiF3 and [(C5H5)3SiO]2TiF2 were not isolated. A reaction was also observed between titanium(IV) chloride fluorides and (CeHs)SSiOH in tetrahydrofuran. 155 154 Addition of (C3H5)3SiOH to yellow TiCl4--TiF4--THF solutions caused them to become colorless. Evaporation of these solu- tions gave only gummy materials and oils. APPENDIX II Agtomatically Controlled Constant Pressure Dry Box A Kewaunee Scientific Company dry box was modified to maintain a constant internal pressure of nitrogen slightly above atmospheric pressure. This served several purposes: 1. The effect of any leaks in the system would be mini- mized by an outward flow of nitrogen. 2. Inserting the gloves into the dry box and manipula- tions in the dry box were made very convenient since the proper working pressure was automatically maintained. Operations such as filtration under vacuum or under nitrogen pressure were easily accomplished. 5. Evacuating and filling the entrance port was greatly simplified. One valve connected the entrance port to the dry box while another connected the entrance port to a vacuum pump. When the entrance port had been evacuated, the connection to the vacuum pump was turned off and the valve leading to the dry box was opened. Since the pressure in the dry box was automatically maintained, the entrance port was automatically filled to the proper pressure. This automatically controlled constant pressure modifi— cation was constructed from one dual action pressure (DAP) switch, two solenoid valves, and two single-pole double-throw (SPDT) center off switches. The system could be operated 155 156 either automatically or manually. One SPDT switch selected either the automatic or manual mode and also functioned as the main power on--off switch. The second SPDT switch operated only in the manual mode and selected either nitrogen or vacuum. In the manual mode, the selection of nitrogen opened a solenoid valve which allowed nitrogen to enter the dry box, thereby increasing the pressure; the selection of vacuum opened a solenoid valve between the dry box and a vacuum pump, thereby reducing the pressure. In automatic mode the DAP switch automatically controlled operation of the solenoid valves to maintain the desired pressure. When pressure in the dry box was below or equal to atmospheric, the first stage of the DAP switch turned on the nitrogen solenoid valve. Introduction of nitrogen increased pressure in the dry box to a comfortable working pressure (P1) slightly above atmospheric, at which time the first stage of the DAP switch turned the nitrogen solenoid valve off. At a slightly higher pressure (P2) caused by insertion of the gloves into the dry box or by various manipulations within the dry box, the second stage of the DAP switch turned on the vacuum solenoid valve, thereby reducing pressure. When the pressure fell to a comfortable working level the second stage of the DAP switch shut off the vacuum solenoid. A schematic diagram of the control circuit is presented on the following page along with a more detailed description of the DAP switch and solenoid valves. 157 Solenoid Valves~ N2 Vacuum % Manual .‘ Nitrogen #. 4.‘ b ) “ Off iiOff - Vacuum 110 V Automatic AC _____ ,_ _ ._ :_ ... _ .. _. R ..-; B]. Y.‘W', Gn I I l W , Br I | First Stage Second Stage I | Dual Action Pressure Switch | The Circuit diagram is represented in the automatic mode with the dry box at a convenient working pressure (P1). Dual Action Pressure Switch: Model D2H—H2, pressure range 0.018--1.7 psi, obtainable from Barksdale Valves, 5125 Alcoa Avenue, Los Angeles, California. First Stage: Actuated at P1 Red--Normally Open At pressures below P1, the red—- White--Common white circuit is open and the B1ue--Normally closed blue-~white circuit is closed. At pressures of P1 and above, the red-«white Circuit is Closéd and the blue-awhite circuit is open. Second Stage: Actuated at P2 Yellow-rNormally Open At pressures below P2, the yellow-- Brown—-Common brown circuit is open and the green-- Green-~Normally closed brown circuit is closed. At pres- sures of P2 and above, the yellow-- brown circuit is Closed and the green-ébrown.circuit'is open. '0 158 Both actuation points may be adjusted to give a suitable working pressure range. Solenoid Valves: "Alco," Type 8115, Maximum pressure 200 psi, obtainable from Alco Valve Co., St. Louis, Missouri. The dry box was also fitted with a recirculating drying train which operated independently of the automatic constant pressure system. This recirculating system consisted of a Sprayit pressure-vacuum pump Model 906CA18 (available from Thomas Industries,Inc.; Sprayit Division; Sheboygan, Wisconsin) and several drying towers which contained Linde Type 4A molecular sieves. The recirculating line was designed so that a large volume cold trap could also be inserted into the line to remove vapors from;the dry box.when such sol- vents as tetrahydrofuran were being handled. An open dish of P205 in the dry box served as a desiccant and indicated when the molecular sieves needed regenerating. Prepurified.' nitrogen, which was passed through a cold trap containing molecular sieves and immersed in liquid nitrogen, acted as the nitrogen source for the dry box. With fresh desiccant in the drying train it was possible to handle TiCl4 for several hours without any observable fuming. MTI)IIIIIIIIIIIII)IIIIIIQ‘IEIII)II))TIII)Es