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Infrared spectroscopic studies of some organotin (IV) and organoantimony (V) derivatives 1965

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The Uni v e r s i t y of B r i t i s h Columbia FACULTY OF GRADUATE STUDIES PROGRAMME OF THE FINAL ORAL EXAMINATION FOR THE DEGREE OF DOCTOR OF PHILOSOPHY of RAM GOPAL GOEL BPSC.~„ University of Lucknow* 3.952 TUESDAY, SEPTEMBER 2 1 S 1.965 IN ROOM 2 6 1 k CHEMISTRY BUILDING COMMITTEE IN CHARGE Chairman; R, C= Mann External Examiner; G.-E, Coa.tes Department of Chemistry The U n i v e r s i t y of Durham Durham Cit.y ; ; England AT 1;30 P.M. F. W, Dalby Co A. McDowell. G, Bo Portar R„ Stewart A, Storr Ro C= Thompson INFRARED SPECTROSCOPIC STUDIES OF SOME ORGANOTIN (IV) ] AND ORGANOANTIMONY(V); DERIVATIVES ABSTRACT Triphenyl-, trimethyl- and dimethyltin(IV). , and trimethylantimony(V), derivatives of a wide v a r i e t y of a c i d s 3 including those of very strong acids, as well, as derivatives of a t r a n s i t i o n metal oxyanion s were synthesized. Their s t r u c t u r a l c h a r a c t e r i s t i c s i n the s o l i d state, under s t r i c t l y anhydrous conditions, were determined from t h e i r i n f r a r e d spectra. These spectroscopic r e s u l t s can only be interpreted in terms of a very strong i n t e r a c t i o n between the organometal group and the corresponding anionic group s and provide strong evidence for coordination or p a r t i a l covalent bonding between the organometal group and the anionic group, Contrary to e a r l i e r r e p o r t s s no evidence i s found for the existence of free R.jSn + s R2Sn^ + or R2Sb^ + cations i n the s o l i d state. GRADUATE STUDIES F i e l d of Study: Inorganic 1 Chemistry Physical Inorganic Chemistry R. M. Hochstrasser H. C. Clark N. B a r t l e t t W. Ro Cullen Topics i n Physical Chemistry J, A. R. Coope A. V. Bree Seminar • W.: A. Bryce Topics i n Inorganic Chemistry No B a r t l e t t H. C. Clark W. R. Cullen Advanced Inorganic Chemistry Molecular Structure S o l i d State Chemistry C r y s t a l Structure H. C. Clark W. R. Cullen C. Reid E. J. Wells L. H. Reeves K„ B. Harvey L, G. Harrison J, T r o t t e r So A= Melzak Grganometallic Chemistry H. C. Clark Topics i n Organic Chemistry J= P. Kutney A. I. Scott F. McCapra PUBLICATION H, C= Clark and R= G. Goel Reactions of Organotin Compoundso V. Studies of Some Further T r i - and Di - organotin Derivatives, Inorg, Chem.s (1965). In press, INFRARED SPECTROSCOPIC STUDIES OF SOME ORGANOTIN(IV) AND ORGANOANTIMONY(V) DERIVATIVES by RAM GOPAL GOEL B.Sc., University of Lucknow, 1952 M.Sc, University of Lucknow, 1955 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Chemistry We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August 1965 In p r e s e n t i n g t h i s t h e s i s i n p a r t j a l f u l f i l m e n t o f th e r e q u i r e m e n t s f o r an advanced d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I agr e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r - m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y " p u r p o s e s may be g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s , I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i - c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f Chemistry The U n i v e r s i t y o f B r i t i s h C o l umbia Vancouver .8, Canada Date September 24, 1965, ABSTRACT Triphenyl-, trimethyl- and dimethyltin(IV), and trimethylantimony(V) derivatives of a wide variety of acids, including those of very strong acids, as well as derivatives of a t r a n s i t i o n metal oxyanion, were synthesized. Their s t r u c t u r a l c h a r a c t e r i s t i c s i n the s o l i d state, under s t r i c t l y anhydrous conditions, were determined from their i n frared spectra. These spectroscopic r e s u l t s can only be interpreted in terms of a very strong i n t e r a c t i o n between the organometal group and the corresponding anionic group, and provide strong evidence for coordination or p a r t i a l covalent bonding between the organometal group and the anionic group. Contrary to e a r l i e r reports, no evidence i s found for the existence of free R 3Sn + , R2Sn 2 + or R 3Sb 2 + cations i n the soli-d state. TABLE OF CONTENTS i i i PAGE CHAPTER 1 : INTRODUCTION 1 CHAPTER 2 : TRIPHENYLTIN(IV) DERIVATIVES 2.1 : Triphenyltin Nitrate 19 2.2 : Triphenyltln Perchlorate 34 CHAPTER 3 : •TRIMETHYLTIN(IV) DERIVATIVES 3.1 : Bis (trimethy lti'n) Sulphate 43 3.2 : Bis(trimethyltin) Chromate 54 CHAPTER 4 : DIMETHYLTIN(IV) DERIVATIVES 4.1 : Dimethyltin D i f l u o r i d e 57 4.2 : Dimethyltin Carbonate 59 4.3 : Dimethyltin Chromate 69 4.4 : Dimethyltin Sulphate 74 4.5 : Dimethyltin Bis(tetrafluoroborate) 94 4.6 : Dimethyltin Hexafluorosilicate 103 4.7 i Dimethyltin Derivatives of Group Vb 104 Hexafluorides 2- 4.8 : The Dimethyltin Derivative of B 1 2 C 1 1 2 1 1 4 CHAPTER 5 : TRIMETHYLANTIMONY(V) DERIVATIVES 5.1 : Trimethylantimony Dihalides 119 5.2 : Trimethylantimony D i n i t r a t e 120 5.3 : Trimethylantimony Carbonate 127 5.4 : Trimethylantimony Sulphate 131 5.5 : Trimethylantimony Chromate 137 5.6 : Trimethylantimony Oxalate 141 5.7 : Trimethylantimony Bis(tetrafluoroborate) 150 CHAPTER 5 5.8 5.9 5.10 CHAPTER 6 CHAPTER 7 BIBLIOGRAPHY iv PAGE (Continued) Trimethylantimony Hexafluorosilicate 154 Trimethylantimony Bis(hexafluoroantimonate) 159 The Trimethylantimony Derivative of 161 B 1 2 C l i 2 2 - CONCLUSION EXPERIMENTAL 165 169 193 V LIST OF TABLES TABLE PAGE 2.1a : V i b r a t i o n a l Frequencies of N O 3 Ion 20 2.1b : Correlation Table for D 3 h, D3, C2v and C s 22 Point Groups 2.1c : V i b r a t i o n a l Frequencies of Unidentate and Bidentate 23 Nitrato Groups 2.Id : Infrared Absorption Spectra of Anhydrous and Wet 28 Triphenyltin Nitrate 2.1e : Infrared Absorption Spectra of The Products Obtained 32 on Heating Anhydrous Triphenyltin Nitrate 2.2a : V i b r a t i o n a l Frequencies of CIO" Ion 35 2.2b : Vibrations of The C10 4 Group i n T d, C 3 v or C 2 v 36 Symmetry 2.2c : Infrared Absorption Spectrum of Triphenyltin 40 Perchlorate 2_ 3.1a : V i b r a t i o n a l Frequencies of SO4 Ion 44 3.1b : Infrared Absorption Spectra of Bis ( t r i m e t h y l t i n ) 49 Sulphate-Methanol Diadduct and Bis(trimethyltin) Sulphate • 2 -3.2 : V i b r a t i o n a l Frequencies of CrO^ Ion 55 2- 4.2a : V i b r a t i o n a l Frequencies of C0 3 Ion 60 4.2b : . V i b r a t i o n a l Modes of The Carbonato Group of C2 V 62 Symmetry 4.2c : Calculated Frequencies of Unidentate and Bidentate 64 Co(III) Carbonato Complexes 4.2d : Infrared Absorption Spectrum of Dimethyltin Carbonate 67 4.3 : Infrared Absorption Spectrum of Dimethyltin Chromate 72 4.4a : Infrared Absorption Spectrum of Dimethyltin Sulphate- 79 Methanol Adduct 4.4b:: Infrared Absorption Spectra of Pyridine Adducts of 83 Dimethyltin Sulphate and Dimethyltin Dichloride v i TABLE PAGE 4.4c : Infrared Absorption Spectra of DMSO Adducts of 89 Dimethyltin Sulphate and Dimethyltin Dichloride 4.4d : Sn-CrU Coupling Constants of Some Dimethyltin(IV) 92 Derivatives 4.4e : S n - C H o Coupling Constants of Dimethyltin Sulphate, 93 Dimethyltin Sulphate-Pyridine, Dimethyltin Sulphate- DMSO and Dimethyltin Dichloride - 2 DMSO 4.5a : Vib r a t i o n a l Frequencies of BF4" Ion 95 4.5b : Infrared Absorption Spectrum of The Mixture of 101 Dimethyltin Bis(tetrafluoroborate) and Dimethyltin Difl u o r i d e 4.7a :. Vi b r a t i o n a l Modes of An Octahedral Group MXg 105 4.7b : Correlation between The Vib r a t i o n a l Modes of An 106 Octahedral Group of Oh, D 4 h, or C 2 v Symmetry 4.8 :. Infrared Absorption Spectrum of The Dimethyltin 116 Derivative of B 1 2 C I 1 2 5.1 : Infrared Absorption Spectrum of Trimethylantimony 121 Dif l u o r i d e 5.2 : Infrared Absorption Spectrum of Trimethylantimony 124 Dini t r a t e 5.3 : Infrared Absorption Spectrum of Trimethylantimony 129 Carbonate 5.4a : Infrared Absorption Spectrum of Trimethylantimony 133 Sulphate 5.4b : Infrared Absorption Spectrum of Dimethyl Sulphate 135 5.5 : Infrared Absorption Spectrum of Trimethylantimony 139 Chromate 2— 5.6a : Vi b r a t i o n a l Modes of C2O4 Ion 141 o 5.6b : Vi b r a t i o n a l Frequencies of C2O4 Ion 143 5.6c : Vibration Modes of The Free Oxalate Ion and 145 The Oxalato Group 5.6d : Infrared Absorption Spectrum of Trimethylantimony 147 Oxalate v i i TABLE PAGE 5.7 : Infrared Absorption Spectrum of The Mixture of 153 Trimethylantimony Bis(tetrafluoroborate) and Trimethylantimony D i f l u o r i d e 5.8 : Infrared Absorption Spectrum of The Mixture of 158 Trimethylantimony Hexafluorosilicate and Trimethylantimony D i f l u o r i d e 5.10 : Infrared Absorption Spectrum of The Trimethylantimony 163 Derivative of B ^ C l - ^ LIST OF FIGURES v i i i FIGURE PAGE 2.1 : Infrared Absorption Spectrum of Triphenyltin 27 Nitrate 2.2 : Infrared Absorption Spectrum of Triphenyltin 39 Perchlorate 3.1a : Infrared Absorption Spectra of Bis(trimethyltin) 47 Sulphate-Methanol Diadduct and B i s ( t r i m e t h y l t i n ) Sulphate 3.1b : Infrared Absorption Spectra of B i s ( t r i m e t h y l t i n ) 48 • Sulphate-Methanol Diadduct and Bis(trimethyltin) .Sulphate 3.1c : Proposed Structure for Bis(trimethyltin) Sulphate- 51 Methanol Diadduct 3.Id : Proposed Structure for B i s ( t r i m e t h y l t i n ) Sulphate 53 4.2 : Infrared Absorption Spectrum of Dimethyltin. 66 Carbonate 4.3 : Infrared Absorption Spectrum of Dimethyltin Chromate 71 4.4a : Infrared Absorption Spectrum of Dimethyltin 77 Sulphate-Methanol Adduct 4.4b : Infrared Absorption Spectrum of Dimethyltin 78 Sulphate-Methanol Adduct 4.4c : Infrared Absorption Spectrum of Dimethyltin Sulphate- 82 Pyridine Monoadduct 4.4d : Infrared Absorption Spectrum of Dimethyltin Sulphate- 88 DMSO Monoadduct 4.5a : Infrared Absorption Spectrum of The Mixture of 99 Dimethyltin Bis(tetrafluoroborate) and Dimethyltin D i f l u o r i d e 4.5b : Infrared Absorption Spectrum of The Mixture of 100 Dimethyltin Bis(tetrafluoroborate) and Dimethyltin D i f l u o r i d e FIGURE ix PAGE 4.7a : Infrared Absorption Spectrum of The Mixture of 109 Bis(hexafluoroarsenate) and Dimethyltin D i f l u o r i d e 4.7b : Infrared Absorption Spectrum of Dimethyltin 111 Bis(hexafluoroantimonate) 4.8 : Infrared Absorption Spectrum of The Dimethyltin 115 Derivative of ^±2^12 5.2 : Infrared Absorption Spectrum of Trimethylantimony 123 D i n i t r a t e 5.3 : Infrared Absorption Spectrum of Trimethylantimony 128 Carbonate 5.4 : Infrared Absorption Spectrum of Trimethylantimony 132 Sulphate 5.5 : Infrared Absorption Spectrum of Trimethylantimony 138 Chromate 5.6 : Infrared Absorption Spectrum of Trimethylantimony 146 Oxalate 5.7 : Infrared Absorption Spectrum of The Mixture of 152 Trimethylantimony Bis(tetrafluoroborate) and Trimethylantimony D i f l u o r i d e 5.8 : Infrared Absorption Spectrum of The Mixture of 157 Trimethylantimony Hexafluorosilicate and Trimethylantimony D i f l u o r i d e 5.9 : Infrared Absorption Spectrum of Trimethylantimony 160 Bis (hexafluoroantimonate) 5.10 : Infrared Absorption Spectrum of The Trimethylanti- 162 mony Derivative of B-j^Cl-^^~ X ACKNOWLEDGMENTS The author i s greatly indebted to Professor H. C. Clark for his thoughtful and stimulating guidance, without which th i s study would not have been possible. The author i s gra t e f u l to many other members of the Chemistry Department who have assisted him i n many ways, i n p a r t i c u l a r to Dr. K. B. Harvey for the use of his spectroscopy laboratory, and to Dr. J . D. Cotton for many valuable discussions. The author also wishes to thank Dr. E. L. Muetterties, of the Central Research Department of E. I. du Pont de Nemours & Co., Wilmington, Delaware, for the g i f t of a chemical and for providing analyses of two compounds. The award of a 1964/65 Graduate Fellowship by the University of B r i t i s h Columbia i s g r a t e f u l l y acknowledged. F i n a l l y , the author wishes to thank his wife for her patient understanding during the years of t h i s study. CHAPTER 1 1 INTRODUCTION Tin (symbol Sn) i s an element of atomic number 50 and occurs i n group IVb and the 5th period of the periodic table. Organotin compounds are substances i n which at least one t i n - carbon bond i s present. The f i r s t organotin compound was described i n 1852 by Lbwig, and many s i g n i f i c a n t contributions were made i n t h i s f i e l d during the next few decades. Although research i n organometallic chemistry s h i f t e d then to other areas, i n t e r e s t i n organotin chemistry was revived in about 1940, and at the present time a vast amount of l i t e r a t u r e exists on the subject. Two excellent reviews (1, 2a) of organotin chemistry appeared i n 1960 covering almost a l l the available l i t e r a t u r e on the subject to that time.* Up to 1960, research i n organotin chemistry was largely confined to preparative reactions. However since 1960, s i g n i f i c a n t contributions have been made towards the study of stereochemistry of organotin compounds. The aim of this discussion i s to review b r i e f l y the stereochemistry of organotin(IV) acid derivatives. A neutral t i n atom has fourteen electrons outside the krypton core, i t s configuration being fjCr] (4d) 1 0 (5s) 2 (5p) 2 . The 3 ground state for the t i n atom i s a P state, derived from the 2 2 s^p configuration. The f i r s t excited state of the t i n atom i s ^"After the completion of t h i s text, a b r i e f review on "Coordination i n Organotin Chemistry" by R. C. P o l l e r , has appeared i n J. Organometal. Chem., 3,321-329(1965). a state a r i s i n g from a sp^ configuration. The known oxidation states of t i n , i . e . Sn(II) and Sn(IV), are derived from the ground state and the f i r s t excited state of the t i n atom respectively. Organotin compounds of both oxidation states are known, however, the Sn(IV) i s more commonly encountered. The t e t r a a l k y l - and tetraary1-tins, R4Sn, are t y p i c a l l y covalent, monomeric, t e t r a - hedral compounds. The lower molecular weight compounds are soluble in common organic solvents but the higher molecular weight sub- stances are soluble only i n more non-polar solvents such as benzene, pyridine or chloroform. If one (or more) R groups i n an R 4Sn compound i s replaced by a halogen or any other anionic group, . then the r e s u l t i n g compound may be considered an organotin(IV) acid derivative e.g. R3SnX, R 2SnX 2 etc. The organotin halides with the exception of f l u o r i d e s are either low-melting s o l i d s or l i q u i d s at room temperature. They are soluble in organic solvents and the lower members in a series are also soluble i n polar solvents such as water and alcohol, and are v o l a t i l e . In general, a l l the organotin f l u o r i d e s are non- v o l a t i l e s o l i d s which are soluble only i n water and usually melt or decompose above 200°. Organotin chlorides, bromides a,nd iodides are usually con- sidered to be covalent compounds derived from the sp^ configuration of the t i n atom. The electron d i f f r a c t i o n studies (3) of (CH 3) 3SnX, (CH 3) 2SnX 2, and (CH 3)SnX 3 (where X = CI, Br or I) have shown that, in the gaseous state, these compounds have a t e t r a - hedral configuration. Raman and infrared studies of a l k y l and a r y l t i n halides (CI, Br, I) (4-8) have demonstrated that the tetrahedral configuration of the t i n atom i s s t i l l maintained i n the l i q u i d and s o l i d state, as well as i n solution i n inert non- polar solvents. In s o l i d t r i m e t h y l t i n chloride and bromide however, halogen bridging has been invoked (7). The dipole moment studies on several organotin chlorides also indicate a tetrahedral configuration of the t i n atom i n these compounds (1). The electron d i f f r a c t i o n r e s u l t s (3) showed that the Sn-X (X=C1, Br, I) bond length increases i n the series SnX^, (CH 3)SnX3 3(CH3)2SnX 2 and (CH 3) 3SnX. A decrease i n the Sn-X bond length with increasing X substitution may be considered to i n d i - cate an increase in the Sn-X bond order. The electron density on the t i n atom may be anticipated to decrease with an increase in the number of electronegative substituents, and th i s may resu l t i n the back donation of the p electrons to the empty 5d t i n o r b i t a l s . From a recent infrared study of methyltin chlorides, a d i s t i n c t f a l l i n the Sn-Cl stretching force constants through the series SnCl 4, (CH 3)SnCl 3, ( C H 3 ) 2 S n C l 2 and (CH 3) 3SnCl has been reported (4). This sequence follows the increasing inductive e f f e c t of the methyl groups f a c i l i t a t i n g the i o n i z a t i o n of the Sn-Cl bond. However, Lorberth and Noth (9) have recently reported on the basis of dipole moment determinations of R4-nSnCl n (where R = CH3, C2H5, C 4 H 9 , or C0H5) an increase i n p o l a r i t y of the Sn-Cl bond with increasing value of n. The authors suggest that the fact that the Sn-Cl bond becomes more polar by increasing the number of chlorine atoms i n spite of a decrease i n Sn-Cl bond distance, apparently shows that dTT-p"jT"bonding i s only weak and cannot compensate for the electron abstraction caused by the negative inductive e f f e c t of the chlorine atoms. Thus the net e f f e c t on the Sn-Cl bond seems to be an increase i n p o l a r i t y of about 10 percent i n going from trimethyltin chloride to methyltin chloride. However, the authors recognize that, considering the assumptions involved i n the calculations of these r e s u l t s , the va r i a t i o n i n the p o l a r i t y of the Sn-Cl bond i s not s i g n i f i c a n t and that other interpretations for th i s v a r i a t i o n are possible, e.g. change i n atomic p o l a r i z a t i o n , and change i n the Sn-R bond moment due to a change i n the Sn-C•distance. There are other divergent views as well on the existence of dTT -PTT bonding i n organotin halides. From the measurements of nuclear quadrupole coupling constants of ^ C l i n mono- and di- n - b u t y l t i n chlorides and mono- and diphenyltin chlorides, i t has been suggested (10) that the IT bond character of the Sn-Cl bond increases with increase i n substitution of the CI atom by an organic group. The u l t r a v i o l e t (11) and infrared (8) spectro- scopic studies of the homologues (CgH^) nSnCl 4_ n have been reported to indicate that the S n - C a r ( a r = aryl) bond has some double bond character. The authors consider that the negative inductive e f f e c t of the chlorine atom re s u l t s i n the donation of the TT electrons from the phenyl groups to the empty 5d o r b i t a l s of the t i n atom. The bonding i n organotin halides has also been recently studied by means of proton n.m.r. and Mossbauer spectra. From a study of the v a r i a t i o n of the 1 1 7Sn-CH 3 and 1 1 9Sn-CH 3 coupling . constants i n methyltin chlorides, Holmes and Kaesz (12) have estimated that the s o r b i t a l p a r t i c i p a t i o n by the t i n atom i n the formation of the Sn-C bond decreases with the increase i n 5 the number of methyl groups. By assuming 25 percent s-character in the t i n o r b i t a l s i n (CH 3) 4Sn, the s- character in the t i n o r b i t a l s involved i n bonding with the methyl groups has been estimated to be 32 percent in dimethyltin dichloride and 48 per- cent i n methyltin t r i c h l o r i d e . From the Mossbauer spectral studies of organotin compounds, Herber and Stoeckler (13) have concluded that the difference i n percentage io n i c character between a 3 2 t i n - sp hybridized carbon atom, a t i n - sp hybridized atom and a t i n - halogen atom bond i n the t r i a r y l or t r i a l k y l cannot be greater than <~^5 percent. From sim i l a r M5ssbauer studies, Hayes (14) has reported that in organotin halides, the r e l a t i v e degrees of i o n i c i t y of the f l u o r i d e , chloride and bromide substituents are 1.0: 0.65: 0.65: (±0.05). Conductivity measurements on various organotin halides (CI, Br, I) have conclusively shown that these compounds are not true e l e c t r o l y t e s i n the pure state (1, 2a). However, when d i s - solved i n water, pyridine, or acetone, these compounds are r e l a t i v e l y good conductors; but i n benzene, ethyl ether, n i t r o - benzene or nitromethane they are poor conductors (1, 2a). The e l e c t r o l y t i c behaviour of a l k y l t i n halides i n hydrolytic solvents or i n Lewis bases i s due to the formation of addition compounds. Aqueous solutions of organotin halides are s l i g h t l y a c i d i c due to hydrolysis (1, 2a). The equilibrium between, say, t r i m e t h y l t i n chloride and pyridine, alcohol, or water has been represented (2a) as shown below: (CH 3) 3SnCl + C 5H 5N ^ ( C H 3 ) 3 S n .N C 5 H 5 + CI" (CH 3) 3SnCl + ROH > (CH3)3Sn.0HR+ + C l " (CH 3) 3SnCl + H20 > (CH 3) 3Sn.0H 2 + + C l ~ (CH 3) 3SnOH^ + H 20 > (CH 3) 3SnOH + H 30 + 6 Rochow and Seyferth (15), and Rochow, Seyferth, and Smith (16), have reported a complete d i s s o c i a t i o n of dimethyltin dichloride in water, according to the following equations: 2+ " - (CH 3) 2SnCl 2 + n H 2 0 ^ (CH3) 2Sn (HgO) + 2C1 2+ ' , ( C H 3 ) 2 S n ( H 2 0 ) n » (CH 3) 2Sn(H 2 0) n_ 1OH + + H 3 0 + These authors have further stated that i n water, amines, or amides, the solvated dimethyltin cation probably remains tetrahedral. Although there i s clear evidence for the i o n i z a t i o n of a l k y l t i n halides (or other acid derivatives) i n the presence of a suitable Lewis base or where the solvent i s also a donor, recent accumulated evidence indicates that the tetrahedral configuration of the t i n atom i s no longer retained i n the solvated R 3Sn + or R2Sn+"J" cat ions. The only experimental evidence for the t e t r a - hedral configuration of the solvated R 3Sn + or R 2 S n 2 + c a t i o n s i s the reported (17, 18) p a r t i a l resolution of (CH 3)(C2H5)(CgHg)SnI from aqueous solution by conversion into the camphor sulphonate, followed by reconversion into iodide. However, attempts to repeat th i s experiment i n the intervening years have not been successful ( 1 9 , 2 0 , 2 1 ) . The 1 1 7Sn-CH 3 and 1 1 9Sn-CH 3 coupling constant data, obtained from the proton n.m.r. spectra of t r i a l k y l t i n chlorides i n water (12) or Lewis bases such as tetramethylene sulphoxide, N,N- dimethylacetamide or N,N-dimethylformamide ( 2 2 ) , indicate a t r i g o n a l bipyramidal configuration around the t i n atom, and a planar t r i a l k y l t i n group. As w i l l be discussed l a t e r , f i v e coordination of the t i n atom has been shown in many other t r i - a l k y l t i n derivatives. 7 S i m i l a r l y , from recent Raman and proton n.m.r. studies of aqueous solutions of dimethyltin perchlorate and n i t r a t e , McGrady and Tobias (21) have concluded that aqueous solutions of d i - methyltin (IV) compounds contain an aquocation with a linear C-Sn-C skeleton and that, i n a l l p r o b a b i l i t y , four water molecules are coordinated to the cation i n the equatorial plane by highly polar bonds. Organotin halides form complexes with halogen ions e.g. 2- R 2SnX 2 + 2X > R 2SnX 4 It has been reported (23) that the s t a b i l i t y of six coordinate anions of t i n f a l l s as the number of electronegative halogen sub- 2- 2- 2- stituents decreases, giving the series SnClg > R S n C l 5 / R 2SnCl 4 y 2- R 3 S n C l 3 . In addition, organotin chlorides, bromides and iodides react with cer t a i n electron-pair donors to form addition com- pounds. The majority of the adducts are of the type R nSnX 4_ n.2L (where R = organic group, X = CI, Br or I, and L = an electron- pair donor)(1). The range and s t a b i l i t y of the addition com- pounds formed appear to decrease as the number of organic groups increases and, for tetraorganotins, there i s no evidence of Lewis acid behaviour. No addition compound of organotin f l u o r i d e s has been reported either. Although addition compounds of organotin halides have been known for a long time, l i t t l e information was available u n t i l very recently on their stereochemistry and structure. E a r l i e r workers (24) favoured an i o n i c formulation for compounds such as ( C H 3 ) 3 S n C l.Py involving a tetrahedral cation i . e . ( C H 3 ) 3 S n P y + C T . However, the c r y s t a l structure determination of 8 this compound, by Beattie, McQuillan, and Hulme (25,26) has shown that (CH^gSnCLPy i s a molecular compound of t r i g o n a l bipyramidal configuration i n which the t r i m e t h y l t i n group i s planar and the chlorine atom and the pyridine molecule occupy the a x i a l posi- tion. Later Clark and O'Brien (27) found that such tri m e t h y l t i n derivatives as perchlorate and n i t r a t e form stable diammonia adducts which contain the f i v e coordinate cation (CHg)^Sn(NHg) 2 in the s o l i d state, as shown by their infrared studies. Clark, O'Brien, and Pickard (28) confirmed the e a r l i e r reports (24) that trimethyltinbromide and chloride form unstable diadducts with ammonia or pyridine which read i l y lose one mole of the base to give stable monoadducts. The i n f r a r e d studies by these authors show that the diadducts can be formulated as (CH3)gSnL2JK (where L = Lewis base, X = halogen). Matwiyoff and Drago (22) have reported the formation of 1:1 addition compounds between t r i a l k y l t i n chlorides and Lewis bases such as tetramethylene sulphoxide, N,N-dimethylacetamide, or N,N-dimethyIformamide. The in f r a r e d spectroscopic and tin-hydrogen coupling constant data (22) of these compounds again indicate t r i g o n a l bipyramidal structures containing planar t r i m e t h y l t i n groups. The existence of a f i v e coordinate t i n atom has also been proposed (29) i n com- pounds of the type R^SnR, where i s an unsaturated organic r a d i c a l containing two nitrogen atoms i n the 1,3 position (e.g. imidazole). Addition compounds of t r i p h e n y l t i n chloride and bromide with nitrogen bases have been described i n the l i t e r a t u r e (1). However, Kupchik and Lanigan (30) recently reported the products of reaction between t r i p h e n y l t i n bromide and amonia to be 9 b i s ( t r i p h e n y l t i n ) oxide and ammonium bromide. These workers con- cluded that the reaction proceeded via an intermediate containing a Sn-N bond which was of low hydrolytic s t a b i l i t y . Unfortunately no other work appears to have been reported on the nitrogen base adducts of t r i p h e n y l t i n halides. D i a l k y l - and diphenyltin dihalides (CI, Br, I) form 1:1 addition compounds with chelate ligands such as 1,10 phenanthroline and 2,2 b i p y r i d y l . With pyridine or i t s hydro- chloride, 1:2 addition compounds are formed. Similar adducts are also formed with methyltin t r i h a l i d e s and t i n tetrahalides. In contrast, t r i a l k y l t i n halides do not form addition compounds with chelate ligands. These addition compounds are apparently six coordinated. The compound ( C H 3 ) 2 S n C l 2.2Py i s a weak e l e c t r o l y t e in a c e t o n i t r i l e (31); therefore an i o n i c formulation for such addition compounds i s most unlike l y . From a survey of the known stereochemistry of MX4.2L (where M = IVb group element, X = halogen) adducts, Beattie (32) has suggested that small ligands tend to give c i s adducts, while ligands which are s t e r i c a l l y hindered tend to give trans adducts. Beattie has further pointed out that by considering the p o s s i b i l i t y of d/f -pTT bonding i n the Sn-X bond, the c i s adduct i s favoured assuming thatTT bonding from X to Sn i s more important thanTT bonding involving L. A strongly coordinating ligand could also have the e f f e c t of reducing d"IT - pTT bonding between the halogen and the t i n atoms,.in which case one factor favouring a c i s configuration i s l o s t . The i n f r a r e d spectroscopic studies of (CHg)gSnC^.2Py and other dimethyltin dic h l o r i d e and methyltin t r i c h l o r i d e addition compounds indicate (33) that these compounds are six coordinate, with trans methyl 10 groups i n the case of coordinated (CHg^SnClg. So far t h i s discussion has been largely concerned with the stereochemistry of organotin(IV) chlorides, bromides and iodides and their addition compounds. As stated e a r l i e r i n contrast to these halides, the organotin(IV) fluorides are high-melting, non-volatile s o l i d s and are insoluble i n organic solvents. On the basis of these differences i n physical properties, the f l u o r i d e s have been considered to be i o n i c compounds. Other organotin acid derivatives, l i k e n i t r a t e s and sulphates, have also been included in t h i s category. Coates(2a) has stated,"Compounds i n which the RgSn or R2Sn group i s combined with a highly electronegative group, such as f l u o r i d e , n i t r a t e , sulphate, or sulphonate, have quite d i f f e r e n t physical properties. Their high melting points and low v o l a t i l i t y indicate a s a l t - l i k e c o n s t i t u t i o n . " Rochow, Seyferth, and Smith (16) reported the preparation of a large number of dimethyltin(IV) acid derivatives, and, from a comparison of t h e i r s o l u b i l i t i e s with those of corresponding s a l t s of bivalent t i n and lead, these authors reported, "In 2 2 dimethyltin dichloride i t i s probable that the 5s and 5p elec- trons are involved i n sp hybrid o r b i t a l s leading to a symmetrical covalent molecule, but i n the dimethyltin cation, the methyl groups probably occupy the 5s o r b i t a l s above, and the other electrons are given up to the anion. In water and amines or amides, the solvated cation probably remains tetrahedral, but we believe that i n anhydrous s a l t s the (CHg^Sn*"^ ion resembles :Sn + + and should also resemble :Pb + + and :T1 + i n structure." The authors further commented that i f the supposition of 11 ion i z a t i o n of the 5p electrons i s correct, the anhydrous (CH 3) 2Sn ion should bei l i n e a r . Afterwards Freeman (34) reported di-n- b u t y l t i n acetate to be an ioni c compound on the basis of the low carbonyl frequency i n the infrared absorption spectrum. Later, a systematic infrared spectroscopic study was made by Okawara, Webster, and Rochow (35) who proposed an ionic structure for d i - and tri m e t h y l t i n carboxylates. The infrared spectra of these compounds showed only one Sn-C stretching frequency i n each case and t h i s was interpreted i n terms of the presence of discrete planar (CHg^Sri1" and linear (CHg^Sn 2* cations. Furthermore, the spectra due to the carboxylate group i n each compound were .similar to the spectrum of the corresponding free carboxylate anion. This fact was considered as evidence for the existence of free carboxylate anions i n these compounds. However, as was pointed out by Beattie and Gilson (36), the e f f e c t i v e symmetry of an ioni c and of a bridging carboxylate group i s the same, and the inf r a r e d spectroscopic r e s u l t s of dimethyltin carboxylates are also consistent with a coordinated structure involving bridging or chelating carboxylate groups and an octahedral configuration around the t i n atom with a linear dimethyltin group. Si m i l a r l y , the infrared spectrum of trimethyl- t i n acetate can be explained i n terms of planar t r i m e t h y l t i n groups linked by bridging acetate groups i n which case the t i n atom will.have a tr i g o n a l bipyramidal configuration. Subsequently, Janssen, Luijten, and van der Kerk (37) showed by detailed i n f r a - red studies that t r i a l k y l t i n acylates ex i s t as lin e a r polymers (in which each t i n atom has a t r i g o n a l bipyramidal configuration) in the s o l i d and molten states and i n concentrated solutions i n 12 non-polar solvents, but are monomeric tetrahedral compounds in d i l u t e solutions. These conclusions were confirmed l a t e r by Okawara and Ohara (38). Okawara, Webster, and Rochow (35) also proposed an ionic structure for t r i m e t h y l t i n f l u o r i d e on the basis of the appear- ance of only one Sn-C stretching frequency in the infrared spectrum of t h i s compound. However, the c r y s t a l structure deter- mination of t h i s compound by Clark, O'Brien, and Trotter (39) has c l e a r l y shown that t r i m e t h y l t i n f l u o r i d e consists of t r i m e t h y l t i n groups and f l u o r i n e atoms arranged a l t e r n a t i v e l y i n a chain-like manner. The electron density d i s t r i b u t i o n can only be interpre- ted i n terms of f i v e coordinate t i n atoms and non-linear . unsymmetrical Sn-F—Sn bridges consistent with a non-ionic type of compound. A s i m i l a r polymeric structure involving f i v e coordinate t i n atoms and Sn-O-Sn bridges has been reported for t r i m e t h y l t i n hydroxide from infrared evidence (40,41) as well as a preliminary study on c r y s t a l structure determination (42). In a systematic study of t r i m e t h y l t i n derivatives of strong acids such as t r i m e t h y l t i n n i t r a t e , perchlorate, t e t r a - fluoroborate, hexafluoroarsenate and hexafluoroantimonate, Clark and O'Brien (27,43) and Clark, O'Brien, and Pickard (28) found no evidence for the existence of (CH 3)gSn + cation i n the s o l i d state. Their r e s u l t s indicate a polymeric structure, (involving bridging anionic groups and planar t r i m e t h y l t i n groups) for these compounds in the s o l i d state. Similar r e s u l t s have been reported by other workers for t r i m e t h y l t i n perchlorate (44) , n i t r a t e (45), and t e t r a - fluoroborate (46). Most of the s t r u c t u r a l evidence for these compounds has been obtained by i n f r a r e d spectroscopic r e s u l t s 13 whereby "coordination" by, say, perchlorate to the trimethyltin group has been deduced from the observation that the perchlorate group has C2v (or lower) symmetry in accord with behaviour as a bidentate or bridging group. Such a lowering of symmetry in the s o l i d state could be attributed to coordination. A l t e r n a t i v e l y , c r y s t a l f i e l d e f f e c t s might produce such spectroscopic e f f e c t s . However, the following discussion shows that the reported spectroscopic e f f e c t s are mainly due to coordination. In discussing the symmetry of the ligand from the infrared spectrum obtained i n the c r y s t a l l i n e state, a knowledge of the s i t e group or factor group analysis i s desirable. However, a survey of the infrared spectra of a variety of i o n i c as well as coordination compounds in which the corresponding io n i c groups act as coordinating ligands shows that, i n general, the e f f e c t s of coordination upon the v i b r a t i o n a l modes of the ligands are more pronounced than the e f f e c t s due to c r y s t a l f i e l d . Infrared spectra of i o n i c and coordination compounds have been reviewed by Nakamoto (47) and the s p e c i f i c examples w i l l be discussed l a t e r i n the text. If the symmetry of the anion i s lowered upon co- ordination, the i n f r a r e d inactive vibrations of the free ion become i n f r a r e d active and appear with moderate i n t e n s i t y and the degenerate vibrations are s p l i t . Moreover, a l l the funda- mentals are more or less s h i f t e d according to their modes of v i b r a t i o n . The i n t e n s i t y of the new permitted bands, the magnitude of the s p l i t t i n g , and the frequency s h i f t s are more pronounced i f the anionic group i s involved i n coordination. Cry s t a l f i e l d e f f e c t s cause the forbidden i n f r a r e d active modes to appear only weakly and the s p l i t t i n g s of the degenerate modes 14 due to t h i s e f f e c t are i n general not very well resolved and are comparatively smaller i n magnitude. Some suggestions to explain the f i v e coordination of the t i n atom i n t r i a l k y l t i n derivatives have been put forward recen- t l y . Janssen, Luij t e n , and van der Kerk (48) have suggested that in f i v e coordinate t i n compounds, the p r i n c i p a l i n t e r a c t i o n involves the donation of d electrons from the f i l l e d 4d o r b i t a l s of t i n into appropriate ligand o r b i t a l s , although some donation of ligand electrons into vacant 5d t i n o r b i t a l s may also be i n - volved. Matwiyoff and Drago (22) consider the use of t i n hybrid o r b i t a l s ( p z •+ d z2) i n the bonding of the a x i a l groups to planar R3Sn. As discussed e a r l i e r , for compounds of the type R 2SnX 2, the p o s s i b i l i t y of t i n achieving a coordination of six through adduct formation arises. Six coordination of the t i n atom i s also indicated (49,50) i n compounds of the type R2SnL 2 (where R = methyl or phenyl and L = chelate ligand such as acetylacetonate 8-quinolinolate etc.).: ] A large number of such compounds have been reported recently. However, no systematic stereochemical studies of R2SnX2 compounds i n which X i s an anionic group derived from an inorganic acid (other than CI, Br, or I) have been made, except recently reported studies on dimethyltin d i n i t r a t e (51) and d i a l k y l hydroxide n i t r a t e s (45). Dimethyltin d i n i t r a t e i s a deliquescent c r y s t a l l i n e s o l i d , soluble i n water and many other polar solvents butvonly s l i g h t l y soluble i n chloroform. The i n f r red spectrum of t h i s compound in the s o l i d state indicates coor- dination by the n i t r a t e group and a tetrahedral configuration around the t i n atom. Its u l t r a v i o l e t absorption spectrum i n non- 15 aqueous solvents i s also consistent with the presence of the n i t r a t o groups. D i a l k y l t i n hydroxide n i t r a t e s are high melting c r y s t a l l i n e substances which are soluble i n water and methanol, but insoluble i n non-polar solvents. The infrared spectra of these compounds also indicate a tetrahedral structure. The preceding discussion thus shows that i n t r i a l k y l t i n compounds the t i n atom tends to increase i t s coordination from four to f i v e and that there i s no evidence for the existence of t r i a l k y l t i n cations i n the s o l i d state. However, no information e x i s t s on analogous t r i a r y l t i n compounds. Exist i n g evidence also indicates coordination of either four or six for the t i n atom i n d i a l k y l - and d i a r y l t i n compounds, though very l i t t l e i s known about the nature of I^SnXg compounds in which X i s a strongly electronegative anion. In view of these conclusions, several questions can be raised: 1) Are the organotin cations such as RgSn"1" and 2+ RgSn unstable, and i f so what i s the nature of i n t e r a c t i o n between the organotin group and the anionic group? 2) Is there any s i m i l a r i t y between analogous a l k y l t i n and a r y l t i n derivatives, since by analogy with the triphenylcarbonium cation, the t r i p h e n y l t i n cation may well possess greater s t a b i l i t y than t r i a l k y l t i n cations? In an attempt to answer these questions a wide variety of trimethyl-, t riphenyl-, and dimethyltin derivatives of acids i n - cluding derivatives of very strong acids and t r a n s i t i o n metal 16 oxyanions were synthesized and examined by infrared spectrosopy in the s o l i d state. While this work was in progress, a report (52) describing an io n i c c o n s t i t u t i o n for trimethylantimony d i - 2 + n i t r a t e appeared. The cations (Crl3)gSn + and (CHg^Sb are i s o - el e c t r o n i c . In view of the accumulated evidence (discussed e a r l i e r ) , as well as evidence based on the findings of this i n - vestigation for the non-existence of tri m e t h y l t i n cation i n the s o l i d state, the reported io n i c structure of trimethylantimony d i n i t r a t e can only be considered anomalous. Therefore a system- a t i c i n f r a r e d study of trimethylantimony(V) acid derivatives was also made. Antimony (symbol Sb, atomic number 51) occurs i n group Vb and the 5th period of the periodic table. The el e c t r o n i c config- uration of a neutral antimony atom i s [kr] 4d-*-(->5s2p3> R2SbX2 (where R = a l k y l or a r y l group, X= halogen or any other anionic group) are derived from the Sb(V) oxidation state of the antimony atom. In addition to dihalides, the derivatives containing (NOg)2> (CNS)g,SO4 etc. r • . have been described i n the l i t e r a t u r e (2b, 53). However, very l i t t l e i s known about the nature of these compounds except the established stereochemistry of dihalides (CI, Br,I). From X-ray crystallography, Wells (54) demonstrated that trimethylantimony dic h l o r i d e , dibromide and diiodide are isomor- phous and have a t r i g o n a l bipyramidal structure i n which three methyl groups are arranged i n the plane of the metal atom and the two halogen atoms l i e at the apices. The Sb-X bond lengths are greater than th e i r appropriate covalent r a d i i sums. This fact led Wells to suggest that these compounds could be intermediate between the molecular and io n i c forms shown as follows. CH. CH. X ;Sb CH, X CH, CH. X" 2+ Sb- CHC x- Jensen (55) assigned a t r i g o n a l bipyramidal structure to t r i - phenylantimony dichloride on the basis of a dipole moment determination. This has been confirmed recently by an X-ray structure determination (56). "Apart from dihalides, no i n f o r - mation exists on the stereochemistry of other I_3SbX2 compounds, except a recent report on d i n i t r a t e and sulphate by Long, Doak, and Freedman (52). From infrared spectroscopic studies, these authors concluded that trimethylantimony d i n i t r a t e i s an i o n i c s o l i d and that trialkylantimony sulphates are covalent compounds. Some solution studies on dihalides have also been made. However, there are divergent views on the species present i n solution. Conductivity measurements of both trimethyl- and triphertylantimony dichlorides and dibromides i n a c e t o n i t r i l e solution have shown that these compounds are e f f e c t i v e l y non- e l e c t r o l y t e s i n t h i s solvent but the diiodides show a conductance d r i f t due to the formation of t r i i o d i d e ion (57,58). Coates (2b) has stated that the dihalides are covalently constituted, but when dissolved i n water and other polar solvents they appear to ionize as shown below: R 3SbX 2 > R 3SbX + + X" Sidgwick (59a) has stated that RgSbX2 compounds appear to ionize to give the cations (R3Sb)2:l"; or more probably R3SbX+. Trimethyl- 18 antimony dihalides form highly conducting solutions i n water. Lowry and Simons (60) have attributed the high conductance values i n water due to the presence of io n i c hydroxy halides. From a detailed study of hydrolysis of trialkylantimony dibromides, Nylen (61) concluded that these compounds are hydrolysed according to the equations: R 3SbBr 2 + 2 H 20 > RgSbBrOH + H3O + Br" RrjSbBrOH » R3SbOH+ + Br" RgSbOH* + H20 > R3SbO + Ĥ O However, as pointed out by Long, Doak, and Freedman (52), a l l the hydrolysis equations must be r e v e r s i b l e , since trialkylantimony dihalides can be recovered quantitatively by r e c r y s t a l l i z a t i o n from water. These authors have also reported that trimethylantimony dihalides can be converted to dihydroxide by passing an aqueous solution of the dihalide through a column containing an anionic exchange r e s i n . As mentioned e a r l i e r , the present investigation i s largely confined to i n f r a r e d studies i n the s o l i d state and in the f o l - lowing chapters, these r e s u l t s are discussed. 19 CHAPTER 2 TRIPHENYLTIN(IV) DERIVATIVES In contrast to t r i m e t h y l t i n derivatives of the type (CHg)gSnX (where X = a highly electronegative group such as C I O 4 , NO3, BF^, AsFg, or SbFg), no systematic study of similar t r i p h e n y l t i n derivatives has been made. In the present i n v e s t i - gation therefore, two such t r i p h e n y l t i n derivatives, t r i p h e n y l t i n n i t r a t e and perchlorate were synthesized. A comparative study of the i r i n frared spectra with those of analogous t r i m e t h y l t i n derivatives was made in an attempt to elucidate their stereo- chemistry and to determine the e f f e c t of phenyl groups on the in t e r a c t i o n between R 3Sn and X. While t h i s work was i n progress a b r i e f report (62) appeared describing the preparation and and apparent i n s t a b i l i t y of t r i p h e n y l t i n n i t r a t e . 2.1 Triphenyltin Nitrate (CgH^SnNOg The i n f r a r e d spectra of n i t r a t e s and n i t r a t o complexes have been widely studied and the subject has recently been reviewed (63,64). Recent research has indicated that compounds of elements (M) and the n i t r a t e group can be divided into two classes according to whether the M-NO3 bond i s predominantly i o n i c or covalent. The term 'nitrate' i s usually applied to a compound i n which the M-NOg bond i s i o n i c , that i s , a compound containing the n i t r a t e ion, and the term 'nitrato-compound' i s generally used for com- pounds i n which the NO3 group i s covalently bonded through one or more of i t s oxygen atoms. A free n i t r a t e ion belongs to the point group Dg^ and has four fundamental modes of v i b r a t i o n . Two of these are each doubly 20 degenerate and the other two are nondegenerate. The fundamental v i b r a t i o n a l frequencies of the NO3" ion are well established (65a) and are l i s t e d i n Table 2.1a. TABLE 2.1a Vib r a t i o n a l Frequencies of NO3- Ion (Poinl; Group D 3 t l) A c t i v i t y (R) (I.R) (R,I.R) (R,I.R) (R = Raman active; I.R = Infrared active) The a l k a l i metal n i t r a t e s , and certa i n of the alk a l i n e earth metal n i t r a t e s , give infrared spectra which resemble closely the predicted spectrum of a free n i t r a t e ion (66-68). On the other hand, many anhydrous metal n i t r a t e s , e s p e c i a l l y the t r a n s i - tion metal n i t r a t e s , are largely covalent i n character and their i n f r a r e d spectra resemble those of non-metal n i t r a t e s (64). In organic n i t r a t e s such as methyl n i t r a t e the bonding i s e s s e n t i a l l y covalent. In metal-nitrato compounds the bond character i s ex- pected to vary from largely i o n i c to near covalent. Addison and Logan (64) have pointed out that metal-nitrato compounds and the i r derivatives are much less reactive as compared to the non- metal n i t r a t e s such as a l k y l n i t r a t e s and f l u o r i n e n i t r a t e which are highly reactive. These authors consider that some form of Vib r a t i o n a l mode v 1(A' 1) V A2> v 3 (E) v 4(^) Assignment NO symmetric stretch Out-of-plane bend Degenerate N0 2 stretch Degenerate N0 2 bend Frequency (cm-1) 1050 831 1390 720 .21 back-donation of electrons from the metal atom to the empty o r b i - t a l s of the n i t r a t e group may make a contribution to the greater s t a b i l i t y of metal-nitrato compounds. Covalent or p a r t i a l covalent bonding between the metal atom and n i t r a t e group can involve one or two of the oxygen atoms of the n i t r a t e group thereby reducing the symmetry of the n i t r a t e group to either C s or C 2 V as shown below: M— o — N: .0 G M 0 c 2 v s y m m e t r y (a) Unidentate n i t r a t o group ^ N —0 C 2 v symmetry C„ symmetry M 0 — N 4 .0 I M C 2 y symmetry (b) Bidentate or bridging n i t r a t o group Upon lowering the symmetry of the NO3 group from D3J- to either C 2 v o r Cs> tbe degeneracy of degenerate modes of the free NO3 ion i s completely removed and, as such, the n i t r a t o group possessing either C 2 v or C s symmetry w i l l give r i s e to six nondegenerate fundamental vibrations, a l l of which are both Raman and in f r a r e d active. The c o r r e l a t i o n between the v i b r a t i o n a l modes of D 3 n , C 2 v and C s point groups i s shown i n Table 2 . 1 b . It may be noted that, i n a unidentate n i t r a t o group, two of the three N-0 bonds w i l l have double bond character while the remaining N-0 bond w i l l have single bond character. On the other hand, i n a bidentate 22 TABLE 2.1b Correlation Table for 0 3 ^ , D 3 , C2\, and Cs Point Groups Vibra t i o n a l Modes Point ^1 v 2 ^3 v 4 Group D3h A ' l ( R ) A" 2(I.R) E'(R,I.R) E(R,I.R) D3 A X(R) A 2 ( I . R ) E(R,I.R) E(R,I.R) C 2 v A 1(R,I.R) B^R.LR) A^(R, I .R) Aj^R^.R) +B2(R, LR) + B 2(R,I.R) C s A ( R , I . R ) A(R,I.R) A ( R , I . R ) + A ( R , I . R ) + A'(R,I.R) A^(R,I.R) or bridging n i t r a t o group, as the bond order of the two M-0 bonds approaches unity, the terminal NO bond approaches a double bond. Due to the considerable gradation to be expected i n the p o l a r i t y of the metal n i t r a t e bond and therefore a corresponding gradation of the n i t r a t e ion, the actual frequencies for the n i t r a t o group cannot be predicted as for the free ion. The infrared absorption frequencies found experimentally for unidentate and bidentate (or bridging) n i t r a t o groups, by various workers (69,70), are shown in Table 2.1c. The v i b r a t i o n a l modes have been numbered according to the convention that within: a point group, v i b r a t i o n a l modes are num- bered from the highest symmetry species, and, within any given symmetry species, from the highest frequency. Though many bidentate (or bridging) nitrato-compounds (63,64,70,72) show the highest n i t r a t e frequency at 1630 cm"1 or even higher, i t must be noted that absorption frequency i n t h i s region cannot be considered a c r i t e r i o n for a bidentate • 1 23 TABLE 2.Ic Vib r a t i o n a l Frequencies of Unidentate and Bidentate Nitrato Groups (C2v Symmetry) Assignment Species Frequency Unidentate (cm"1) Bidentate or b r i d g i NO2 symmetric stretch (Al) ^1(1290-1253) V2 ( 985) NO stretch (Ai) V2(1030-970) v i (1630) NO2 symmetric bend (Ai) ^ ( ^ 739) v 3 ( 785) NO2 asymmetric stretch (B2> v 4(1550-1480) v 4 (1250) NO2 asymmetric bend (B 2) ^ 5 ( ^ 7 1 3 ) ^5 ( 750) Out-of-plane rock (Bi) v 6(800-781) v 6 ( 700) Note: These authors c l a s s i f i e d modes V4 and V 5 as belonging to B i species and $Q to B 2 . This c l a s s i f i c a t i o n has been reversed in conformity with the c o r r e l a t i o n tables i n Wilson, Decius, and Cross (71). or bridging n i t r a t o group. Cotton, Goodgame, and Soderberg (73) have shown that the highest n i t r a t e frequency i n the infrared spectrum of Co [(CH3) 3P0] 2 (NO3) 2 , where the presence of bidentate n i t r a t e groups has been established by X-ray crystallography (74), occurs at 1517 cm-1. Si m i l a r l y uranyl n i t r a t o compounds containing bidentate n i t r a t o groups show the highest n i t r a t e frequency i n the region 1560 - 1454 cm - 1 (63). SnF2(N03)2 i s reported (75) to be tetrahedral but the inf r a r e d absorption frequencies of the n i t r a t o group i n th i s compound are very sim- i l a r to those of Sn(N03) 4 which i s reported (70) to contain 24 bidentate n i t r a t o groups. Since the asymmetric N0 2 stretching frequency of a unidentate n i t r a t o group can appear at frequencies as high as 1550 cm-''", and other n i t r a t e bands appear i n similar regions for unidentate and bidentate (or bridging) n i t r a t o groups, i t i s not, i n general, possible to distinguish between a uni- dentate, bidentate or bridging n i t r a t o group. ' The symmetry of the n i t r a t e ion i n the s o l i d state can also be lowered i f i t i s subjected to the f i e l d of a c r y s t a l l a t t i c e . Buijs and Schutte (66) consider that, i n io n i c c r y s t a l s , the cohesive energy i s of the same order as the bond energies of covalent compounds. Though i n s o l i d state infrared spectra, the degenerate in f r a r e d active modes are usually s p l i t , and Raman active modes appear weakly due to the c r y s t a l f i e l d e f f e c t s , a survey of the spectra of i o n i c n i t r a t e s (66-68,76) suggests that any i n t e r a c t i o n with the metal ion i s i n s u f f i c i e n t to r e s t r i c t the normal vibrations of the n i t r a t e ions. By comparing the spectra of io n i c n i t r a t e s , metal-nitrato compounds and covalent n i t r a t e s , some estimation may be made of the degree of covalent character i n the metal-nitrate bond. The following points can be stressed i n t h i s connection: (a) In i o n i c n i t r a t e s the NO stretching v i b r a t i o n shows only a very weak absorption i n the 1050 cm~l region, even i n cases where the s i t e symmetry of the n i t r a t e ion i s lowered to C s, as in potassium n i t r a t e (66,76). In n i t r a t o compounds, the NO stretching v i b r a t i o n appears as a strong band and varies between the observed frequency (1050 cm - 1) for an ionic n i t r a t e to that observed (854 cm - 1) for methyl n i t r a t e (77). Gatehouse, Livingston, and Nyholm (69) have used th i s c r i t e r i o n to place a 25 number of metal-nitrato complexes i n the order of the covalent character of the metal-nitrate bond. (b) The out-of-plane rocking mode i n n i t r a t o compounds occurs almost invariably at lower frequency than that for the free n i t r a t e ion (64). (c) The degenerage mode V3 of the free n i t r a t e ion i s s p l i t into v^ and v*4 i n the n i t r a t o group and the value of the difference & v* = (v^-v^) (in case of bidentate n i t r a t o groups &v = v^-v^) , increases progressively with an increase i n the covalent character of bonding of the n i t r a t e group. The values of Av 1 give the same sequence for covalency as does the variation i n the NO stretching frequency (64). Ferraro (67) has suggested that the extent of t h i s s p l i t t i n g v^-v-^ i s a c r i t e r i o n of the strength of the covalent bond. In methyl n i t r a t e V4 and \)i are found at 1672 and 1287 cm - 1 respectively (77) and (^4-^1) i s 385 cm~l. In metal-nitrato complexes, the value of (^4-^1) i s , i n general, less than 385 cm - 1 (63) but, on the other hand, the observed s p l i t t i n g of ^3 due to c r y s t a l f i e l d e f f e c t s are comparatively much smaller. In potassium n i t r a t e no s p l i t t i n g of V3 i s observed (£6,76). The infrared spectra of metal n i t r a t e s have also been studied i n organic solvents (78,79). In general, the 0̂  and v^ frequencies of the ni t r a t o group are independent of the solvent, but strongly dependent on the metal ion. From a detailed study of the inf r a r e d spectra of many metal n i t r a t e s dissolved i n t r i b u t y l phosphate, Katzin (78) concluded that a (v^-v-^) s p l i t t i n g of less than 100 cm - 1 can be attributed to e l e c t r i c a l asymmetry rather than to covalent bonding, but a (^4-^1) s p l i t t i n g greater than 125 cm" 26 i s undoubtedly due to the effects of p a r t i a l covalent bonding. Triphenyltin n i t r a t e was prepared by the metathetical reaction of t r i p h e n y l t i n chloride and s i l v e r n i t r a t e under anhydrous conditions, as well as by using an aqueous solution of s i l v e r n i t r a t e as described by Shapiro and Becker (62). The infrared absorption bands of t r i p h e n y l t i n n i t r a t e are . l i s t e d , with their r e l a t i v e i n t e n s i t i e s and assignments, for both preparations of the compound in Table 2.Id. A portion of the spectrum of anhydrous n i t r a t e i s shown in Figure 2.1. As can be seen from Table 2.Id, the anhydrous n i t r a t e does not show any bands due to the free n i t r a t e ion while the bands attributed to the n i t r a t o group are present at 1515-1492, 1288-1257, 978 and 798 cm - 1. The other two bands due to the n i t r a t o group cannot be observed due to the presence of two strong phenyl absorptions at 729 and 692 cm - 1. The n i t r a t e absorption i n t r i p h e n y l t i n n i t r a t e i s very s i m i l a r to that shown by t r i m e t h y l t i n n i t r a t e (28, 45). As regards the absorptions of the t r i p h e n y l t i n group, there are no apparent differences be- tween the spectra of t r i p h e n y l t i n chloride (5,8), t r i p h e n y l t i n azide (80), t r i p h e n y l t i n n i t r a t e , and t r i p h e n y l t i n perchlorate (to be discussed l a t e r ) . T r iphenyltin chloride i s reported (5,8) to be non-associated so that the t r i p h e n y l t i n groups should be non-planar, while t r i p h e n y l t i n azide i s considered (81) to contain planar t r i p h e n y l t i n groups bridged by azide groups. Moreover, there i s a considerable disagreement concerning the frequencies at which absorption due to the symmetric and asym- metric stretching vibrations of the phenyl-iin bonds should be observed. G r i f f i t h s and Derwish (8) have assigned a weak band 27 28 TABLE 2.Id Infrared Absorption Spectra of Anhydrous and Wet Triphenyltin Nitrate Anhydrous Frequency Relative (cm-1) 3060 2990 1965 1880 1815 1770 1750 1515 1508 1492 int e n s i t y (cm - 1) Wet Frequency Relative 1483 1437 1339 1325 1305 1288 1271 1257 m w w w w w vw s s s sh s m m m s s s ) 3060 2990 1965 1880 1820 1760 1393 1483 1434 1334 1303 1278 int e n s i t y m w w w w w vs m s m m m Assignment C-H s t r . Phenyl ring, NO2 asymi. . s t r . , (V4) or NO s t r , , ( V i ) NOQ asyiru . s t r . ,(i) Skeletal C-C vibrations (3 C-H NO2 sym..str., (^l) or N O o asym.str., ( $ 4 ) Table 2.Id continued 1190 vw 1155 vw 1076 m 1075 1062 1044 w . 1024 m 1022 996 m 996 978 m 826 798 m 729 s 729 692 s 695 450 s 450 29 /Sc-H m /3C-H w NO s t r . , (v-^ m ftC-H m Phenyl ring NO s t r . , ( v 2 ) or N0 2 sym.str.,(v 2) m N03~ out-of-plane bend, (v^) ON02 out-of-plane rock, (^6) s C-H vib. s C-H.vib. s Sn-Phenyl m = mediumj s = strong; vs = very strong; vw = very weak; w = weak. 30 at 1164 cm--'- i n the spectrum of t r i p h e n y l t i n chloride to the phenyl-tin asymmetric stretching mode, but Kriegsmann and Geissler(5) have assigned t h i s mode to the strong band observed at 450 cm"-'-. The l a t t e r i s probably more correct, but without more precise information, i t i s not possible to describe the configuration of the t r i p h e n y l t i n group in t r i p h e n y l t i n n i t r a t e with any certainty. As discussed e a r l i e r , no conclusion can be reached about the unidentate, bidentate or bridging nature of the n i t r a t o group from the infrared spectrum. However, the infr a r e d spectrum of t r i p h e n y l t i n n i t r a t e c e r t a i n l y shows that free NO3 and ( C 6 H 5 ) 3 S n + ions are not present in anhydrous t r i p h e n y l t i n n i t r a t e and therefore an ioni c structure i s not possible for t h i s compound. Like t r i m e t h y l t i n n i t r a t e , triphenyl- t i n n i t r a t e may have either a tetrahedral, monomeric structure containing a unidentate n i t r a t o group, or a polymeric structure containing f i v e coordinate t i n atoms and bridging n i t r a t o groups. In contrast to the anhydrous compound, the infrared spec- trum of t r i p h e n y l t i n n i t r a t e prepared from wet acetone c l e a r l y shows the presence of the free n i t r a t e ion. The absorptions at 1515-1492 and 1288-1257 cm~l i n the anhydrous compound are re- placed by a single very strong broad band at 1393 cm - 1 which i s c h a r a c t e r i s t i c of the free n i t r a t e ion. The other expected absorptions at 1062 and 826 cm--*- are also present; the band expected at approximately 720 cm - 1 i s probably masked by strong phenyl absorption. The same spectrum i s also observed when anhydrous t r i p h e n y l t i n n i t r a t e i s exposed to moist a i r , the changes i n the inf r a r e d spectrum being complete after an ex- posure of 24 hours. Thus there i s a c o n s t i t u t i o n a l difference between anhydrous and wet t r i p h e n y l t i n n i t r a t e . 31 Since samples of anhydrous t r i p h e n y l t i n n i t r a t e appeared stable, a confirmation of the reported i n s t a b i l i t y was sought. Shapiro and Becker (62) have reported that t r i p h e n y l t i n n i t r a t e , prepared i n wet acetone, decomposes spontaneously at 25° accor- ding to the equation ( C 6H 5) 3SnN0 3 ^ C 6 H 5 N 0 2 (87%) + ( C g H s ) 2SnO (100%) and at higher temperatures, according to the equation ( C 6H 5)-SnN0 3 9 C 6H 5N0 2 (33%) + C g H p (65%) + ( C 6 H 5 ) 2 S n 0 + N 0 2 A l l t h e i r products were characterized except the oxide of n i t r o - gen. In t h i s investigation the anhydrous n i t r a t e showed no apparent changes i n infrared spectrum, as well as i n appearance, after storage i n the dry box for more than two months. When a sample of anhydrous t r i p h e n y l t i n n i t r a t e was heated under vacuum at 150° for one and one-half hours, some spectroscopic changes were observed i n the s o l i d , and a very small amount of vapour was evolved. The infrared spectra of the heated s o l i d and the evolved vapour are recorded i n Table 2.1e. In the spectrum of the heated s o l i d , a l l the phenyl absorptions; are unchanged, while the n i t r a t e absorptions occur at 1550, 1277, 965 and 790 cm - 1. In addition, two strong bands appear at 606 and 558 which may be possibly associated with tin-oxygen vibrations. Monophenyltin oxide, diphenyltin oxide and b i s ( t r i p h e n y l t i n ) oxide show the c h a r a c t e r i s t i c strong absorptions of the tin-oxygen v i b r a t i o n at 572(82), 575(82) and 774(83) cm - 1 respectively. None of TABLE 2.1e Infrared Absorption Spectra of The Products Obtained On Heating Anhydrous Triphenyltin Nitrate S o l i d Vapour Frequency Relative Frequency Relative (cm~l) in t e n s i t y (cm - 1) int e n s i t y 3080 w 3070 m 1550 s 2980 w 1535 s 1685-1665 s 1485 m 1485 w 1335 w 1050 w 1277 s 990 m 1265 sh 850 sh 1075 m 825 s. 1065 sh 800 sh 1022 m 685 m 998 m 670 s 965 s 660 m 920 w 615 im 790 m 572 w 730 s 694 s 655 w 606 s 558 s 450 s m = medium; s = strong; sh = shoulder; w = weak. 33 these absorptions are found in the spectrum of the heated s o l i d . The infrared spectrum of the vapour indicates the absence of any nitrogen oxides. Some of the absorptions can be assigned to benzene but other bands could not be characterized. From the above spectroscopic data, i t may be concluded that decomposition of the anhydrous t r i p h e n y l t i n n i t r a t e under these conditions i s s l i g h t , and that, although some s t r u c t u r a l changes must occur, the n i t r a t e group i s s t i l l apparently retained with either C 2v or C s symmetry. Even the product obtained from wet acetone i s much more stable than the product described by Shapiro and Becker. Samples were always pale yellow i n colour, and did not show any change i n appearance or spectra over periods of several days. When a sample of the compound was heated with o-dichlorobenzene as described by Shapiro and Becker, decomposition was found to be considerable, the f i n a l residue being shown by i t s infrared spectrum to contain no n i t r a t e , and also, from the reduced inten- s i t i e s of the phenyl absorptions (as compared with those observed for the o r i g i n a l compound i n a mull of approximately similar con- centration) , to have lo s t phenyl groups. No absorptions charac- t e r i s t i c of bis(triphenyltin)noxide.were observed. It i s concluded, therefore, that pure t r i p h e n y l t i n n i t r a t e i s stable under anhydrous conditions, and that the i n s t a b i l i t y observed by Shapiro and Becker i s associated with the presence of c a t a l y t i c impurities and, to some degree, with the presence of moisture. .Trimethyltin n i t r a t e , by reaction with ammonia, readi l y forms a diadduct which i s formulated (28) as (CH 3) 3Sn(NH 3) 2 +N02. Similar reactions of t r i p h e n y l t i n n i t r a t e with anhydrous ammonia 34 were car r i e d out. However, no addition compound could be i s o - lated; instead a mixture of ammonium n i t r a t e and b i s ( t r i p h e n y l t i n ) oxide was obtained which was characterized by i t s X-ray powder photograph and infrared spectrum (83). The reaction of t r i p h e n y l t i n n i t r a t e with ammonia must therefore proceed as follows: (CgH 5) 3SnN0 3 + NH3 >(CgHg)gSnNOgNHg H 2 ° r n 2(C 6H 5) 3SnN0 3NH 3 ^ K C6 H5 )3 S l^J 2° + 2 N H 4 N 0 3 Similar r e s u l t s have been reported by Kupchik and Lanigan (30) who found the products of reaction between t r i p h e n y l t i n bromide and ammonia to be b i s ( t r i p h e n y l t i n ) oxide and ammonium bromide. It seems that, i n contrast to ammonia adducts of a l k y l t i n compounds, the ammonia adducts of t r i p h e n y l t i n derivatives have a very low hydrolytic s t a b i l i t y , for either k i n e t i c or thermodynamic reasons, and that i n the present case hydrolysis occurred even under care- f u l l y controlled conditions. 2.2 Triphenyltin Perchlorate (CgH 5) 3SnC10 4 The free perchlorate ion (C10 4~) i s of tetrahedral(T d) symmetry (65b) and hence should have nine v i b r a t i o n a l modes giving r i s e to four fundamental v i b r a t i o n a l frequencies. These fundamen- t a l frequences which have been established (65a) from the Raman spectra of perchlorates are shown in Table 2.2a. The v^ mode i s nondegenerate, v^ i s doubly degenerate, and V3 and are each t r i p l y degenerate. In the s o l i d state in f r a r e d spectra of io n i c perchlorates (68,84), v^, which i s i n f r a - TABLE 2.2a Vi b r a t i o n a l Frequencies of C10 4 Ion (Point Group T d) V i b r a t i o n a l Assignment mode v, (A,) v"2 (E) ^3 <F2> h (Fo) Symmetric stretch Symmetric bend Asymmetric stretch Asymmetric bend Frequency (cm-1) 935 462 1102 628 A c t i v i t y (R) (R) (R.I.R) (R,I.R) (R = Raman active; I.R = Infrared active.) red inactive i s usually observed as a very weak absorption at about 930 cm - 1. Vg appears as a broad, strong band, usually s p l i t i n the 1050-1150 region. Anhydrous copper perchlorate and some other t r a n s i t i o n metal perchlorates have infrared spectra (85) very d i f f e r e n t from other metal perchlorates. From a detailed study of their spectra, Hathaway and Underhill (85) showed that, i n these compounds, the perchlorate groups are strongly coordinated to the metal atoms. The infrared spectrum of t r i m e t h y l t i n per- chlorate (27) also indicates that perchlorate groups act as bridging ligands between the planar t r i m e t h y l t i n groups. The spectroscopic r e s u l t s are completely consistent with a polymeric structure containing f i v e coordinate t i n atoms. If the perchlorate group i s involved i n such coordination, i t s symmetry i s lowered from T d to or according to whether one or two of i t s oxygen atoms p a r t i c i p a t e i n such bonding. The c o r r e l a t i o n between the v i b r a t i o n a l modes of the perchlorate group for T d, or C 2 v symmetry (85) i s shown in Table 2.2b. If Symmetry -o - C 1 0 3 c 3 v CIO, c i o 2 c 2 v TABLE 2.2b Vibrations of The C 1 0 4 Group in T d, C 3 v or C 2 v Symmetry v2 A 1(I.R) Aj(R) sym.str, Ai(I.R) C 1 0 | sym.str, ^6 E(I.R) ^2 E(R) sym.bend Vibrational Modes AiU.R) E(I.R) k F 2(I.R) asym.str, A ^ L R ) J 5 E (I.R) _ V5 ^ v 6 v g 0 3 v 7 v 9 A X(I.R) A 2(R) A X(I.R) Bid.R.) B 2(I.R) A^I.R) B ^ L R ) B 2(I.R) G10* 2 Torsion C 1 0 2 C 1 0 2 C 1 0 2 C 1 0 2 rocking rocking sym.bend sym. asym. asym. sym. s t r . s t r . s t r . bend * denotes oxygen atoms involved i n bonding. the symmetry of the perchlorate group i s lowered to C3 V s then the v*i mode of the perchlorate ion becomes infrared active, and modes ^3' ^4 e a c n s p l i t into two modes which are also infrared active. On further lowering of the symmetry to C2v, the v^ and v1^ modes each s p l i t into three infrared active modes. Ross (84) considers that, i n view of the known i n s t a b i l i t y of covalent perchlorates, i t i s unlikely that covalent bonding can contribute to any extent i n metal perchlorates, and that the s p l i t t i n g s i n the s o l i d state infrared spectra of various per- chlorates described by Hathaway and Underhill might be due to the d i s t o r t i o n of the perchlorate ion in the c r y s t a l l a t t i c e . The observed (68,84) infrared spectra of some io n i c perchlorates do show lowering of the perchlorate ion symmetry due to the c r y s t a l f i e l d , however, the observed s p l i t t i n g s of the degen- erate modes i n a l l these cases are not as well defined and are of a smaller order. Also, the forbidden mode 0-̂  shows only a weak absorption. For example, i n potassium and ammonium per- chlorates (84), the perchlorate ion symmetry i s distorted to C2v but, i n both these cases, the v*̂  mode shows a s p l i t t i n g of about 50 cm--'- as compared to the s p l i t t i n g of about 200 cm~^ observed for the same mode i n anhydrous copper perchlorate (85) and t r i m e t h y l t i n perchlorate (27). Trimethyltin perchlorate shows four strong, well resolved bands at . 1212-1192, 1112, 998 and 908 cm - 1 and three medium bands at 625, 606 and 468 cm - 1. Coordination by the perchlorate group i n trimethyltin perchlorate i s further supported by i t s infrared spectrum (28) i n methanol solution where c r y s t a l f i e l d e f f e c t s are completely absent. While th i s work was i n progress, further evidence of coordina- tion by the perchlorate group has been reported i n the following 38 compounds: Ni(3,5-lutidine)(ClO^) (86) shows perchlorate group absorptions at 1135, 1030 and 930 cm~"l and the magnetic moment of this compound i s i n accord with the six coordination- of the nic k e l atom. Ni(CH 3CN) 4(C10 4) 2 and Ni(CHgCN) 2(C10 4) (87) have perchlorate absorption bands at 1135, 1012, 912 cm - 1 and 1195, 1106, 1000 and 920 cm"-'- respectively, and the coordination by perchlorate groups in these compounds i s further supported by their electronic spectra. Thus the proceeding examples demonstrate that the s o l i d state infrared spectrum can be used to distinguish between an io n i c and a coordinated perchlorate group. Anhydrous t r i p h e n y l t i n perchlorate was obtained as a white s o l i d . The observed infrared absorption bands of the anhydrous compound are l i s t e d , with t h e i r r e l a t i v e i n t e n s i t i e s and suggested assignments, i n Table 2.2c. A portion of the spectrum i s shown in Figure 2.2. The bands which can be assigned to the perchlorate group occur at 1200, 1112, 985, 905, 625, 610-604, 455, 449 and 439 cm~l. The remaining bands are i d e n t i c a l with those observed in the spectrum of t r i p h e n y l t i n n i t r a t e and can be assigned to the vibrations associated with the t r i p h e n y l t i n group. The four strong perchlorate bands at 1200, 1112, 985 and 905 cm - 1 are almost i d e n t i c a l with those observed for t r i m e t h y l t i n perchlorate (27), and c l e a r l y indicate the C 2 v symmetry of the perchlorate group. This i s also supported by the bands at 625, and 610-604, which are observed for t r i m e t h y l t i n perchlorate. Trimethyltin perchlorate shows absorption bands at 468 and 450 cm - 1. In tr i p h e n y l t i n perchlorate there i s a strong absorption band i n 450 cm--*- region due to the t r i p h e n y l t i n group and thi s may over- lap perchlorate absorption i n t h i s region. There i s , however,  40 TABLE 2.2c The Infrared Absorption Spectrum of Triphenyltin Perchlorate requency (cm-1) Relative Intensity Assignment Frequency (cm - 1) Relative Intensity Assignment 3070 m ) 1158 m /SC-H 2990 2990 m w ) C-H s t r . 1112 1075 vs s CIO2 sym.str., £C-H 1990 vw Phenyl ring 1020 m /SC-H 1967 w Phenyl ring 995 sh Phenyl ring 1905 vw Phenyl ring 985 vs C I O 2 asym. str.,(v* g) 1884 w Phenyl ring 905 s C I O 2 sym. s t r . , (v*2) 1818 .'W Phenyl ring 728 vs C-H deform. 1765 w 690 vs C-H deform. 1644 w 673 . w 1582 w ) ) ) ) Skeletal C-C 664 w 1483 m vibrations 625 m C I O 2 sym. bend,(v*g) 1435 1335 s m ) ) ) 610 604 sh sh ) ) ) Rocking C I O 4 , (v 7) 1300 1200 w vs /.C-H C I O 2 asym. s t r . , (v 6) 455 449 439 sh s sh ) ) ) ) Rocking C I O 4 , (0 9)? C1Q 2 s v m ' bend, (v 1) ? and Sn-pheny1. vs = very strong; s = strong; m = medium; w = weak; vw = very weak; sh = shoulder. * denotes the two bridging oxygen atoms. 41 l i t t l e doubt that the perchlorate symmetry in this compound i s not higher than C2 V. Triphenyltin perchlorate, l i k e t r i m e t h y l t i n perchlorate, i s highly soluble i n ether and methanol and i s very hygroscopic. On exposing t r i p h e n y l t i n perchlorate to a i r , the four intense bands at 1200, 1112, 985 and 905 were replaced by an intense broad band i n the 1075-1150 cm - 1 region and a very weak band at 940 cm - 1. These are c h a r a c t e r i s t i c bands of the free perchlorate ion which i s formed by the hydrolysis of the anhydrous t r i p h e n y l t i n perchlorate. Identical spectral changes occur i n t r i m e t h y l t i n perchlorate (27). Thus i n view of the almost i d e n t i c a l spectra of t r i p h e n y l t i n perchlorate and t r i m e t h y l t i n perchlorate, and their i d e n t i c a l behaviour upon hydrolysis, i t can be concluded that both these compounds are almost similar i n structure. Hathaway and Underhill (85) have suggested assignments for the fundamental frequencies of the perchlorato group of C2 V symmetry by comparison with the assignments for sulphuryl f l u o r i d e , and the bidentate sulphate group. These workers have * suggested the following assignments for the C I O 2 and ClOg i * stretching vibrations : 1270 - 1245 cm - 1, asymmetric ClOg stretch (v"g) ; 948-920 cm - 1, symmetric C10*2 stretch (v^) ; 1130 cm"1 asymmetric C I O 2 stretch (ve)5 and 1030 cm - 1, symmetric C I O 2 stretch ( ^ 1 ) . However, these assignments are not consistent with the reported assignments for sulphuryl f l u o r i d e (88) and dimethyl sulphate (89). Moreover, the bond order of the two Cl-0 bonds (involving oxygen atoms not p a r t i c i p a t i n g i n co- ordination) should be higher than that of the remaining two Cl-0 bonds (0 denotes oxygen atoms p a r t i c i p a t i n g i n coordination). 42 Therefore the ClOg stretching v i b r a t i o n should occur at higher frequencies, compared with frequencies for the ClOg stretching modes. In dimethyl sulphate the stretching vibrations charac- t e r i z i n g the two double sulphur-oxygen bonds occur near 1400 and 1200 cm~^ whereas the stretching vibrations of the two single sulphur-oxygen bonds occur at 825 and 752 cm-'*' (see section 5.4) . Therefore i n t r i p h e n y l t i n perchlorate the four strong perchlorate absorption bands i n the 1200-900 cm - 1 region are assigned as follows: 1200 cm~\ ^lOg a symmetric stretch (v'g) ; 1112 cm"1, C I O 2 symmetric stretch (v^); 985 cm~^ CIO2 asymmetric stretch (v"g) ; and 905 cm - 1, ClO^ symmetric stretch (v^) . In the lower frequency region, there i s no obvious method to distinguish between the v i b r a t i o n a l frequencies of O3, v*y, and Og modes and the assignments suggested by Hathaway and Underhill are used. Trimethyltin perchlorate forms an additional compound with anhydrous ammonia which has been formulated as (CH3)gSn.2NH3CIO4 (27). However, the reaction of t r i p h e n y l t i n perchlorate with ammonia resulted i n the formation of ammonium perchlorate and b i s ( t r i p h e n y l t i n ) oxide. A s i m i l a r reaction between ammonia and t r i p h e n y l t i n n i t r a t e has been discussed and the formation of ammonium perchlorate and b i s ( t r i p h e n y l t i n ) oxide in t h i s reaction can be explained i n a s i m i l a r manner. 43 CHAPTER 3 TRIMETHYLTIN(IV) DERIVATIVES To seek further information about the nature of the i n t e r - action between R 3Sn and the anionic group, some trime t h y l t i n derivatives containing t r a n s i t i o n metal oxyanions were sought. It was considered that the e l e c t r o n i c spectra of such deriva- tives might provide some information about the electronic description of the i n t e r a c t i o n . Perchlorates, tetrafluoroborates, and permanganates of the same cation are frequently isomorphous and the three anions have many similar features including t h e i r regular tetrahedral symmetry. Therefore an attempt was made to prepare tri m e t h y l t i n permanganate, but t h i s compound could not be i s o l a t e d due to i t s instantaneous decomposition i n the presence of a range of s o l - vents. B i s ( t r i m e t h y l t i n ) chromate, [ ( C H 3 ) 3 S n J 2 C r 0 4 > however, could r e a d i l y be synthesized. In t h i s compound, formally at least, 2- a doubly charged anion C r04 i s present so that the stoichiometry i s quite d i f f e r e n t from that.of a t r i m e t h y l t i n derivative con- taining univalent anion such as perchlorate. Therefore, to provide a comparison, b i s ( t r i m e t h y l t i n ) sulphate [ ( C H 3 )_SnJ_ S 0 ^ was also studied. Both the sulphate ion and the chromate ion have regular tetrahedral symmetry and belong to the point group T d (47a). 3.1 B i s ( t r i m e t h y l t i n ) Sulphate [TcH 3 )gSnj 2 S0 4 The i n f r a r e d and Raman spectra of sulphates have been widely studied (47a). The fundamental v i b r a t i o n a l frequencies 2- of the free SO4 ion as shown in Table 3.1a, have been established 44 from, the Raman spectra (65b) i n aqueous solutions. TABLE 3.1a 2- Vib r a t i o n a l Frequencies of SO4 Ion (Point Group T d) Vib r a t i o n a l Frequency mode Assignment (cm-1) A c t i v i t y (Aj) Symmetric stretch 981 (R) v 2 (E) Symmetric bend 451 (R) v 3 (F g) Asymmetric stretch 1104 (R,I.R) V4 (F 2) Asymmetric bend 613 (R,I.R) ( R = Raman active; I.R = Infrared active.) In the s o l i d state i n f r a r e d spectra of io n i c sulphates, the i n f r a r e d inactive mode v'j shows a weak absorption and the degenerate frequencies and v^ appear very strongly and -often display s p l i t t i n g due to c r y s t a l f i e l d e f f e c t s (90). The c r y s t a l f i e l d e f f e c t s observed i n the spectra of c r y s t a l l i n e i o n i c s u l - phates are s i m i l a r . i n nature and magnitude to those discussed i n connection with perchlorates (90). From i n f r a r e d studies, Nakamato and coworkers (91) have shown coordination by the sulphate group i n certa i n ammino-cobalt (III) complexes. Their conclusions have been confirmed by Barraclough and Tobe (92) i n an in f r a r e d study of ethylenediamine cobalt(III) complexes. Coordination by the sulphate grqpp has also been reported recently i n some ethylenediamine and b i p y r i d y l complexes of copper (93,94). The sulphate absorptions i n a l l these sulphato complexes occur i n the following frequency (cm"1) ranges: 45 Unidentate sulphato group ^1 ^2 *3 *4 965-978(m) 438(m) 1114-1143(s) 615-645 ^3v symmetry 1032-1070(s) 602-625(s) Bidentate sulphato group 961-995(m) 462(m) 1163-1211(s) 632-647(s) 1096-1176(s) 602-632(s) 1000-1060(s) 515-595(m) C2 V symmetry (m = medium; s = strong) A l k y l t i n sulphates are well known, but no work has been done to determine their constitution, except e a r l i e r studies by Werner and P f e i f f e r (95) and a br i e f study by G i l l e s p i e and Robinson (96). Werner and P f e i f f e r obtained a low value for the molecular weight of d i e t h y l t i n sulphate i n water, which led them to conclude that the compound was p a r t i a l l y dissociated into d i e t h y l t i n and sulphate ions. As i t did not melt or sub- lime, Werner and P f e i f f e r c l a s s i f i e d the compound as s a l t - l i k e ; however they also stated that the compound should be planar with a c i s configuration. G i l l e s p i e and Robinson have b r i e f l y re- ported that, i n anhydrous sulphuric acid solution, bis(trimethyltin) sulphate i s ionized giving four p a r t i c l e s for every molecule of can be interpreted equally well i n terms of solvated ions. In t h i s investigation, t r i m e t h y l t i n sulphate was prepared under anhydrous conditions by the metathetical reaction of trime t h y l t i n bromide and s i l v e r sulphate using methanol as 46 solvent. The f i r s t product of the preparation was a methanol completely removed by heating under vacuum at 100° for about four hours. Part of the infrared spectra of the adduct (curve 1) and the nonsolvated product (curve 2) are shown i n Figures 3.1a and 3.1b. Infrared absorption bands of both the products are l i s t e d i n Table 3.1b, with th e i r r e l a t i v e i n t e n s i t i e s and suggested assignments. For both the methanol adduct and the nonsdlvated bis(trimethyltin) sulphate, the t r i m e t h y l t i n group shows absorption at 3000-2900, (C-H stretch); 1410-1400, (C-H asymmetric bend); 1205-1195, (C-H symmetric bend); 785-780. (Sn-CH3 rock); and 552, (Sn-C asymmetric stretch) cm - 1. It may be noted that only the t i n carbon asymmetric stretch appears i n the spectra, and i t s frequency i s s h i f t e d to higher wave number as compared to the value of 545-540 cm - 1 observed i n tri m e t h y l t i n chloride (4). This s h i f t to higher frequencies from 545-540 cm - 1 observed for tetrahedral t r i m e t h y l t i n compounds i s observed in other t r i m e t h y l t i n derivatives (27, 28, 33, 45) containing a planar t r i m e t h y l t i n group i n a t r i g o n a l bipyramidal configuration around the t i n atom. In at least one of these derivatives, (CH3)gSnCl.Py, both the planarity of the t r i m e t h y l t i n group and the f i v e coordination of the t i n atom have been conclusively established by an X-ray structure determination and i n f r a r e d spectroscopic studies (25, 26, 33). Thus the presence of only the Sn-C asymmetric stretch and i t s s h i f t to a higher frequency i n - dicate that both i n b i s ( t r i m e t h y l t i n ) sulphate and i t s methanol adduct, the t r i m e t h y l t i n group i s planar. In the methanol adduct absorption bands due to the sulphate group are observed at 1165, 1095, 1065, 1021, 989, 630, 595, 558 and 447 cm - 1. Free adduct. from which the methanol was 1300 1200 1100 1000 900 800 700 W A V E N U M B E R c m - ' a o L I I 1 I 700 600 500 450 400 W A V E N U M B E R c m - ' 00 TABLE 3.1b Infrared Absorption Spectra of Bis(trimethyltin) Sulphate-Methanol Adduct and Bis(trimethyltin) Sulphate |(CH3)3Sn] 2 S 0 4 2 ( C H 3 0 H ) [(CH 3) 3s3 SO4 Frequency Relative Frequency Relative (cm~l) Intensity (cm"1) Intensity 3150-3100 3020 2920 2800 1410 1195 1165 1095 ip65 1021 989 785 630 595 558 552 447 b = broad: w = weak. s, b w w w m, b w s s, sh s m m sh s m, b 3000 2900 1400 1205 1100 780 630 552 w w m w vs s s Assignment 0-H s t r . C-H asym. s t r . C-H sym.str. C-H asym.bend C-H sym. bend S 0 2 asym.str.,(^g) ^ 3 ( s o 4 2 - ) S 0 2 sym. s t r . , (0-̂ ) S 0 2 asym. s t r . , S 0 2 sym. s t r . , (v 2) CH 3 rock v 4 ( S 0 4 2 - ) S 0 4 rock, (v 7) S 0 2 bend, 0 3) S 0 4 rock, (v 9) Sn-C asym. s t r . Sol bend, (v\.) m = medium; s = strong; sh = shoulder; v = very; * denotes the oxygen atoms involved i n bonding. ^Assign- ments for the S0 4 absorption bands i n the adduct have been made assuming that S0 4 acts as a bridging group. 50 methanol also has a strong absorption band i n the 1100-1000 cm"1 region. However, in the bis(trimethyltin) sulphate-methanol adduct, the 1021 cm"1 band i s sharp and of only medium int e n s i t y i n contrast to the strong broad absorption at 3150-3100 cm - 1; therefore t h i s (1021 cm"1) band i s unlikely to be due to methanol. The 1095 cm - 1 shoulder i s probably due to the methanol and the 1100-1000 cm~^ region methanol band i s masked by the strong sulphate absorption at 1065 cm"1. The sulphate absorption in the spectrum of the tr i m e t h y l t i n sulphate-methanol adduct c l e a r l y shows that the symmetry of the sulphate group i s . reduced to C 2v. The V3 and v^ modes are c l e a r l y s p l i t each into three frequencies and the v^ and v^ modes appear with moderate i n t e n s i t i e s . The absorption frequencies are i n r ^ NH2 3_ the same range as reported for I (NHQ) 4Co-^ 7>Co(NH 3) 4 ion L ^ S 0 _ j ~-i (91). Therefore i t can be concluded that each sulphate group i s coordinated to two t r i m e t h y l t i n groups. Moreover the 0-H absor- ption of the methanol i s observed as a broad band at 3105-3100 cm"1 lowered from the 3400 cm - 1 band observed for methanol i t s e l f . This indicates that the methanol molecules are also coordinated to the t r i m e t h y l t i n group. The entire spectrum of the methanol adduct of b i s ( t r i m e t h y l t i n ) sulphate i s thus consistent with the structure shown in Figure 3.1c, which contains planar tr i m e t h y l t i n groups, a bridging sulphato group and two coordinated methanol molecules, making the t i n atoms f i v e coordinate. The sulphate absorption i n the spectrum of non-solvated b i s ( t r i m e t h y l t i n ) sulphate shows only the t r i p l y degenerate v i - brations ^ 3 at 1100-1090, and V 4 at 630 cm - 1 i n d i c a t i n g the presence of the regular tetrahedral sulphate group. As pointed out e a r l i e r , only the Sn-C asymmetric stretch i s observed at F I G U R E 3 1 c 52 552 cm"1, indicating the planarity of the tri m e t h y l t i n groups. The structure shown in Figure 3.Id i s proposed to incorporate these features, but t h i s can be interpreted i n terms of ions, (CH-)_Sn + and SO^-, or equally well i n terms of a coordinated model where every oxygen of the sulphate group i s coordinated to a t i n atom. As a res u l t of the molecular stoichiometry, the in f r a r e d spectrum does not d i f f e r e n t i a t e between these two models. Both the bi s ( t r i m e t h y l t i n ) sulphate-methanol adduct and bi s ( t r i m e t h y l t i n ) sulphate showed marked changes i n th e i r i n f r a - red spectra on exposure to a i r . In the bi s ( t r i m e t h y l t i n ) : sulphate-methanol adduct, i n addition to the appearance of water bands, the s p l i t t i n g of the and 0^ bands gradually disappeared and f i n a l l y these were replaced by a strong broad band at 1105 cm - 1 and a strong sharp band at 613 cm - 1; both the 989 and 447 cm""1 bands gradually disappeared and were replaced by a weak band at 983 cm - 1. Again t h i s change i n the sulphate spectrum, upon exposing the s o l i d to a i r , suggests that free sulphate ions and hydrated tri m e t h y l t i n cations are produced as a r e s u l t of hydrolysis. Since the position and i n t e n s i t y of the. .Sn-C asymmetric stretch does not change, i t can be concluded that t r i m e t h y l t i n group i s s t i l l planar and f i v e coordinate. However, i n the i n f r a r e d spectrum of a sample of bi s ( t r i m e t h y l t i n ) sulphate-methanol adduct which was exposed to a i r for about two months, the Sn-C asymmetric stretch at 552 cm - 1was replaced by a strong band at 541 and a medium band at 513 cm"'1, probably i n d i - cating the formation of a tetrahedral tri m e t h y l t i n species. Si m i l a r l y i n non-solvated b i s ( t r i m e t h y l t i n ) sulphate, the sulphate absorptions showed gradual changes in the infrared spectrum upon  54 exposing the s o l i d to a i r . After a short exposure, i n addition to the appearance of water bands, the mode showed bands at 1140,1100 and 1065, a medium band appeared at 989 cm - 1, and 630 -1 1 cm band became broad, and a strong band at 613 cm and a medium band at 475 cm - 1 appeared. After a longer exposure, the V3 mode appeared at 1100-1090 as a single broad band, the v*-̂  mode showed only a weak absorption at 885 cm - 1 and V4 appeared strongly at 6 1 3 cm"1. This gradual change i n the sulphate part of the spectrum indicates that, immediately after exposure of bis(trimethyltin) sulphate to a i r , the sulphate symmetry i s reduced to C 2 v as a res u l t of p a r t i a l hydrolysis and, on further hydrolysis, free sulphate ions are produced. This behaviour on hydrolysis i s again consistent with a coordinated structure. 3.2 Bis (trimethyltin) Chromate QcHg) 3S11J 2 c r 0 4 The infrared and Raman spectra of chromates have been studied (68, 97, 98). The e a r l i e r assignments for the fundamental frequencies of the chromate ion have been revised by Stammreich, Bassi and Sala (97). The fundamental v i b r a t i o n a l frequencies and the revised assignments of the free chromate ion are shown i n Table.3.2. It may be mentioned that these authors could not be certain whether the assignment i s 0 2 = 348, v*̂  = 368 or vice versa,' but preferred the former. However, M i l l e r and coworkers (98) have reported that the inf r a r e d band for the chromate ion in the cesium bromide region i s observed at 370-420 cm - 1; therefore the assignments shown i n Table 3.2 are considered to be correct. Some chromato complexes of cobalt have been reported and from the elec t r o n i c spectral studies of these complexes, Shimura 55 TABLE 3.2 2 -V i b r a t i o n a l Frequencies of C r04 Ion (Point Group T<j) V i b r a t i o n a l Frequency mode Assignment (cm-1) A c t i v i t y (A^) Symmetric stretch 847 (R) V s . (E) Symmetric bend 348 (R) V3 (F 2) Asymmetric stretch 884 (R,I.R) ^4 ^ F2^ Asymmetric bend 368 (R,I.R) (R = Raman active; I.R = Infrared active) 2~ and Tsuchida (99) have indicated the early position of CrO^ i n the spectrochemical series, but no infrared studies on coordinated chromates have been reported. However, the symmetry of the chro- mate group, and therefore the number of infrared active modes, w i l l change upon coordination i n a si m i l a r manner as that discussed for other tetrahedral anions. The observed i n f r a r e d spectrum of b i s ( t r i m e t h y l t i n ) chromate i s very si m i l a r to that of non-solvated t r i m e t h y l t i n sulphate. The main features of the spectrum are the \?3 mode of the chromate group at 885 cm"1, the Sn-CHg rock at 750 cm - 1, and the Sn-C asymmetric stretch at 554 cm - 1. No absorption was observed below 554 cm - 1. The mode usually observed as a weak doublet for c r y s t a l l i n e i o n i c chromates at 368 cm"1 was not observed even i n highly concentrated nujol mulls. The spectrum indicates that the chromate group has symmetry and that the t r i m e t h y l t i n group i s planar. The structure proposed for the non-solvated tr i m e t h y l t i n sulphate (see Figure 3.Id) i s also applicable to 56 trimet h y l t i n ehromate and again the infrared spectrum i s not hel p f u l i n elucidating,the nature or the extent of anion-cation i n t e r a c t i o n . Trimethyltin chromate, i n contrast to trimethyltin sulphate, did not form a methanol adduct nor did i t hydrolyse on exposure to a i r . The u l t r a v i o l e t and v i s i b l e diffuse reflectance spectrum of t r i m e t h y l t i n chromate was examined and compared with the spec- trum of powdered potassium chromate. Trimethyltin chromate showed absorption maxima at 310 and 420 nj^, showing very l i t t l e change from the maxima observed at 275 and 375 m// for potassium chromate. This i s i n agreement with the reported spectrum of the complex Co( N H 3 )gCrO^ (100), which i s very si m i l a r to that of 2- CrO^ ion showing that coordination by chromate through an oxygen atom has l i t t l e e f f e c t on the charge transfer band. 57 CHAPTER 4 DIMETHYLTIN(IV) DERIVATIVES As mentioned e a r l i e r , very l i t t l e work has been done on structure elucidation of d i a l k y l - or diphenyltin acid derivatives. In the present investigation, attempts were made to synthesize and examine, by inf r a r e d spectroscopy, a wide variety of dimethyltin acid derivatives such as dimethyltin carbonate, chromate, bis(tet r a f l u o r o b o r a t e ) , h e x a f l u o r o s i l i c a t e , bis(hexafluorophos- phate), bis(hexafluoroarsenate), bis(hexafluoroantimonate), 2 - and the dimethyltin derivative of P12CI12 . In addition, the known compounds, dimethyltin d i f l u o r i d e and sulphate were also studied^ 4.1 Dimethyltin D i f l u o r i d e (CH3) 2SnF 2 In a comparison of methyltin chlorides, Taimsalue and Wood (4) reported a d i s t i n c t f a l l i n the Sn-Cl stretching force constants, i n the series SnCl^, (CH^SnClg, (CHg^SnClg and (CHg^SnCl. This sequence follows the increasing inductive e f f e c t of the methyl groups, f a c i l i t a t i n g the i o n i z a t i o n of the Sn-Cl bond. A sim i l a r comparison of the inf r a r e d spectra of dimethyltin d i f l u o r i d e and tr i m e t h y l t i n f l u o r i d e was consi- dered desirable. The infrared spectrum of dimethyltin d i f l u o r i d e and the Sn-F vi b r a t i o n frequency i n tr i m e t h y l t i n f l u o r i d e have not been reported and were measured in t h i s work. In the inf r a r e d spectrum of dimethyltin d i f l u o r i d e , the absorption bands were observed at 3040(w), 2940 (vw), 1410 (vw,b) 1210(w,sp), 785(m), 595(m,sp) and373(s) cm - 1. These 58 bands can be assigned as, 3040 cm - 1, C-H asymmetric stretch; 2940 cm - 1, C-H symmetric stretch; 1410 cm - 1, C-H asymmetric bend; 1210 cm-'1", C-H symmetric bend; 785 cm - 1, CH3 rock; and 595 cm - 1 Sn-C asymmetric stretch. The strong band at 373 cm - 1 must be associated with the Sn-F bond. In the spectrum of t r i m e t h y l t i n f l u o r i d e , a strong band was observed at 355 cm - 1 which can be assigned to the Sn-F asymmetric stretching v i b r a t i o n . The pre- sence of only one Sn-C stretching frequency i n dimethyltin d i f l u o r i d e indicates that the dimethyltin group i s l i n e a r . Thus dimethyltin d i f l u o r i d e and t r i m e t h y l t i n f l u o r i d e apparently have di f f e r e n t stereochemistry, and the Sn-F stretching frequency in each compound should arise from a d i f f e r e n t v i b r a t i o n a l mode. Nevertheless, i t i s i n t e r e s t i n g to note that^Sn-F frequency i n dimethyltin d i f l u o r i d e occurs at higher wave number compared to the Sn-F frequency i n t r i m e t h y l t i n f l u o r i d e . As me-flftioned e a r l i e r , the c r y s t a l structure of t r i m e t h y l t i n f l u o r i d e (39) cannot be interpreted as i o n i c , and strongly sug- gests that some type of coordinative i n t e r a c t i o n between tri m e t h y l t i n groups and f l u o r i n e atoms i s involved. From a comparison of the Sn-F frequency i n dimethyltin f l u o r i d e with that of t r i m e t h y l t i n f l u o r i d e , and i n view of the non-ionic nature of t r i m e t h y l t i n f l u o r i d e , i t should therefore be consi- dered that dimethyltin d i f l u o r i d e cannot have a purely io n i c structure. As was pointed out by Beattie and Gilson (36), dimethyltin d i f l u o r i d e may have a polymeric structure, i n which two methyl groups occupy trans positions and the four bridging f l u o r i n e atoms occupy the four corner positions i n the equatorial plane making the t i n atom six coordinate. The e f f e c t i v e 59 symmetry of such a trans octahedral unit would be D 4 h and f i v e i n f rared active vibrations of the species 2A 2 u + 3E U would be expected. Of these f i v e v i b r a t i o n a l modes, only two fsn-C asymmetric stretch (A 2 u) , and Sn-F asymmetric stretch (E U)^J would have v i b r a t i o n a l frequencies above 300 cm--'-. Thus the observed infrared spectrum of dimethyltin d i f l u o r i d e i s consis- tent with such a structure. The Sn-F frequency (373 cm"1) in dimethyltin d i f l u o r i d e compares well with the reported (50) value (400 cm - 1) for the Sn-0 asymmetric stretching frequency i n the dimethyltin acetylacetonato complex, ( C H 3 ) 2Sn(C5Hy0 2) 2 which i s also indicated to have a trans octahedral structure, on the basis of i t s Raman and i n f r a r e d spectra. It i s known that a l k y l t i n d i f l u o r i d e s form complexes with + 2- a l k a l i metal f l u o r i d e s of the type M 2 R 2SnF 4 (2a). If the 2 + d i a l k y l t i n d i f l u o r i d e contains the free ions RgSn and F", i . e . the f l u o r i d e ions are outside the coordination sphere of the RgSn group, then the formation of a complex, i n which four f l u o r i d e ions are now within the coordination sphere, can only be considered somewhat of an anomaly. 4.2 Dimethyltin Carbonate (CH 3) 2SnC0 3 2- The free carbonate ion (CO3 ) i s t r i g o n a l planar and belongs to the point group D 3h (65a). The infrared and Raman spectra of carbonates have been widely studied (47b) and the fundamental frequencies of the carbonate ion, shown in Table 4.2a are well established (65a). The spectra of c r y s t a l l i n e i o n i c carbonates f a l l , gener- a l l y , into one of two groups according to whether the compound i s of the c a l c i t e or aragonite type (47b). The difference 60 TABLE 4.2a 2— Vi b r a t i o n a l Frequencies of CO3 Ion (Point Group D 3 n ) V i b r a t i o n a l Frequency mode Assignment Xcm~l) A c t i v i t y v1- CO symmetric stretch 1063 (R) v 2 A'g Out-of-plane bend 879 (I.R) v 3 E ' Degenerate stretch 1430 (R,I.R) v 4 E / Degenerate bend 680 (R,I.R) (R = Raman active; I.R = Infrared active) between the two groups arises mainly from the intermolecular coupling of the out-of-plane bending .... mode vVj (101) , and the lower symmetry of the carbonate ion i n the c r y s t a l (47b). The s i t e symmetry of the carbonate ion i n a c a l c i t e type c r y s t a l i s D 3, whereas i t i s C s i n aragonite (47b). As seen from the cor- r e l a t i o n Table 2.1b, there i s no change i n the selection rules in going from Dgj. to D^ symmetry. The spectrum of c a l c i t e i s very si m i l a r to that of a free carbonate ion and the inf r a r e d absorption bands appear at 1430 (vs), 874 (s) and 710 (m) cm - 1 (91). \In the inf r a r e d spectrum of aragonite, the O j mode shows a weak absorption at 1080 cm - 1 and the V4 mode s p l i t s into two bands at 710 and 696 cm - 1, but there i s no s p l i t t i n g of the A)3 mode (91). From a study of the s o l i d state i n f r a r e d spectra of the carbonates of main group and f i r s t row t r a n s i t i o n metals, Ross and Goldsmith (102) have concluded that the c r y s t a l f i e l d i n carbonates cannot be very strong. These authors observed that the s p l i t t i n g s of the ^3 and v" 4 modes are usually small and sometimes absent. Infrared spectra of anhydrous a l k a l i metal carbonates also show only small s p l i t t i n g s of degenerate modes (103) . Only i n anhydrous lithium carbonate does the \)g mode show a s p l i t t i n g of about 60 cm - 1, and no s p l i t t i n g for thi s mode i s observed i n sodium and potassium carbonates. Metal-carbonato complexes of cobalt(III) have been known for a very long time. From the existence of Co(NH 3) 4C0 3 + and •Co(NHg)gCO^ i t became evident that the C0 3 group sometimes i s a bidentate and sometimes a unidentate ligand. The bidentate nature of the carbonate group i n Co(NH 3) 4C0 3 has recently been proved by an X-ray c r y s t a l structure determination (104). The carbonate ion can coordinate to the metal atom (M) i n one of the following ways: M M \ /\ , , 0 1 0 0 1 M—-0 0 M 1 : \ / \ / c c c / \ I l! n o o n o n o n Unidentate Bidentate Bridging C s symmetry C 2 v symmetry C 2 v symmetry (OI represents oxygen atoms involved i n coordination, O i l represents oxygen atoms not involved i n coordination.) As discussed in section 2.1, upon lowering the carbonate ion symmetry to either C s or C2V> t n e infrared jlictive mode of the free ion becomes inf r a r e d active and the degenerate modes of the free ion are each resolved into twx> cmodesi;:thu;s /giying r i s e to a t o t a l of six infrared active vibrations. In the infrared spectra of carbonato complexes, the v^ mode of the free C0^~ ion appears with moderate i n t e n s i t y , and the degenerate modes show larger s p l i t t i n g s than those causedby c r y s t a l f i e l d e f f e c t s . i Gatehouse, Livingston, and Nyholm (105) suggested the v i b r a t i o n a l modes of a coordinated carbonato group, assuming C2 V symmetry which are shown i n Table 4.2b. TABLE 4.2b Vib r a t i o n a l Modes of The Carbonato Groups of C 2 v Symmetry «!> C0 2 symmetric stretch (Aj) CO stretch h ( A J ) C0 2 bend h (B 2) Asymmetric stretch h (82) Planar rock • Non-planar rock Note: These authors c l a s s i f i e d modes and v" as belonging to 5 the Bj species, and v'g to B 2. This c l a s s i f i c a t i o n has been re- versed here i n conformity with the co r r e l a t i o n tables i n Wilson, Decius, and Cross (71). From a s o l i d state i n f r a r e d study of a number of metal- carbonato complexes containing both unidentate and bidentate carbonato groups, these authors found that the v i b r a t i o n a l frequencies of the carbonato group f a l l i n the following ranges: Vi b r a t i o n a l . . mode v 4 Vj v*2 v g v*. or \) 5 Frequency (1080-1055 (cm-1) 1577-1493 1338-1260 (1050-1021 889-824 809-738 These authors showed that the s p l i t t i n g of the ^3 mode of the 2 — free CO3 ion increases along the series : basic c a r b o n a t e s ^ carbonato complexes < acid carbonates organic carbonates. However, these authors did not d i f f e r e n t i a t e between the vibra- t i o n a l modes of unidentate and bidentate (or bridging) car- bonato groups. Nakamoto and coworkers ( 9 1 ) examined the infrared spectra of both unidentate and bidentate carbonato groups and found that the s p l i t t i n g of the Vg mode i s greater for the bidentate than for the unidentate carbonato group, but that there i s no s i g n i f i c a n t difference i n the frequencies of the four remaining bands. However, as recently pointed out by E l l i o t and Hathaway ( 1 0 6 ) the change from a unidentate to a bidentate carbonate group may be considered to involve an increase i n the double bond character of the C - 0 stretching vibration, (v^), r e s u l t i n g i n an increase i n the C - 0 stretching frequency, and a lowering of the double bond character of the C 0 2 group with a consequent lowering of the frequencies of the symmetric and asymmetric CO2 stretching v i b r a t i o n . The resul t of this change i s to al t e r the assignments of the f i r s t three high frequency bands of the bidentate carbonato group to v i (A x) v 4 (B 2) v_ (Aj) C"s--0 symmetric C 0 2 asymmetric C O g symmetric stretch stretch stretch 1 5 7 7 - 1 4 9 3 1 3 3 8 - 1 2 6 0 ( 1 0 8 0 - 1 0 5 5 ( 1 0 5 0 - 1 0 2 1 It can be seen that the v i b r a t i o n a l modes suggested by Gatehouse, Livingston, and Nyholm for the carbonato group i n fact represent the v i b r a t i o n a l modes of a unidentate carbonato group. The 63 v i b r a t i o n a l modes of unidentate and bidentate carbonato groups would be si m i l a r to those of unidentate and bidentate n i t r a t o groups and the same convention has been used i n numbering the v i b r a t i o n a l modes. Later, F u j i t a , Martell and Nakamoto (107) reported the res u l t s of a normal coordinate analysis of unidentate and b i - dentate carbonato groups. These authors used models based on C s as well as symmetry for the unidentate carbonato group. A model based on a four membered chelate ring of symmetry was used for the bidentate carbonato group. Their calculated r e s u l t s are shown i n Table 4.2c. TABLE 4.2c Calculated Frequencies of Unidentate and Bidentate Co(III) Carbonato Complexes (cm - 1) Unidentate V i b r a t i o n a l mode Assignment ( C-°II> s t r . ( C - 0 n ) s t r . + (C-0j)str, (C-0!) s t r . + bend ( C - 0 n ) s t r . ^3 6̂ ( O n C O H ) ( O n C O n ) rock Frequency ^2v Bidentate V i b r a t i o n a l mode Assignment 1483 1482 v i (C-O n) s t r . 1373 1376 1039 1069 (G-Oj) (C-Oi) str.+ s t r . (OiCOn)bend 765 772 ^3 Ring def, •+ (Co-p; str, 711 676 *6 (OlCOn) bend + ( C - O i)str, +(Co-Gi) s t r . Frequency 1595 1282 1038 771 669 .65 The numbering of modes used by these workers i s s l i g h t l y d i f f e r - ent because v i b r a t i o n a l frequencies involving metal-oxygen bonds have also been included i n the above shown assignments. These re s u l t s confirm the general conclusions, about the infrared spectra of the coordinated carbonato group, reached by e a r l i e r workers (91, 105). However, these r e s u l t s show coupling between various v i b r a t i o n a l modes i n metal-carbonato complexes containing four membered rings. Very recently E l l i o t and Hathaway (106) have reported the p o l a r i z a t i o n data for single c r y s t a l s of Co(NHg^COsBr. Their r e s u l t s confirm the normal coordinate analysis model i n - volving covalent bonding of the carbonate oxygen atoms to the cobalt ion. The infrared spectrum of dimethyltin carbonate was measured on a mixture of dimethyltin carbonate and s i l v e r chloride, which was obtained by the metathetical reaction of dimethyltin dichloride and s i l v e r carbonate i n methanol followed by removal of the solvent under vacuum. X-ray powder photographs of the mixture were examined and no l i n e s due to either dimethyl- t i n chloride or s i l v e r carbonate were found. Therefore i t may be considered that the i n f r a r e d spectrum thus; obtained i s largely due to dimethyltin carbonate. A portion of the observed spectrum i s shown i n Figure 4.2, and the frequencies, together with the r e l a t i v e i n t e n s i t i e s of the absorption bands i n the region 2000- 250 cm - 1 and t h e i r suggested assignments, are l i s t e d i n Table 4.2d. The absorption bands due to the dimethyltin group can be e a s i l y distinguished and assigned, i . e . 1415 cm - 1, C-H asymmetric bend; 1200 cm - 1, C-H symmetric bend; 785 cm - 1, CH 3 rock; 576 cm - 1, Sn-C asymmetric stretch; and 523 cm - 1 Sn-C symmetric stretch. The absorptions due to the carbonate group occur at Frequency (cm - 1 ) 67 TABLE 4. 2d Infrared Absorption Spectrum of Dimethyltin Carbonate Frequency (cm - 1) 1510 1415 1385 1200 1105 1068 832 785 700 655 576 523 500 340 275 Relative Intensity vs sh vs m w m m s m s s m s m m ; r ; Assignment C=0 sym. s t r . ^ v p C - H asym.bend COo asym.str., (v 4) C - H sym. bend CO2 sym.str., COo out-of-plane def., (v 6) CH3 rock CO2 sym.bend , ( ^ 3 ) C 0 2 asym.bend , (^5) Sn-C asym. s t r . Sn-C sym. s t r . Sn-0 asym. s t r . and L a t t i c e modes ? m = medium; s = strong; sh = shoulder; v = very; w = weak. Assignments for the carbonate absorption bands have been sug- gested, assuming that the carbonate group i s bridging. 1 68 1510, 1385, 1105, 1068, 832, 700, 655, 500, 340 and 275 cm - 1. It i s evident that the strong bands at 1510 and 1385 em - 1 correspond to the doubly degenerate mode v'g of the free carbonate ion which has s p l i t into these two strong bands. The 1105 and 1068 cm"1 bands correspond to the infrared inactivepnode ^ of the free ion, the 832 cm - 1 band corresponds to the out-of-plane bending mode Og of the free ion, and the bands at 700 and 655 are the two components of the doubly degenerate mode T)̂  of the free ion. The absorption bands i n the region 500-275 cm - 1 are l i k e l y to be associated with the Sn-0 stretching vibrations as well as with the absorptions of the l a t t i c e modes. Similar absorption bands at 450, 375 and 250 cm"1 were also observed i n the spectrum of trimethylantimony carbonate (to be discussed l a t e r ) . It i s known (108) that the carbonates have a l a t t i c e - t y p e absorption in t h i s region. M i l l e r and coworkers (98) have reported si m i l a r bands i n the spectra of some metal carbonates^ ;e.g. lithium carbonate shows strong absorption bands at 498 and 420 cm - 1, lead(II) carbonate has a strong broad band at 400 cm"1, and c a l c i t e has a strong band at 320 cm~l. The infrared spectrum of dimethyltin carbonate c l e a r l y shows that the symmetry of the carbonate group i s lowered from Dgjj to C 2 v or C s, and the magnitude of the s p l i t t i n g s observed for degenerate modes indicates that the carbonate group i s co- ordinated to the dimethyltin group. Moreover, the presence of two Sn-C stretching vibrations of medium in t e n s i t y suggests that the dimethyltin group i s non-linear. These two Sn-C stretching frequencies at 576 and 523 cm - 1 can be compared with those of dimethyltin dichloride (4) which occur at 567 and 515 cm - 1. Therefore the p o s s i b i l i t y of any s i g n i f i c a n t amount of dimethyltin dichloride being present i n the mixture i s very low. Though the observed s p l i t t i n g of the 0- mode in dimethyltin carbonate i s less than that reported (107) for bidentate carbonato complexes, the entire i n f r a r e d spectrum of dimethyltin carbonate suggests that the t i n atom has a tetrahedral configuration which w i l l imply; some sort of coordinate bonding between the dimethyltin group and two of the oxygen atoms of the carbonate group. A polymeric structure consisting of non-linear dimethyltin groups and bridging carbonato groups, making the t i n atom tetrahedral, i s suggested. A monomeric structure containing a bidentate carbonato group coordinated to a non-linear dimethyltin group i s also possible, but i s considered less l i k e l y due to the i n s o l u - b i l i t y and n o n - v o l a t i l i t y of the compound. 4.3 Dimethyltin Chromate (CH 3) 2SnCr0 4 In an attempt to prepare dimethyltin chromate, Rochow, Seyferth, and Smith (16) obtained a basic dimethyltin chromate by the reaction between dimethyltin dichloride and sodium chromate i n aqueous solution. In the present investigation, dimethyltin chromate could be prepared by the metathetical re- action between dimethyltin dichloride and s i l v e r chromate i n acetone or a c e t o n i t r i l e . However, l i k e dimethyltin carbonate, due to the i n s o l u b i l i t y of dimethyltin chromate i n any suitable solvent (from which the compound could be recovered without decomposition), the dimethyltin chromate formed i n the meta- t h e t i c a l reaction could not be i s o l a t e d free from s i l v e r chloride. Therefore the i n f r a r e d spectrum of t h i s compound 7Q was studied using the mixture of dimethyltin chromate and s i l v e r chloride. A portion of the observed infrared spectrum i s shown in Figure 4.3. The absorption frequencies are l i s t e d together with t h e i r r e l a t i v e i n t e n s i t i e s and suggested assignments, i n Table 4.3. 2— The fundamental frequencies of the chromate ion (Cr0 4 ) have already been given i n section 3.2. In the infrared spectrum of dimethyltin chromate, the absorption bands due to the dimethyl- t i n group occur at 2940, (C-H s t r e t c h ) ; 1405, (C-H asymmetric bend); 1195 (C-H symmetric str e t c h ) ; 785, (CH 3 rock); 573, (Sn-C asymmetric stretch); and 512, (Sn-C symmetric stretch) cm - 1. The bands at 975, 928, 880, 750, 465, 390, 348, and 305 cm"1 are due to absorption by the chromate group. Since the spectrum was obtained for a mixture of s i l v e r chloride and dimethyltin chromate, the p o s s i b i l i t y must be considered that some of these bands may be due to some unreacted s i l v e r chromate or dimethyltin d i c h l o r i d e . This can be rejected, however, on the following grounds: (a) the quantitative amount of s i l v e r chloride was obtained on dissolving the mixture i n water a c i d i f i e d with acetic acid; (b) X-ray powder photographs of the mixture did not show any l i n e s due to either s i l v e r chromate or dimethyltin d i c h l o r i d e ; (c) the Sn-Cl stretching vibrations, which are observed i n the i n f r a r e d spectrum (4) of dimethyltin d i c h l o r i d e at 332 and 307 cm - 1 as strong bonds, do not appear i n the i n f r a r e d spectrum of the mixture; (d) the observed Sn-C stretching frequencies i n the spectrum of the mixture d i f f e r s l i g h t l y from those of dimethyltin dichloride (567 and 515 cm - 1). The observed spectrum i s therefore due only to dimethyl- Me 2 SnCr0 4 I I I I l l l l l i I 1200 1000 8 0 0 6 0 0 4 0 0 2 0 0 WAVENUMBER (cm-1) TABLE 4.3 Infrared Absorption Spectrum of Dimethyltin Chromate Frequency (cm"1) Relative Intensity 2940 vw 1405 w 1195 m 975 vs 928 vs 880 vs 785 vs 750 vs 573 m 512 m 465 ms 390 m 348 m 305 m Assignment C-H s t r . C-H asym.bend C-H sym.bend CrOg asym. s t r . >(v6) C r 0 2 sym.str C r 0 2 sym.str.,(^3) CH3 rock C r 0 2 sym.str., Sn-C asym.str. Sn-C sym.str. CrO^ rock, (v"7) C r 0 2 bend,(v3) C r 0 4 rock,(^ 9) C r 0 2 sym.bend m = medium; s = strong; v = very; w = weak. Note: The cromate absorption bands have been assigned by analogy with SO4 group of C 2 v symmetry. 73 t i n chromate. The presence of two Sn-C stretching frequencies indicates that the dimethyltin group i s non-linear i n dimethyltin chromate. The chromate absorption bands i n dimethyltin chromate are re- markably d i f f e r e n t from those of io n i c chromates. The 0- mode observed at 884 cm - 1 for the chromate ion i s resolved into three strong bands at 975, 928 and 880 cm"'1'. The mode observed only as a very weak band at 845 cm""-1- for the chromate ion, shows strong absorption at 750 cm-'1' appearing as one of the components of a broad band giving r i s e to strong absorption i n the 800-720 cm - 1 region; another component i s the Sn-CHg rocking frequency. At lower frequencies, the free chromate ion shows only a weak band due to the t r i p l y degenerate mode 0 ,̂ usually observed as a doublet i n the 420-370 cm"1' region. The appearance of well defined absorption bands of medium i n t e n s i t y at 465, 390, 348 and 305 cm"1, i n the inf r a r e d spectrum of dimethyltin chromate, shows that the ̂  mode of the free ion has s p l i t into three modes and the mode has become infrared active, although Sn-0 v i - brations may possibly also cause absorption i n t h i s region. Certainly the chromate absorption bands i n dimethyltin chromate can only be interpreted i n terms of a C2 V(&r possibly lower) symmetry of the chromate group. As i n the case of other s o l i d state spectra, the lower symmetry of the chromate group observed i n t h i s spectrum could be attributed to c r y s t a l f i e l d e f f e c t s . However, recent studies made by Campbell (109) on a large number of chromates, containing a wide variety of cations, showed that c r y s t a l f i e l d e f f e c t s do not cause s i g n i f i c a n t changes i n the inf r a r e d spectra of c 74 chromates. Not even i n ammonium chromate, where hydrogen bonding i s known to occur (109) were such large and well defined s p l i t t i n g s of the mode observed, and only minor e f f e c t s were observed i n the 500-250 cm - 1 region i n contrast to the pronounced s p l i t t i n g s observed for dimethyltin chromate. The entire infrared pattern and extent of s p l i t t i n g s observed for dimethyltin chromate are quite d i f f e r e n t from those which could be attributed to c r y s t a l f i e l d e f f e c t s . Therefore the infrared spectrum of dimethyltin chromate can only be explained i n terms of a coordinated structure in which the chromate group i s coordinated to the non-linear dimethyltin group through two of i t s oxygen atoms, making the t i n atom tetrahedral. A polymeric structure similar to that of t r i - methyltin perchlorate (27) i s therefore proposed, the CrO^ groups acting as bridging groups between non-linear (CHg^Sn units. A monomeric structure containing a bidentate chromate group i s also possible, although less l i k e l y i n view of the i n s o l u b i l i t y and n o n - v o l a t i l i t y of thi s compound. The u l t r a v i o l e t and v i s i b l e d iffuse reflectance spectrum of a powdered sample of the dimethyltin chromate and s i l v e r chloride mixture was examined. Two absorption bands showing maxima at 280 and -380 nj// were observed. This r e s u l t i s sim i l a r to that obtained for b i s ( t r i m e t h y l t i n ) chromate as well as reported (100) for Co(NHg)gCrO^. 4.4 Dimethyltin Sulphate (CH o) nSnS0^ — * — o 2 4 In t h i s investigation the preparation of dimethyltin sulphate was attempted i n d i f f e r e n t solvents, and the infrared spectra of the products were examined. Some addition compounds 75 of dimethyltin sulphate were also prepared and examined by infr a r e d spectroscopy. The metathetical reaction between dimethyltin dichloride and s i l v e r sulphate i n aqueous solution resulted i n the formation of dimethyltin sulphate and s i l v e r chloride, and dimethyltin sulphate was obtained as a non-hygroscopic s o l i d . The infrared absorption spectra (obtained on samples made as mulls i n nujol showed absorption bands at 1238 (w,sp), 1095 (vs,b), 805(s), 670 (m,sp), and 600 (s,sp) cm - 1. The bands at 1238, 805 and 600 cm - 1 are due to the dimethyltin group and can be assigned as 1238 cm 1 , C-H asymmetric stretch; 805 cm - 1, CHg rock; and 600 cm"1, Sn-C asymmetric stretch. The band at 1095 cm - 1 corresponds v 2- l to the Vg mode of the SO^ ion and the 670 cm _ i band i s due to the mode of the SO4 ion. It may be noted that the frequency of the mode i n dimethyltin sulphate i s considerably s h i f t e d towards higher wave number as compared with the value (^613 cm - 1) observed i n ionic sulphates. Nevertheless, the symmetry of the sulphate group i n thi s compound i s tetrahedral. The dimethyltin group shows only one Sn-C stretching mode and i t s frequency i s almost the same as observed for dimethyltin d i f l u o r i d e . The 2+ 2— spectrum can be interpreted i n terms of (CT^^Sn and SO^ ions. However, i t can be interpreted equally well i n terms of a poly- : meric sturcture, i n which every oxygen of the sulphate group i s coordinated to a t i n atom making the t i n atom six coordinate, as shown below: 76 In such a structure, the T d symmetry of the sulphate groups and l i n e a r i t y of the dimethyltin groups are preserved. A three dimensional polymeric structure containing l i n e a r dimethyltin and tetrahedral sulphate groups i s also possible. The metathetical reaction between dimethyltin dichloride and s i l v e r sulphate was also c a r r i e d out i n acetone, a c e t o n i t r i l e and methanol. In both acetone and a c e t o n i t r i l e , the reaction product was a mixture of s i l v e r chloride and dimethyltin sulphate, which was characterized i n each case by the r e s u l t s of X-ray powder photographs and the infrared absorption spectra, of the mixtures. However, when the metathetical reaction was c a r r i e d out i n methanol, a mixture of s i l v e r chloride and a methanol adduct of dimethyltin sulphate was obtained. Though the methanol adduct of dimethyltin sulphate could not be i s o l a t e d free from s i l v e r chloride on account of i t s i n s o l u b i l i t y i n a range of solvents, except water, i t s formation and presence i n the mix- ture i s demonstrated by i n f r a r e d spectroscopic evidence. The infrared absorption spectrum of the mixture was found to be very d i f f e r e n t from that observed for dimethyltin sulphate. The i n f r a r e d absorption bands, together with the r e l a t i v e i n t e n s i - t i e s and assignments, are l i s t e d i n Table 4.4a and a portion of the spectrum i s shown i n Figures 4.4a and 4.4b. (The broken curves refer to the spectrum of the anhydrous sulphate.) Absorption bands due to the sulphate group i n the mixture appear at 1210, 1175, 1065, 995, 665, 606, 585 and 475 em - 1. The absorption bands associated with the dimethyltin group appear at 2960, (G-H stretch); 1415,(C-H asymmetric bend); 1230, (C-H symmetric bend); 795,(CH 3 rock); and 595, (Sn-C asymmetric I I I I I I 1 I I 1 2 0 0 1 1 0 0 1 0 0 0 9 0 0 8 0 0 C m 1 00 79 TABLE 4.4a The Infrared Absorption Spectrum of the Mixture of Dimethyltin Sulphate-Methanol Adduct and S i l v e r Chloride T Frequency (cm"1) Relative Intensity Assignment 3110 m 0-H Str. 2960 vw C-H s t r . 2800 V 1455 w C-H asym.bend 1415 vw 1230 m C-H sym.bend 1210 m S0 2 asym.str.,(^6 1175 s S0 2 sym.str.,(0].) 1140 sh 1065 s SOg asym.str„(0g 995 s S0<2 sym. s t r .,(02) 795 s CHg rock 655 s S0 4 rock,(0 7) 606 s S0 2 bend, (\)g) 595 s Sn-C asym.str. 585 sh S0 4 rock, (vg.) 475 m S0 2 bend , (04) m = medium; s = strong; sh = shoulder; v = very; w = weak. * denotes the oxygen atoms (of the S0 4 group) involved i n bonding. The assignments for the S0 4 group have been suggested assuming C 2 v symmetry. 80- stretch) cm - 1. There i s no band which can be attributed to the Sn-C symmetric stretch. The bands at 3110, 2800, and 1455 cm - 1 are due to methanol. The*. 0-H stretching frequency has been con- siderably lowered as compared with methanol, suggesting that the methanol i s coordinated to dimethyltin sulphate.A Similar shift; i n 0-H frequency occurs in the methanol adduct of bis(trimethyltin) sulphate, as discussed e a r l i e r . The sulphate portion of the spectrum i s completely consistent with the presence of coordinated 2 - sulphato 1 group of C2v symmetry and indicates that no free SO^ ions are present i n the mixture. The entire spectrum of the mix- ture strongly suggests that a methanol adduct;of dimethyltin sulphate i s present and that, in th i s adduct, both the methanol and sulphate group are coordinated to the linear dimethyltin group. However, i n view of the uncertainty i n the number of methanol molecules present i n the adduct, no conclusions can be drawn about i t s detailed stereochemistry. The methanol adduct of dimethyltin sulphate was hydrolysed on exposing to a i r , as shown by changes i n i t s in f r a r e d spectrum. However, a sample of the mixture kept i n the dry box did not show any changes i n i n f r a r e d spectrum. S i m i l a r l y , a sample of the mixture did not show any change i n in f r a r e d spectrum after being pumped for several hours at room temperature. However, when the mixture was heated under vacuum at 100° for about four hours, the methanol was completely removed and the infrared spectrum of the heated s o l i d was i d e n t i c a l to that of dimethyl- t i n sulphate. Thus i t i s evident that, during t h i s treatment, the coordinated methanol i s l o s t from the adduct and dimethyltin sulphate i s formed. 81: Dimethyltin sulphate also formed 1:1 addition compounds with pyridine and dimethyl sulphoxide. These addition compounds are stable and do not hydrolyse i n a i r . A 1:2 addition compound of dimethyltin dichloride with pyridine has been described (33). A si m i l a r addition compound of dimethyltin dichloride was obtained with dimethyl sulphoxide. A comparison of the infrared spectra of these compounds i s made below. The i n f r a r e d spectra of pyridine complexes and pyridinium s a l t s have been studied (110). Coordinated pyridine can be d i s - tinguished by the presence of a weak band between 1250 and 1235 cm"1; by a s h i f t i n the strong 1578 cm"1 band to 1600 cm"1; and by s h i f t s of the 601 and 403 cm"1 bands to 625 and 420 cm"1 respectively (110). The i n f r a r e d absorption spectra of both dimethyltin sulphate-pyridine monoadduct and dimethyltin dichloride-pyridirie diadduct are recorded, together with the r e l a t i v e i n t e n s i t i e s of the absorption bands and suggested assignments, i n Table 4.4b. A portion of each spectrum i s shown i n Figure 4.4c; curve (a) refers to the dichloride adduct and curves (b) and (c) re f e r to the sulphate adduct. The p y r i - dine absorption bands i n both the compounds occur at almost the same frequencies and are i n agreement with the pyridine absorption bands reported for other pyridine complexes. From a comparison of the spectrum of the dimethyltin sulphate adduct with that of the dimethyltin dichloride adduct, the sulphate absorption bands i n the dimethyltin sulphate adduct can be distinguished unambiguously. In the dimethyltin d i - chloride adduct, there are four strong very sharp absorption bands at 1210, 1062, 1037 and 1010 cm"1, due to pyridine. In M e 2 S n S 0 4 . P y 1200 1000 8 0 0 6 0 0 4 0 0 Frequency (cm"1) 83 TABLE 4 • 4b Infrared Absorption i Spectra of Pyridine Adducts of Dimethyltin Sulphate and Dimethyltin Dichloride (CH 3) 2SnS0 4.Py •equency Relative !cm~l) i n t e n s i t y (CH3) 2SnGl2.2Py Frequency Relative (cm-1) in t e n s i t y Assignment 3100 ) 3050 ) 2940 ) w 3100 ) 3040 ) 2940 ) w C-H s t r . 2450 1605 vw s 1605 1570 s vw 1492 m 1490 s 1450 s 1450 s 1410 w C-H asym.bend 1360 vw 1360 vw 1245 sh 1245 w 1232 ) ) 1217 ) m C-H sym. bend 1208 sh 1210 s 1200 1185 w so 2 asym. s t r .pCvg) 1160 vw 1160 vw 1090 s so 2 sym. str . X v'i) 1066 s 1062 1037 • s s 1025 s * so 2 asym. s t r .,(^8) 1013 sh 1010 s 992 m 973 vw so 2 sym. s t r . s ( ' ) 2 ) 84 Table 4.4b continued 950 wv 887 wv 800 s 780 765 s 760 745 700 692 s 690 655 s 637 s 630 598 s 560 590 576 m 510 vw 465 m 425 m 425 417 sh s CHg rock s WW ) ) s ) SO. rocking, 4 (v 7) s s Sn-C asym.str. S 0 2 bend,(0 3) S 0 4 rock,(v- 9) S 0 2 bend, (v 4) ms m = medium; s = strong; v = very; w = weak. * denotes the oxygen atoms (of the SO4 group) involved i n bonding. The assignments for the SO4 group have been made assuming C2v symmetry. No assignments have been made for the absorption bands due to pyridine. 85 the dimethyltin sulphate adduct, the bands at 1208, 1066 and 1010 correspond to three of the above four bands while the band at 1037 cm - 1 i s apparently masked by a strong band at 1023 cm"1. Thus the absorption bands at 1200, 1090, 1025 and 992 cm"1 i n the spectrum of dimethyltin sulphate-pyridine adduct can be attributed to the sulphate group. S i m i l a r l y , i n the lower frequency region, the bands at 655,. 590, 576 and 465 cm"1 are due to the sulphate group. As regards the absorption bands due to the dimethyltin group, the bands at 598 and 800 cm"1 i n the sulphate adduct can be assigned to the Sn-C asymmetric stretch, and CH^ rocking modes respectively. The corresponding frequencies i n the dichloride adduct occur at 560 and 780 cm"1 respectively. In both compounds, only the Sn-C asymmetric stretching frequency appears. Therefore the dimethyl- t i n group i s apparently linear i n both compounds. There i s a very weak absorption band at 510 cm - 1 i n the sulphate adduct, i t may either be due to a s l i g h t deviation from l i n e a r i t y of the (CHg^Sn group, or more l i k e l y to a forbidden band, because of i t s very weak i n t e n s i t y . Thus the i n f r a r e d spectrum of dimethyltin sulphate-pyridine monoadduct again indicates that the sulphate group i s coordinated to the dimethyltin group and that i t acts either as a bidentate or a bridging ligand. The C^v symmetry of the sulphate group and the l i n e a r i t y of the dimethyltin group suggest that the t i n atom i s f i v e coordinate i n t h i s compound. Considering the f i v e co- ordination of the t i n atom, two stereochemical configurations can be suggested. One involves a t r i g o n a l bipyramidal arrangement containing the two methyl groups i n the a p i c a l positions; the pyridine molecule and two oxygen atoms of the sulphate group being coordinated to the central t i n atom i n the three a x i a l 1*6 positions. The other possible configuration can be that of a square pyramid i n which the lin e a r dimethyltin group i s coor- dinated to two oxygen atoms i n trans positions; the pyridine molecule being coordinated to the t i n atom at the apex. However, i t must be considered that a tr i g o n a l bipyramidal configuration for t h i s compound involves coordinated groups i n the a x i a l plane, while the covalently bonded methyl groups are placed at the api c a l positions. Therefore such a configuration i s most unlikely. The assignments for v i b r a t i o n a l frequencies of dimethyl sulphoxide (DMSG) have been made (111) and the S-0 stretching frequency has been well established. It gives r i s e to a very strong absorption band at 1057 cm - 1 (in a l i q u i d f i l m ) . There i s another very sharp, much less intense absorption at 950 cm - 1, and a weaker, broad peak at 915 cm"-1, both of them being assigned to CHg rock. DMSO has an unshared pair of electrons on both sulphur and oxygen, and can coordinate through the sulphur atom or through the oxygen atom. As Cotton and Francis (112) have pointed out, the S-0 bond i n sulphoxides has at least p a r t i a l double bond character which may be considered to re s u l t from the superposition of pTT" -d"TT bonding from 0 to S upon the S-0 sigma bond. Therefore coordination through the oxygen atom should decrease pTT - dlT" back bonding and hence lower the S-0 bond order and the stretching frequency. On the other hand, coordination v i a sulphur would be expected to increase pTT-dTT"* back bonding and thus rai s e the S-0 stretching frequency. Cotton, Francis, and Horrocks (113) have reported that, i n sulphoxides, the oxygen atom i s the donor in the majority of 1 the metal complexes studied. In such cases, the S-0 stretch a? i s s h i f t e d to lower frequencies. With an acceptor such as Pt(II) or Pd(II), sulphur seems to be the donor atom and the S-0 stretch- ing frequency i s higher i n the complex than i n the free ligand. Though there i s hardly any doubt that i n DMSO complexes such as Co(DMSO) 6CoCl 4 and SnCl 4(DMSO) 2, the oxygen atom of DMSO acts as the donor atom, the assignments of the v i b r a t i o n a l frequencies have been disputed. In Co(DMSO)gCoCl4, Cotton, Francis,and Horrocks (113) have assigned the S-0 stretching mode to a very strong band at 950 cm - 1 and the CH3 rocking mode to a strong band in the 1000 cm"-'- region. Contrary to these assignments, Drago and Meek (114) have assigned the 950 cm - 1 band to the CH3 rock and 1000 cm - 1 band to the S-0 stretch. The infrared absorption bands of DMSO adducts of dimethyltin sulphate and dimethyltin dic h l o r i d e are l i s t e d , together with their r e l a t i v e i n t e n s i t i e s and suggested assignments in Table 4.4c, and a portion of the spectrum of the sulphate adduct i s shown i n Figure 4.4d. The absorption bands due to DMSO i n both compounds occur at almost the ̂ame frequencies. In addition to the DMSO bands which can be recognized e a s i l y , the main features of the spectrum of the dichloride adduct are the absorption bands at 788, 573, 508 (vw), 415, 340, 312 and 255 cm - 1. The bands at 788, 573, and 415 cm"1 can be assigned to CH3 rock [ in(CH3)2 group], the Sn-C asymmetric stretch and Sn-0 asymmetric stretch respectively. The very weak band at 508 may be an overtone of the 255 cm"1 band. Of the three bands at 340, 312 and 255 cm - 1, most probably only one band i s due to the Sn-Cl stretching v i - bration. In DMSO, there are absorption bands at 382 and 333 cm"1 which have been assigned (111) to the symmetric and asymmetric Frequency (cm - 1 ) oo oo 89 TABLE 4.4c Infrared Absorption Spectra of DMSO Adducts of Dimethyltin Sulphate and Dimethyltin Dichloride (CH3)2SnS04.DMSO Frequency Relative (cm"1) i n t e n s i t y 3040 2960 1455 1443 1420 1323 1300 1225 1202 1193 1080 1045 1000 989 945 915 805 783 727 w J w ) sh ms w m w m s s, sh s m m s w s sh m CH 3) 2SnCl 2.2DMS0 Frequency Relative (cm - 1) int e n s i t y 3030 2930 1457 1430 1410 1365 1320 1300 ) 1295 ) 1034 995 943 »910 788 720 w w sh s m vw ms m s s s m s m Assignment C-H stretch S0 2 asym. str.,(v^) S0 2 sym. s t r . , (v n) S0 2 asym.str., S0 2 sym.str. , (v 2 ) vHS-O) (DMSO) CH- rock 90 Table 4.4c continued 655 s 597 s 573 590 s 508 468 m 437 s 415 330 m 340 312 255 m 255 S O 4 rock s Sn-C asym.str. S 0 2 bend ,(v 3) vw S 0 2 bend ,(v4) s Sn-0 stretch s s Sn-Cl s t r . m m = medium; s = strong; sh = shoulder; v = very; w = weak; * denotes the oxygen atoms (of the SO4 group) involved i n bonding. The assignments for the SO4 group have been made assuming C 2 v symmetry as i n C I O 4 . No assignments have been made for DMSO absorption bands except the vXS-O). 913 C-S-0 deformation. These bands are shi f t e d to 330 and 255 cm - 1 i n the dimethyltin sulphate adduct. Therefore i t i s suggested that i n the dimethyltin dichloride adduct, the 312 cm - 1 band i s associated with the Sn-Cl stretching v i b r a t i o n and the bands at 340 and 255 cm - 1 are due to the DMSO ligand. Thus only one frequency i s indicated for each of the Sn-C, Sn-0 and Sn-Cl stretching vibrations i n the infrared spectrum of the dimethyltin dichloride-DMSO diadduct. In view of these spectral features,a trans octahedral structure i s suggested for t h i s compound. As regards the assignments for the S-0 stretching frequency, there are two strong bands of almost equal i n t e n s i t y at 995 and 943 cm"1 and i t i s not possible to distinguish which of the two bands cor- responds to the S-0 stretch. However, i n dimethyltin sulphate- DMSO adduct the most intense band due to DMSO appears at 945 cm"1 and therefore t h i s band i s assigned to the S-0 stretch. On thi s basis, the 943 cm"1 band i n the dichloride adduct can be assigned to the S-0 stretch and the 995 cm~l band to CH 3 rock (DMSO). The main features of the infrared spectrum of the dimethyl- t i n sulphate-DMSO adduct are the absorption bands at 1207-1193, 1080, 1045, 989, 655, 590 and 468 cm"1. Comparing the DMSO part of the spectrum of the sulphate adduct with that of the dichloride adduct, i t can be seen that no bands due to DMSO occur i n these regions except a band at 1034 cm - 1 which i s masked by the strong sulphate band at 1045 cm"1. The sulphate absorption bands i n the dimethyltin sulphate-DMSO adduct are almost i d e n t i c a l to those observed for the dimethyltin sulphate-pyridine adduct. Thus the i n f r a r e d spectrum of dimethyltin sulphate-DMSO adduct also shows coordination between the sulphate and the dimethyltin groups. 92 The Sn-C and Sn-0 vibrations i n the dimethyltin sulphate-DMSO adduct appear at 597 and 437 cm"1 respectively. It may be noted that only the Sn-C asymmetric stretching and Sn-0 asymmetric stretching vibrations appear. The stereochemical features sug- gested for dimethyltin sulphate-pyridine adduct can also be suggested for the DMSO adduct because of the almost i d e n t i c a l spectrum of the dimethyltin and the sulphate groups i n both compounds. •'• The coordination by the sulphate groups i n the adducts of dimethyltin sulphate with methanol, pyridine and DMSO as shown by the above spectroscopic r e s u l t s , i s not consistent with an io n i c c o n s t i t u t i o n of dimethyltin sulphate and suggests a coordinated structure for t h i s compound. Proton n.m.r. studies on dimethyltin(IV) compounds have recently been used to estimate the percentage s-character in the t i n o r b i t a l s directed to the methyl groups, by the measurement of the 1 17sn-CH- or ̂ ^Sn-CHg coupling constants. Coupling constant data reported (50) for some dimethyltin compounds cXYfc shown in Table 4.4d. TABLE 4.4d Sn-GH.3 Coupling' Constants of Some Dimethyltin (IV) Derivatives Compound Solvent J( 1 1 7Sn-CH 3) J( 1 1 9Sn~CH 3) c.p.s. c.p.s. (CH3).2Sn(C104)2 H20 102 107 (CH 3) 2Sn(N0 3) 2 H20 104.3 108. 7 (CH 3 ) 2 S n C l 2 HC1 92.5 97.5 (CH 3)2Sn(C5H70 2) 2 CDC13 95.0 99.3 ( C H 3 ) 2 S n C l 2 CDC13 66.5 69.8 (CH 3) 2Sa(OCH 3) 2 c c i 4 71.3 74.4 93 Raman and infrared studies on aqueous solutions of dimethyl- t i n compounds (21) indicate the presence of the aquodimethyltin cations with a linear C-Sn-C skeleton and four water molecules coordinated i n the equatorial plane. Bis(acetylacetonato) dimethyltin(IV), (CHg) gSn^sHyOg) 2 i s also considered, from Raman and infrared and proton n.m.r. studies (50), to be octahedral with trans methyl groups. The configuration of the l a s t two compounds l i s t e d above, i . e . dimethyltin dichloride (4) and dimethoxy dimethyltin (115), i s reported to be tetrahedral i n chloroform solution. As seen from Table 4.4d, the coupling constant values for the octahedral species are markedly d i f f e r - ent from those of tetrahedral species. In t h i s i nvestigation the proton n.m.r. spectra of dimethyltin sulphate as well as i t s adducts with pyridine and DMSO, and dimethyltin chloride-DMSO adduct were determined. The values of the coupling constants obtained are shown i n Table 4. 4e. TABLE 4.4e Sn-CHg Coupling Constants of Dimethyltin Sulphate, Dimethyltin Sulphate-Pyridine, Dimethyltin Sulphate-DMSO, and Dimethyltin Dichloride-2DMSO Compound Solvent J( 1 1 7Sn-CH 3) J( 1 1 9Sn-CH 3) c.p.s. c.p.s. (CH 3) 2SnS04 H20 104.5 109.5 (CH 3) 2SnS04.Py H20 91.0 95.0 (CH 3) 2SnS0 4-DMS0 H20 104.5 109.5 (CH3)2Sn.Cl2-2DMSO H20 102.0 107.0 ( C H 3 ) 2 S n C l 2 , 2 D M S O CHC13 82.5 86.5 Note: Dimethyltin sulphate and i t s addition compounds with pyridine and DMSO are not soluble i n organic solvents such as CHC13 or CCl^. 94 The coupling constant values for aqueous solutions of dimethyltin sulphate, the dimethyltin sulphate-DMSO adduct and the dimethyl- t i n dichloride-DMSO adduct are i n good agreement with the values reported for dimethyltin perchlorate and n i t r a t e , and i t can be inferr e d that l i k e dimethyltin perchlorate and n i t r a t e , these compounds are also dissociated i n aqueous solution to form six coordinate aquodimethyltin cations. The values for the coupling constants of the dimethyltin sulphate-pyridine adduct are lower but they are of the same order as those reported i n Table 4.4d for dimethyltin dichloride in hydrochloric acid solution. The coupling constants for dimethyltin dichloride-DMSO adduct are lower compared with those for bis (acetylacetonato)dimethyltin (IV) . According to the lin e a r r e l a t i o n (12) between coupling constant and percentage s-character i n the t i n o r b i t a l s directed to methyl groups, s-character i n the Sn-CH3 bond i s about 40 percent i n dimethyltin dichloride-DMSO adduct and 46 percent i n b i s - (acetylacetonato)dimethyltin(IV). The Sn-0 stretching frequen- cies i n these two.compounds occur at 415 and 400 cm - 1 res- Hie. pectively, i n d i c a t i n g greater Sn-0 bond strength i n dimethyltin A dichloride-DMSO adduct. However, the Sn-C stretching frequencies i n the two compounds occur at 573 and 570 cm"1 respectively, i n d i c a t i n g very l i t t l e change in the Sn-C bond strength i n the two compounds. 4.5 Dimethyltin Bis(tetrafluoroborate) ( C H 3 ) 2 S n ( B F 4 ) 2 The tetrahedral symmetry(T d)of the tetrafluoroborate ion has been established by in f r a r e d and Raman studies (116, 117). However, the frequencies of the fundamental vibrations of the 9 5 tetrafluoroborate ion reported by two groups of workers (116, 117) are s l i g h t l y d i f f e r e n t and both sets of values are l i s t e d i n Table 4.5a. TABLE 4.5a Vib r a t i o n a l Frequencies of BF^- Ion (Point Group T^) Vib r a t i o n a l \ ^2 mode ^3 ^4 (Al) (E) (F2> (F 2) (R) (R) (R,I.R) (R,I.R) Frequency (cm-1) (116) 786 369 1100 541 (117) 769 353 984,1016 524 (R:= Raman active; I.R = Infrared active) The detailed i n f r a r e d spectra of some io n i c t e t r a f l u o r o - borates have been studied (118-120). C r y s t a l l i n e t e t r a f l u o r o - borates give many absorption bands other than the fundamentals, the most prominent feature being the s p l i t t i n g of the v*3 mode, a doublet for^v^ mode and the appearance of the forbidden v-̂ mode. Cote and Thompson (118) considered t h i s s p l i t t i n g to be a r e s u l t of the lowering of the s i t e symmetry of the anion i n the c r y s t a l . From an inf r a r e d spectroscopic study of potassium tetrafluoroborate containing an enriched isotope r a t i o of (10B : NB), Greenwood (120) showed that the s p l i t t i n g and broadening of peaks i n potassium tetrafluoroborate i s due to a combination of the lowering of s i t e symmetry and the presence of the two isotopes of boron. However, the infrared spectrum (43) of t r i m e t h y l t i n tetrafluoroborate i s considerably d i f f e r e n t from 96 the i n f r a r e d spectra of the ionic tetrafluoroborates. While i n ion i c tetrafluoroborates, the Vg mode appears as a very strong broad band i n the region 1050-1075 cm - 1 showing s p l i t t i n g i n the form of fine structure, i n trime t h y l t i n tetrafluoroborate, t h i s mode i s c l e a r l y resolved into three strong bands at 1170, 1070, and 930 cm"1. Sim i l a r l y , the mode appears only as a weak "forbidden" t r a n s i t i o n at 771 cm - 1 i n the spectra of ioni c tetrafluoroborat.es, but i n the spectrum of trime t h y l t i n t e t r a - f luoroborate, the A)J mode shows a strong absorption at 746 cm - 1. Another important feature of the spectrum of tri m e t h y l t i n tetrafluoroborate i s the appearance of a broad band at 446 cm - 1. These features of the infrared spectrum of tri m e t h y l t i n t e t r a - fluoroborate are consistent with the suggested C 2y symmetry of the tetrafluoroborate group and indicate strong i n t e r a c t i o n between the tetrafluoroborate and tri m e t h y l t i n groups. Coordination by the tetrafluoroborate group has also been reported (86) i n N i ( 3 , 5 - l u t i d i n e ) 4 ( B F 4 ) 2 . The i n f r a r e d spectra (121) of Mn(II) and Zn(II) t e t r a - fluoroborate-(methyl cyanide) complexes also d i f f e r from the infr a r e d spectra of s i l v e r and potassium tetrafluoroborates. Attempts were made to prepare dimethyltin b i s ( t e t r a f l u o r o - borate) by the metathetical reaction between dimethyltin dichloride and s i l v e r tetrafluoroborate. However, the metathetical reaction, c a r r i e d out i n methanol as well as i n ether, resulted i n the formation of dimethyltin b i s ( t e t r a f l u o r o b o r a t e ) , dimethyltin d i f l u o r i d e , boron t r i f l u o r i d e and s i l v e r chloride. The evolution of boron t r i f l u o r i d e was confirmed by the formation of boron trifluoride-amine adducts. When the metathetical 97 reaction was done i n methanol, the quantitative amount of s i l v e r chloride was precipitated. Upon removal of the methanol from the f i l t r a t e , an extremely hygroscopic white s o l i d was obtained. The i n f r a r e d spectrum, a n a l y t i c a l r e s u l t s and the X-ray powder photographs of the s o l i d showed i t to be a mixture of dimethyltin bis(tetrafluoroborate) and dimethyltin d i f l u o r i d e . The analy- t i c a l r e s u l t s indicate that the mixture contained nearly 46 percent dimethyltin bis(tetrafluoroborate) and 54 percent of dimethyltin d i f l u o r i d e . The mixture did not show any change, either spectroscopically or a n a l y t i c a l l y , when i t was heated to 60 - 70° under vacuum for about six hours. Therefore i t i s concluded that the decomposition of dimethyltin b i s ( t e t r a - fluoroborate) i s not due to i t s thermal i n s t a b i l i t y under experimental conditions. Quantitative p r e c i p i t a t i o n of s i l v e r chloride shows that the metathetical reaction i n methanol goes to completion,i.e. ' * CH 3 0H ( C H 3 ) 2 S n C l 2 + 2 A g B F 4 ^ ( C H 3 ) 2 S i ? (Solvated) + 2 B F 4 ~ + 2 A g C l (1) The formation of dimethyltin d i f l u o r i d e can be explained i n the following manner: o-f —CH3OH (CH 3) 2Sn (solvated)+ 2 B F 4 (CH 3) 2SnF 2 + 2 B F 3 . . ( 2 ) The formation of dimethyltin d i f l u o r i d e upon removal of the s o l - vent also indicates that dimethyltin bis(tetrafluoroborate) i s stable i n methanol but p a r t i a l l y decomposes upon removal of the solvent according to equation ( 2 ) . These re s u l t s indicate a very strong interaction between (CHg^Sn and B F 4 groups in the s o l i d state, apparently causing t h i s p a r t i a l decomposition. This in t e r a c t i o n i s further sup- ported by the spectroscopic r e s u l t s . The metathetical reaction between dimethyltin dichloride and s i l v e r tetrafluoroborate was also.done i n l i q u i d sulphur dioxide but dimethyltin bis (tetrafluoroborate) could not be i s o l a t e d i n the pure form. Although only a s o l i d mixture of dimethyltin b i s - (tetrafluoroborate) and dimethyltin d i f l u o r i d e was obtained, the in f r a r e d spectrum of this mixture shows very i n t e r e s t i n g fea- tures and suggests strong i n t e r a c t i o n between (CH^gSn and B F 4 groups. The i n f r a r e d absorption spectrum obtained on a nujol mull sample of the s o l i d i s recorded together with the r e l a t i v e i n t e n s i t i e s and suggested assignments of the absorption bands, i n Table 4.5b and part of the spectrum i s shown i n Figures 4.5a and 4.5b. The absorption bands at 1280, 1207, 1195, 1157, 1095, 1066, 1047, 1030, 940, 760, 525-510, 455 and 410 cm - 1, can be attributed to the tetrafluoroborate group. It i s evident that the spectrum i s markedly d i f f e r e n t from that of the free BF4" ion. The t r i p l y degenerate mode v 3 of the free ion i s c l e a r l y resolved into three strong bands at 1157, 1066, and 940 cm - 1; the infrared forbidden mode v^ of the free ion appears as a strong sharp band at 760 cm - 1, and the t r i p l y degenerate mode O4 of the free ion which usually appears as a doublet at 536 and 525 cm"1 now shows one medium absorption band at 525-510 em""1 and two strong bands at 455 and 410 cm - 1. The other absorption bands which are a l l weak, apparently are due to the isotope 1 I 1 I I I I I I I 1 2 0 0 1 1 0 0 1 0 0 0 9 0 0 8 0 0 C m F I G U R E 4-5b i i i _ J i i i i i i _ 6 0 0 5 O . o 4 0 0 3 0 0 2 0 0 C m " 1 o o TABLE 4.5b Infrared Absorption Spectrum of The Mixture of Dimethyltin Bis(tetrafluoroborate) and Dimethyltin D i f l u o r i d e 101 Frequency (cm"1) Relative Intensity 1280 1225 1207 1195 1157 1095 1066 1047 1030 940 815 760 604 525 518 510 455 410 375-350 w w,sp vw vw s sh s sh sh s s s m m s, b s, b sh Assignment C-H sym. bend BF 9 asym.str., (v«) BF 2 sym.str.,(v^) BF 2 asym. s t r . , (\)g) CH 3 rock BF^ sym. s t r . ^ V g ) Sn-C asym.str. BF 2 bend, (v^) (BF 4) rock, (v 7) (BF 4) rock, ( i ) 9 ) Sn-F s t r . , ^(CHg^SnF^ b = broad; m = medium; s = strong; sh = shoulder; v = very; w = weak. * denotes the f l u o r i n e atoms involved i n bonding. The assignments for the BF^ group have been suggested by analogy with C10 4 group of C 2 v symmetry. 102 e f f e c t as well as to overtones and combination bands. The bands at 1225, 815, and 604 cm - 1 can be assigned to the C-H symmetric bend, CH3 rock and Sn-C asymmetric stretching modes respectively. Dimethyltin d i f l u o r i d e has absorption bands at 1210, 787, 595 and 373 cm - 1. These bands are masked by the bands due to dimethyltin b i s ( t e t r a f l u o r o b o r a t e ) . The strong broad band at 410 cm"1 c l e a r l y has a shoulder in the 375 cm -l region and t h i s i s probably due to the 373 cm"1 band of dimethyltin d i f l u o r i d e . The observed spectrum i s therefore largely due to dimethyltin b i s ( t e t r a f l u o r o - borate) . The observed spectrum i s almost i d e n t i c a l to that reported (43) for t r i m e t h y l t i n tetrafluoroborate and both spectra can only be interpreted i n terms of coordinated tetrafluoroborate groups of Cgy o r lower symmetry. Due to the presence of t e t r a f l u o r o - borate absorption bands i n the 525-510 cm 1 region, i t i s d i f f i c u l t to say whether the Sn-C symmetric stretch i s also present. However, the Sn-C asymmetric stretching v i b r a t i o n i n this compound occurs at almost the same frequency as that observed i n dimethyltin d i f l u o r i d e , dimethyltin sulphate, and dimethyltin sulphate adducts. Since the i n f r a r e d spectra of these compounds suggest the presence of a l i n e a r dimethyltin group, i t i s very l i k e l y that the dimethyltin group i s linear in dimethyltin b i s ( t e t r a f l u o r o b o r a t e ) . Considering the probable l i n e a r i t y of the dimethyltin group and the presence of coordinated tetrad, fluoroborate groups of C 2 v symmetry, i t can be suggested that i n dimethyltin b i s ( t e t r a f l u o r o b o r a t e ) , four f l u o r i n e atoms are co- ordinated to the l i n e a r dimethyltin group, i n the equatorial i i ' plane making the t i n atom six coordinate. 103 Like t r i m e t h y l t i n tetrafluoroborate, dimethyltin bis(tetrafluoroborate) i s extremely hygroscopic, and marked changes i n the infrared spectrum of the mixture were observed on exposing i t to a i r for a few seconds. The strong bands at 1157, 1066, 940, 760, 455 and 410 cm - 1 and the medium band at 525-510 cm - 1 disappeared and the spectrum showed c h a r a c t e r i s t i c bands of the BF^ ion, i . e . a broad strong band at 1110-1025 cm - 1 and a doublet at 535 and 520 cm"1. The methyl rocking and the Sri-C asymmetric stretching vibrations were s h i f t e d to 790 and 575 cm"1 respectively. The marked changes in the spectrum upon exposing the mixture to a i r again indicate that free BF^ ions and hydrated (CH^JgSn ' cations are produced by hydrolysis of the anhydrous product. 4.6 Dimethyltin Hexafluorosilicate (CHg^SnSiFg An attempt to prepare t h i s derivative was not successful. Nevertheless, the reaction products from the attempted prepara- ti o n are i n t e r e s t i n g i n that they show a very strong i n t e r a c t i o n between (CHg^Sn and SiFg groups. The • metathetical reaction between dimethyltin dichloride and s i l v e r h e x a f l u o r o s i l i c a t e in methanol resulted i n instantaneous p r e c i p i t a t i o n of s i l v e r chloride. However, after pumping off the solvent (at room temperature) from the f i l t e r e d solution, pure dimethyltin d i f l u o r i d e was obtained, as shown by a n a l y t i c a l r e s u l t s , i n f r a - red spectrum and X-ray powder photographic data. The recovered methanol was highly a c i d i c and contained s i l i c o n and f l u o r i n e . The r e s u l t s can only be interpreted according to the scheme: ( C H 3 ) 2 S n C l 2 + A g 2 S i F 6 2 + (CH 3) 2Sn (solvated)+ SiF, CH30H 2 - 6 104 The metal f l u o r o s i l i c a t e s are stable, being only about one per- cent hydrolysed i n aqueous solution (59b). The decomposition of 2 - the SiFg ion in aqueous solution i s considered to proceed i n the following manner (122): SiFg 2" » S i F 4 + 2F" . . . . (1) followed by the rapid hydrolysis S i F 4 + 3H20 * 4HF + HgSiOg . . . .(2) The value of the equilibrium constant K, for the 1st reaction i s reported (122) to be 1x10" at 20 . The heat of formation 2- &H-f of SiFg ion i n aqueous solution i s -558.5kcal/mole (123). Although the corresponding values i n methanol solution would be d i f f e r e n t , s t i l l i t can be seen from these figures that complete decomposition of dimethyltin h e x a f l u o r o s i l i c a t e must involve a very strong i n t e r a c t i o n between (CHg^Sn and SiFg groups. 4.7 Dimethyltin Derivatives of Group Vb Hexafluorides Phosphorus, arsenic and antimony form stable hexafluoride anions of the formula MXg. These anions have octahedral sym- metry and belong to point group 0^. An octahedral molecule, or ion, should have f i f t e e n normal vibrations d i s t r i b u t e d between six v i b r a t i o n a l modes (47c) as shown in Table 4.7a. If the MXg group i s involved i n coordination then i t s symmetry would be lowered. A c o r r e l a t i o n between the modes of v i b r a t i o n of a octahedral group, having Oh, D 4 h or C 2 v symmetry i s shown in Table 4.7b. If the hexafluoride ion acts as a trans bridging ligand, then the Oh symmetry of the hexafluoride ion i s lowered to D 4h and t h i s should r e s u l t i n f i v e infrared active fundamental 105 TABLE 4.7a Vib r a t i o n a l Modes of An Octahedral Group MXg Vib r a t i o n a l mode Assignment A c t i v i t y (A l g) M-X symmetric stretch (R) <Eg) X-M-X stretch (R) <Flu> X-M-X bend (I.R) <Flu> M-X asymmetric stretch (I.R) X-M-X bend (R) <F2u> X-M-X bend (out-of-plane) (Inactive) (R = Raman active; I.R = Infrared active) vibrations belonging to (2A 2 u + 3E U) species. Moreover, the bond lengths of one pair of trans M-X bonds would be expected to increase, and as a resu l t of this elongation, the infrared active antisymmetric F-M-F stretching mode (corresponding to the A 2 u fundamental a r i s i n g from the s p l i t t i n g of the degenerate mode V g — • A 2 u + E u) should s h i f t to a lower frequency. This e f f e c t has been observed (43) i n the infrared spectrum of tri m e t h y l t i n hexafluoroarsenate, i n which the v^ mode of the AsFg" ion s p l i t s into two bands at 675 cm""1 and 710 cm 1 . If the hexafluoride ion acts as a c i s bridging ligand, then i t s symmetry i s lowered to C 2 v . In that case, the degeneracy of infrared active modes i s completely removed and the number of infrared active fundamental modes i s increased to thirteen. Complete removal of degeneracy of the V3 mode has been observed (43) i n the infrared spectrum of t r i m e t h y l t i n hexafluoroantimonate in which the Oo mode of 1£>6 the SbFg ion s p l i t s into three modes at 675, 656 and 640 cm""1. TABLE 4.7b Correlation Between Ahe Vi b r a t i o n a l Modes of An Octahedral Group of Oh, D4h, or: C2v Symmetry D4h °h C2v A l g A l g A l A l g + B l g E g A l + B l 2A 2 u+ 2E U 2 F l u 2A X + 2B X + 2B 2 B 2 g + Eg F 2 g A l + A 2 B 2 u + E u F 2 u A l + A 2 + B l Vibrations of species Vibrations of Vibrations of species A 2 u and Eu are infra= species F i u are A i , B i , and B 2 are red active i n f r a r e d active i n f r a r e d active S p l i t t i n g s of the degenerate infrared active modes of the octahedral anions due to c r y s t a l f i e l d e f f e c t s have also been reported (124) i n the s o l i d state i n f r a r e d spectra of ammonium hexafluorogermanate and barium hexafluorogermanate. The reported (125) s p l i t t i n g of the V3 mode of barium h e x a f l u o r o s i l i c a t e probably i s also due to the same e f f e c t . However, i n a l l these cases, the Raman active modes of the hexafluoride ion do not appear with any s i g n i f i c a n t i n t e n s i t y i n the in f r a r e d spectra. Unfortunately only very few studies on the v i b r a t i o n a l spectra of hexafluoride ions have been made, probably due to great experimental d i f f i c u l t i e s involved i n such studies. In this investigation an attempt was made to prepare dimethyltin derivatives of hexafluorophosphate, hexafluoro- arsenate and hexafluoroantimonate. Derivatives of both 107 hexafluorophosphate and hexafluoroarsenate decomposed p a r t i a l l y to give dimethyltin f l u o r i d e and the corresponding Lewis acid as described below. When stoichiometric amounts of s i l v e r hexafluorophosphate and dimethyltin dichloride were allowed to react i n methanol, s i l v e r chloride was preci p i t a t e d instantaneously. However, upon removal of the methanol under vacuum at room temperature, a sticky s o l i d was obtained which could not be further dried and which was not completely soluble i n methanol or water. The infrared spec- trum of the s o l i d showed intense bands at 1210, 1110, 1050, 815, 800, 495 and 475 cm*"1. The recovered methanol was highly a c i d i c and contained f l u o r i n e as well as phosphorus as shown by q u a l i - t a t i v e t e s t s . When the above metathetical reaction was performed i n l i q u i d sulphur dioxide, the product was a white s o l i d which gave inf r a r e d absorption bands at 1260, 1150, 920, 885, 810, 600, 590, 565, 535, and 480 cm - 1. An X-ray powder photograph of the s o l i d showed the presence of dimethyltin d i f l u o r i d e , and the recovered sulphur dioxide contained some phosphorus o x y t r i - f l u o r i d e , POF3, which was i d e n t i f i e d by i t s infrared spectrum. Since s i l v e r hexafluorophosphate can best be prepared from l i q u i d sulphur dioxide (126), POF3 cannot arise from dire c t reaction of PFg~ with S0 2. Therefore, the re s u l t s can only be interpreted i n the following manner: (CH 3 ) 2 S n C l 2 + 2AgPF 6 • S ° 2 y ( C H 3 ) 2Sn(PF 6) 2 + 2Ag d l ( C H 3 ) 3 S n ( P F 6 ) 2 > (CH 3) 2SnF 2 + 2PF 5 PF 5 + S0 2 > POF3 + SGF 2 108 Similar r e s u l t s have been reported (43) for the reaction between tri m e t h y l t i n bromide and s i l v e r hexafluorophosphate. The metathetical reaction between dimethyltin dichloride and s i l v e r hexafluoroarsenate in methanol resulted i n instantan- eous p r e c i p i t a t i o n of s i l v e r chloride. Upon removal of the solvent from the f i l t r a t e a hygroscopic white s o l i d was obtained which gradually turned yellowish. The recovered methanol was highly a c i d i c and contained arsenic and f l u o r i n e . An X-ray powder photograph of the s o l i d showed the presence of dimethyltin d i f l u o r i d e . The inf r a r e d spectrum of the s o l i d as described below indicated the presence of the hexafluoroarsenate group. These r e s u l t s can be explained in terms of p a r t i a l decomposition of dimethyltin bis (hexaf luoroarsenat<e) to give dimethyltin d i f l u o r i d e and arsenic pentafluoride. The infrared spectrum of the mixture i n a nujol mull showed absorption bands at 1210, 825, 800, 760, 718, 595, 475, and 375 cm - 1. The spectrum i n the 850 - 250 cm - 1 region i s shown i n Figure 4.7a. The AsFg" ion has two inf r a r e d active v i b r a t i o n a l modes, and v^. The mode gives a strong, broad, but symmetrical band at approximately 700 cm"1 (127), while the V1,. mode i s reported to occur at 400 cm - 1 (128) . In 4 addition subsidiary bands at 1300, 1065, 970 and 825 cm"1 also appear i n the inf r a r e d spectrum (127). In the spectrum of the mixture, the bands at 1210, 800, and 595 cm - 1 can be assigned to the C-H symmetric band, the CHg rock, and the Sn-C asymmetric stretching modes respectively. The bands at 760 and 718 cm - 1 are the two components of the v*_ mode of the hexafluoroarsenate group. S i m i l a r l y the bands at 375 and 475 are probably the two Frequency (cm-1) 110 components of the V4 mode, although dimethyltin d i f l u o r i d e w i l l also absorb at 375 cm"1. Thus i t appears that the symmetry of the ASFQ group has been lowered from 0 n to D4 n. The spectrum of the mixture thus shows features s i m i l a r to those reported (43) for t r i m e t h y l t i n hexafluoroarsenate. The spectroscopic r e s u l t s and the p a r t i a l decomposition of the dimethyltin bis(hexafluoro- arsenate) both suggest very strong i n t e r a c t i o n between (CHg^Sn and ASFQ groups r e s u l t i n g i n the p a r t i a l decomposition of AsFg group. .Dimethyltin bis(hexafluoroantimonate) could be prepared by the metathetical reaction between dimethyltin dichloride and s i l v e r hexafluoroantimonate i n methanol. However, the product could not be obtained free from methanol even after pumping the s o l i d for 24 hours at 60°. When the s o l i d was heated to 120° under vacuum, decomposition of the hexafluoroantimonate occurred and some antimony pentafluoride was formed. The metathetical reaction between dimethyltin dichloride and s i l v e r hexa- fluoroantimonate was also performed i n l i q u i d sulphur dioxide. An anhydrous, extremely hygroscopic white s o l i d was obtained. X-ray powder photographs of the s o l i d did not show any l i n e s due to dimethyltin d i f l u o r i d e . However, no analysis of the product was obtained. Nujol mull samples of the s o l i d prepared for the measurements of the infrared spectrum reacted rapidly with s a l t windows but reproducible spectra could be obtained on nujol mull samples by using s i l v e r chloride or polythene sheets. The i n f r a r e d spectrum has features s i m i l a r to those re- ported for t r i m e t h y l t i n hexafluoroantimonate. The spectrum i n the 750 - 250 cm"1 region i s shown i n Figure 4.7b. Other bands  .112 were observed at 1210(w), 990(m), 910(m), 828(m), 782(w) and 760(vw). Only one i n f r a r e d active frequency (the O3 mode) has been reported (128) for the SbFg ion. In order to compare the spectrum of dimethyltin bis(hexafluoroantimonate) with that of the SbFg ion, the in f r a r e d spectrum of s i l v e r hexafluoroantimonate was also measured under comparable conditions. The spectrum showed a very strong broad band at 660 cm"1 (with a shoulder at 560 cm"1) and another strong band showing peaks at 310, 290 and 270 cm"1. The 660 cm - 1 band i s due to the reported V3 mode and the band i n the 310-270 cm - 1 region i s evidently due to the v^ mode which i s s p l i t due to c r y s t a l f i e l d e f f e c t s . In the spec- trum of dimethyltin bis(hexafluoroantimonate), the bands at 1210 and 828 cm"1 can be assigned to the C-H symmetric band and the CH3 rocking modes respectively. The spectrum of s i l v e r hexa- fluoroantimonate does not show any bands i n the 1000-800 cm"1 region. The medium bands at 990 and 910 cm"1 are therefore the v i b r a t i o n a l modes, in f r a r e d inactive for the octahedral SbFg ion, which have become inf r a r e d active as a r e s u l t of d i s t o r t i o n of the SbFg group by (CHg^Sn. S i g n i f i c a n t l y , as can be seen from the Figure 4.7b, the O3 mode for dimethyltin bis(hexa- fluoroantimonate) i s s p l i t and shows peaks at 675, 650 and 635 cm"1, and additional bands which do not appear i n the spectrum of s i l v e r hexafluoroantimonate are present at 595, 545, 445 and 365 cm"1. The band at 595 cm - 1 can be assigned to the Sn-C asymmetric stretch but the bands at 540 and 445 cm"1 are c e r t a i n l y due to the hexafluoroantimonate group. Thus the hexafluoroantimonate absorption i n dimethyltin bis(hexa- fluoroantimonate) i s s i g n i f i c a n t l y d i f f e r e n t from that of the 1.13 SbFg ion. The appearance of 540 and 445 cm - 1 bands cannot be attributed to c r y s t a l f i e l d e f f e c t s , and indicate strong i n t e r - action between (CHg^Sn and SbFg groups as a res u l t of which the 0^ symmetry of the SbFg group i s distorted (probably to C 2v) . Although the stereochemistry i n t h i s compound cannot be determined with any certainty, the infrared r e s u l t s are consistent with a configuration i n which li n e a r (CHg) 2Sn groups are coordinated i n the equatorial plane by c i s f l u o r i n e atoms of the SbFg group making the t i n atom six coordinate. Coordination between (CH 3) 2Sn and SbFg i s also indicated by the marked changes brought about i n the spectrum when the compound was exposed to a i r . The bands at 990, 910, 782, 760, 545, 445 and 365 cm - 1 completely disappeared and the bands at 675, 650 and 635 were replaced by a broad band showing a maximum at 660 cm - 1. Thus, upon exposure of dimethyltin bis(hexafluoroantimonate) to a i r , free SbFg ions are produced as a res u l t of hydrolysis. ; The dimethyltin derivatives of group Vb hexafluorides are very s i m i l a r to the analogous tr i m e t h y l t i n derivatives (43 ). Trimethyltin hexafluorophosphate i s unstable, the hexafluoro- arsenate and antimonate which are derived from progressively stronger Lewis acids AsFg and SbFg are stable, the anion i n the former acting as a trans, and i n the l a t t e r as a c i s bridging group. The s t a b i l i t i e s of corresponding dimethyltin derivatives follow the same sequence though dimethyltin d e r i - vatives are apparently less stable than the t r i m e t h y l t i n derivatives. 1-14 , v 2 -4.8 The Dimethyltin(IV) Derivative of B 1 2 C I 1 2 2 — The B i 2 c l i 2 i o n i s considered (129) to have an icosa- 2 - hedral structure s i m i l a r to that of B12H12 • T n e icosahedral structure of B 1 2 H 1 2 2 ~ n a s b e e n established (130) by X-ray crystallography. A molecule or ion belonging to point group 1^ should give r i s e to two strongly polarized Raman Lines of species Ag, and four depolarized Raman Lines of species H g, and three infrared active fundamentals of species F^ u. However, only a single strong l i n e at 300 cm - 1 i s observed i n the Raman spectrum of B 1 2 C 1 1 2 ~ ( 1 2 9 ) • J t h a s b e e n suggested (129) that the f a i l u r e to observe other strong Raman li n e s may be a consequence of a c c i - dental c a n c e l l a t i o n of p o l a r i z a b i l i t y changes of oppositely char- ged boron and halogen atoms i n t o t a l l y symmetric vibrations. Only one fundamental i n f r a r e d absorption frequency at 1030 cm - 1 2 has been reported (129) for &i2^12ion- 2 - The dimethyltin derivative of B-j^Cl-j^ was obtained as a hygroscopic white s o l i d which contained some methanol. The methanol could not be removed from the solvated product even after heating for 24 hours at 100° under vacuum. The a n a l y t i c a l r e s u l t s of the heated s o l i d indicate that the product contained about one to two moles of methanol per mole of (CHg) gSnB-j^Cl-^. Due to the very high molecular weight of (CHg) gSnB-^Cl-^ i t i s rather d i f f i c u l t to ascertain the exact amount of methanol in the 2 - product. However, no decomposition of the &\2^12 group occurred and the recovered methanol was neither a c i d i c nor con- tained any chlorine or boron. 1 The i n f r a r e d spectrum of the dimethyltin B^gCl.^ derivative i s recorded i n Table 4.8 and part of the spectrum i s shown i n  TABLE 4.8 Infrared Absorption Spectrum of The Dimethyltin Derivative of Frequency (cm "*") Relative Intensity 3460 ; s 3080 vw 2960 vw 1600 w 1455 m 1400 w 1250 w 1220 vw 1170 vw 1144 w 1040 s 1002 m 950 ) ) m 925 ) 857 s,sh 824 s 590 vw 535 vs 480 m 425 w 328 w m = medium; s = strong; sh = shoulder; v = very; w = weak. 117 Figure 4.8 (curve b). For comparison, the infrared spectrum of s o l i d Ag 2B 12Clj2 w a s a l s ° measured and i s also shown i n Figure .. 4.8 (curve a). In the spectrum of the dimethyltin derivative, the absorption bands at 1040, 1002, 950, 925, 824, 535, 480, 425 and 328 cm - 1 can be attributed to the B-j^Cl]^ group. The other absorption bands are due to the methanol and the dimethyltin group. The CHg rocking mode of (CHg^Sn group i s probably masked by the strong band at 824 cm - 1. It may be noted that the Sn-C asymmetric stretch appears at 590 cm"1; however, i t i s not possible to ascertain whether the Sn-C symmetric stretch i s also present. Comparing the B - ^ C l ^ part of the spectrum i n the dimethyl- t i n derivative with that of the s i l v e r s a l t i t becomes evident that, i n the dimethyltin s a l t , the spectrum of the B ^ C l - j ^ group 2 - i s very d i f f e r e n t from that of the free B-j_2Cl]_2 ion. Though i t i s d i f f i c u l t to derive any d e f i n i t e conclusions about the stereo- chemistry i t can be i n f e r r e d that the symmetry of B-^Cl]^ n a s been lowered i n th i s compound as a r e s u l t of which the infrared inactive modes of the free B i 2 C l j 2 ion have become inf r a r e d active. This can be explained either i n terms of c r y s t a l f i e l d e f f e c t s or i n terms of an i n t e r a c t i o n between the dimethyltin group and the B-^Cl]^ group. In view of the i n f r a r e d spectro- scopic r e s u l t s of other dimethyltin derivatives, i t i s suggested that the changes i n the B 1 2 C 1 1 2 part of the spectrum of the dimethyltin derivative may be due to some form of coordination between (CHg) 2Sn and Bi2^ : 112 groups. This i s further supported by the gradual changes i n the i n f r a r e d spectrum of th i s com- pound upon exposure of the compound to a i r . The bands at 950, 118 925, 824, 480, 425 and 328 gradually diminished i n i n t e n s i t y and after an exposure of three days, these bands disappeared and the CHo rocking mode appeared at 790 cm"1. 110 CHAPTER 5 TRIMETHYLANTIMONY(V) DERIVATIVES' Apart from the c r y s t a l structure determination of t r i - methylantimony dic h l o r i d e , dibromide and diiodide, very l i t t l e i s known about the stereochemistry of trimethylantimony d e r i - vatives of the type RgSbXg. Recently Long, Doak, and Freedman (52) reported infrared spectra of trimethylantimony dihalides, the d i n i t r a t e and the sulphate. However, some of the r e s u l t s obtained by these workers appear rather anomalous. In the present investigation, some of the work reported by these workers was repeated. In addition, a wide variety of acid derivatives of trimethylantimony(V) were prepared and th e i r i n f r a r e d spectra were examined. 5.1 Trimethylantimony Dihalides Cr y s t a l structure determinations (54) of trimethylantimony dichloride,dibromide and diiodide have shown that these dihalides are tr i g o n a l bipyramidal molecules containing a planar trimethyl- antimony group i n the equatorial p o s i t i o n . The general conclusions of Long, Doak, and Freedman (52) are consistent with the t r i - gonal bipyramidal structure. The main features of the spectra of these dihalides reported by these workers are the C-H asymmetric stretch in the 3020-3010 cm - 1 region, the symmetric C-H stretch in the 2928 - 2920 cm""1 region, the C-H asymmetric bend i n the 1403-1387 cm"1 region, the CH 3 rock i n the 870i- 860 cm - 1 region and the Sb-C asymmetric stretch i n the 587-554 cm - 1 region. However, these authors reported that, i n the spectrum of \ trimethylantimony d i f l u o r i d e , complex bands occur i n the 1120- 120 1050, 730, and 540 - 450 cm - 1 regions, and the Sb-C asymmetric stretch at 587 cm - 1 i s p a r t i a l l y masked. In view of t h i s incon- sistency i n the spectrum of the d i f l u o r i d e , the spectrum of this compound was studied again. The observed absorption bands, with their r e l a t i v e i n t e n s i t i e s and assignments, are l i s t e d i n Table 5.1. The main features of the spectrum are the C-H asymmetric stretch at 3065 cm - 1, the C-H symmetric stretch at 2965 cm - 1, the C-H asymmetric bend at 1415 cm - 1, the C-H symmetric bend at 1235 and 1221 cm - 1, the CH 3 rock at 855 cm"1, the Sb-C asymmetric stretch at 585 cm - 1, and the Sb-F asymmetric stretch at 475 cm - 1. Contrary to the reports of Long, Doak, and Freedman, the spectrum of the d i f l u o r i d e does not show any complex bands i n the 1120-1050, 730, and 540 - 450 cm"1 regions. The observed spectrum i s com- pl e t e l y consistent with a t r i g o n a l bipyramidal structure. The additional bands observed by Long, Doak, and Freedman must therefore be associated with impurities present i n th e i r sample. Trimethylantimony d i f l u o r i d e sublimes, at room temperature under vacuum, and i s soluble i n organic solvents such as methanol, acetone and chloroform. It i s therefore largely co- valent l i k e other dihalides. A comparison of the Sb-F stretching frequency (475 cm - 1) i n trimethylantimony d i f l u o r i d e with the Sn-F stretching frequency (355 cm - 1) i n t r i m e t h y l t i n f l u o r i d e also indicates the covalent nature of trimethylantimony d i f l u o r i d e . 5.2 Trimethylantimony D i n i t r a t e (CH 3) 3Sb(N0 3) Long, Doak, and Freedman (52) described the infrared spectrum of trimethylantimony d i n i t r a t e and from i t concluded 121 TABLE 5.1 Infrared Absorption Spectrum of Trimethylantimony D i f l u o r i d e Frequency (cm - 1) Relative Intensity Assignment 3065 w C-H asym. s t r . 2965 w C-H sym. s t r . 2450 vw 2110 vw 1812 w 1768 w 1415 m C-H asym. bend 1235 ) ) m,sp C-H sym.bend 1221 ) 855 vs CH 3 rock 585 s,sp Sb-C asym. s t r . 475 vs Sb-F asym. s t r . m = medium; s = strong; sp = sharp; v = very; w = weak. that t h i s compound has an io n i c structure. They observed the ni t r a t e absorption frequencies at 1516(s), 1457(s), 1050(vw), 83.4(s), and 728(w) cm - 1. In view of the recently accumulated evidence for the nonexistence of the trime t h y l t i n cation i n the s o l i d state, the ioni c structure for trimethylantimony d i n i t r a t e seems rather surprising. Therefore, i n thi s work, trimethylanti mony d i n i t r a t e was prepared under anhydrous conditions, and the infr a r e d and u l t r a v i o l e t spectra of thi s compound were studied. Reliable infrared spectra of trimethylantimony d i n i t r a t e could only be obtained on samples made as mulls and placed between s i l v e r chloride sheets. When the spectra were measured either on mulls placed between potassium bromide plates or on samples made i n potassium bromide p e l l e t s , considerable ex- change occurred between trimethylantimony d i n i t r a t e and potas- sium bromide. The spectra measured by using s i l v e r chloride sheets were always reproducible. The spectrum of trimethylanti- mony d i n i t r a t e i n the 1650-650 cm - 1 region obtained in a nujol mull i s shown i n Figure 5.2. The absorption frequencies (in the 4000 - 400 cm - 1 region) together with th e i r r e l a t i v e i n - t e n s i t i e s and assignments, are l i s t e d i n Table 5.2. The absorption bands due to the n i t r a t e group occur at 1550-1510, 1290-1275, 965, 795, 730, and 708 cm'1. It can be c l e a r l y seen that the n i t r a t e group i n trimethylantimony d i n i t r a t e shows infrared absorption c h a r a c t e r i s t i c of a n i t r a t o group (see section 2.1). The c h a r a c t e r i s t i c bands of a free n i t r a t e ion are absent i n the observed spectrum. Therefore trimethylanti- mony n i t r a t e must have a non-ionic structure and the n i t r a t e groups are apparently coordinated to the trimethylantimony Frequency (cm"1) to 124 TABLE 5.2 Infrared Absorption Spectrum of Trimethylantimony Dinitr a t e Frequency (cm - 1) Relative Intensity Assignment 3070 m C-H asym. s t r . 2960 m C-H sym. s t r . 2820 w 2260 w 1990 w 1820 w 1765 w 1675 w 1530 s, b N0 2 asym. str.,(v*4) 1415 m C-H asym. s t r . 1290 s ) 1275 s ) N0 2 sym. s t r . , (0-̂ ) 1245 m ) 1230 m C-H sym. bend 965 s NO s t r . , (02) 865 s CHg rock 795 728 m s NOg out-of-plane rock, (Vg) N0 2 sym. bend, (^3) 708 m N0 2 asym.bend,(^5) 580 ms Sb-C asym. s t r . 520 w, b Sb-C sym. s t r . ? b = broad; m =.medium; s = strong; w = weak. Nitrate absorption bands have been assigned assuming that the n i t r a t e group i s unidentate. 1 2 5 group. The a b s o r p t i o n s due t o t h e t r i m e t h y l a n t i m o n y group can be a s s i g n e d by comparison w i t h the s p e c t r a of t r i m e t h y l - antimony d i b r o m i d e , and d i f l u o r i d e , i . e . 3070 cm - 1 , C-H asym- m e t r i c s t r e t c h ; 2960 cm - 1 , C-H symmetric s t r e t c h ; 1415 cm" 1, C-H asymmetric bend; 1245, 1230 cm" 1, C-H symmetric bend; 865 c m - 1 , CH3 r o c k ; and 580 c m - 1 , Sb-C asymmetric s t r e t c h . The p r e s e nce of o n l y one Sb-C s t r e t c h i n g f r e q u e n c y o f medium s t r o n g i n t e n s i t y , i n d i c a t e s t h a t the t r i m e t h y l a n t i m o n y group i s p l a n a r . A n o n - p l a n a r c o n f i g u r a t i o n of t h e t r i m e t h y l a n t i m o n y group would g i v e r i s e t o a symmetric Sb-C s t r e t c h i n g band of medium i n t e n s i t y i n a d d i t i o n t o the asymmetric Sb-C s t r e t c h i n g band w i t h an i n t e n - s i t y r a n g i n g from medium to s t r o n g . Long, Doak, and Freedman (52) o b s e r v e d a weak band a t 528 c m - 1 i n the i n f r a r e d s p e c t r a o f [(CH 3) gSbCl] 2 0 and [(CH3) 3SbC10^j 2 0 . These a u t h o r s have s u g g e s t e d t h a t t h i s band may be a s s o c i a t e d w i t h the antimony-oxygen s t r e t c h i n g v i b r a t i o n o r may r e p r e s e n t the d i s t o r t i o n of the p l a n e c o n t a i n i n g the carbon and antimony atoms. Very r e c e n t l y C u l l e n , Deacon, and Green (131) examined the i n f r a - r e d and Raman s p e c t r a of [ ( C H 3 )^SbjHg I 3 and found t h a t the i n f r a r e d f o r b i d d e n Sb-C symmetric s t r e t c h appears weakly a t 529 cm-1 i n the i n f r a r e d spectrum. In t r i m e t h y l a n t i m o n y d i n i t r a t e and i n o t h e r t r i m e t h y l a n t i m o n y d e r i v a t i v e s such as c a r b o n a t e and chromate which w i l l be d e s c r i b e d l a t e r , a s i m i l a r weak a b s o r p t i o n o c c u r s i n the 530-520 cm 1 r e g i o n . Though a Sb-0 s t r e t c h i n g f r e q u e n c y can a l s o o c c u r i n t h i s r e g i o n i n t h e s e compounds, i t i s more l i k e l y t h a t the weak a b s o r p t i o n i n t h i s r e g i o n i s a s s o - c i a t e d w i t h the Sb-C symmetric s t r e t c h i n g v i b r a t i o n w hich may appear as a symmetry f o r b i d d e n mode. A l t e r n a t e l y , the p r e s e n c e of t h i s weak band may be due t o the s l i g h t d i s t o r t i o n of the 126 plane containing the carbon and antimony atoms. Thus the entire spectrum of trimethylantimony d i n i t r a t e can be interpreted in terms of a t r i g o n a l bipyramidal structure i n which each n i t r a t e group occupies the a p i c a l position and i s bonded through one oxygen atom to the trimethylantimony group situated i n the equatorial plane. Further evidence of p a r t i a l covalent bonding between n i t r a t e groups and the antimony atom i s provided by the u l t r a - v i o l e t absorption spectrum which was measured i n aqueous and chloroform solutions. In aqueous solution, the absorption maximum occurs at 302 m^, and in chloroform solution, at 280nyi4. The absorption maximum at 302 m^ i n aqueous solution i s char- a c t e r i s t i c of the free n i t r a t e ion and i s attributed to the symmetry forbidden n—*u * t r a n s i t i o n in the n i t r a t e ion (64). A l l such n >TT* tr a n s i t i o n s show a blue s h i f t ( i . e . the absorption maximum i s displaced to higher frequency) i n a series of solvents with increasing d i e l e c t r i c constant (132). Since chloroform has a lower d i e l e c t r i c constant (D = 4.8) than water, the free n i t r a t e ion i n t h i s solvent would be ex- pected to show an n—»JT* t r a n s i t i o n at longer wave lengths than in water. The observed maximum at 280m/4 i n chloroform solution indicates that trimethylantimony d i n i t r a t e dissociates i n aqueous solution to produce n i t r a t e ions, but i n chloroform solution, no n i t r a t e ions are present. Similar s h i f t s of absorption maxima in going from water to a solvent of lower d i e l e c t r i c constant have been observed for other n i t r a t o com- pounds, e.g. t r a n s i t i o n metal n i t r a t e s , i n t-butyl alcohol, show absorption maxima at 270-275 m/* (133), and dimethyltin n i t r a t e in ethyl alcohol shows absorption maximum at 285m/̂ < (51) . 127 The proton resonance spectrum of trimethylantimony d i n i t r a t e i n chloroform solution shows one peak, atY7.85. Under the same conditions, trimethylantimony dibromide shows a peak a t r 7.3. 5.3 Trimethylantimony Carbonate (CH3)3SbC03 The v i b r a t i o n a l frequencies of the carbonate ion and the carbonato group have been discussed e a r l i e r . The infrared spec- trum of trimethylantimony carbonate was measured on samples made as mulls, as well as on samples made as p e l l e t s i n potassium bromide. Both methods gave i d e n t i c a l r e s u l t s . A portion of observed spectrum i s shown i n Figure 5.3, and the absorption frequencies, together with their r e l a t i v e i n t e n s i t i e s and sug- gested assignments, are l i s t e d i n Table 5.3. The absorption bands due to the trimethylantimony group appear at 2950 , (C-H asymmetric stretch); 2880,(C-H symmetric stretch); 1405- 1385,(C-H asymmetric bend); 1225, (C-H symmetric bend); 875, (CH3 rock); and 575, (Sb-C asymmetric stretch) cm - 1. Since only one absorption band of medium intensity appears i n the region 575-500 cm - 1, the trimethylantimony group i s apparently planar i n t h i s compound. The absorption bands which can be attributed to the carbonate group occur at 1730, 1280, 1115, 1110, 790, 740, 632, 450, 375, and 250 cm - 1. The weak bands -1 at 1460, 1075, 1040 and 510 cm are probably overtones and combination bands. The appearance of the weak band at 525 cm - 1 has already been discussed i n connection with trimethylantimony d i n i t r a t e . The carbonate absorption bands i n t h i s compound c l e a r l y show that the carbonate group i s involved in . p a r t i a l M e 3 S b C 0 3 O r I I I I I I I I I 1 : I _1 I 1 1 1 1 1 2000 1800 1600 1400 1200 1000 800 600 400 200 Frequency ( c m - 1 ) 129 TABLE 5.3 Infrared Absorption Spectrum of Trimethylantimony Carbonate Frequency (cm - 1) Relative Intensity 2950 2880 1730 1460 1405-1385 1280 1225 1115 1100 1075 1040 875 790 740 632 575 525 510 450 375 250 m sh s w w s w s s vw vw vs vs s w w m m s Assignment C - H asym.str. C - H sym. s t r . C ̂ ^0 sym. s t r . , C - H asym.bend C0 o asym. s t r . , 2 (v 4) C - H sym.bend C O g sym. s t r . , (v 0) C H g rock C O g out-of-plane def.,(vg) C O g sym.bend, C O o asym.bend, Sb - C asym. s t r . Sb - C sym. s t r . ? Sb-Ostr. ? La t t i c e modes ? m = medium; s = strong; v = very; w = weak. Assignments for the carbonate group have been suggested assuming that the C O g group i s bridging. 130 c o v a l e n t bonding with the trimethylantimony group and that i t s symmetry cannot be higher than C 2 v • T n e doubly degenerate mode Vg observed i n i o n i c carbonates at 1415 c m - 1 has s p l i t i n t o two st r o n g w e l l d e f i n e d bands at 1730 and 1280 cm" 1. In f a c t these two f r e q u e n c i e s can be compared with the C=0 and C-C*2 (* r e p r e s e n t s oxygen atoms i n v o l v e d i n bonding) s t r e t c h i n g f r e q u e n c i e s of dimethyl carbonate which occur at 1750 and 1280 c m - 1 r e s p e c t i v e l y (134). S i m i l a r l y , the Raman a c t i v e mode v^ of the f r e e i o n now appears as an i n t e n s e band, s p l i t i n t o a doublet at 1115 and 1100 cm - 1; the corresponding band i n dimethyl carbonate occurs at 965 cm - 1 and at 1078 c m - 1 i n eth y l e n e carbonate ( s o l i d ) (135). The s p l i t t i n g of t h i s mode i s a l s o observed i n metal-carbonato com- plexes (105). The other degenerate mode of the f r e e i o n has s p l i t i n t o two str o n g bands at 740 and 632 c m - 1 and the ou t - o f - plane mode ^ G f the f r e e i o n shows a s t r o n g a b s o r p t i o n at 790 cm - 1. The bands at 450, 375 and 250 c m - 1 are s i m i l a r to those observed i n d i m e t h y l t i n carbonate ; and may be due to the l a t t i c e modes, although Sb-0 v i b r a t i o n s may p o s s i b l y a l s o cause a b s o r p t i o n i n 500 - 400 c m - 1 r e g i o n . The i n f r a r e d spectrum of trimethylantimony carbonate undoubtedly i n d i c a t e s t h at t h i s compound c o n t a i n s a penta-covalent antimony atom, and the spec- trum can only be i n t e r p r e t e d i n terms of a polymeric s t r u c t u r e i n which each carbonato group i s bonded to pl a n a r t r i m e t h y l a n t i - mony groups through two oxygen atoms. The other p o s s i b l e arrangement i n which a carbonato group i s bonded to any two corner p o s i t i o n s of a t r i g o n a l b i p y r a m i d a l monomer, would i n - v o l v e a h i g h l y s t r a i n e d s t r u c t u r e and may be r u l e d out. S i m i l a r l y a monomeric s t r u c t u r e i n which the carbonate group i s 131 unidentately bonded to the trimethylantimony group would not be consistent with the planarity of the trimethylantimony group as well as with the observed frequencies of the carbonate group. 5.4 Trimethylantimony Sulphate The i n f r a r e d spectrum of trimethylantimony sulphate was reported recently by Long, Doak, and Freedman (52). These authors concluded, from their infrared r e s u l t s , that trimethyl- antimony sulphate i s covalent. However, these authors remarked that the observed infrared bands do not correspond well with those given for sulphato complexes containing either unidentate or bidentate sulphato groups, and that the spectrum i s d i f f i - c u l t to interpret. These authors also reported that pronounced changes occurred i n the spectrum very rapidly when a potassium bromide p e l l e t containing trimethylantimony sulphate was exposed to the atmosphere. In view of this inconclusive report, the infrared spectrum of trimethylantimony sulphate was studied again in t h i s work. The infrared spectra were measured on anhydrous samples made as mulls i n the dry box, as well as on samples which were exposed to a i r and made as mulls or potassium bromide p e l l e t s . Both the anhydrous samples and samples exposed to a i r gave i d e n t i c a l spectra by both methods ( i . e . as mulls or potassium bromide p e l l e t s ) . A portion of the spectrum obtained on a nujol mull sample i s shown i n Figure 5.4. The absorption frequencies together with their r e l a t i v e i n t e n s i t i e s and sug- gested assignments are l i s t e d i n Table 5.4a. The absorption bands due to the trimethylantimony group occur at 3050, (C-H asymmetric stretch); 2950, (C-H symmetric stretch); 1415, (C-H asymmetric bend); 1230, (C-H symmetric bend); and 860, 0 !- I i i i i i i I I I I I 1 1 1600 1400 1200 1000 8 0 0 6 00 4 0 0 2 0 0 Frequency ( cm - 1 ) 133 TABLE 5.4a Infrared Absorption Spectrum of Trimethylantimony Sulphate Frequency (cm - 1) Relative Intensity Assignment 3050 w C-H asym. s t r . 2950 w C-H sym. s t r . 2120 vw 1760 vw > 1415 m C-H asym. bend 1285 s SC>2 asym. s t r . , (Og) 1230 m C-H sym. bend 1145 s SO2 sym. str.,(v^) 980 sh 950 s SO2 asym. str.,(0g) 860 s CHg rock 825 s SO2 sym.str.,(v 2) 650 s S 0 4 rocking,(0^) 600 s S 0 2 bend, (v 3) 495 m Rocking ( S 0 4 ) ,. (v Q) 428 w SO* bend, (v4> 250 s La t t i c e mode ? m = medium; s = strong; sh = shoulder; sp = sharp; w = weak; v = very. * denotes the oxygen atoms involved i n bonding. 134 (CH 3 rock) cm"1. The absorption bands at 1285, 1145, 980, (sh), 950, 825,650>, 600, 495 and 428 can be attributed to the vibrations of the sulphate group. The number of sulphate absorption: bands observed i n the spectrum of trimethylantimony sulphate c l e a r l y 2 - shows that t h i s compound does not contain free SO4 ions and that the symmetry of the sulphate group i n thi s compound cannot be higher than C 2 v. It i s true that the observed bands do not correspond well with those reported (91) for metal sulphato complexes containing unidentate or bidentate sulphato group. However, i t must be con- sidered that the changes i n the v i b r a t i o n a l frequencies of the ligand upon coordination to a metal atom, would depend upon the degree of covalent i n t e r a c t i o n between the ligand and the metal atom. It has already been shown that the C -0 stretching frequen- cies i n trimethylantimony carbonate correspond to the C-0 s t r e t - ching frequencies observed i n organic carbonates, rather than to those observed i n metal-earbonato complexes. The s i t u a t i o n i n trimethylantimony sulphate seems to be very s i m i l a r . In order to make a comparison, the infr a r e d spectrum of dimethyl sulphate was measured. The observed absorption frequencies with th e i r r e l a t i v e i n t e n s i t i e s are l i s t e d i n Table 5.4b. The infr a r e d active v i b r a t i o n a l modes of the sulphate group of C 2 v symmetry are s i m i l a r to those of CIO4 group of C 2 v symmetry described i n Table 2.1b. In dimethyl sulphate, two of the four S - 0 bonds i n the sulphate group should have double bond character while the remaining two S-0 bonds w i l l e s s e n t i a l l y have single bond character. The (0=S=0) and (0-S-O) vibrations i n dimethyl sulphate have been reported (89) to occur at 1400, [asymmetric (0=S=0) stretch] ; 1200, [symmetric (0=S=0) s t r e t c h ] ; 875, [asymmetric (0-S-O) s t r e t c h ] ; and 752,[symmetric (0 -S-0) stretch] cm"1. The value of the (0-S-O) asymmetric stretching frequency seems 135 TABLE 5.4b Infrared Absorption Spectrum of Dimethyl Sulphate Frequency Relative (cm - 1) in t e n s i t y 3100 1460 1395 1200 1010 985 825 752 615 592 573 520 502 428 m m s sh s s m sh m m sh s m Assignment (SO4 group) (0=S=0) assymetric stretch (vg) (0=S=0) symmetric stretch ime (v x) (O-S-0) asymmetric stretch (vg) (O-S-0) symmetric stretch (v 2) SO4 rocking (v^) (0=S=0) bend ( A ) 3 ) S 0 4 rocking (v g) (0-S-O) bend (v 4) to be erroneous because no band was observed at 875 cm - 1 i n the spectrum of dimethyl sulphate. Instead a band i s observed at 825 cm - 1 and i t i s now suggested that the value of the (O-S-0) • asymmetric stretching frequency i s 825 cm \ The inf r a r e d spectrum of dimethyl sulphate has not been reported previously for the potassium bromide region. From a comparison with the inf r a r e d spectrum of sulphuryl d i f l u o r i d e (88), the four observed bands i n this region can be assigned as follows: 592 cm - 1, S 0 4 rocking; 573 cm - 1, (0=S=0) bend; 502 cm - 1, S0 4 rocking; and 428 cm - 1, : (O-S-0) bend. - 136 The four sulphate absorption bands at 1285, 1145, 950, and 825 cm - 1 observed i n the spectrum of trimethylantimony sulphate correspond to the four sulphate bands at 1395, 1200, 825 and 752 cm - 1, observed in the spectrum of dimethyl sulphate. Therefore, these bands can be assigned to the same v i b r a t i o n a l modes, i . e . 1285 cm - 1, S0 2 asymmetric stretch; 1145 cm - 1, S0 2 symmetric stretch; 950 cm" , S0 2 asymmetric stretch; and 825 cm - 1, S0 2 symmetric stretch (* denotes the oxygen atoms involved i n bonding with the antimony atom). Si m i l a r l y , -the four sulphate absorption bands in low frequency region can be assigned as 650 cm"1, rocking; 600 cm - 1, S0 2 bend; 495 cm"1, rocking; and 428 cm - 1, S0 2 bend. The broad band in the 250 cm - 1 region i s ; probably due to a l a t t i c e mode. It i s evident from the sulphate absorption bands that trimethylantimony sulphate i s largely covalent. There i s no absorption band i n the region 600-495 cm"1. This indicates that the trimethylantimony group i s planar, the Sb-C asymmetric stretch being apparently masked by the strong sulphate band at 600 cm"1. The i n f r a r e d spec- trum of trimethylantimony sulphate i s thus completely consistent with a polymeric structure containing bridging sulphato groups, each group being bonded through two of i t s oxygen atoms to the planar trimethylantimony group, making the antimony atom f i v e co- ordinated. As mentioned i n connection with trimethylantimony carbonate, the p o s s i b i l i t y of a monomeric structure containing a bidentate sulphate group can be ruled out due to the large s t r a i n involved i n such a structure. The potassium bromide p e l l e t containing trimethylantimony sulphate was exposed to a i r and no change in the spectrum was ob- served on short exposure. However, after about four hours exposure to a i r , additional bands due to io n i c sulphate and a band at 137 565 cm - 1 appeared. After twenty-four hours, the int e n s i t y of the i o n i c sulphate bands had increased considerably while the bands due to the sulphato group became less intense. This change in the spectrum of the potassium bromide p e l l e t of trimethylan- timony sulphate, on exposure to a i r , must be due to the exchange reaction between trimethylantimony sulphate and potassium bromide. Long, Doak,and Freedman (52) consider that the Sb-C asymmetric stretching frequency i n trimethylantimony sulphate occursat 564 cm"1. However, th i s absorption i s due to the Sb-C asymmetric stretching v i b r a t i o n of the trimethylantimony dibromide (which i s formed i n the p e l l e t ) and not due to the Sb-C asymmetric stretching mode of trimethylantimony sulphate because th i s band appears only after the exchange reaction i n the p e l l e t takes place. 5.5 Trimethylantimony Chromate Trimethylantimony chromate was obtained by the metathetical reaction of trimethylantimony dibromide and s i l v e r chromate i n water. The inf r a r e d spectrum of t h i s compound was measured on samples made as mulls, as well as on potassium bromide p e l l e t s . Identical spectra were obtained by these methods. A portion of the observed spectrum i s shown i n Figure 5. j^. The absorption frequencies, together with t h e i r r e l a t i v e i n t e n s i t i e s and suggested assignments, are l i s t e d i n Table 5.£>. The absorption bands at 3040, 2940, 1410, 1230, 852, and 575 cm - 1 can be assigned to the C-H asymmetric stretch, C-H symmetric stretch, C-H asymmetric bend, C-H symmetric bend, CHg rock and Sb-C asymmetric stretch, respectively. The weak band at 530 i s probably due to the f o r - bidden Sb-C asymmetric stretching mode. The absorption bands due to the chromate group occur at 964, 940, 838, 700, 420, 390 Me3SbCr04. 1 0 0 h en 8 0 - o CD - ^ — 6 0 - CD O - o 4 0 - -*— "E - CO 2 0 -d o - 0 1 2 0 0 1 0 0 0 Frequency (cm-') F I G U R E 5-5 I _J I . I I 6 0 0 4 0 0 2 0 0 CO oo 139 TABLE 5.5 Infrared Absorption Spectrum of Trimethylantimony Chromate Frequency (cm"1) Relative Intensity Assignment 3040 vw C-H asym. s t r . 2940 vw C-H sym. s t r . 1410 w C-H asym. bend 1230 m C-H sym. bend 964 s Cr0 2 asym. s t r . , (v̂ g) 940 s Cr0 2 sym. s t r . , (v^) 852 s CHg rock 838 s(sh) CrOg asym. s t r . , ( ^ 8 ) 700 vw, b Cr0 2 sym. s t r . , (v'g) 575 ms Sb-C asym. s t r . 530 w Sb-C sym. s t r . ? 420 m Cr0 4 rock, (v"7) 390 m Cr0 2 bend, (v*g) 355 m Cr0 4 rock, ( ) Q ) 313 m Cr0 2 bend, (v^) b = broad; m = medium; s = strong; sh = shoulder; y = very; w = weak. * denotes the oxygen atoms involved i n bonding. The assignments for the Cr0 4 group have been suggested by comparison with the SO group of C 2 v symmetry. 140 355 and 313 cm - 1. It can be noticed that the infrared spectrurm of the chromate group i n trimethylantimony chromate i s almost i d e n t i c a l to the chromate spectrum observed i n dimethyltin chromate. The eight observed bands: show c l e a r l y that the symme- try of the chromate group has been lowered from T^ to (o r lower). The Vg mode of the free chromate ion i s resolved into three strong bands at 964, 940 and 838 cm - 1. Though the 838 cm"1 band i s par t l y masked by the strong band at 852 cm - 1 (CHg rocking mode), nevertheless the bands at 852 and 832 show two absorption maxima. The Raman active mode ^ of the free ion now shows very strong absorption at 700 cm - 1. The three medium bands at 420, 390 and 355 cm"'1' correspond to the t r i p l y degenerate mode 0̂  of the free ion and the Raman active mode ^2 of the free ion shows medium absorption at 313 cm - 1. The presence of only one sharp band of medium i n t e n s i t y i n the region 575-500 again indicates , the planarity of the trimethylantimony group. The chromate 2 — absorption i n thi s compound evidently shows that free CrO^ ions are not present. The entire i n f r a r e d spectrum of trimethylan- timony chromate i s again consistent with a polymeric structure i d e n t i c a l to that proposed for trimethylantimony sulphate. Like trimethylantimony sulphate, the inf r a r e d spectrum of trimethyl- antimony chromate did not show any change upon exposing the compound to a i r . Both the compounds are insoluble i n organic solvents but soluble i n water, are perf e c t l y stable, and are non-volatile. 141 5.6 Trimethylantimony Oxalate (CH 3) 3SbC 204 The structure determination of sodium oxalate (136) indicates that the oxalate ion i s planar and has the following interatomic distances and bond angles: n Ov >o i i o C - r C i 124° I 0 I However, i t i s considered (137-139) that the oxalate ion has Vh symmetry and the d i f f e r e n t values for the angles C-C-Oi and C - C - O J I might be due to errors i n the X-ray analysis (138). An oxalate ion of V n symmetry should have twelve normal vibrations as shown i n fable 5.6a (65c). TABLE 5.6a 2- Vi b r a t i o n a l Modes of C 204 Ion (Point Group Vh) Vi b r a t i o n a l mode A c t i v i t y Assignment CAg) R symmetric (O-C-O) stretch C A g ) R C-C stretch C A g ) R symmetric (O-C-O) bend (A u) Inactive C-C torsion (B l g) R symmetric(O-C-O) stretch (Big) ,R C 0 2 rock or symmetric (C-C-0) ( Blu> : I.R Out-of-plane CO2 wagging ^8 (B 2 g) R Out-of-plane CO2 wagging 0 9 (B2u) I.R Asymmetric (O-C-O) stretch v 1 0 ( B 2 u ) I.R CO2 rock or symmetric (C-C-•0) ^12 (B 3u) (B3u> I.R I.R Symmetric (O-C-O) stretch Asymmetric (O-C-O) bend (R = Raman active; I.R = Infrared active) 142 Assignments of the fundamental frequencies of the oxalate ion have been reported by several workers (137-139), but there are some differences in the reported r e s u l t s . Murata and Kawai (137) reported that the rule of mutual exclusion holds i n the Raman and inf r a r e d spectra of the oxalate ion, and therefore the oxalate ion should have V n symmetry. Schmelz and coworkers (139,) have also reported V n symmetry for the oxalate ion. However, these workers have reported two additional Raman bands at 1600 and 1310 cm - 1 i n aqueous solutions of potassium oxalate monohydrate and have assigned them to the v^j(B3u) and V g ( B 2 u ) modes which are forbidden i n the Raman spectrum by the selection rules for symmetry. Hence these workers concluded that the symmetry of the oxalate ion i n aqueous solution i s changed to V, i. e . the oxalate ion i s no longer planar^ and consequently, the and Vg modes become Raman active. In addition to t h i s , there i s disagreement i n the assignments of the lower frequency vib r a t i o n s . Murata and Kawai reported the Vg(Big) Raman frequency at 545 cm - 1 while Schmelz and coworkers reported that t h i s frequency occurs at 317 cm - 1. Murata and Kawai, and Schmelz and coworkers, from a normal coordinate analysis, c a l - culated the frequency for the v^ 0(B2 u) mode to be 295 and 222 cm - 1 respectively, while F u j i t a , Nakamoto and Kobayashi (138) have assigned the 518 cm - 1 i n f r a r e d band to t h i s mode. Schmelz and coworkers have also reported a strong i n f r a r e d band at 514 cm - 1 i n sodium oxalate but have not suggested an assignment for i t . In view of these c o n f l i c t i n g r e s u l t s the inf r a r e d spectrum of sodium oxalate was measured. The observed values are i n agreement with the values reported by F u j i t a , Nakamoto and 143 Kobayashi. Therefore the assignments made by F u j i t a , Nakamoto and Kobayashi are preferred and are recorded i n Table 5.6b. TABLE 5.6b _1 2-Vib r a t i o n a l Frequencies (cm ) of • ^2^4 I o n Vibration Raman Infrared mode (Aqueous XSolid) Assignment solution) *1 1485, 1450 Inactive Symmetric (C-0) stretch ^2 898 Inactive (C-C) stretch ^3 443 Inactive Symmetric (0-C-O) bend ^4 Inactive Inactive — ^5 1664 Inactive Asymmetric (C-0) stretch ^6 545 Inactive Asymmetric (C-C-0) bend ^7 Inactive — ^8 Inactive Inactive 1630 Asymmetric (C-0) stretch V Inactive 518 Symmetric (C-C-0) bend v i i Inactive 1335,1316 Symmetric (C-0) stretch v12 Inactive 768 Asymmetric (0-C-O) bend The oxalate group i s a very common ligand and numerous metal oxalato complexes are reported i n the l i t e r a t u r e (140). In metal oxalato complexes i n which the oxalate group i s b i - dentate (with unidentate carboxylic groups), arid i n c i s diakyl oxalates, the symmetry of the oxalate group i s lowered to C 2 v as shown below: 144 C -C A -Qf I I — — 0 " l —fs- (01 represents the oxygen atoms involved i n bonding.) The c o r r e l a t i o n between the point groups V n and C2 V (138) i s shown i n Table 5.6c. Thus an oxalato group of symmetry w i l l have ten infrared active fundamental vibrations. The infrared spectra of metal-oxalato complexes have been studied by several workers (47d). F u j i t a , M a r t e l l , and Nakamoto (141) have done a normal coordinate analysis for metal-oxalato-complexes, using Urey-Bradley force f i e l d approximations. The oxalate group acts as chelating ligand i n these complexes forming a four membered chelate ring. The res u l t s of Fuita, Martell and Nakamoto show strong coupling between various v i b r a t i o n a l modes due to the presence of the chelate ring. However, i t i s expected that i f both the 0 j oxygen atoms i n the oxalate group p a r t i c i p a t e i n bonding, the C - 0 i bond length w i l l increase and the C - O n bond w i l l be shortened, r e s u l t i n g i n the s h i f t s of the C - 0 i and C - O n stretching frequencies to lower and higher frequencies respectively. An X-ray structure determination of K^rC204(H 20) 2"]3H 20 (142) indicates that the two C-̂ Oj bonds coordinated to the metal atom are lengthened (1.39^) and the o two C -Ou bonds shortened ( 1 . 1 7 A ) . In metal-oxalato complexes the frequencies of the C - O J I stretching vibrations ( 1 7 0 0 - 1 6 0 0 cm - 1 region) increase, and those of the C-Oj stretching vibra" ( 1 4 5 0 - 1 3 5 0 cm - 1 and 1 3 0 0 - 1 2 0 0 cm - 1 regions) decrease as the 1 4 5 TABLE 5.6c The V i b r a t i o n a l Modes of Th® Free Oxalate Ion (V h Symmetry and The Oxalato Group ( C 2 V Symmetry) Assignment eim C 2 V ; V ( C-O), v ( C - C ) , sym. S (0-C-O) Out-of-plane v ( C-O), asym. $ ( C - C-0) Out-of-plane Out-of-plane v(C-O) ,• sym. S ( C - C-O) v ( C-O), asym. §(0-C -O) frequency of the metal-oxygen stretching vib r a t i o n increases. In c i s dimethyl oxalate, each Oi oxygen atom i n the oxalate group i s covalently bonded to a methyl group and the C - O n and C - O i stretching frequencies appear at 1 7 7 6 , 1 7 7 0 and 1 3 2 5 , 1 1 6 5 cm - 1 respectively. Other frequencies are also sh i f t e d , e.g. the (i0 - C-0n) bend (A^) and the ( J O - C - O J I ) bend (B^) frequencies appear at 4 0 4 and 8 5 1 cm""1 respectively and the C - C stretch (Ai) appears at 8 6 2 cm"1 ( 1 3 9 ) . A portion of the infr a r e d spectrum of trimethylantimony oxalate i s shown i n Figure 5 v 6 , and the frequencies, together with th e i r i n t e n s i t i e s and probable assignments are l i s t e d i n Table 5 . 6 d . The spectra were obtained on samples made as mulls, as well as on potassium bromide p e l l e t s . Both the methods gave i d e n t i c a l spectra. The trimethylantimony part of the spectrum can be ea s i l y assigned, i . e . 3 0 3 5 cm - 1, C - H v h 3 A g (R) 1 A u (Inactive) 2 B l g (R) 1 B l u (I.R) 1 B 2 g (R) 2 B 2 u (I.R) 2 B 3 u H.R) 3 A X (R,I.R) 1 A 2 (R) 2 B i (R,I.R) 1 B 2 (R,I.R) 1 A 2 (R) 2 A x (R,I.R) 2 B1 (R,I.R) M e 3 S b C 2 0 4 i O O h 2000 1800 1600 1400 1200 1000 800 600 400 200 Frequency ( c m - 1 ) 147 TABLE 5.6d Infrared Absorption Spectrum of Trimethylantimony Oxalate Frequency (cm"1) Relative Intensity 3035 w 2950 m 2570 1665 1620 1375 1250 1227 1215 855 827 755 585 575 525 420 w vs s, sh m vs s, sh s w m s Assignment C-H asym. s t r . C-H sym. s t r . ( C - 0 n ) s t r . , (B-L) ( C - O J J ) str.-, (A x) (C-0j) s t r . , (Ai) (C-Oj) s t r . , (B-L) CHg rock C-C s t r . , (A x) (Oj.-C-Pu) asym. bend, ( B ^ (C-C-O) asym. bend, ( B ^ Sb-C asym. s t r . (C-C-O) sym. bend, (A±) (Oj-C-Ou) sym. bend, (A^) m = medium; s = strong; sh = shoulder; v = very; w = weak. Gj denotes oxygen atomsinvolved i n bonding. 148 asymmetric stretch; 2950 cm - 1^ C-H symmetric stretch; 855 cm - 1 CHg rock; and 575 cm - 1, Sb-C asymmetric stretch. Absorption bands due to the oxalate group occur at 1665, 1620, 1375, 1250-1215, 827, 755, 585, 525 and 420 cm"1. The infrared absorption bands i n sodium oxalate occur at 1640(s,b), 1420(w), 1340-1315(s,b), 777(s,sp) and 515(s,b) em"1. By comparison with the spectrum of the free oxalate ion i t can.be seen that the spectrum of trimethylantimony oxalate 2 - i s quite d i f f e r e n t from that of the C2O4 ion. The absorption bands at 1665 and 1250-1215 cm - 1 correspond to the C - 0 u and C -0 i stretching frequencies observed i n metal-oxalato complexes. 2 - Moreover the Raman active modes for the free C2O4 ion now appear with moderate or strong i n t e n s i t y . The oxalate spectrum in trimethylantimony oxalate i s completely i n accord with the presence of an oxalate group of C 2 v symmetry. Though nothing conclusive can be said about the presence of the Sb-C symmetric stretch due to the presence of a strong band i n the 525 cm"1 region, i t may be noted that the Sb-C asymmetric stretching frequency i n thi s compound appears in the same frequency region and with almost the same in t e n s i t y as i n trimethylantimony carbonate, the d i n i t r a t e , and the dibromide, which indicates that the geometry of the trimethylantimony group i n trimethyl- antimony oxalate i s not s i g n i f i c a n t l y d i f f e r e n t from that found in these l a t t e r compounds. Considering the planarity of the trimethylantimony group and the C 2 v symmetry of the oxalate group, i t i s suggested that the oxalate groups act as bridging ligands between planar trimethylantimony groups making the antimony atom f i v e coordinate. Therefore a polymeric structure 149 s i m i l a r to that proposed for trimethylantimony carbonate, sulphate and chromate can also be proposed for the oxalate. The alter n a t i v e monomeric structure containing a chelate ring would involve a considerable d i s t o r t i o n of the trimethylantimony group to a non-planar arrangement as well as lengthening of the C-C bond to a great extent; i t i s very unlikely that such a struc- ture could be possible. Like trimethylantimbny sulphate and chromate, the oxalate i s insoluble i n organic solvents and i s non-volatile. In a polymeric structure involving planar trimethylantimony groups and bridging oxalato groups, the coupling between the various v i b r a t i o n a l modes of the oxalate group may not be so strong as compared with metal-oxalato complexes containing a chelate ring. Therefore the f ollowing;.assignments, based on the c o r r e l a t i o n between the v i b r a t i o n a l modes of the free oxalate ion and the coordinated oxalato group of C 2 v symmetry, are suggested for the absorption frequencies of the oxalate group i n trimethylantimony oxalate: (a) The bands at 1375, 827 and 420 cm - 1 correspond to the three Raman active modes of A^g species i n the oxalate ion ( i . e . 1485-1450, 898 and 443 cm" 1). These bands are therefore assigned to the C-Oj stretch (A^), the C-C stretch (A^) and the symmetric (Oj-C -0n) bend (A.]_) respectively. (b) The two Raman active modes of B^g species i n the Vh point group become inf r a r e d active modes of B^ species i n the C 2 v point group, therefore the bands at 1665 and 585 cm~l are assigned to the C -O.n stretch (B^) and the asymmetric (C-C-0) bend (Bj_) respectively. i5o;> (c) The bands at 1620 and 525 cm - 1 correspond to the two infrared active modes (B2 U) at 1640-1630 and 515 cm - 1 of the oxalate ion. Therefore these bands are assigned to the (C-0jj) stretch (Ai) and the symmetric (C-C-O) bend (A^) respectively. (d) The bands at 1250-1215, and 755 cm - 1 correspond to the two infrared active modes of the free ion and are assigned to the C-Oj stretch (B]^) , and the asymmetric (l0-C-0n) bend (Bi) respectively. 5.7 Trimethylantimony Bis(tetrafluoroborate) ( C H 3 ) 3 S b ( B F 4 ) 2 The metathetical reaction between trimethylantimony dibromide and s i l v e r tetrafluoroborate i n methanol resulted i n instantaneous p r e c i p i t a t i o n of s i l v e r bromide. Upon removal of the methanol, a white s o l i d was obtained. The recovered methanol contained boron t r i f l u o r i d e which was i d e n t i f i e d by i t s infrared spectrum and q u a l i t a t i v e t e s t s . The in f r a r e d spectrum of the s o l i d indicated the presence of the tetrafluoroborate group, but the a n a l y t i c a l r e s u l t s do not correspond to (CH 3) 3Sb(BF 4) 2. An X-ray powder photograph of the s o l i d showed the presence of trimethylantimony d i f l u o r i d e . On the basis of spectroscopic, a n a l y t i c a l , and X-ray powder photographic r e s u l t s , i t i s con- cluded that the s o l i d i s an approximately 1:1 mixture of trimethylantimony bis(tetrafluoroborate) and trimethylantimony d i f l u o r i d e . The mixture sublimed read i l y at 50° under vacuum and the in f r a r e d spectrum, a n a l y t i c a l r e s u l t s and X-ray powder photographs of the sublimed product were i d e n t i c a l to that of the unsublimed mixture, in d i c a t i n g that no further decomposition had occurred during sublimation. 151 These re s u l t s can be explained i n the following manner: CHgOH 2 4- (CH 3) 3SbBr 2 > 2AgBF 4 > (CH3)'3.Sb (solvated) + 2BF4~ + 2AgBr . . . (1) 2 + -solvent (CH 3) 3Sb (solvated) + 2BF 4 — > (CH 3) 3SbF 2 + 2BF 3 . . .(2) In the infrared absorption spectrum of the mixture, no bands were observed i n the 4000-1500 cm - 1 region except weak bands at 3050-2900 cm-1 due to C-H stretching vibrations. The absorption bands (in 1500-250 cm - 1 region), together with t h e i r r e l a t i v e i n t e n s i t i e s and suggested assignments, are l i s t e d i n Table 5.7 and part of the spectrum i s shown i n Figure 5.7. The absorption bands at 1410, 1235, 885 and 587 are associated with the trimethylantimony group and can be assigned as 1410 cm - 1, C-H asymmetric bend; 1235 cm - 1, C-H symmetric bend; 880 cm - 1, CH 3 rock; and 587 cm - 1, Sb-C asymmetric stretch. The bands at 1287, 1150, 1100, 1053, 1040, 1015, 760, 572, 545, 515 and 400 cm - 1 can be attributed to the tetrafluoroborate group. The absorption bands due to trimethylantimony d i f l u o r i d e would be expected to occur at 1415, 1235, 855, 586 and 475 cm - 1. Apparently the bands at 855 and 475 cm - 1 are masked by strong bands at 880 and 400 cm - 1. The broad shoulder i n the 475, cm - 1 region indicates the presence of a band i n t h i s region. The strong bands at 1100 and 1053 cm - 1 correspond to the t r i p l y degenerate mode ^ 3 of BF 4 ion and the weak band at 760 cm"-'-, corresponds to the Raman active mode v1, of the free ion. In x? the low frequency region, the bands at 572 and 515 cm~l are Frequency (cm - 1 ) CJl TABLE 5.7 Infrared Absorption Spectrum of The Mixture of Trimethylantimony Bis(tetrafluoroborate) and Trimethylantimony D i f l u o r i d e Frequency (cm"1) Relative Intensity Assignment 1410 w C-H asym. bend 1287 m 1235 m C-H sym. bend 1150 sh 1100 s B-F s t r . , ) 1053 s BFg sym. str.,(v*-j_) 1040 sh 1015 sh 880 s CH3 rock 760 w B-F* s t r . , (v 2) 587 ms Sb-C asym. s t r . 572 s BFg asym.bend,(05) 545 w 515 ms BFg sym. bend, (\)g) 475 sh S-F asym. s t r . , [(CH3)3SbF2] 400 s BF 4 rocking, (0g) m = medium; s = strong; sh = shoulder; v = very; w = * F represents the f l u o r i n e atom involved i n bonding. weak. 154 probably two components of the t r i p l y degenerate mode ^ 4 . The broad band at 4 0 0 cm - 1 may be correlated with the Raman active mode v 2 of the free ion. On exposing the mixture to a i r , the absorption bands attributed to the tetrafluoroborate group showed marked changes. The bands at 1100 and 1 0 5 3 were replaced by a very strong broad band at 1 0 5 5 cm"1 which i s c h a r a c t e r i s t i c of the free BF4"" ion. The bands at 760 and 573 cm - 1 disappeared and the intensity of 4 0 0 cm - 1 band was diminished. New bands appeared in the 5 0 0 - 4 5 0 region. The spectroscopic r e s u l t s thus suggest that trimethyl- antimony bis(tetrafluoroborate) i s present i n the mixture and that the tetrafluoroborate groups are coordinated to the trimethylantimony group through, one of the f l u o r i n e atoms. The v o l a t i l i t y of the mixture also indicates a non-ionic con- s t i t u t i o n for trimethylantimony bi s ( t e t r a f l u o r o b o r a t e ) . Considering the r e s u l t i n g C$v symmetry of the tetrafluoroborate group, the following assignments for the absorption bands of the tetrafluoroborate groups are suggested: 1 1 0 0 cm - 1, B-F stretch v^ ( E ) ; 1 0 5 3 cm"1, B F 3 symmetric stretch v^A-^); 760 cm - 1, B-F* stretch ^ ( A ^ ) ; 5 7 2 cm - 1, B F 3 asymmetric bend T ) 5 ( E ) ; 5 1 5 cm - 1, B F 3 symmetric bend vg (A].) ; and 4 0 0 cm"1, rocking mode v ^ ( E ) . (F* represents the fl u o r i n e atom involved in coordination.) These assignments have been suggested by comparison with the v i b r a t i o n a l assignments reported ( 1 4 3 , 1 4 4 ) for the perchloryl f l u o r i d e , C I O 3 F . 5.8 Trimethylantimony Hexaf l u o r o s i l i c a t e (CH^^SbSiFg The h e x a f l u o r o s i l i c a t e ion (SiFg)* i s octahedral and 155 belongs to point group 0 n . The v i b r a t i o n a l modes of an octa- hedral group have already been discussed. Only three fundamental v i b r a t i o n a l frequencies v^, Vg, and V4 of the S i F g " ion are known. Raman active frequency v^ occurs at 656 cm"1 (145) and the i n f r a - red active frequencies v*g and v"4 occur at 726 and 480 cm"1 respectively (128). C r y s t a l l i n e potassium and ammonium hexa- f l u o r o s i l i c a t e s show no s p l i t t i n g of the degenerate modes but, i n barium h e x a f l u o r o s i l i c a t e , the mode shows a s p l i t t i n g of 1 2-about 20 cm" (125). No example of coordination by the SiFg ion has been reported so f a r . The metathetical reaction between trimethylantimony dibromide and s i l v e r h e x a f l u o r o s i l i c a t e i n methanol resulted i n instantaneous p r e c i p i t a t i o n of s i l v e r bromide. Upon removal of the solvent under vacuum, a white c r y s t a l l i n e , hygroscopic s o l i d was obtained. X-ray powder photographic d a t a 3 i n f r a r e d spectrum and a n a l y t i c a l r e s u l t s of the s o l i d showed i t to be a mixture of trimethylantimony h e x a f l u o r o s i l i c a t e and trimethyl- antimony d i f l u o r i d e containing about 52 percent hexafluoro- s i l i c a t e and 48 percent d i f l u o r i d e . The recovered methanol was highly a c i d i c and contained s i l i c o n and f l u o r i n e . The s o l i d sublimed rea d i l y under vacuum at 50° and the infrared spectrum, X-ray powder photograph and a n a l y t i c a l r e s u l t s of the sub- limate were i d e n t i c a l to those of unsublimed mixture in d i c a t i n g that no further decomposition had occurred during sublimation. The p a r t i a l decomposition of trimethylantimony he x a f l u o r o s i l i c a t e can be explained i n a manner sim i l a r to that suggested for the p a r t i a l decomposition of the trimethylantimony b i s ( t e t r a f l u o r o - borate) , i . e. 156 CH30H 2 + (CH 3) 3SbBr 2 +• A g 2 S i F 6 -> (CH 3) 3Sb^ (solvated) + S i F 6 2 " + 2AgBr . . . ( 1 ) 9+ o solvent (CH 3) 3Sb^ (solvated) + S i F ^ " —> (CH 3) 3SbF 2 + S i F 4 . . . ( 2 ) The i n f r a r e d spectrum of the mixture i s recorded, together with the r e l a t i v e i n t e n s i t i e s of the absorption bands, in Table 5.8. Part of the spectrum i s shown i n Figure 5.8. Except for the. C-H stretching vibrations i n the region 3050-2900 cm - 1, no bands were observed i n the 4000-1500 cm"1 region. The absorption bands at 1410, 1240, 880-855, and 586 cm"1 can be assigned to the C-H asymmetric bend, the C-H symmetric bend, the CH 3 rock, and the Sb-C asymmetric stretch respectively. The 475 cm 1 band can be attributed to the Sb-F asymmetric stretching v i b r a t i o n of the trimethylantimony d i f l u o r i d e . The remaining medium or strong bands are therefore associated with the h e x a f l u o r o s i l i c a t e group. This i s further supported by the change i n the spectrum when the mixture was exposed to a i r . A sample of the mixture exposed to a i r showed c h a r a c t e r i s t i c 2— i n f r a r e d absorption bands of the SiFg ion, i . e . a strong broad band at 735 cm~l and a strong band i n the 480 cm - 1 region. Thus spectroscopic r e s u l t s indicate the presence of trimethylantimony he x a f l u o r o s i l i c a t e i n the mixture. Since the h e x a f l u o r o s i l i c a t e spectrum i n the anhydrous mixture i s s i g n i f i c a n t l y d i f f e r e n t 2- from that of the SiFg ion, i t can be concluded that trimethyl- antimony h e x a f l u o r o s i l i c a t e i s non-ionic, but on exposure to a i r , 2- i t i s hydrolysed ,to produce free SiFg ion. The v o l a t i l i t y of  158- TABLE 5.8 Infrared Absorption Spectrum of The Mixture of Trimethylantimony Hexafluorosilicate and Trimethylantimony D i f l u o r i d e Frequency (cm"1) Relative Intensity Assignment 50-2900 w C-H s t r . 1495 m 1410 w C-H asym. bend 1288 ms 1240 w C-H sym. bend 1057 w 997 ms 880 sh ) ) CH 0 rock 855 s ) o 785 s 720 m 586 m Sb-C asym. s t r . 555 s 533 w 475 s Sb-F asym. s t r . 445 m 350 m m = medium; s = strong; sh - shoulder; v = very; w = weak. No assignments are suggested for the absorption bands due to the SiFg group. 159 the mixture also indicates a non-ionic constitution. However, due to the presence of a large number of bands i n the spectrum, no conclusions can be reached about the possible stereochemistry of trimethylantimony h e x a f l u o r o s i l i c a t e . 5.9 Trimethylantimony Bis(hexafluoroantimonate) (CHg)gSb(SbFg) 2 This compound was obtained, as an extremely hygroscopic white s o l i d , by the metathetical reaction between trimethyl- antimony dibromide and s i l v e r hexafluoroantimonate i n l i q u i d sulphur dioxide. X-ray powder photographs of the s o l i d did not show any l i n e s due to either trimethylantimony d i f l u o r i d e or the dibromide; however, the f l u o r i n e percentage i n the sample was found to be f i v e percent lower than the calculated value. The substance reacted rapidly with s a l t windows, but reproducible spectra could be obtained by using s i l v e r chloride and polythene sheets. A portion of the in f r a r e d spectrum, on a nujol mull sample, i s shown i n Figure 5 f9. Other bands were observed at 1180(m) and 880(m) cm - 1. The 880 cm - 1 band can be assigned to the CHg rocking mode. The other band which can be attributed to the trimethylantimony group occurs at 585 cm - 1 and can be assigned to the Sb-C asymmetric stretch. The rest of the bands must therefore be associated with the hexafluoroantimonate group. As can be seen from Figure 5.9, the spectrum i n th i s region shows additional bands of medium i n t e n s i t y at 550 and 445 cm - 1, and a shoulder i n the 370 cm - 1 region. Moreover, the \)g mode which — 1 appears as a broad, symmetrical band at 660 cm A i n the spec- trum of the SbFg ion, i s now s p l i t , and shows peaks at 665 and 640 cm - 1. As described e a r l i e r , almost similar spectroscopic  161 features are observed for dimethyltin bis(hexafluoroantimonate). However, i n dimethyltin bis(hexafluoroantimonate), the mode shows three peaks. Thus i t appears that, in trimethylantimony bis(hexafluoroantimonate), the octahedral symmetry of the SbFg group i s lowered to probably C^ v or D^. The almost similar spectroscopic e f f e c t s observed for t r i m e t h y l t i n hexafluoroanti- monate, dimethyltin bis(hexafluoroantimonate), and trimethyl- antimony bis(hexafluoroantimonate) strongly suggest that these spectroscopic e f f e c t s are due to coordination. This i s further supported by the change i n the inf r a r e d spectrum when the anhydrous compound was exposed to a i r . The bands at 1180, 550, and 445 disappeared, and the ^3 mode showed a single broad symmetrical peak at 660 cm - 1. 2 5.10 Trimethylantimony(V) Derivative of B ^ g C l ^ 2 — The trimethylantimony(V) derivative of B i 2 ^ 1 1 2 w a s obtained as a crimson red, hygroscopic s o l i d . The colour of the s o l i d changed to white on exposure of the anhydrous s o l i d to water or .methanol vapour. The aqueous or methanol solution of MegSbB-j^Clig was also colourless. However, the recovered s o l i d from these solutions was always coloured. The infrared spectrum of the anhydrous s o l i d i s recorded i n Table 5.10 and part of the spectrum i s shown i n Figure 5.10. The absorption bands due to the trimethylantimony group appear at 3000-2900,(C-H stretch); 1405, (C-H asymmetric bend); 1245, (C-H symmetric bend); 865, (CH3 rock); and 570, (Sb-C asymmetric stretch) cm - 1. The absorption bands at 1030', 1000, 827, 532, 450, and 320 cm"1 can be attributed to the &\2^\2 g r o u P « By comparing the spec- 1200 1000 8 0 0 6 0 0 4 0 0 2 0 0 Frequency (cm - 1) 163 TABLE 5.10 Infrared Absorption Spectrum of Me3SbBi2Cli2 Frequency Relative (cm-1) i n t e n s i t y Assignment 3000 - 2900 vw C-H stretch 1405 vw C-H asymmetric bend 1307 vw 1245 w C-H asymmetric bend 1030 vs 1000 m 865 s CH 3 rock 827 s 570 w Sb-C asymmetric stretch 532 vs 450 m, b 320 m, b b = broad; m = medium; s = strong; v = very; w = weak No assignments have been suggested for the absorption bands due to the B12CI12 group 164 trum of M e 3 S b B 1 2 C l 12 with that of Ag^BigCl-^ i t becomes evident that inMe^SbB^2Cli2 the symmetry of B ^ C l - ^ group i s reduced. There i s no appreciable change i n the trimethylantimony part of the spectrum as compared with trimethylantimony dibromide, though i t i s d i f f i c u l t to determine whether the Sb-C symmetric stretch i s also present i n the spectrum of MegSbB^Cl^. The bands at 827, 450 and 320 cm - 1 disappeared on exposing MegSbB-j^Cl^ ^° a i r ^ o r ^ hours. Thus i t i s reasonable to conclude that the symmetry of the B 1 2 C I 1 2 group i s appreciably distorted i n MegSbB^Cl-j^ and that t h i s e f f e c t i s most l i k e l y ; due to the coordination between MegSb and B ^ C l ^ g groups. 165 CHAPTER 6 CONCLUSION The re s u l t s of th i s investigation demonstrate the existence of an intense i n t e r a c t i o n between the organometal group, i . e . (CgH(j)gSn, (CH3>3Sn, (CHgJgSn, or ( C ^ ^ S b and the anionic group i n a l l the organotin(IV) or organoantimony(V) acid derivatives studied. The decomposition of the organometal derivatives of strong Lewis acids such as BFg and SiF^, into the organometal f l u o r i d e and the corresponding Lewis acid, indicates t h i s strong i n t e r a c t i o n . The infrared spectra of a l l the compounds uniformly show marked changes i n the spectrum of the anionic group, i . e . s i g n i f i c a n t l y large s p l i t t i n g s of the degenerate modes and the appearance of the Raman active modes with moderate to strong i n t e n s i t i e s . From a comparison with the in f r a r e d spectroscopic data of a large number of corresponding i o n i c s a l t s , i t becomes obvious that these spectroscopic observations cannot be attributed to c r y s t a l f i e l d e f f e c t s . In view of the p o s s i b i l i t y of unknown factors:, i n interpreting the spectra of s o l i d s , the re s u l t s of a single spectrum may be open to question. However, the p r o b a b i l i t y of almost i d e n t i c a l e f f e c t s occurring i n a wide variety of com- pounds i s exceedingly s l i g h t . The observed spectroscopic e f f e c t s can therefore be attributed to coordination or p a r t i a l covalent bond formation between the organometal and the anionic groups. A l t e r n a t i v e l y , a very strong p o l a r i z a t i o n by the organometal cation may produce these e f f e c t s . However, there i s no obvious reason why these simple cations of low charge density should be more p o l a r i z i n g than any other known cation. Consequently, i t 166 i s concluded that these spectroscopic e f f e c t s are due to coordin- ation or p a r t i a l covalent bonding between the organometal and the anionic groups. Unfortunately, there i s no obvious experimen- t a l method which w i l l d istinguish unambiguously between terms such as 'strong p o l a r i z a t i o n ' , ' p a r t i a l covalent bonding 1 and coordination. However,1 none of these compounds appear to contain free organometal cations, i . e . ( C e H s^Sri*" , (CHg^Sn"4" , (CHg^Sn2"1" 2 + or (CHg) 3Sb , although i t must be stressed that the bonding between the metal atom and the anionic group cannot be described i n the same covalent terms as that between the metal and the or- ganic groups. The bonding between the metal atom and the anionic group i s presumably less covalent than the metal-carbon bond. The i n s t a b i l i t y of the organotin cations in the s o l i d state probably arises partly from the tendency of the t i n atom to increase i t s coordination number. The findings of t h i s i n v e s t i - gation, as well as other recent studies on organotin compounds, demonstrate the tendency of the t i n atom to increase i t s coor- dination r e a d i l y to f i v e or s i x . Tetrakis(8-quinolinato) t i n (IV)'- has been reported (146) to be an eight coordinate tin(IV) compound. In trimethyltin(IV) derivatives f i v e coordination of the t i n atom i s attained through a polymeric structure involving bridging anionic groups and a t r i g o n a l bipyramidal configuration around the t i n atom. Dimethyltin.(IV) derivatives are apparently either tetrahedral or six coordinated, and polymeric structures i n - volving bridging anionic groups are also indicated for these derivatives. The i n s o l u b i l i t y i n non-polar solvents and non- v o l a t i l i t y of such derivatives are not suitable c r i t e r i a for con- sidering these compounds as io n i c and these physical properties 167 can be attributed to polymeric structures. Like trimethyltin(IV) derivatives, a t r i g o n a l bipyramidal configuration i s also indicated for trimethylantimony(V) deriva- t i v e s . These re s u l t s are consistent with the general stereo- chemistry of group Vb elements. From n.m.r. studies of a variety of f i v e coordinate compounds including a number of mono-, d i - , and t r i s u b s t i t u t e d pentahalides of group Vb elements, Muetterties and coworkers (147,148) have shown that a t r i g o n a l bipyramidal configuration with the most electronegative groups occupying the a p i c a l positions i s the most favoured configuration for such compounds. Compounds of the type RgSnX2 such as trimethylantimony dihalides and d i n i t r a t e are monomeric. In compounds of the type R3SbY, such as trimethylantimony carbonate,sulphate, chromate and oxalate, the t r i g o n a l bipyramidal configuration can be attained through a polymeric structure , involving bridging anionic groups i n a manner sim i l a r to that i n R3SnX derivatives. The 2+ i n s t a b i l i t y of the R3Sb cation again r e f l e c t s the preference of the antimony atom to a t t a i n a higher coordination. However, the electronic: description of bonding i n these compounds i s not known with any certainty. The most widely used explanation of the penta- and hexacoordinated molecules i s given by assuming the hybridization of the available s and p o r b i t a l s with one or two d o r b i t a l s respectively (149), i . e . the t r i g o n a l bipyramidal configuration can be explained by sp^d hybridization and an octahedral configuration by sp^d 2 hybridization^ Both t i n and antimony have empty d o r b i t a l s available i n t h e i r valence s h e l l s and hence are capable of accepting more than four electrons. For t r i g o n a l bipyramidal compounds, i t has been suggested (22,147) that the three hybrid .orbitals of the central atom i n the equatorial plane may be constructed from a combination of the s and p o r b i t a l s (5s and 5p i n the case of t i n or antimony) and those on the a p i c a l axis from a (p_+ d ) combination X5p z and 5d ^ i n the case of t i n and antimony). Janssen, Luij t e n , and van der Kerk (48) consider that, i n f i v e coordinate t i n compounds, the p r i n c i p a l i n t e r a c t i o n involves the donation of electrons from f i l l e d d o r b i t a l s of the metal atom into suitable o r b i t a l s of the ligand. Gn the other hand, McGrady and Tobias (50) consider that i n dimethyltin chelate complexes (R2SnL2) the t i n 5s and 5p z o r b i t a l s are involved almost e n t i r e l y i n the two tin-carbon bonds and the bonding o r b i t a l s i n the equatorial plane are mainly derived from 5p xand 5py o r b i t a l s according to the molecular o r b i t a l treatment of Rundle (150). 169 CHAPTER 7 EXPERIMENTAL G e n e r a l P r e p a r a t i o n o f Compounds The compounds s t u d i e d i n t h i s i n v e s t i g a t i o n were s y n t h e - s i z e d ' by the m e t a t h e t i c a l r e a c t i o n between an o rganometal h a l i d e and the a p p r o p r i a t e s i l v e r s a l t i n a s u i t a b l e s o l v e n t . O r g a n o t i n h a l i d e s were o b t a i n e d from M & T C h e m i c a l s . T r i m e t h y l a n t i m o n y d i b r o m i d e was s y n t h e s i z e d by the r e a c t i o n of a G r i g n a y d r e a g e n t on antimony t r i c h l o r i d e and subsequent r e a c t i o n w i t h bromine. Anhydrous s i l v e r s a l t s were o b t a i n e d from the f o l l o w i n g s o u r c e s : S i l v e r P e r c h l o r a t e - F r e d e r i c Smith C h e m i c a l Co. . S i l v e r N i t r a t e ) S i l v e r S u l p h a t e )' - B.D.H., A.R. grade S i l v e r C arbonate • ). - M a l l i n c k r o d t , A.R.grade S i l v e r Chromate J - F i s h e r S c i e n t i f i c Co. S i l v e r O x a l a t e - K & K L a b o r a t o r i e s S i l v e r Permanganate ) S i l v e r H e x a f l u o r o s i l i c a t e ) - A l f a I n o r g a n i c s , I n c . S i l v e r T e t r a f l u o r o b o r a t e ) S i l v e r Hexafluor©phosphate ) - Ozark Mahoning Co. S i I v e r H e x a f l u o r o a r s e n a t e ) S i l v e r H e x a f l u o r o a n t i m o n a t e ) J S i l v e r S a l t of B i 2 C l i 2 ~ - G i f t from Dr. E. L. M u e t t e r t i e s , C e n t r a l R esearch L a b o r a t o r y , E . I . du Pont de Nemours Co., W i l m i n g t o n , Delaware. O r g a n i c s o l v e n t s were of e i t h e r anhydrous A.R. M a l l i n c k r o d t or A.R. S p e c t r o grade. Methanol was f u r t h e r d r i e d by the method d e s c r i b e d by V o g e l (151) and acetone was d r i e d over d r i e r i t e . 170 The sulphur dioxide and ammonia used were Matheson anhydrous grade. Sulphur dioxide was further dried over sulphuric acid and then fractionated, and ammonia was dried over sodium metal. Except where otherwise stated, compounds were prepared and handled i n an atmosphere of dry nitrogen i n the dry box which was constantly flushed with nitrogen, dried f i r s t over sulphuric acid, then sodium hydroxide and f i n a l l y s i l i c a g el. Fresh phos- phorus pentoxide was maintained i n the dry box at a l l times. The reactants were weighed i n a i r - t i g h t weighing bottles which were transferred to the dry box. Sintered glass funnels with Quic k f i t j o i n t s were used for f i l t r a t i o n . Mixing of the reac- tants and f i l t r a t i o n of insoluble s i l v e r halide were performed i n the dry box and solvents were removed under vacuum; then the evacuated flasks were transferred again to the dry box. Gonventional vacuum techniques were used for the manipu- l a t i o n of v o l a t i l e substances. An apparatus described by Parry, Schultz and Girardot (152) was used for carrying out reactions i n l i q u i d sulphur dioxide. The apparatus was f i r s t evacuated, then transferred to the dry box where organometal halide and s i l v e r s a l t were added. The closed apparatus was then evacuated again and anhydrous sulphur dioxide was condensed on to the reactants. The mixture was shaken and then the sulphur dioxide was frozen. The apparatus was inverted and pr e c i p i t a t e d s i l v e r halide.was f i l t e r e d off and retained on the sintered glass f i l t e r . F i n a l l y , the sulphur dioxide was removed under vacuum and the evacuated apparatus was transferred to the dry box. Analysis C, H, N, S, and F analyses were performed either in the 171 microanalytical laboratory of t h i s department or at Microan- alytisches Laboratorium im Max-Planck-Institut, Miilheim (Ruhr), Germany, or at the Schwarzkopf Microanalytical Laboratory, New York. B and Cl analyses were obtained by courtesy of Dr. E.L. Muetterties ait the Central Research Laboratory of E.I. dut- Pont de Nemours Co., Wilmington, Delaware. Other analyses were performed according to the methods described by Vogel (153) or Scott (154). Most of the analyses were done i n duplicate. Measurement of Spectra Infrared absorption spectra i n the range 4000-700 cm - 1 were recorded on a Perkin Elmer model 21 spectrophotometer. Spectra i n the region 2000-250 cm - 1 were measured on a Perkin Elmer model 421 grating spectrophotometer. Perkin Elmer model 137 infracords f i t t e d with sodium chloride or potassium bromide optics were also used for a few measurements. Except where otherwise stated, samples were prepared i n the dry box as mulls in nujol, hexachlorobutadiene or halocarbon o i l . Samples were placed between plates of cesium iodide, potassium bromide or 0.1 cm. thick sheets of s i l v e r chloride or polythene. Salt plates were wrapped with polyvinyl tape. Specially designed c e l l s with t e f l o n rings were used to mount s i l v e r chloride and polythene sheets. Several spectra of each substance were recorded at varying concentrations. Spectra were also recorded after ex- posing the substance to a i r . Blanks were often run on c e l l windows and mulling agents. In a few cases, spectra of f i n e l y powdered samples could be obtained without any mulling agents. Spectra of some compounds were also measured i n potassium bromide p e l l e t s using freshly dried potassium bromide. Infra- 172 red spectra of v o l a t i l e substances were measured using potassium bromide or s i l v e r chloride gas c e l l s . E l e c t r o n i c spectra i n the u l t r a v i o l e t and v i s i b l e region were recorded on a Cary Model 14 spectrophotometer. The proton n.m.r. measurements were made with a Varian A60 spectrometer at 60 Mc/sec. X-ray Powder Photographs X-ray powder photographs were obtained by using copper Kc< radiati o n with a n i c k e l f i l t e r on a General E l e c t r i c X-ray unit. Quartz C a p i l l a r y tubes of either 0.5 mm. or 0.3 mm. dia- meter were f i l l e d with samples i n the dry box and the open ends of the c a p i l l a r y tubes were sealed. Photographs were taken i n a 14.32 cm. diameter camera. Trip h e n y l t i n Nitrate (a) T r i p h e n y l t i n chloride (2.26 g.) and s i l v e r n i t r a t e (1.00 gi) were mixed i n 50 ml. of acetone and the mixture was shaken for three days. The pr e c i p i t a t e d s i l v e r chloride was f i l t e r e d off and acetone removed under vacuum. The same reaction was also performed, more rapidly and without shaking, i n methanol owing to the greater s o l u b i l i t y of s i l v e r n i t r a t e i n t h i s solvent. The product was a white s o l i d . Analysis, calcd. for C^gH-j^SnNOg: C, 52.42; H, 3.67; N, 3.39. Found: C, 51.90; H, 3.70; N, 3.32. (b) Triphenyltin n i t r a t e was also prepared by mixing solutions of t r i p h e n y l t i n chloride (3.855 g.) i n 50 ml. acetone and s i l v e r n i t r a t e (1.698 g.) i n 5 ml. of water. S i l v e r chloride was f i l - tered off and the solvent removed under vacuum. The product and the removed solvent were both yellow i n color suggesting some 173 decomposition. Analysis, calcd. for CigH-j^SnNOg: C, 5 2 . 4 2 ; H, 3 . 6 7 ; N, 3 . 3 9 . Found: C, 5 3 . 5 3 ; H, 4 . 4 0 ; N, 3 . 2 3 . (c) S t a b i l i t y of Triphenyltin Nitrate: Anhydrous t r i p h e n y l t i n n i t r a t e was found to be stable at room temperature i n the dry box for more than two months. After t h i s time, there was no change i n appearance, nor i n the infrared spectrum. However, exposure of the anhydrous compound to a i r caused marked changes in the infrared spectrum. Some changes also occurred when a sample of the anhydrous compound was heated to 150° i n vacuum for one and one half hours. A sample of the n i t r a t e prepared from wet acetone was heated i n 6-dichlorobenzene as described by Shapiro and Becker (62) and the infrared spectra of the residue and of the yellow d i s t i l l a t e were recorded. (d) Reaction with Ammonia: Anhydrous ammonia was condensed on to a sample of the anhydrous t r i p h e n y l t i n n i t r a t e and on to a solution of t r i p h e n y l t i n n i t r a t e i n methanol. Both mixtures were kept at - 7 0 ° for 24 hours, after which the excess ammonia and solvent were removed under vacuum, to leave white s o l i d s . Ana- l y t i c a l r e s u l t s of the s o l i d s were not reproducible but were always of the same order, a t y p i c a l r e s u l t being as follows. Analysis, calcd. for C 1 8H 1 5SnN0 3(NH 3) 2: C, 4 8 . 4 4 ; H, 4 . 7 5 ; N, 9 . 4 2 . Galcd. for C 1 8H 1 5SnN0 3(NH 3): C, 5 0 . 3 5 ; H, 4 . 2 3 ; N, 6 . 5 3 . Found: C, 5 0 . 3 1 ; H, 4 . 7 6 ; N, 5 . 8 8 . X-ray powder photo- graphs and the infrared spectra of the products showed them to be mixtures containing ammonium n i t r a t e and b i s ( t r i p h e n y l t i n ) o x - ide. 174 Triphenyltin Perchlorate (a) Triphenyltin chloride (2.030 g.) and s i l v e r perchlorate (1.092 g.) were mixed i n a f l a s k with 50 ml. of ether and the mixture was shaken for three days. Precipitated s i l v e r chloride was f i l t e r e d off and the f i l t r a t e was removed under vacuum, at room temperature to leave a white s o l i d . Analysis, calcd. for C l gH 1 5SnC10 4: C, 48.20; H, 3.34. Found: C, 48.9; H, 3.38. Triphenyltin perchlorate i s very soluble i n methanol and ether. It i s very hygroscopic and hydrolyses immediately on exposure to a i r as shown by marked changes i n the i n f r a r e d spectrum. (b) Reaction with Ammonia: Triphenyltin perchlorate as an anhydrous s o l i d or i n methanol solution, was allowed to react with excess ammonia, under the same conditions as described e a r l i e r for t r i p h e n y l t i n n i t r a t e . The products were white s o l i d s which likewise gave non-reproducible a n a l y t i c a l r e s u l t s , the following being t y p i c a l ; Analysis, calcd. for CigHi5SnC104(NH3)g: C, 44.75; H, 4.35; N, 5.79. Calcd. for C 1 8H 1 5SnC10 4(NH 3): C, 46.35; H, 3.86; N, 3.00. Found: C, 44.63; H, 4.63; N, 3.99. X-ray powder photographs and the infrared spectra of the products showed them to be mixtures containing ammonium perchlorate and b i s ( t r i p h e n y l t i n ) o x i d e . Trimethyltin Permanganate Attempts to prepare t h i s compound were not successful. The metathetical reaction between tr i m e t h y l t i n bromide or chloride and s i l v e r permanganate, using methanol, acetone, or water as solvent, resulted i n the p r e c i p i t a t i o n of the s i l v e r halide but the reaction was accompanied by the decomposition of the 175 permanganate. No reaction occurred when t-butyl alcohol, chloroform, a c e t o n i t r i l e , or ether was used as solvent. Attempts to react s o l i d t r i m e t h y l t i n halide and potassium per- manganate or s i l v e r permanganate at 50° i n a closed system were also unsuccessful. B i s ( t r i m e t h y l t i n ) Sulphate Trimethyltin bromide (1.220 g.) and s i l v e r sulphate (0.781 g.) were mixed i n 50 ml. of methanol, and the mixture was shaken for three days. The preci p i t a t e d s i l v e r bromide was f i l t e r e d off (0.949 g., calcd. 0.941 g.) and, on removal of the methanol under vacuum at room temperature, white cry- s t a l s of bi s ( t r i m e t h y l t i n ) sulphate-methanol adduct were obtained. Analysis, calcd. for (C 3H 9Sn) 2 S 0 4(CH 3OH) 2: C, 19.68; H, 4.13; S 0 4 , 19.70. Found: C, 19.00; H, 4.59; SO4, 20.48. On heating the methanol adduct at 100° under vacuum for about four hours, the methanol was completely removed and anhydrous bi s ( t r i m e t h y l t i n ) sulphate was obtained as a white s o l i d . Analysis, calcd. for (CgHgSn) 2 S0 4: C, 17.01; H, 4.25. Found: C, 17.55; H, 4.46. Both b i s ( t r i m e t h y l t i n ) sulphate and i t s methanol adduct are soluble i n water and methanol, but insoluble i n solvents such as acetone, ether, and a c e t o n i t r i l e . Both the compounds are hydrolysed on exposure to a i r as shown by changes i n t h e i r i n f r a r e d spectra. B i s ( t r i m e t h y l t i n ) Chromate Trimethyltin bromide (2.793 g.) and s i l v e r chromate (1.901 g.) were allowed to react i n 50 ml. of methanol. Pre- c i p i t a t e d s i l v e r bromide (2.142 g., calcd. 2.152 g.) was imme- 176 diately f i l t e r e d o f f . The methanol was quickly removed under vacuum at room temperature and yellow c r y s t a l s of b i s ( t r i m e t h y l - tin) chromate were obtained. Analysis, calcd. for (C^HgSn) gCrO^.: C, 16.24; H, 4.06; Cr0 4, 26.17. Found: C, 16.08; H, 4.00; Cr0 4, 25.46. Bis( t r i m e t h y l t i n ) chromate i s soluble i n water and methanol but decomposes slowly i n solution as shown by the grad- ual darkening of colour. It i s only s l i g h t l y soluble i n acetone and insoluble i n ether or chloroform. Unlike b i s ( t r i m e t h y l t i n ) sulphate, i t i s not hydrolysed on exposure to a i r . Samples exposed to a i r for three days showed no changes spectroscopically. Dimethyltin D i f l u o r i d e Dimethyltin d i f l u o r i d e was prepared by the reaction of potassium f l u o r i d e (2.8206 g.) and dimethyltin dichloride (5.332 g.) in 50 ml. of water. The p r e c i p i t a t e d s o l i d was f i l t e r e d and washed with water and ethanol. The product was r e c r y s t a l l i z e d from a 40 percent aqueous solution of hydrofluoric acid i n a platinum dish. Analysis, calcd. for C2HeSnF2: C, 12.90; H, 3.23. Found: C, 12.98; H, 3.60. Dimethyltin Carbonate Dimethyltin d i c h l o r i d e (1.0850 g.) and s i l v e r carbonate (1.3624 g.) were mixed i n 50 ml. of methanol and the mixture was shaken for three days. After removal of the solvent under vacuum at room temperature, a mixture of s i l v e r chloride and dimethyltin carbonate was obtained which was characterized by i t s infrared spectrum and X-ray powder photograph. No l i n e s due to either dimethyltin dichloride or s i l v e r carbonate appeared i n the powder photograph. However, dimethyltin carbonate could not be i s o l a t e d free from s i l v e r chloride due to i t s i n s o l u b i l i t y i n a suitable solvent. It i s insoluble i n methanol, acetone, a c e t o n i t r i l e or dimethyl sulphpxide but dissolves i n hot water with decom- posi t i o n to give dimethyltin oxide as the f i n a l product. The infrared spectrum of a sample of the mixture exposed to a i r did not show any change i n d i c a t i n g that dimethyltin carbonate i s not hydrolysed on exposure to a i r . Dimethyltin Chromate (a) Dimethyltin dichloride ( 1 . 8 0 0 g.) and s i l v e r chromate (2.718 g.) were allowed to react i n 50 ml. acetone, as well as i n 50 ml. of a c e t o n i t r i l e i n the same manner as described for dimethyltin carbonate. After removal of the solvent under vacuum at room temperature, i n each case a yellow mixture of s i l v e r chloride and dimethyltin chromate was obtained, as shown by i n f r a r e d spectra and X-ray powder photographs of the s o l i d s . X-ray powder photographs did not show any l i n e s due to either dimethyltin dichloride or s i l v e r chromate. On addition of the mixture to water a c i d i f i e d with acetic acid, there was no p r e c i - p i t a t i o n , only the previously formed s i l v e r chloride s e t t l e d and was recovered i n quantitative amounts. From the f i l t r a t e , the quantitative weight of barium chromate was precipitated, confirming that there had been no reduction of chromium. The mixture of dimethyltin chromate and s i l v e r chloride did not show any spectroscopic changes on exposure to a i r , i n d i c a t i n g that dimethyltin chromate i s not hydrolysed in a i r . On treating the mixture with hot water, dimethyltin chromate dissolved to give a yellow solution, but pure dimethyltin chromate could not be recovered from the aqueous solution due to p a r t i a l decomposition 178 of the chromate. (b) The above metathetical reaction was also done in methanol. S i l v e r chloride was precipitated instantaneously, but the dimethyltin chromate formed reacted with the solvent as shown by a rapid darkening i n colour. Dimethyltin Sulphate (a) Dimethyltin dichloride (1.2300 g.) and s i l v e r sulphate (1.7454 g.) were allowed to react i n 50 ml. of water, and p r e c i - pitated s i l v e r chloride was f i l t e r e d off (1.6036 g., calcd. 1.6040 g.). The f i l t r a t e was evaporated on a water bath to give a white s o l i d which was dried under vacuum. Analysis, calcd. for C 2H 6SnS0 4: C, 9.80; S, 2.47. Found: C, 9.67; H, 2.46. Di- methyltin sulphate i s soluble i n water but insoluble i n organic solvents such as methanol, acetone, a c e t o n i t r i l e , and dimethyl sulphoxide. It i s not hydrolysed i n a i r , a sample exposed to a i r for 24 hours showed no change i n the infrared spectrum. (b) Dimethyltin dichloride (1.0346 g.) and s i l v e r sulphate (1.4690 g.) were mixed i n 50 ml. of methanol and the mixture was shaken for three days. An insoluble mixture was precipitated which was recovered by evaporating the solvent under vacuum at room temperature. The infrared spectrum and an X-ray powder photograph of the dried s o l i d showed i t to be a mixture of s i l v e r chloride and a methanol adduct of dimethyltin sulphate. However, the dimethyltin sulphate-methanol adduct could not be i s o l a t e d free from the s i l v e r chloride due to i t s i n s o l u b i l i t y i n a suitable solvent. The infrared spectrum of the mixture showed marked changes when the s o l i d was exposed to a i r indicating hydrolysis of the dimethyltin sulphate-methanol adduct. The methanol adduct dissolved i n water and upon evaporating the aqueous solution, pure dimethyltin sulphate was recovered. When a portion of the methanol adduct and s i l v e r chloride mixture was heated to 100° under vacuum for about four hours, the methanol was completely removed leaving a mixture of dimethyltin sulphate and s i l v e r chloride, as shown by the i n f r a r e d spectrum of the heated mixture. (c) Dimethyltin dichloride and s i l v e r sulphate were allowed to react i n acetone, as well as i n a c e t o n i t r i l e , i n the manner described above. Insoluble s i l v e r chloride and dimethyltin sulphate were formed i n each case, as shown by the infrared spectra and X-ray powder photographs of the anhydrous mixtures obtained after removing the solvent under vacuum. (d) Reaction with Pyridine: Solid dimethyltin sulphate was refluxed with excess pyridine for 24 hours. Insoluble white s o l i d was f i l t e r e d o f f , washed with chloroform and dried under vacuum. The product was found to be dimethyltin sulphate- pyridine monoadduct. The same product was also p r e c i p i t a t e d when excess pyridine was added to an aqueous solution of d i - methyltin sulphate. The p r e c i p i t a t e was dissolved i n water and dimethyltin sulphate-pyridine monoadduct was c r y s t a l l i z e d , washed with chloroform and dried under vacuum. Analysis, calcd. for C 2H 6SnS0 4 ( C 5H 5N): C, 27.64; H, 3.91; N, 4.61. Found: C, 26.14; H, 3.74; N, 4.40. Dimethyltin sulphate-pyridine adduct i s insoluble i n pyridine and organic solvents such as 180 methanol, acetone, a c e t o n i t r i l e , and chloroform, but soluble i n water. (e) Reaction with Dimethyl Sulphoxide (DMSO): So l i d dimethyltin sulphate was shaken with excess DMSO for 24 hours. The insoluble s o l i d was f i l t e r e d o f f , washed with chloroform and dried under vacuum. The product was found to be dimethyltin sulphate-DMSO monoadduct. Another preparation of dimethyltin sulphate-DMSO adduct was performed i n aqueous solution, and c r y s t a l l i n e dimethyltin sulphate-DMSO monoadduct was obtained i n a similar manner as described above. Analysis, calcd. CgHgSnSO^(CHg)gSO: C, 15.34; H, 3.86; S, 20.50. Found: C, 15.59; H, 3.84; S, 20.56. Dimethyltin sulphate-DMSO adduct i s insoluble i n DMSO and organic solvents such as methanol, acetone, a c e t o n i t r i l e , and chloroform, but soluble i n water. Dimethyltin Dichloride Adducts (a) Dimethyltin dichloride-pyridine diadduct was prepared by the method described by Beattie and McQuillan (33). (b) Dimethyltin dichloride-DMSO diadduct was prepared by adding excess DMSO to a solution of dimethyltin dichloride i n chloro- form, followed by addition of excess of ether. A white c r y s t a l - l i n e p r e c i p i t a t e was obtained which was washed with ether and r e c r y s t a l l i z e d from chloroform. Analysis, calcd. for C 2H 6SnCl 2 \iCn3)2s6^2- C , 19.16; H, 4.82; S, 17.07. Found: C, 19.14: H, 4.64; S, 16.97. Dimethyltin dichloride-DMSO adduct i s soluble i n polar solvents such as water and methanol as well as i n non-polar organic solvents such as chloroform. 181 Dimethyltin Bis(tetrafluoroborate) (a) Dimethyltin dichloride (0.6470 g.) and s i l v e r t e t r a f l u o r o - borate (1.470 g.) were allowed to react i n about 25 ml. of methanol. Precipitated s i l v e r chloride was f i l t e r e d off (0.8370 g. calcd. 0.8440 g.) and the f i l t r a t e was removed under vacuum at room temperature to give a white s o l i d (1). Analysis, calcd. for for C 2H 6Sn(BF 4) 2: C, 7.44; H, 1.87; F, 47.14. Found: C, 10.47; H, 2.82; F, 32.47. As indicated by the analysis, p a r t i a l decom- position of dimethyltin bis(tetrafluoroborate) occurred to give boron t r i f l u o r i d e and dimethyltin d i f l u o r i d e . This was confirmed by the following experimental r e s u l t s : i) A portion of the recovered methanol was condensed on to about 10 ml. of pyridine. Upon evaporation of the mixture under vacuum, a white s o l i d (II) was l e f t , whose inf r a r e d spec- trum was i d e n t i c a l to that reported (155) for the boron t r i f l u o r i d e - p y r i d i n e adduct, BFg.Py. i i ) Another portion of the recovered methanol gave a p o s i t i v e test for f l u o r i n e and boron and was found to be markedly a c i d i c . i i i ) Upon redissolving the s o l i d (I) i n methanol, about one-half of the s o l i d was found to be insoluble i n methanol. This insoluble s o l i d was i d e n t i f i e d (from i t s infrared spectrum, X-ray powder photograph and a n a l y t i c a l results) to be dimethyltin d i f l u o r i d e . Analysis, calcd. for C 2HgSnF 2: C, 12.90; H, 3.23, Found: C, 12.85; H, 3.21. iv) The infrared spectrum of the s o l i d (I) was very sim i l a r to that reported (43) for t r i m e t h y l t i n tetrafluoroborate. Upon exposure of the s o l i d to a i r for a few seconds, the infrared 182 spectrum showed c h a r a c t e r i s t i c absorption bands of the free BF4~ ion. (b) The thermal s t a b i l i t y of the mixture of dimethyltin bis(tetrafluoroborate) and dimethyltin d i f l u o r i d e ( s o l i d I) was examined by heating the s o l i d at 60 - 70° under vacuum for about 6 hours, The s o l i d did not sublime nor did i t show any change i n i t s infrared spectrum and analysis (found: C, 10.57; ,H, 2.60). No boron t r i f l u o r i d e was evolved. Cc) Dimethyltin dichloride (0.8444 g.) and s i l v e r t e t r a - fluoroborate (1.4968 g.) were mixed i n about 25 ml. of ether. This resulted i n p r e c i p i t a t i o n of s i l v e r chloride and an insoluble product. After shaking the mixture for f i v e minutes, the ether was removed under vacuum at room temperature. The residue was sticky and the q u a l i t a t i v e analysis showed the presence of s i l v e r chloride i n i t . The infrared spectrum of the residue showed a l l the absorption bands shown by the mix- ture of dimethyltin bis(tetrafluoroborate) and dimethyltin d i f l u o r i d e ( s o l i d I described above), and, on exposing the residue to a i r , the same changes were observed i n the infrared spectrum as described above for the previous mixtures. About 5 ml. of trimethylamine was condensed onto the recovered ether, and the ether and excess trimethylamine were removed under vacuum at room temperature. A white s o l i d was obtained. The inf r a r e d spectrum of th i s s o l i d was found to be i d e n t i c a l to that reported (156, 156) for boron trifluoride-trimethylamine adduct, BF3.N(CH3) 3. 183 (d) Dimethyltin dichloride (0.7708 g.) and s i l v e r t e t r a f l u o r o - borate (1.2774 g.) were allowed to react i n about 20 ml. of l i q u i d sulphur dioxide. The insoluble product was f i l t e r e d off and the sulphur dioxide was pumped o f f . Only a trace of s o l i d was l e f t behind after removal of sulphur dioxide from the f i l - tered solution. A portion of the f i l t e r e d residue gave a po s i t i v e test for s i l v e r chloride. The infrared spectra of the residue, under anhydrous conditions as well as after exposure to a i r , were i d e n t i c a l to those obtained for the previously described mixture of dimethyltin bis(tetrafluoroborate) and dimethyltin d i f l u o r i d e ( s o l i d I ) . Dimethyltin Hexafluorosilicate An attempt to prepare th i s compound was not successful. When dimethyltin dichloride (0.6402 g.) and s i l v e r hexafluoro- s i l i c a t e (1.0426 g.) were mixed i n about 25 ml. of methanol, s i l v e r chloride was precipitated. Upon removal of the methanol, under vacuum at room temperature, the product was found to be dimethyltin d i f l u o r i d e which was characterized by i t s X-ray powder photograph, i n f r a r e d spectrum, and a n a l y t i c a l r e s u l t s . Analysis, calcd. for CgHgSnFg: C, 12.90; H, 3.23. Found: C, 12.82; H, 3.07. The recovered methanol was highly a c i d i c and contained s i l i c o n and f l u o r i n e which were i d e n t i f i e d by the q u a l i t a t i v e analysis of hydrolysis products of the recovered- methanol. Dimethyltin Bis(hexafluorophosphate) (a) Attempts to prepare th i s compound were not successful. The metathetical reaction between dimethyltin dichloride (1.542 g.) and s i l v e r hexafluorophosphate (3.505 g.) i n 25 ml. of methanol resulted in the p r e c i p i t a t i o n of s i l v e r chloride. Upon removal of the solvent from the f i l t e r e d solution under vacuum at room temperature, a white product was obtained which was insoluble i n methanol. The i n f r a r e d spectrum of t h i s product was measured but the product could not be characterized by i t s infrared spec- trum. The recovered methanol was highly a c i d i c and contained both f l u o r i n e and phosphorus. This i d e n t i f i c a t i o n was accom- plished by q u a l i t a t i v e analysis. (b) The above metathetical reaction was also performed i n a sulphur dioxide solution. The p r e c i p i t a t e d s i l v e r chloride was shown by an X-ray powder photograph to contain dimethyltin d i f l u o r i d e . Fractionation of the v o l a t i l e material from the sulphur dioxide solution gave a sample r i c h i n phosphorus o x y t r i f l u o r i d e , POF^, as shown by i t s infrared spectrum. The s o l i d remaining on removal of the sulphur dioxide under vacuum also contained dimethyltin d i f l u o r i d e which was i d e n t i f i e d by an X-ray powder photograph. Dimethyltin Bis(hexafluoroarsenate) Dimethyltin dichloride (0.7790 g.) and s i l v e r hexafluoro- arsenate (2.1044 g.) were mixed i n 25 ml. of methanol and the p r e c i p i t a t e d s i l v e r chloride was f i l t e r e d o f f . The methanol was removed from the f i l t e r e d solution under vacuum at room temper- ature to give a hygroscopic white s o l i d which gradually turned yellowish-white. The i n f r a r e d spectrum of the s o l i d was very si m i l a r to that reported (43) for trimethyltin hexafluoroarsenate i n d i c a t i n g the presence of the hexafluoroarsenate group i n i t . An X-ray powder photograph of the s o l i d showed the presence : of dimethyltin d i f l u o r i d e . Thus the s o l i d was a mixture of dimethyltin d i f l u o r i d e and the bis(hexafluoroarsenate). When the s o l i d was exposed to a i r , i t s infrared spectrum showed the ch a r a c t e r i s t i c strong band of AsFg ion at 720 cm - 1. The recovered methanol was highly a c i d i c and contained both f l u o r i n e and arsenic as shown by q u a l i t a t i v e tests. Dimethyltin Bis(hexafluoroantimonate) (a) The metathetical reaction between dimethyltin dichloride (1.0606 g.) and s i l v e r hexafluoroantimonate (3.3178 g.) was per- formed i n 25 ml. methanol i n the manner described above. The product was a hygroscopic white s o l i d which contained some methanol as shown by i t s i n f r a r e d spectrum. The recovered meth- anol was not a c i d i c and did not show presence of any fl u o r i n e or antimony in d i c a t i n g that no decomposition of hexafluoroanti- monate had occurred. When the recovered s o l i d was heated up to 120° under vacuum to remove the methanol, decomposition of the s o l i d occurred and o i l y drops of antimony pentafluoride, SbFg were condensed i n the trap. Qualitative tests on t h i s o i l showed the presence of antimony and f l u o r i n e . (b) Dimethyltin dichloride (1.038 g.) and s i l v e r hexafluoroanti- monate (3.2476 g.) were allowed to react i n 25 ml. of l i q u i d sulphur dioxide and the pre c i p i t a t e d s i l v e r cls&jvide was f i l t e r e d o f f . Removal of sulphur dioxide under vacuum gave a very hygroscopic s o l i d . X-ray powder photographs of the s o l i d and the s i l v e r chloride did not show any l i n e s due to dimethyltin d i f l u o r i d e . The inf r a r e d spectrum of the s o l i d showed similar features to those reported (43) for trimethylantimony hexafluoro?- antimonate and the infrared spectrum of a sample of the solid' 186 exposed to a i r showed c h a r a c t e r i s t i c band of the SbFg" ion at 660 cm"1. However, no analysis of the s o l i d was obtained. The* Dimethyltin Derivative of B i 2 C l 1 2 2 ~ Dimethyltin dichloride (0.2030 g.) and A g 2 B 1 2 c l 1 2 (0.7118 g.) were allowed to react i n 25 ml. methanol. P r e c i p i - tated s i l v e r chloride was f i l t e r e d off and the solvent was removed under vacuum at room temperature to give a white product which contained methanol as shown by i t s infrared spectrum. The methanol could not be removed from the s o l i d even after heating i t under vacuum at 100° for 24 hours. The recovered methanol was not a c i d i c and gave negative tests for boron and chlorine i n d i c a t i n g that no decomposition of the &\2^12 g r o u P n a c * occurred. Analysis, calcd. for C 2 H g S n B 1 2 C l i 2 ( C H 3 O H ) : B, 17.6; C l , 57.8; calcd. for C 2 H g S n B 1 2 C l 1 2 ( C H 3 O H ) ± 5 : B, 17.26; C l , 56.6; calcd. for C 2 H 6 S n B 1 2 C l 1 2 ( C H 3 O H ) 2 : B, 16.9; C l , 55.4. Found: B, 16.4; C l , 57.8. The dimethyltin derivative of B 1 2 ^ 1 1 2 i s soluble i n polar solvents such as methanol and water but insoluble i n chloroform. It i s very hygroscopic and hydrolyses on exposure to a i r as shown by changes i n i t s infrared spectrum. Trimethylantimony Dibromide This was prepared by the method described by Morgan and Davies (157). Trimethylstibine was prepared from freshly d i s - t i l l e d A.R. grade antimony t r i c h l o r i d e and methyl magnesium iodide. The trimethylstibine and ether were c o - d i s t i l l e d i n a nitrogen atmosphere and the d i s t i l l a t e treated with a carbon tetrachloride solution of bromine. Precipitated trimethylanti- mony dibromide was f i l t e r e d off and r e c r y s t a l l i z e d from water. Analysis, calcd. for C 3H 9SbBr 2: C, 11 . 2 0 ; H, 2.80; Br, 48.92. 187 Found: C, 11.09; H, 2.46; Br, 48.90. Trimethylantimony D i f l u o r i d e An aqueous solution of s i l v e r f l u o r i d e was made by d i s - solving s i l v e r carbonate i n 40 percent aqueous solution of hydrofluoric acid i n a platinum dish. 20 mi. of t h i s solution which contained 0.7160 g. of s i l v e r f l u o r i d e , was allowed to react with 0.9214 g. of trimethylantimony dibromide. S i l v e r bromide was f i l t e r e d off and the f i l t r a t e was evaporated to dryness. The product was then r e c r y s t a l l i z e d from ethanol and further p u r i f i e d by sublimation under vacuum at room temperature. Analysis, calcd. for C 3H 9SbF 2: C, 17.58; H, 4.39. Found: C, 17.00; H, 4.29. Trimethylantimony d i f l u o r i d e i s a white c r y s t a l l i n e s o l i d . It i s soluble i n water, methanol and chloroform and i s not hydrolysed i n a i r . Trimethylantimony D i n i t r a t e Trimethylantimony dibromide (0.6472 g.) and s i l v e r n i t r a t e (0.6732 g.) were allowed to react i n 25 ml. of methanol. Pre- c i p i t a t e d s i l v e r bromide was f i l t e r e d off and the solvent removed under vacuum at room temperature. White flakes of trimethyl- antimony d i n i t r a t e were obtained which were r e c r y s t a l l i z e d from chloroform. Analysis, calcd. for CgHgSb(NO3) 2: C, 12.40; H, 3.10; N, 9.63. Found: C, 12.78; H, 2.95; N, 9.89. Trimethylantimony d i n i t r a t e i s soluble i n water, methanol and chloroform. It i s hydrolysed slowly i n the presence of moisture. However, the hydrolysis i s revers i b l e and the hydrated product was converted into anhydrous d i n i t r a t e by drying under vacuum. The hydration and dehydration could be followed by 188 observing the changes i n the in f r a r e d spectrum. ' ' Trimethylantimony Carbonate Trimethylantimony dibromide (0.9712 g,) and s i l v e r car-, bonate (0.8200 g.) were allowed to react i n 20 ml. of l i q u i d sulphur dioxide. S i l v e r bromide was f i l t e r e d off and, after removal df sulphur dioxide under vacuum, white trimethylantimony carbonate was obtained.. Analysis, calcd. for C3 Hg Sb CO3: C, 21.17 H, 4.00. Found: C, 21.37; H, 4.23. It i s soluble i n l i q u i d sulphur dioxide, water and methanol, but insoluble i n chloroform. It did not sublime under vacuum up to 100° and no changes were observed i n the in f r a r e d spectrum on exposing the s o l i d to a i r . Trimethylantimony Sulphate Trimethylantimony dibromide (0.6274 g.) and s i l v e r sulphate (0.5992 g.) were allowed to react i n about 25 ml. water. P r e c i p i t a t e d s i l v e r bromide was f i l t e r e d off and the f i l t r a t e evaporated to dryness on a steam bath/. :;A white cry- s t a l l i n e s o l i d was obtained which was r e c r y s t a l l i z e d 'from water and dried under vacuum. Analysis, calcd. for CsHgSbSO^: C, 13.70 H, 3.45.; Found: C, 13.78; H, 3.87. Trimethylantimony sulphate i s insoluble i n organic solvents such as methanol, a c e t o n i t r i l e and chloroform, but soluble in water. It i s not hydrolysed i n a i r . Trimethylantimony Chromate Trimethylantimony chromate was obtained as a yellow c r y s t a l l i n e s o l i d from trimethylantimony dibromide (1.0706 g.) and s i l v e r chromate (1.0872 g.) using the same method as that described for trimethylantimony sulphate. Analysis, calcd. for 189 C 3H 9SbCr0 4: C, 12.73; H, 3.20; Cr0 4, 41.03. Found: C,.12.66; H, 3.12; Cr0 4, 41.29. It i s also insoluble i n methanol and a c e t o n i t r i l e and i s not hydrolysed i n a i r . Trimethylantimony Oxalate This compound was prepared from trimethylantimony dibromide (1.1064 g.) and s i l v e r oxalate (1.0280,g1.) i n the manner described for trimethylantimony sulphate. Analysis, calcd. for C3H 9 SbC 20 4: C, 23.55; H, 3.56; C 20 4, 34.54. Found: C, 23.51; H, 3.68; C 20 4, 34.36. Trimethylantimony oxalate i s soluble i n water but insoluble i n methanol and a c e t o n i t r i l e . It i s not hydrolysed i n a i r . Trimethylantimony Bis(perchlorate) Trimethylantimony dibromide (0.5410 g.) and s i l v e r perchlorate (0.6868 g.) were allowed to react i n 25 ml. of methanol and s i l v e r bromide was f i l t e r e d o f f . Most of the methanol was removed under vacuum at room temperature but the l a s t traces were removed by warming to about 60°. An . anhydrous s o l i d was obtained which exploded v i o l e n t l y on scratching with a n i c k e l spatula. Consequently, no further work was done on i t . Trimethylantimony Bis(tetrafluoroborate) ^ v - Trimethylantimony dibromide (0.5614 g.) and s i l v e r tetrafluoroborate (1.0268 g.) were allowed to react i n 25 ml. of methanol. S i l v e r bromide was f i l t e r e d o f f . After removing the solvent under vacuum at room temperature, a white s o l i d was obtained which was sublimed under vacuum at 50°. The ana- l y t i c a l r e s u l t s and in f r a r e d spectra of both unsublimed and 190 sublimed products were i d e n t i c a l . Analysis, calcd. for C 3H 9Sb(BF 4) 2: C, 10.57; H, 2.66. Found: C, 14.28; H, 3.60. As indicated by the a n a l y t i c a l r e s u l t s , p a r t i a l decomposition of the tetrafluoroborate group had occurred. This was con- firmed i n the following manner: X-ray powder photographs of the sublimed s o l i d showed the presence of trimethylantimony d i f l u o r i d e . The recovered methanol was highly a c i d i c and contained boron t r i f l u o r i d e , which was i d e n t i f i e d by i t s infrared spectrum and by the presence of boron and f l u o r i n e i n a portion of the recovered methanol. Thus the product was a mixture of trimethylantimony bis(tetrafluoroborate) and difluovude. The presence of the tetrafluoroborate group i n the product was infe r r e d from the in f r a r e d spectrum. Trimethylantimony Hexafluorosilicate Trimethylantimony dibromide (1.0160 g.) and s i l v e r hexa- f l u o r o s i l i c a t e (1.1132 g.) were allowed to react i n 25 ml. of methanol and a colourless, deliquescent, c r y s t a l l i n e s o l i d was obtained after removal of the methanol as described above. The s o l i d was sublimed under vacuum at 50°. The a n a l y t i c a l r e s u l t s and in f r a r e d spectra of both the unsublimed and sublimed s o l i d were i d e n t i c a l . Analysis, calcd. for CgHgSbSiFg-. C, 11.65; H, 2.93, F, 36.90. Found: C, 14.99; H, 3.71; F, 28.00 X-ray powder photographs of the sublimed s o l i d showed the presence of trimethylantimony d i f l u o r i d e . Thus the product was a mixture. The infrared spectrum of a sample of the mixture exposed to a i r 2- showed the c h a r a c t e r i s t i c absorption bands of the SiFg ion at 735 and 480 cm"1. The recovered methanol was highly a c i d i c and and gave po s i t i v e tests for both s i l i c o n and f l u o r i n e . 191 Trimethylantimony Bis(hexafluoroantimonate) (a) Trimethylantimony dibromide (0.7240 g.) and s i l v e r hexa- fluoroantimonate (1.5236 g.) were allowed to react i n 25 ml. of methanol. The s i l v e r bromide was f i l t e r e d off and most of the methanol was removed from the f i l t r a t e under vacuum at room tem- perature. The l a s t traces of the methanol could not be removed even on prolonged pumping at 100°, and the product could not therefore be i s o l a t e d i n a pure state. However, the recovered methanol neither showed any a c i d i t y nor gave a p o s i t i v e test for either f l u o r i n e or antimony, i n d i c a t i n g that no decomposition of hexafluoroantimonate had occurred. (b) The metathetical reaction between trimethylantimony dibromide (1.1080 g.) and s i l v e r hexafluoroantimonate (2.3304 g.) i n 25 ml. of l i q u i d sulphur dioxide gave, following removal of the p r e c i - pitated s i l v e r bromide and evaporation of the sulphur dioxide, an extremely hygroscopic white s o l i d . Analysis, calcd. for C 3H 9Sb(SbF 6) 2: F, 35.72. Obtained: F, 30.90. X-ray powder photographs of the s o l i d did not show any l i n e s due to trimethyl- antimony d i f l u o r i d e and the in f r a r e d spectrum of the s o l i d confirmed the presence of hexafluoroantimonate group i n i t . 2- The Trimethylantimony Derivative of B12CI12 Trimethylantimony dibromide (0.3320 g.) and A g 2 B i 2 C l i 2 (0.7836 g.) were allowed to react i n methanol. After f i l t e r i n g off the p r e c i p i t a t e d s i l v e r bromide, a colourless solution was obtained,'which was evaporated under vacuum at room temperature to give a pink red s o l i d which contained some methanol as i n d i - cated by i t s in f r a r e d spectrum* The recovered methanol was not 192 a c i d i c and gave negative tests for boron and chlorine, indicating that no decomposition of the B12CI12 group had occurred. The s o l i d was then heated at about 60° under vacuum for about 6 hours. Analysis, calcd. for C 3 H 9 S b B 1 2 C l 1 2 : B, 17.9; C l , 58.9. Calcd. for C 3H 9SbB 1 2Cl 1 2(CH 3OH): B, 17.3; C l , 56.4. Found: B, 17.3; C l , 56.0. However, the infrared spectrum of the heated s o l i d did not show any absorption bands due to methanol. The compound d i s - solved i n water or methanol to give a colourless solution but the recovered s o l i d from these solutions was always coloured. 193 BIBLIOGRAPHY 1. R. K. Ingham, S.D. Rosenberg, and H. Gilman, Chem. Rev., 60, 459 (1960) 2. G. E. Coates, "Organo-Metallic Compounds", Methuen & Co. Ltd., London, 1960; (a) p. 117; (b) p. 214. 3. H. A. Skinner and L. E. Sutton, Trans. Faraday, S o c , 40, 164 (1944) 4. P. Taimsalue and J. L. Wood, Spectrochim. Acta, 20, 1043 (1964) 5. H. Kriegsmanh and H. Geissler, Z. anorg. ailgem. Chem., 323, 170 (1963) 6. W. F. Edgell and C. H. Ward, J . Mol. Spectroscopy, 8, 343 (1962) 7. H. Kriegsmann, S. Pischtschen, Z. dnorg. ailgem. Chem., 308, 212 (1961) 8. V. S. G r i f f i t h s and G. A. W. Derwish, J . Mol. Spectroscopy, 2, 148 (1960) 9. J . Lorberth and H. Noth, Chem. Ber., 98, 969 (1965), 10. E. D. Swiger and J . D.Graybeal, J . Am. Chem. S o c , 87, 1464 (1965) 11. V. S. G r i f f i t h s and G. W. A. Derwish, J. Mol. Spectroscopy, 3, 165 (1959) 12. J. R. Holmes and H. D.Kaesz, J. Am. Chem. S o c , 83, 3903 (1961) 13. R. H. Herber and H. A. Stoeckler, Abstract, Proceedings of 148th Meeting, Am. Chem. S o c , 1964 194 C. Hayes, J . Inorg. Nuclear Chem., 26, 2306 (1964) G. Rochow and ,D. Seyferth, J . Am. Chem. S o c , 75, 2877 (1953) G. Rochow, D. Seyferth, and A. C. Smith, J. Am. Chem. Soc., 75, 3099 (1953) J. Pope and S. J . Peachy, Proc. Chem. S o c , 42 (1900) J. Pope and S. J . Peachy, Proc. Chem. S o c , 116 (1900) N. Naumov and Z. M. Manuilkin, Acta Univ. Asiae, Mediae, 31, 12 (1937) N. Naumov and Z. M. Manuilkin, J . Gen. Chem. (U.S.S.R.), 5, 281 (1935) M. McGrady and R. S. Tobias, Inorg. Chem., 3, 1157 (1964) A. Matwiyoff and R. S. Drago, Inorg. Chem. , 3_, 337 (1964) Seyferth and S. O. Grim, J . Am. Chem. S o c , 83, 1610 (1961) A. Kraus and W. N. Greer, J . Am. Chem. S o c , 45, 2946 (1923) R. Beattie, G. P. McQuillan, and R. Hulme, Chem. and Ind., 1429 (1961) Hulme, J . Chem. S o c , 1524 (1963) C. Clark and R. J . O'Brien, Inorg. Chem., 2, 740 (1963) C. Clark, R. J . O'Brien, and A. L. Pickard, J . Organometal. Chem., 3, 000-000 (1965) J. M. van der Kerk, J . G. A. Luijten, and M. J. Janssen, Chimia, 16, 10 (1962) J. Kupchik and T. Lanigan, J . Org. Chem., 27, 3661 (1962) 195 31. A. Thomas and E. G. Rochow, J . Inorg. Nuclear Chem., 4, 205 (1957) 32. I. R. Beattie, Quart. Rev., 17, 382 (1963) 33. I. R. Beattie and G. P. McQuillan, J . Chem. S o c , 1519 (1963) 34. J . P. Freeman, J . Am. Chem. S o c , 80, 5954 (1958) 35. R. Okawara, D. E. Webster, and E. G. Rochow, J. Am. Chem. Soc., 82, 3287 (1960) 36. I. R. Beattie and T. Gilson, J . Chem. S o c , 2585 (1961) 37. M. J . Janssen, J . G. A. Luijten, and G. J. M. van der Kerk, Rev. Trav. Chim., 82, 90 (1963) 38. R. Okawara and M. Ohara, B u l l . Chem. Soc. Japan, 3_6, 625 (1963); J . Organometal. Chem., 1, 360 (1964) 39. H. C. Clark, R. J . O'Brien,and J . Trotter, Proc. Chem. S o c , 85 (1963); J„ Chem. S o c , 2332 (1964) 40. H. Kriegsmann, H. Hofmann,and S. Pischtschan, Z. anorg. ailgem. Chem., 315, 283 (1962) 41. R. Okawara and K. Yashuda, J . Organometal. Chem., 1, 356 (1964) 42. N. Kasi, K. Yashuda,and R. Okawara, J . Organometal. Chem., 3, 172 (1965) 43. H. C. Clark and R. J.. O'Brien, P r o c Chem. S o c , 113 (1963); Inorg. Chem., 2, 1020 (1963) 44. R. Okawara, B. J . Hathaway,and D. E. Webster, P r o c Chem. Soc , 13 (1963) 45. K. Yasuda and R. Okawara, J . Organometal. Chem., 3, 76 (1965) 196 46. B. J . Hathaway and D. E. Webster, Proc. Chem. Soc., 14 (1963) 47. K. Nakamoto, "Infrared Spectra of Inorganic and Coordination Compounds", John Wiley & Sons, Inc., New York, 1963; (a) p. 107; (b) p. 92; (c) p. 118; (d) p. 210. 48. M. J. Janssen, J . G. A. Luijten, and G. J. M. van der Kerk, J . Organometal. Chem., 1., 286 (1964) 49. W. H. Nelson and D. F. Martin, J. Inorg. Nuclear Chem., 27, 89 (1965) 50. M. M. McGrady and R. S. Tobias, J. Am. Chem. S o c , 87, 1909 (1965) 51. C. C. Addison, W. B. Simpson, and A. Walker, J . Chem. S o c , 2360 (1964) 52. G. G. Long, G. O. Doak, and L. D. Freedman, J . Am. Chem. S o c , 86, 209 (1964) 53. E. Krause and A. von Grosse, "Die Chemie der metall- organischen Verbindungen", Borntraeger, B e r l i n , 1937; p.p. 600-601; p.p. 629-630. 54. A. F. Wells, Z. K r i s t , 99, 367 (1938) 55. K. A. Jensen, Z. anorg. allgem. Chem., 250, 268 (1943) 56. T. N. Polynova and M. A. Porai-koshits, J . Struct. Chem. (U.S.S.R.)(Engl. Transl.), 1, 146 (1960) 57. A. Hantzsch and H. Hibert, Ber., 40, 1508 (1907) 58. A. D. Beveridge, Ph.D. Thesis, University of Glasgow, 1964 59. N. V. Sidgwick, "The Chemical Elements and Their Compounds" Oxford University Press, London, 1950, v o l . 1; (a) p. 777; (b) p. 615. 197 60. T. M. Lowry and J . H. Simons, Ber., 63, 1595 (1930) 61. P. Nylen, Z. anorg. ailgem. Chem., 246, 227 (1941) 62. P. Shapiro and E. I. Becker, J . Org. Chem., 27, 4663 (1962) 63. B.O. F i e l d and C. J . Hardy, Quart. Rev., 18, 361 (1964) 64. C. C. Addison and N. Logan, in "Advances i n Inorganic Chemistry and Radiochemistry", edited by H. J . Emeleus and A. G. Sharpe, Academic Press Ltd., New York, 1964, vo l . 6, p. 72. 65. G. Herzberg, "Infrared and Raman Spectra of Polyatomic Molecules", D. Van Nostrand Co., Inc., New York, 1962; (a) p. 178; (b) p. 167; (c) p. 150. 66. K. Buijs and C„ J. H. Schutte, Spectrochim. Acta, 18, 307 (1962) 67. J. R. Ferraro, J . Mol. Spectroscopy, 4, 99 (1960) 68. F. A. M i l l e r and C. H. Wilkins, Anal. Chem., 24, 1253 (1952) 69. B. M. Gatehouse, S. E. Livingstone, and R. S. Nyholm, J. Chem. S o c , 4222 (1957) 70. C. C. Addison and W. B. Simpson, J . Chem. S o c , 598 (1965) 71. E. B. Wilson, J r . , J . C. Decius, and P. C-, Cross, "Molecular Vibrations", McGraw-Hill Book Co., Inc., New York, 1955, p. 336. 72. C. C. Addison, C. D. Garner, W. B. Simpson, D. Sutton, and S. C. Wallwork, P r o c Chem. S o c , 367 (1964) 73. F. A. Cotton, D. M. L. Goodgame, and R. H. Soderberg, Inorg. Chem., 2, 1162 (1963) 74. F. A. Cotton and R. H. Soderberg, J. Am. Chem. S o c , 85, 2402 (1963) 75. K. Dehnicke, Chem. Ber.,98,280 (1965) 198 76. R. K. Khanna, J . Lingscheid, and J . C. Decius, Spectrochim. Acta, 20, 1109 (1964) 77. J. C. D. Brand and T. M. Cawthon, J. Am. Chem. S o c , 77, 319 (1955) 78. L. I. Katzin, J . Inorg. Nuclear Chem., 24, 245 (1962) 79. J . M . P. J. Verstegen, J . Inorg. Nuclear Chem., 26, 25 (1964) 80. J . S. Thayer and R. S. West, Inorg. Chem., 3, 406 (1964) 81. J. G . A. Luijten, M. J . Janssen, and G . J . M. van der Kerk, Rec. Trav. Chim., 81, 202 (1962) 82. R. A. Cummins, Aust. J . Chem., 18, 98 (1965) 83. B. Kushlefsky,, I. Simmons, and A. Ross, Inorg. Chem... 2, 187 (1963) 84. S. D. Ross, Spectrochim. Acta, 18, 225 (1962) 85. B. J. Hathaway and A. E. Underbill, J . Chem. S o c , 3091 (1961 86. S. Buffagani, L . M. Va l l a r i n o , and J . V. Quagliano, Inorg. Chem., 3, 671 (1964) 87. A. E. Nickenden and R. A. Krause, Inorg. Chem., 4, 404 (1965) 88. D. R. . Lide, J r . , D. E. Mann, and J . J . Comeford, v Spectrochim. Acta, 21, 497 (1965) 89. S. Detoni and D. Hadzi, Spectrochim. Acta, 11, 601 (1957) 90. s. D. Ross, Spectrochim. Acta, 18, 1575 (1962) 91. K. Nakamoto, J. F u j i t a , S. Tanaka, and M. Kobayashi, J. Am. Chem. S o c , 79, 4904 (1957) 92. C. G . Barraclough and M. L. Tobe, J . Chem. S o c , 1993 (1961) 93. M. E. Baldwin, Spectrochim. Acta, 19, 315 (1963) 94. w. R. McWhinne, J . Inorg. Nuclear Chem., 26, 21 (1964) 199 95. A. Werner and P. P f e i f f e r , Z. anorg. allgem. Chem., 17_, 83 (1898) 96. R. J. G i l l e s p i e and E. A. Robinson, i n "Advances i n Inorganic and Radiochemistry", edited by H. J. Emeleus and A. G. Sharpe, Academic Press Ltd., New York, 1959, v o l . 1, p. 414. 97. H. Stammereich, D. Bassi, and 0. Sala, Spectrochim. Acta, 12, 403 (1958) 98. F. A. M i l l e r , G. L. Carlson, F. F. Bentley, and W. H. Jones, Spectrochim. Acta, 1<6, 135 (1960) 99. Y. Shimura and R. Tsuchida, B u l l . Chem. Soc. Japan, 29, 311 (1956) 100. R. Tsuchida and M. Kobayashi, B u l l . Chem. Soc. Japan, 13, 472 (1938) 101. J . C. Decius, J . Chem. Phys., 22, 1946 (1954); 23, 1290 (1955) 102. S. D. Ross and J . Goldsmith, Spectrochim. Acta, 20, 781 (1964) 103. K. Buijs and C. J. H. Schutte, Spectrochim. Acta, 17, 917, 921, 927 (1961) 104. G. A. Barclay and B. F. Hos;*kins, J. Chem. S o c , 586 (1962) 105. B. M. Gatehouse, S. E. Livingstone, and R. S. Nyholm, J. Chem. S o c , 3137 (1958) 106. H. E l l i o t and B. J . Hathaway, Spectrochim. Acta, 21, 1047 (1965) 107. J . F u j i t a , A. E. Martell^and K. Nakamoto, J . Chem. Phys. 36, 339 (1962) 200 108. C. Schaeffer and F. Matossi, "Das Ultra-rote Spektrum", Springer, B e r l i n , 1930, p. 340. 109. J. A. Campbell, Private communications. 110. N. S. G i l l , R. H. N u t t a l l , D. E. Scaife, and D. W. A. Sharp, J . Inorg. Nuclear Chem., 18, 79 (1961) 111. W. D. Horrocks, J r . , and F. A. Cotton, Spectrochim. Acta, 17, 134 (1961) 112. F. A. Cotton and R. Francis, J . Am. Chem. Soc., 82, 2986 (1960) 113. F. A. Cotton, R. Francis,and W. D. Horrocks, J r . , J. Phys. Chem., 6 4 , 1534 (1960) 114. R. S. Drago and D. Meek, J. Phys. Chem., 65, 1446 (1961) 115. W. Gerrard, J . B. Leane, E. F. Mooney, and R. G. Rees, Spectrochim. Acta, 19, 1964 (1963) 116. J . O. Edwards, G. C. Morrison, V. F. Ross,and J . W. Schultz, J . Am. Chem. S o c , 77, 266 (1955) 117. J. Goubeau and W. Bues, Z. anorg. ailgem. Chem., 268, 221 (1952) 118. G. L. Cote' and H. W. Thompson, P r o c Roy. S o c , 210A, 217 (1951) 119. D. W. A. Sharp and A. G. Sharpe, J. Chem. S o c , 1855 (1956) 120. N. N. Greenwood, J. Chem. S o c , 3811 (1959) 121. B. J . Hathaway, D. G. Holah,and A. E. Underbill, J . Chem. S o c , 2444 (1962) 122. A. G. Rees and L. J . Hudleston, J . Chem. S o c , 1334 (1936) 123. "Tables of Selected Values of Chemical Thermodynamic Properties", U.S.Bureau of Standards, Washington, 1947 201 124. J . E. G r i f f i t h s and D. E. I r i s h , Inorg. Chem., 3, 1134 (1964) 125. I. R. Beattie, G. P. MacQuillan, L. Rule, and M. Webster, J . Chem. S o c , 1514 (1963) 126. D. R. Russell and D. W. A. Sharp, J . Chem. S o c , 4689 (1961) 127. D. W. A. Sharp and A. G . Sharpe, J . Chem. S o c , 1855, (1956) 128. R. D. Peacock and D. W. A. Sharp, J . Chem. S o c , 2762 (1959) 129. (a) E. L. Muetterties, R. E. M e r r i f i e l d , H. C. M i l l e r , W. H. Knoth, J r . , and J . R. Downing, J . Am. Chem. Soc., 84, 2506 (1962) (b) W. H. Knoth.-,. H. C. M i l l e r , J . C. Sauer, J . H. Bal t h i s , Y. T. Chia, and E. L. Muetterties, Inorg. Chem., 3, 159 (1964) 130. J. A. Wunderlich and W. N. Lipscomb, J . Am. Chem. S o c , 82, 4427 (1960) 131. W. R. Cullen, G . B. Deacon, and J . H. S. Green, Can. J . Chem., i n press 132. H. McConnel, J . Chem. Phys., 20, 700 (1952) 133. L. I. Katzin, J . Chem. Phys., 18, 789 (1950) 134. J . L. Hales, J . I. Jones, and W. Kynaston, J . Chem. S o c , 618 (1957) 135. C. L. Angel, Trans. Faraday S o c , 52, 1178 (1956) 136. G. A. Jeff r e y and G . S. Parry, J . Am. Chem. S o c , 76, 5283 (1964) 202 137. H. Murata and K. Kawai, J . Chem. Phys., 25, 589 (1956) 138. J . F u j i t a , K. Nakamoto,and M. Kobayashi, J. Phys. Chem., 61, 1014 (1957) 139. M. J. Schmelz, T. Miyazawa, S. Mizushima, T. J. Lane, and J . V. Quagliano, Spectrochim. Acta, 9, 51 (1957) 140. C. K. JizJrgensen, "Inorganic Complexes", Academic Press Ltd., New York, 1963, p. 95 141. J. F u j i t a , A. E. Mart e l l , and K. Nakamoto, J. Chem. Phys., 36, 324, 331 (1962) 142. J . N. van Nikerk and F. R. L. Schoening, Acta Cryst., 4, 35 (1951) 143. D. R. Lide, J r . , and D. E. Mann, J. Chem. Phys., 25, 1128 (1956) 144. F. X. Powell and E. R. Lippincott, J. Chem. Phys., 32, 1883 (1960) 145. L. A. Woodwards and L. E. Anderson, J. Inorg. Nuclear Chem., 3, 326 (1956) 146. K. Ramaiah and D. R. Martin, Chem. Comm., 130 (1965) 147. E.L. Muetterties, W. Mahler, and R. Schmutzler, Inorg. Chem., 2, 613 (1963) 148. E. L. Muetterties, W. Mahler, K. J . Packer, and R. Schmutzler, Inorg. Chem., 3, 1298 (1964) 149. D. P. Craig, A. Maccoll, R. S. Nyholm, L. E. Orgel, and L. E. Sutton, J . Chem. S o c , 332 (1954) 150. R. E. Rundle, J . Am. Chem. S o c , 85, 112 (1963) 151. A. I. Vogel, "A Text-Book of P r a c t i c a l Organic Chemistry" Longmans, Green & Go. Ltd., London, 1961, p. 169 203 152. R. W. Parry, D. R. Schultz, and P. R. Girardot, J. Am. Chem. S o c , 80, 1 (1958) 153. A. I. Vogel, "A Teat-Book of Quantitative Inorganic Analysis", Longmans, Green & Co, Ltd., London, 1961 154.. W. W. Scotts, "Standard Methods for Chemical Analysis", D. Van Nostrand Co., Inc., New York, 1939 155.. A. R. Katritzky, J . Chem. S o c , 2049 (1959) 156. R. L. Amster and R. C. Taylor, Spectrochim. Acta, 20, 1487 (1964) 157. G. T. Morgan and G. R. Davies, Proc. Roy. Soc. . '. .. A l i o , 523 (1926)

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