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The synthetic and spectroscopic study of some new tin (IV) and organotin (IV) fluorine compounds Levchuk, Larry E. 1971

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THE SYNTHETIC AND SPECTROSCOPIC STUDY OF SOME NEW TIN(IV) AND ORGANOTIN(IV) FLUORINE COMPOUNDS BY LARRY E. LEVCHUK B.Sc. (Hons.), University of B r i t i s h Columbia, 1963 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of CHEMISTRY We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA Ju l y , 1971 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver 8, Canada Date - i i -ABSTRACT The s o l v o l y s i s of m e t h y l t i n ( I V ) c h l o r i n e compounds of the general type ( C H . j ) n S n C l 4 _ n w i t h n ranging from 0 to 4, i s s t u d i e d i n aqueous and anhydrous hydrogen f l u o r i d e under a v a r i e t y of c o n d i t i o n s . The s t u d i e s i n anhydrous HF have r e s u l t e d i n the s y n t h e s i s of the new compounds m e t h y l t i n ( I V ) t r i f l u o r i d e , d i m e t h y l t i n ( I V ) c h l o r i d e f l u o r i d e and m e t h y l t i n ( I V ) d i c h l o r i d e f l u o r i d e . M e t h y l t i n ( I V ) c h l o r o d i f l u o r i d e c o u l d not be s y n t h e s i z e d i n t h i s way. A s p e c i a l monel r e f l u x r e a c t o r was u t i l i z e d f o r these r e a c t i o n s . Attempts to s o l v o l y z e v i n y l - and p h e n y l t i n compounds w i t h anhydrous HF d i d not y i e l d pure products. In these cases, the evidence i n d i c a t e s t h a t cleavage of the Sn-Cl and Sn-C bonds occurs i n an u n p r e d i c t a b l e manner. A convenient method f o r the p r e p a r a t i o n of SnCl2F2 i s found i n the s o l v o l y s i s of SnCl^ w i t h anhydrous HF. I n t e r a c t i o n of t h i s compound w i t h e i t h e r S~0,F~ or C10S0-F r e s u l t s i n the formation of SnF„(SO.F) 0. Z O Z Z Z J _ Attempts to f i n d a l t e r n a t i v e s y n t h e t i c routes to SnF2(S0 3F)2 were u n s u c c e s s f u l . S t r u c t u r a l proposals f o r these compounds are based on i n f r a r e d , 119 Raman and Sn Mossbauer s p e c t r a . A l l the new compounds are found t o be polymeric v i a f l u o r i n e or f l u o r o s u l p h a t e b r i d g e s , r e s u l t i n g i n penta- or h e x a c o o r d i n a t i o n around t i n . D i a l k y l t i n ( I V ) d i f l u o r i d e s are e a s i l y obtained when the correspond-i n g c h l o r i d e s are s o l v o l y z e d i n aqueous hydrogen f l u o r i d e . D i m e t h y l t i n , d i e t h y l t i n , d i p r o p y l t i n , d i b u t y l t i n and d i o c t y l t i n d i f l u o r i d e s are prepared i n t h i s way. However, d i v i n y l t i n ( I V ) d i f l u o r i d e and d i p h e n y l t i n ( I V ) - i i i -d i f l u o r i d e cannot be made v i a t h i s route. A l s o , CH^SnF^ and the m e t h y l t i n ( I V ) c h l o r i d e f l u o r i d e s cannot be s y n t h e s i z e d from s o l v o l y s i s r e a c t i o n s i n v o l v i n g aqueous HF. - i v -TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES v ± LIST OF FIGURES v i i ACKNOWLEDGEMENTS v i i i I. INTRODUCTION 1 A. General Remarks i B. Synthesis of Organotln Halides 2 C. Hydrogen Fl u o r i d e 7 D. S t r u c t u r a l Features of Organotin Compounds 9 E. A p p l i c a t i o n of V i b r a t i o n a l Spectroscopy 12 F. A p p l i c a t i o n of Mossbauer Spectroscopy 15 on G. Summary J U I I . EXPERIMENTAL 3 2 oo A. Preparation and Sources of S t a r t i n g Materials OO B. General Apparatus C. Anhydrous HF S o l v o l y s i s Apparatus 3 6 OC D. Reactions i n Anhydrous Hydrogen Fl u o r i d e O Q E. Reactions i n Aqueous Hydrogen Fluoride O Q F. Fluorosulphonating Reactions G. P h y s i c a l Methods 3 9 H. Analysis and Characterization ^ - v - Page I I I . RESULTS AND DISCUSSION 43 A. Synthesis 43 1. Reactions i n anhydrous HF 43 2. Reactions i n aqueous 48%) HF 5 1 3. Preparation of S n F 2 ( S 0 3 F ) 2 5 2 B. V i b r a t i o n a l Spectra 54 C. Mossbauer Spectra 67 D. General Conclusions 77 REFERENCES 8 1 - v i -LIST OF TABLES Table Page 1 S t r u c t u r a l Aspects of Some Methyltin(IV) Compounds and Tin(IV) Halides 10 2 V i b r a t i o n a l Data f o r Some Methyltin(IV) Compounds.... 14 3 Mossbauer Parameters f o r Some Methyltin(IV) Compounds and Tin(IV) Halides 29 4 Reactions of Various Methyltin(IV) Compounds and T i n Tet r a c h l o r i d e with Anhydrous HF 45 5 S o l v o l y s i s Reactions of V i n y l t i n ( I V ) Compounds with Anhydrous HF 50 6 V i b r a t i o n a l Frequencies of Some Methyltin(IV) Fluorine Compounds 55 7 V i b r a t i o n a l Spectrum of S n F 2 ( S 0 3 F ) 2 and Related Compounds 63 8 V i b r a t i o n a l Frequencies of S n C l ^ 6 5 119 9 Sn Mossbauer Data of Some Methyltin(IV) Fluorides and D i a l k y l t i n ( I V ) D i f l u o r i d e s 6 8 119 10 Sn Mossbauer Data of Some Tin(IV) F l u o r i n e - C h l o r i n e and F l u o r o s u l f a t e Compounds ?1 - v i i -LIST OF FIGURES Figure Page _ 119m , 1 Decay of i^Sn 1 7 2 Block Diagram of a Mbssbauer Spectrometer 18 3 Is o m e r s h i f t 6 (mm/sec) 21 4 D i s t r i b u t i o n of 6 f o r Sn(IV) 2 3 5 Quadrupole S p l i t t i n g A (mm/sec) 2 ^ 6 HF Monel Metal Reflux Reactor 3 7 7 Monel Vacuum Line 3 8 8 I n f r a r e d Spectrum of M e t h y l t i n ( I V ) T r i f l u o r i d e 5 6 9 Tin-Carbon S t r e t c h i n g Frequencies f o r the M e t h y l t i n ( I V ) F l u o r i n e Compounds 61 119 10 Sn Mossbauer Spectrum of M e t h y l t i n ( I V ) T r i f l u o r i d e at 298°K 6 9 11 Comparison of Mossbauer Parameters of D i a l k y l t i n ( I V ) D i f l u o r i d e s , b i s - D i f l u o r o p h o s p h a t e s , b i s - F l u o r o -sulphates and b i s - T r i f l u o r o m e t h y l s u l p h o n a t e s 7 ^ 12 C o r r e l a t i o n Between Sums of T a f t Constants and Quadrupole S p l i t t i n g s f o r Y 2 S n F 2 where Y = CH 3 > C l or F. 74 13 Suggested C o n f i g u r a t i o n s Around T i n f o r the Fluoro 7 8 D e r i v a t i v e s - v i i i -ACKNOWLEDGEMENTS I wish to express my s i n c e r e g r a t i t u d e to Dr. F. Aubke f o r h i s constant encouragement and advice during the p e r i o d of t h i s work. He has been not only an i n v a l u a b l e research d i r e c t o r but a l s o a c o u n s e l l o r and f r i e n d . Thanks are extended to Mr. P h i l Yeats w i t h whom I have worked and have had numerous d i s c u s s i o n s . His views on v a r i o u s aspects of t h i s work have been g r e a t l y a p p r e c i a t e d . I would a l s o l i k e to thank Dr. J.R. Sams f o r h e l p f u l d i s c u s s i o n s w i t h respect to the Mossbauer s p e c t r a and Mrs. A. S a l l o s f o r t e c h n i c a l a s s i s t a n c e w i t h the s p e c t r a . Messrs. S. Rak and J . Molnar of the Glassblowing Shop have been extremely cooperative i n the f a s h i o n i n g of the g l a s s apparatus and Mr. Emil Matter of the Mechanical Shop has c a r r i e d out an immense job i n the c o n s t r u c t i o n of the metal apparatus. Miss Diane Johnson i s thanked f o r t y p i n g the manuscript. I g r a t e f u l l y a p p r e c i a t e the Standard O i l Co. of B r i t i s h Columbia's f e l l o w s h i p f o r 1970-71 and the Vancouver School Board's grant of a two years' leave of absence. F i n a l l y , I wish to thank my w i f e , Leona, f o r her pa t i e n c e and understanding during the p e r i o d of my s t u d i e s . - 1 -I . INTRODUCTION A. General Remarks Over the years, a l a r g e number of o r g a n y l t i n ( I V ) h a l i d e s of the general formula R nSnX^_ n w i t h R = a l k y l or a r y l , X = F, C l , Br and I and n ranging from 1-4 have been sy n t h e s i z e d and c h a r a c t e r i z e d . In g e n e r a l , a number of examples of each h a l i d e type are found to e x i s t . However, there are two i n t e r e s t i n g exceptions: (1) no o r g a n y l t i n ( I V ) t r i f l u o r i d e appears to have been s y n t h e s i z e d ; (2) Except f o r some 1 2 3 badly c h a r a c t e r i z e d d i o r g a n y l t i n ( I V ) chloride-bromides ' ' and 3 c h l o r i d e - i o d i d e s , no mixed h a l i d e s are known. In p a r t i c u l a r , no c h l o r i d e - f l u o r i d e s are reported. Whether these two omissions are due to an inherent i n s t a b i l i t y of such products toward l i g a n d rearrangement or to the l a c k of s u i t a b l e s y n t h e t i c r o u t e s , presents an i n t e r e s t i n g problem. The approach taken i n t h i s study was to attempt the s y n t h e s i s and h o p e f u l l y the s t r u c t u r a l c h a r a c t e r i z a t i o n of some m e t h y l t i n ( I V ) f l u o r i d e s and c h l o r i d e - f l u o r i d e s . As w i l l be discussed i n g r e a t e r d e t a i l l a t e r , the use of hydrogen f l u o r i d e as a f l u o r i n a t i n g agent l e d to the d e s i r e d compounds. Both anhydrous HP and ^48% UF/E^O s o l u t i o n were employed. S t r u c t u r a l proposals are based on the complementary use of v i b r a t i o n a l , 119m„ .... , spectroscopy and Sn Mossbauer spectroscopy. - 2 -A meaningful d i s c u s s i o n of the r e s u l t s and c o n c l u s i o n s should l o g i c a l l y be preceded by some comments on the s t a t e of knowledge i n the f o l l o w i n g areas: (1) A v a i l a b l e s y n t h e t i c routes to a l k y l t i n ( I V ) h a l i d e s w i t h s p e c i a l emphasis on the f l u o r i d e s ; (2) the use of anhydrous and aqueous hydrogen f l u o r i d e as f l u o r i n a t i n g agents w i t h s p e c i a l emphasis on the t e c h n i c a l problems encountered i n these s o l v e n t s ; (3) s t r u c t u r a l d e t a i l s of o r g a n o t i n h a l i d e s as derived from X-ray and e l e c t r o n d i f f r a c t i o n s t u d i e s ; (4) the p r i n c i p a l f e a t u r e s of v i b r a t i o n a l s p e c t r o -scopy and ^ ^ S n Mossbauer spectroscopy. Since the l a t t e r i s a r e l a t i v e l y recent s t r u c t u r a l t o o l , a b r i e f elementary i n t r o d u c t i o n i n t o the Mossbauer e f f e c t w i l l be presented. I t i s hoped that t h i s i n t r o d u c t i o n i n t o these v a r i o u s areas w i l l s i m p l i f y the general d i s c u s s i o n p a r t of t h i s study. B. Synthesis of Organotin H a l i d e s The present s t a t e of knowledge i n t h i s f i e l d has been w e l l documented 4-8 i n s e v e r a l reviews and books. For convenience, the most important s y n t h e t i c routes to these compounds may be broken down i n t o f i v e general methods: Method 1. Cleavage. The Sn-C bonds i n or g a n o t i n compounds may be cleaved by the halogens or by the hydrogen h a l i d e s : R,Sn + X 2 > R„SnX + RX R 3SnX + X 2 * R2SnX, 2 + RX 2 + X 2 SnX '4 + 2RX - 3 -R.Sn + HX • R.SnX + RH 4 3 R 3SnX + HX • R 2SnX 2 + RH R = organyl group X = C l , Br, I I t should be noted that compounds of the type RSnX^ apparently are not a v a i l a b l e from t h i s method. A l s o , an e m p i r i c a l s e r i e s has been 4 developed r e l a t i n g to the ease of cleavage of the Sn-C bond f o r var i o u s organyl groups: phenyl > b e n z y l > v i n y l > methyl > e t h y l > p r o p y l > b u t y l > amyl > h e x y l > h e p t y l > o c t y l . Thus, the phenyl group i s most e a s i l y cleaved whereas cleavage of the o c t y l group i s very d i f f i c u l t . Method 2. T e t r a o r g a n o t i n compounds may undergo l i g a n d r e d i s t r i b u t i o n (comproportionation or l i g a n d scrambling) r e a c t i o n s w i t h t i n t e t r a -h a l i d e s : 3R.Sn + SnX. >• 4R 0SnX 4 4 3 R.Sn + SnX. >• 2R„SnXn 4 4 2 2 R.Sn + 3SnX. • 4RSnX 0 4 4 3 e.g. 9 3(CH 2=CH) 4Sn + S n C l 4 • 4(CH 2=CH) 3SnCl (CH 2=CH) ASn + SnCl^ »- 2 (CH2=CH) 2 S n C l 2 (CH 2=CH) 4Sn + 3 S n C l 4 • 4(CH 2=CH)SnCl 3 For commercial q u a n t i t i e s of organotin h a l i d e s , t h i s method i s o f t e n used. However, t h i s route i s r e s t r i c t e d to the s y n t h e s i s of o r g a n y l t i n - A -chlorides, bromides and iodides. No fluorides have been obtained via ligand scrambling. Method 3. Tin or tin(II) halide may react with an organohalide in a direct synthetic route: Sn + 2RX • R2SnX2 SnX2 + RX • RSnX3 e.g. Sn + 2CH3C1 >. (CH 3) 2SnCl 2 1 0 V i p o t - 1 1 SnCl 2 + CH3C1 > CH 3SnCl 3 This method is extremely limited in practice as only the synthesis of the chlorides i s reported. Method A. Organyl transfer reactions may occur from organomercury compounds or from Grignard reagents: R2Hg + SnX2 • R2SnX2 + Hg RMgX + SnX^ • RSnX3 + MgX2 2RMgX + SnX4 f R2SnX2 + 2MgX2 3 RMgX + SnX4 • R^nX + 3MgX2 e.g. R2Hg + SnCl 2 • R 2SnCl 2 + Hg Again, no fluorides have been synthesized by the use of this method. Method 5. Halogen exchange of organotin halides may be accomplished with metallic halides such as KF and AgF. - 5 -e.g. R 3SnCl + KF >- R^SnF + KCI Synthesis of org a n o t i n f l u o r i d e s p r e v i o u s l y has been accomplished mainly by method 5 of t h i s s y n t h e t i c s e r i e s , however, no s u c c e s s f u l s y n t h e s i s of e i t h e r organotin(IV) t r i f l u o r i d e s or c h l o r i d e - f l u o r i d e s has been reported. One r e c e n t l y p u b l i s h e d attempt to prepare d i ( t e r t -b u t y l ) t i n c h l o r i d e - f l u o r i d e using the a c t i o n of an alcoholic-aqueous s o l u t i o n of KF on (0^.^)^5x101^ r e s u l t e d i n an impure product c o n t a i n i n g t 12 conside r a b l e amounts of (C^HQ ) 2 S n F 2 > This r e s u l t f a i r l y w e l l r u l e s out halogen exchange as a s u i t a b l e s y n t h e t i c route to e i t h e r m e t h y l t i n ( I V ) t r i f l u o r i d e or any m e t h y l t i n ( I V ) c h l o r i d e - f l u o r i d e s . Methods 2, 3, and 4 are e q u a l l y u n s u i t a b l e because a fundamental s t r u c t u r a l d i f f e r e n c e e x i s t s between SnF 2, SnF^, ( C H ^ S n F , ( C H 3 ) 2 S n F 2 and the corresponding c h l o r i d e s , bromides or i o d i d e s . These f e a t u r e s w i l l be discussed i n more d e t a i l i n l a t e r s e c t i o n s of t h i s i n t r o d u c t i o n . The polymeric s t r u c t u r e s of the f l u o r i d e s create a d i f f e r e n t s o l u b i l i t y p a t t e r n than that found f o r the r e s t of the h a l i d e s which are best regarded as molecular compounds w i t h only weak a s s o c i a t i o n . Thus, only method 1 or a m o d i f i c a t i o n of i t i s l e f t as a promising route to the d e s i r e d compounds. I t i s obvious that the use of elemental f l u o r i n e i n t h i s context would be unprecedented, hazardous and c e r t a i n l y d i f f i c u l t to c o n t r o l i f c h l o r i d e - f l u o r i d e s are d e s i r e d . This leaves e i t h e r aqueous or anhydrous HF as the best worthwhile a l t e r n a t i v e s even though only one example where hydrofluoric a c i d was reacted w i t h 13 ^ C 4 H 9 ^ 3 S n C H 2 C N t 0 y i e l d ( C 4 H 9 ^ 3 S n F could be found i n the e x i s t i n g l i t e r a t u r e . The f o l l o w i n g three s e r i o u s l i m i t a t i o n s of the intended s o l v o l y s i s - 6 -r e a c t i o n s w i l l have to be considered r a t h e r c a r e f u l l y : (1) Only one r e a c t i o n product should be formed i d e a l l y , s i n c e no s e p a r a t i o n methods are s u i t a b l e f o r the expected polymeric compounds. This means, i n essence, that the intended s o l v o l y s i s r e a c t i o n should go to completion i n a u n i d i r e c t i o n a l manner. (2) V i r t u a l l y a l l previous r e p o r t s use t e t r a o r g a n o t i n ( I V ) compounds as s t a r t i n g m a t e r i a l s . The use of m e t h y l t i n ( I V ) c h l o r i d e s as intended i n t h i s study can r e s u l t i n cleavage of the Sn-C or the Sn-Cl bond. The usefulness of t h i s s y n t h e t i c route w i l l be dependent upon whether the two p o s s i b l e cleavage r e a c t i o n s w i l l , under reasonable experimental c o n d i t i o n s , proceed i n two c l e a r l y d i s t i n c t i v e steps and whether the r e a c t i o n s lead to i s o l a b l e i n termediate products r a t h e r than complete f l u o r i n a t i o n y i e l d i n g SnF^ as the s o l e product. (3) The expected r e a c t i o n products, i n p a r t i c u l a r the m e t h y l t i n ( I V ) c h l o r i d e - f l u o r i d e s , are i n a l l p r o b a b i l i t y moisture s e n s i t i v e and would not be o b t a i n a b l e from aqueous s o l u t i o n s . whether these l i m i t a t i o n s can be overcome or reduced i s a q u e s t i o n which can only r e a l l y be answered by experiment. In t h i s connection, i t was i n t e r e s t i n g that s o l v o l y s i s of the m e t h y l t i n ( I V ) c h l o r i d e s e r i e s i n s t r o n g , monobasic p r o t o n i c a c i d s such as HS0 3F, H S 0 3 C F 3 j 1 ^ - 1 6 a n d H P O ^ 1 7 proceeded i n a c o n t r o l l e d stepwise manner thereby a l l o w i n g the s y n t h e s i s of a number of m e t h y l t i n d e r i v a t i v e s . In these s t u d i e s , the Sn-Cl bond was p r e f e r e n t i a l l y cleaved over the Sn-C bond w i t h e i t h e r one or two C l or CH 3 groups being s u b s t i t u t e d by the a c i d i c group. I t was hoped that s o l v o l y s i s i n HF would f o l l o w the same course. - 7 A case where the Sn-C bond i s p r e f e r e n t i a l l y cleaved over the 18 Sn-Cl bond by p r o t o n i c a c i d s was reported r e c e n t l y when (CH^^SnCl was reacted w i t h a number of p e r f l u o r o c a r b o x y l i c a c i d s . As a r e s u l t of these c o n f l i c t i n g o b s e r v a t i o n s , any p r e d i c t i o n of the nature of the s o l v o l y s i s i n anhydrous HF i s imp o s s i b l e . The need f o r a systematic study i n HF i s q u i t e apparent. C. Eydrogen F l u o r i d e L i t e r a t u r e p e r t a i n i n g to hydrogen f l u o r i d e has been s l a n t e d mainly toward a c o n s i d e r a t i o n of the p h y s i c a l p r o p e r t i e s of the pure substance 19 20 and i t s use as a non-aqueous s o l v e n t . ' Pioneer work i n t h i s s o lvent system was c a r r i e d out by the Fredenhagens as e a r l y as 1 9 3 0 <21,22,22a,23,24 R e l a t i v e l y l i t t l e i n f o r m a t i o n i s reported on the a p p l i c a t i o n of anhydrous HF as a f l u o r i n a t i n g agent. To some extent t h i s can be e a s i l y e x p l a i n e d by the d i f f i c u l t i e s encountered i n the ha n d l i n g of HF. Both g l a s s and quartz are r e a d i l y attacked by e i t h e r anhydrous or aqueous HF. Therefore, u n t i l q u i t e r e c e n t l y , only some p l a s t i c s , copper, n i c k e l or monel c o n t a i n e r s were s u i t a b l e f o r any s t u d i e s . P r i o r to t h i s , i n e r t metals such as platinum and platinum/gold a l l o y s were o f t e n used. With the advent of p o l y t e t r a f l u o r o e t h y l e n e (Teflon) and p o l y -c h l o r o t r i f l u o r o e t h y l e n e (Kel-F) handling of HF and f a b r i c a t i o n of apparatus have been much s i m p l i f i e d . A wide range of c e l l s and instruments, s u i t a b l e f o r anhydrous HF, has been designed which a l l o w the a p p l i c a t i o n of p h y s i c a l measurements and s p e c t r o s c o p i c techniques. 19 Hyman and Katz have summarized many p r o p e r t i e s of HF such as i t s e l e c t r i c a l c o n d u c t i v i t y , vapor pr e s s u r e , v i s i b l e , u l t r a v i o l e t and - 8 -i n f r a r e d spectrum and proton magnetic resonance spectrum. Some emphasis i s a l s o placed on i t s solvent p r o p e r t i e s but chemical r e a c t i o n s i n v o l v i n g i t s use as a f l u o r i n a t i n g agent are not mentioned. C l i f f o r d ^ ^ ' 2 ^ a has c a r r i e d out v a r i o u s s t u d i e s concerned w i t h the use of HF as a non-aqueous solvent and has considered, i n p a r t i c u l a r , the acid-base p r o p e r t i e s of the substance. Again, no mention of i t s f l u o r i n a t i n g powers are made. A good review on HF as s o l v e n t and r e a c t i o n medium has r e c e n t l y 26 appeared which a l s o d e s c r i b e s i t s use as a f l u o r i n a t i n g agent. In 27 accordance w i t h a r e p o r t by Sharpe, the a p p l i c a t i o n of HF i s r e s t r i c t e d mainly to the s y n t h e s i s of low valency b i n a r y f l u o r i d e s of the main group and t r a n s i t i o n a l elements and to the s y n t h e s i s of a number of organic f l u o r o c a r b o n d e r i v a t i v e s . No a p p l i c a t i o n to the s y n t h e s i s of o r g a n o m e t a l l i c compounds seems to have been re p o r t e d p r e v i o u s l y . The f i r s t use of anhydrous HF as a f l u o r i n a t i n g agent f o r t i n 28 compounds was reported by Ruff and P l a t o i n 1904. Anhydrous HF was reacted w i t h SnCl^ to y i e l d f i r s t l y an intermediate product formulated as "SnCl^.SnF^" and by f u r t h e r h e a t i n g e v e n t u a l l y pure SnF^. The r e a c t i o n was of i n t e r e s t to us on two accounts: (1) Experimental proof i s provided that anhydrous HF i s capable of c l e a v i n g the Sn-Cl bond; (2) the cleavage appears to occur over an i n t e r m e d i a t e "SnCl^.SnF^" 29 which Sidgwick suggested to be the only s t a b l e mixed s t a n n i c h a l i d e , SnCl2F2- We became i n t e r e s t e d i n t e s t i n g t h i s p r o p o s a l and thus in c l u d e d the study of "SnCl^.SnF^" i n our program. Most c e r t a i n l y , at t h i s p o i n t , i t seemed that HF could w e l l have some promise i n the s y n t h e s i s of t i n - f l u o r i n e compounds. - 9 -A l a s t point concerning the handling of anhydrous hydrogen f l u o r i d e remains to be made. The compound i s very v o l a t i l e (b.p. 19.5°) and presents a considerable health hazard due to i t s corrosiveness. HF burns are most dangerous and extremely p a i n f u l . Safe handling i s p o s s i b l e only when the following requirements are met: (1) A safe and leak t i g h t vacuum system must be a v a i l a b l e which i s able to withstand a s l i g h t p o s i t i v e pressure; (2) a w e l l v e n t i l a t e d fumehood should house the vacuum l i n e ; (3) appropriate remedies f o r HF burns must be at hand i n the laboratory. Such a substance i s a high molecular weight 30 quaternary ammonium compound "Hyamine 1622" which i s reported to be superior to previous remedies such as magnesium sulphate or i n j e c t i o n s of calcium gluconate. D. S t r u c t u r a l Features Of Organotin(IV) Compounds Detailed molecular structures have been obtained f o r some of the methyltin(IV) h a l i d e s and tetramethyltin using d i f f r a c t i o n techniques. The d e t a i l s of the r e s u l t s are a v a i l a b l e from several s o u r c e s ^ 3 ' ^ a ' ' and are summarized i n Table 1. Several points may be made regarding the s o l i d compounds upon examination of the r e s u l t s i n Table 1: (1) Generally, t e t r a h e d r a l or d i s t o r t e d t e trahedral configuration i s observed around the t i n atom i n the organotin halides. However, a tendency toward coordination expansion i s noted f o r the f l u o r i d e s and, to a l e s s e r extent, the c h l o r i d e s . In the s o l i d s t a t e , polymeric, halogen bridged structures with coordination numbers f i v e and s i x are observed. The coordination around t i n i s now better described as a d i s t o r t e d t r i g o n a l bipyramid or a d i s t o r t e d octahedron r e s p e c t i v e l y . Where extensive bridging e x i s t s - 10 -TABLE 1 S t r u c t u r a l Aspects of some M e t h y l t i n ( I V ) Compounds and Tin ( I V ) H a l i d e s Compound Sn-C(A) Sn-X(A) Method Ref. Remarks (CH 3) 4Sn (g) 2.18±0.03 (CH 3) 3SnCl(g) 2.19±0.03 2.37±0.03 ( C H 3 ) 2 S n C l 2 ( g ) 0,2.17 2.34±0.03 ( C H 3 ) 2 S n C l 2 2.2110.08 2.40±0.04 (s) 3.54±0.05 (br i d g i n g ) CH 3SnCl 3(g) 2.19±0.03 2.32±0.03 S n C l 4 (g) - 2.31+0.01 %2.1 %2.1 (CH 3) 3SnF(s) ^2.2-2.6 (b r i d g i n g ) ( C H 3 ) 2 S n F 2 ( s ) 2.08±0.01 2.12±0.01 SnF 4 (s) 1.88±0.01 2.02±0.01 (br i d g i n g ) a 33 T e t r a h e d r a l molecule a 33 T e t r a h e d r a l molecule a 33 T e t r a h e d r a l molecule b 34 Polymeric w i t h s t r u c t u r e s u b s t a n t i a l l y d i s t o r t e d from t e t r a -h e d r a l toward o c t a -h e d r a l . T i n atoms are zig-zagged r a t h e r than c o l l i n e a r w i t h each t i n atom j o i n e d to each of i t s two neighbours by two " b r i d g i n g " c h l o r i n e atoms. a 33 T e t r a h e d r a l molecule a 35 T e t r a h e d r a l molecule b 36 Polymeric s t r u c t u r e w i t h e s s e n t i a l l y penta-coordinated t i n atoms and n o n - l i n e a r Sn-F-Sn. T r i m e t h y l t i n groups are p l a n a r . b 37 Polymeric s t r u c t u r e arranged of o c t a h e d r a l l y coordinated t i n i n a s h e e t - l i k e f a s h i o n v i a f l u o r i n e b r i d g i n g . The d i m e t h y l t i n group i s l i n e a r b 38 Same s t r u c t u r e as ( C H 3 ) 2 S n F 2 except that t e r m i n a l f l u o r i n e r e places the methyl groups a - e l e c t r o n d i f f r a c t i o n ; b - X-ray d i f f r a c t i o n - l i -as i n the f l u o r i d e s , the C-Sn-C arrangement i s l i n e a r and the SnC^ group i s t r i a n g u l a r planar with Sn i n the center; (2) the tendency toward bridge bonding i s seen to decrease with decreasing e l e c t r o -n e g a t i v i t y of the halogen. Thus, f o r the stannic h a l i d e s , only SnF^ e x h i b i t s coordination number 6 as can be seen from the table. The bridging F atoms can be equidistant from both t i n nearest neighbours as found for SnF^ and (CH 3) 2SnF 2 but t h i s i s probably not so f o r (CH 3) 3SnF although no d e f i n i t e conclusions can be drawn from the rather approximate interatomic distances reported f o r the compound; (3) the tin-carbon distance i n dimethyltin d i f l u o r i d e i s the shortest of any methyltin h a l i d e . This has been a t t r i b u t e d to the octahedral structure i n which the l i n e a r C-Sn-C group involves mainly sp h y b r i d i z a t i o n on the t i n and the increased s character tends to shorten the bond. This i s best expressed by the " i s o v a l e n t h y b r i d i z a t i o n " model proposed 39 by Bent where s character i s seen to be concentrated i n the bonds to the l e s s electronegative atoms surrounding the c e n t r a l atom. In s o l u t i o n , the s i t u a t i o n changes rather markedly, whereas methyltin cations are not present i n the s o l i d s t a t e , evidence e x i s t s +2 + f o r both the (CH^^Sn and (CH^J^Sn cations i n solvated form i n water 40 41 s o l u t i o n as w e l l as i n other polar solvents. ' Such an i o n i z a t i o n i n polar solvents provides a r a t i o n a l e for the success of the KF method for preparing f l u o r i d e s from chlorides which was mentioned e a r l i e r and also hints at the p o s s i b i l i t y of using aqueous HF f o r the s o l v o l y s i s of some organotin c h l o r i d e s . - 12 -E. A p p l i c a t i o n of V i b r a t i o n a l Spectroscopy This p h y s i c a l technique when coupled w i t h Mbssbauer spectroscopy can y i e l d a great d e a l of i n s i g h t i n t o the s t r u c t u r a l f e a t u r e s of o r g a n o t i n compounds where d i f f r a c t i o n methods cannot be r e a d i l y a p p l i e d . Since f o r a l l m e t h y l t i n ( I V ) h a l i d e s a l l v i b r a t i o n a l modes due to the CH^ group are found i n the same region (CH^ s t r e t c h e s at 2900-3000 cm - 1, CH 3 bends at 1400 and 1200 cm"1 and Sn-CH 3 rock at 800 cm 1 ) , the s t r u c t u r a l i n f o r m a t i o n i s d e r i v e d from the f o l l o w i n g " d i a g n o s t i c " v i b r a t i o n s : (1) Tin-carbon s t r e t c h e s . Both the asymmetric and the symmetric Sn-C s t r e t c h e s are g e n e r a l l y found i n the range 500-600 cm 1 w i t h the former always at higher f r e q u e n c i e s . Both w i l l be i n f r a r e d and Raman a c t i v e where a bent SnC^ or a non-planar SnC 3 s k e l e t o n are found i n d i m e t h y l t i n or t r i m e t h y l t i n d e r i v a t i v e s , e.g. ( C R ^ ^ S n C ^ and ( C H 3 ) 3 S n C l . when the SnC^ s k e l e t o n i s l i n e a r and SnC 3 p l a n a r , only the asymmetric s t r e t c h i s found i n the i n f r a r e d spectrum and o n l y the 32 symmetric s t r e t c h i s Raman a c t i v e . Examples are the m e t h y l t i n ( I V ) f l u o r i d e s , (CH 3) 2 S n F 2 and ( C H ^ S n F . (2) Tin-halogen s t r e t c h e s . Again the mutual e x c l u s i o n r u l e can be a p p l i e d as a t e s t f o r l i n e a r i t y and p l a n a r i t y . For c h l o r i d e s , the Sn-Cl s t r e t c h e s are found i n the range 330-375 cm \ again the asymmetric s t r e t c h being found at higher wavenumber. Frequency s h i f t s from the s o l i d s t a t e to the l i q u i d (melt or s o l u t i o n ) s t a t e and then to the gaseous s t a t e are taken as evidence f o r halogen bridges i n the 32 42 s o l i d s t a t e and perhaps even the l i q u i d s t a t e . ' - 13 For the m e t h y l t i n ( I V ) f l u o r i d e s , ( C H 3 ) 2 S n F 2 and ( C H ^ S n F , the absence of bands i n the r e g i o n 550-650 cm 1 had been taken as evidence 43 f o r the i o n i c nature of these compounds, however, very strong and broad a b s o r p t i o n bands at ^350 cm 1 (IR) are due to b r i d g i n g f l u o r i n e -t i n s t r e t c h e s . This r e g i o n i s g e n e r a l l y unresolved making a d e t a i l e d assignment i m p o s s i b l e . In a d d i t i o n , no corresponding bands are 44 45 d e t e c t a b l e i n the Raman s p e c t r a of the compounds. ' The p o s i t i o n of Sn-C and Sn-Hal deformation modes i s not known w i t h great c e r t a i n t y f o r a l l compounds. Detailed assignments reaching down i n t o the r e g i o n of the ceformation modes are a v a i l a b l e only f o r 46 the s e r i e s (CH„) SnCl, . The deformation modes are expected i n the 3 n 4-n f a r i n f r a r e d r e g i o n . Complications a l s o a r i s e because of the incomplete Raman s p e c t r a f o r the f l u o r i d e s and because of the i n a b i l i t y to o b t a i n p o l a r i z e d Raman s p e c t r a . The v i b r a t i o n a l r e s u l t s are summarized i n Table 2. Good reviews on v i b r a t i o n a l spectroscopy as a p p l i e d to orga n o t i n ( I V ) A 2 32 h a l i d e s can be obtained from Adam's book and Okawara and Wada's review. However, l i t t l e i n f o r m a t i o n p e r t a i n i n g to the p o s i t i o n of a t e r m i n a l t i n - f l u o r i n e s t r e t c h i s a v a i l a b l e . In a n i o n i c compounds such as 2- 47 2- 44 -1 SnF 6 • and ( C H 3 ) 2 S n F 4 , a range of 560 to 590 cm f o r the i n f r a r e d a c t i v e s t r e t c h i n g mode v3 has been reported f o r the former whereas 347 and 397 cm 1 are reported f o r the l a t t e r suggesting a 48 s t r o n g l y p o l a r Sn-F bond. For S n C l 2 F 2 , where the v i b r a t i o n a l spectrum i s i n t e r p r e t e d i n terms of a t e t r a h e d r a l l y coordinated molecule, the symmetric and asymmetric s t r e t c h e s are found at 491 and 555 cm 1 r e s p e c t i v e l y . However, f o r S n ( N 0 3 ) 2 F 2 , which i s sy n t h e s i z e d from - 14 -TABLE 2 V i b r a t i o n a l Data f o r Some M e t h y l t i n ( I V ) Compounds Compound v (Sn-C) v (Sn-C) s as v (Sn-s X) v (Sn-X) as Ref ( C H 3 ) 4 S n (1) 508(R) 524(IR) 530(R) - - 53 (CH 3) 3'SnCl (1) 514(IR) 545(IR) 518(R) 548(R) 318(R) 46 C C H 3 ) 2 S n C l 2 ( l ) 524(IR) 563(IR) 521(R) 566(R) 344(R) 344(R) 46 C3I 3SnCl 3 CD 548(IR) 550(R) 358(R) 376(R) 46,54 C H 3 S n C l 3 Cs) 545(IR) 546(R) 352(R) 370(R) 54 (CH 3) 3SnF (s) 517(R) 556(IR) 350(IR) 45 ( C H 3 ) 2 S n F 2 (s) 532(R) 598(IR) * 360(IR) 44 S n C l 2 F 2 by i n t e r a c t i o n w i t h C10N0 2 and r e p o r t e d l y contains monodentate co v a l e n t n i t r a t e groups, the two SnF 2 s t r e t c h i n g modes are found at 578 and 630 cm 1 . Frequency values between 550 and 600 cm 1 are a l s o 49 r e p o r t e d f o r a number of o c t a h e d r a l SnF^ complexes, however, no assignment i s made by the authors. Therefore, i t seemed reasonable to expect the p o s i t i o n of a t e r m i n a l t i n - f l u o r i n e s t r e t c h to occur at 6^00 cm 1 . - 15 -Some c l a r i f i c a t i o n could be expected from a v i b r a t i o n a l a n a l y s i s of the p o s s i b l e compound, SnF2(S0.jF)2, which could conceivably be s y n t h e s i z e d from S n C l 0 F 0 and C10S0-F or S o0,F o. For the SO„F group, z z / z b z j a symmetry lowering from f o r the f r e e i o n to C g f o r the mono- or b i d e n t a t e SO^F group i s expected as found by P.A. Yeats et a l . ~ ^ E x t e n s i v e s t u d i e s on b i d e n t a t e b r i d g i n g and monodentate SO^F groups have been d o n e ^ i n order to a l l o w a d i s t i n c t i o n to be made between the p o s s i b i l i t i e s . T his previous work w i l l have much bearing on the i n t e r p r e t a t i o n of the v i b r a t i o n a l spectrum of S n F 2 ( S 0 3 F ) 2 where b r i d g i n g could occur over e i t h e r f l u o r i n e or SO^F. F. A p p l i c a t i o n of Mossbauer Spectroscopy T i n i s an element which e x h i b i t s the Mossbauer e f f e c t f o r one 119 of i t s n a t u r a l l y o c c u r r i n g i s o t o p e s , Sn. The n a t u r a l abundance of 8.58% i s s u f f i c i e n t f o r o b t a i n i n g w e l l r e s o l v e d s p e c t r a without having to e n r i c h the samples. An e x c e l l e n t general i n t r o d u c t i o n i n t o the e f f e c t and i t s use i n chemistry i s given by G r e e n w o o d . A f a i r l y l a r g e number of monographs and review a r t i c l e s on the s u b j e c t has appeared. The i n t e n t i o n of t h i s s e c t i o n w i l l be to b r i e f l y present the b a s i c fundamentals of the technique w i t h respect to i t s a p p l i c a t i o n to s t r u c t u r a l and bonding problems. In a second p a r t , previous work on organotin(IV) h a l i d e s and r e l a t e d compounds w i l l be summarized. 1. Fundamental P r i n c i p l e s of " ^ ^ S n Mossbauer Spectroscopy The Mossbauer e f f e c t a r i s e s from the r e c o i l l e s s emission and resonant r e a b s o r p t i o n of y - r a d i a t i o n and t h e r e f o r e the e f f e c t i s a l s o - 16 -termed " y~ray resonance spectroscopy" i n f o r example, the S o v i e t Union. The e f f e c t i n v o l v e s t r a n s i t i o n s between the n u c l e a r energy l e v e l s of the e m i t t e r and absorber of y - r a d i a t i o n . _ 119m„ , .. , ., , i n Sn Mossbauer spectroscopy, a sample of a t i n compound (e.g. BaSnO^) enriched w i t h 1"'"9inSn acts as the source of the y - r a d i a t i o n . As can be seen from Figure 1, a r e l a t i v e l y slow decay under y-emission occurs w i t h subsequent descent to the f i r s t e x c i t e d n u c l e a r s t a t e C l - 3/2) of 1 1 9 S n . At t h i s stage, a second r a p i d decay under f u r t h e r y-ray emission occurs r e s u l t i n g i n the nucleus now undergoing t r a n s i t i o n i n t o the ground s t a t e (I = 1/2). Mossbauer spectroscopy of t i n u t i l i z e s t h i s t r a n s i t i o n between the ground s t a t e and the f i r s t 119 e x c i t e d s t a t e of Sn. This second t r a n s i t i o n i s c h a r a c t e r i z e d by two f a c t o r s : Cl) the energy of the y-rays emitted i n the second stage of the decay process, normally l a b e l l e d y , and hence c h a r a c t e r i s t i c of the d i f f e r e n c e between the two s t a t e s (23.875 KeV) i s i n the range where both the r e c o i l l e s s emission and r e a b s o r p t i o n can be e a s i l y achieved without e l a b o r a t e low temperature c o n t r o l u n i t s . The , . 119m„ _ „ 119m_ . . . . . , , source (mostly SnC^ or Ba SnO^) i s a polymeric molecular substance or o f t e n i s imbedded i n a y - i n e r t , heavy metal which allows r e c o i l l e s s emission. The absorber can be cooled to l i q u i d tempera-tur e to ensure r e c o i l l e s s a b s o r p t i o n . I f the energy d i f f e r e n c e were l a r g e r , experimental problems would a r i s e i n that both the source and the absorber would have to be cooled to very low temperature ( l i q u i d Re), i n an attempt to o b t a i n r e c o i l l e s s emission and r e a b s o r p t i o n . F i g u r e 2 shows a b l o c k diagram of a Mossbauer spectrometer. - 17 -F i g u r e 1 H 9 m _ D e c a y of S n 5 0 s t E x c . S t a t e f + Ground S ta te 4j + 119 rn • f 2 4 5 d S n y =65 .66 Kev T 2 2 3 . 8 7 5 1.84 x i o ~ 8 s e c I I9 S n - 18 -Figure 2. B L O C K D I A G R A M O F A M O S S B A U E R S P E C T R O M E T E R W A V E F O R M G E N E R A T O R S O U R C E I I E L E C T R O - M E C H A N I C A L T R A N S D U C E R A N D V E L O C I T Y S E N S O R T O M E M O R Y D E T E C T O R T O O S C I L L O S C O P E A B S O R B E R IN D E W A R - 19 -(2) The h a l f - l i f e of the f i r s t e x c i t e d s t a t e of the Sn —8 nucleus (1.84 x 10 sec) i s i n a range where the l i n e widths of the s p e c t r a w i l l be o p t i m a l . Short l i f e t i m e s (< 10 sec) r e s u l t i n the appearance of resonance l i n e s w i t h l a r g e n a t u r a l widths and long l i f e -times G 10 ^ sec) y i e l d narrow l i n e s such t h a t s e r i o u s experimental d i f f i c u l t i e s would a r i s e i n the d e t e c t i o n of the resonance. In order to use t h i s r a d i a t i o n from such a s h o r t - l i v e d e x c i t e d n u c l e a r s t a t e , i t i s necessary to take as the source of r a d i a t i o n the l o n g - l i v e d P^Fent i s o t o p e "^ mSn, the decay of which passes through the Mossbauer l e v e l . The chemical a p p l i c a t i o n of the technique a r i s e s from the f a c t t h a t the spacings of the n u c l e a r energy l e v e l s depend minutely on the e x t r a n u c l e a r e l e c t r o n d i s t r i b u t i o n i n the valence s h e l l (5s and 5p) which i n t u r n i s c h a r a c t e r i s t i c of the chemical environment of the nucleus. Thus i f the source of the y - r a d i a t i o n and the absorber are d i f f e r e n t compounds, the energy d i f f e r e n c e s between t h e i r ground and f i r s t e x c i t e d s t a t e s w i l l be s l i g h t l y d i f f e r e n t . As a r e s u l t , no resonant a b s o r p t i o n would occur. To b r i n g the absorber and source i n t o resonance, the frequency of the y r a d i a t i o n i s modulated by moving the source of Y - r a y s r e l a t i v e to the absorber, i . e . the Doppler e f f e c t . Thus a Mossbauer spectrum c o n s i s t s of a p l o t of Y - r a y counts v s . r e l a t i v e v e l o c i t y of source toward absorber. At some v e l o c i t y , there i s resonant a b s o r p t i o n and the count-rate drops. Three parameters are obtained from a Mossbauer spectrum which are u s e f u l when s t r u c t u r a l proposals are put f o r t h : (a) the isomer or chemical s h i f t , 6, measured i n mm/sec, (b) the quadrupole s p l i t t i n g , A', again i n mm/sec,and (c) the room temperature e f f e c t . A f o u r t h 20 parameter, the h y p e r f i n e magnetic i n t e r a c t i o n , i n d i c a t i v e of a hyper-f i n e Zeeman s p l i t t i n g of n u c l e a r energy l e v e l s , can be observed only when an e x t e r n a l magnetic f i e l d i s a p p l i e d and i s g e n e r a l l y not of i n t e r e s t where Mossbauer spectroscopy i s used as a t o o l i n the study of s t r u c t u r a l e f f e c t s . A l s o of minor i n t e r e s t i n the i n t e r p r e t a t i o n of a spectrum i s the li n e w i d t h at h a l f peak h e i g h t , r» i n mm/sec. (a) Isomer s h i f t The isomer s h i f t (IS or 6) i s the measure of the source v e l o c i t y r e q u i r e d to b r i n g a p a r t i c u l a r absorber i n t o resonance w i t h the source. I t can be expressed i n the f o l l o w i n g s i m p l i f i e d manner: 6 = const. - A | ^ s ( 0 ) | 2 (1) where Ar = r . , - r , e x c i t e d ground = d i f f e r e n c e i n nu c l e a r r a d i i A | ^ s ( 0 ) | = d i f f e r e n c e i n " s " e l e c t r o n d e n s i t y at the nucleus between the source and the absorber, (see F i g u r e 3). The isomer s h i f t i s thus dependent on a nuclear f a c t o r A r / r and an 2 e x t r a - n u c l e a r f a c t o r A | ^ s ( 0 ) | . For t i n , i t i s known that A r / r i s p o s i t i v e , that i s r ._ , > r ,, t h e r e f o r e a l a r g e p o s i t i v e value r e x c i t e d ground' ° r f o r 6 i m p l i e s a high " s " e l e c t r o n d e n s i t y around t i n , i . e . groups of low e l e c t r o n e g a t i v i t y . Hence, isomer s h i f t can be used as a measure of the " s " e l e c t r o n d e n s i t y around the t i n nucleus and y i e l d s i n f o r m a t i o n regarding the valence s t a t e of t i n i n the absorber. Thus i f the chemical s h i f t f o r Sn02 i s set at 0 mm/sec as i s cu s t o m a r i l y done, - 21 -f i g u r e 3 . l y i o s s b a u e r . s p e c t r u m Isomershift S ( m m / s e c ) A b s o r p t i o n / o E x c i t e d s ta te G r o u n d state •2 -I o +l Ve loc i ty in m m / s e c :o a S o u r c e A b s o r b e r IS = E — E _ a s l z r 7 p 2 2 Br 5 ^ r r 2 2 W O ) a b s o r b e r — s o u r c e = c o n s t . S r . r v// ( O ) s Figure 4 . Distribution of S for Sn(iv) increasing bond polarity Sn II 4 + Sn 5s° 5p° - 0 . 4 3 3 K S n F 2 . 6 Snf^ - 0 . 5 O 0 . 4 2 K S n C l methylt in f luo r ides and ch lor ides 1 . 2 - 1 . 6 0 . 8 0 SnCL S n B r 4 . 4 1 + 0 .5 1 . 2 9 | ( C H 3 ) 4 S n r 1 . 0 S n (iv) 5s 1 5 p 3 1 . 9 3 a - S n ( 7 7 ° ) to Snl^ _L_ 1.5 Cmm/sec) 2.0 S n Q . - 22 -although $ - t i n has a l s o been used as a zero r e f e r e n c e , then that f o r grey t i n i s 1.3 mm/sec and that f o r S n C ^ i s 3.7 mm/sec where the 0 1 3 e l e c t r o n c o n f i g u r a t i o n s are approximately 5s (SnO^), 5s 5p (grey t i n ) 2 and 5s (SnC^) . F i g u r e 4 i l l u s t r a t e s the v a r i a t i o n i n chemical s h i f t f o r some t i n (IV) compounds. (b) Quadrupole s p l i t t i n g N u c l e i which have a s p i n , I > 1/2, possess a n u c l e a r quadrupole 119 moment, Q. The f i r s t e x i c t e d s t a t e of Sn has 1 = 3 / 2 and t h e r e f o r e posesses a n u c l e a r quadrupole moment whose o r i e n t a t i o n i s dependent on the e l e c t r i c f i e l d g r a d i e n t , q. Thus the degeneracy of the I = 3/2 nucl e a r s t a t e may be l i f t e d and s p l i t t i n g of Mbssbauer peaks i s p o s s i b l e i f an e l e c t r i c f i e l d g radient i s present i n the molecule, i . e . i f an unsymmetrical e l e c t r o n d i s t r i b u t i o n e x i s t s around t i n . This s p l i t t i n g i s c a l l e d the quadrupole s p l i t t i n g and i s gi v e n by the f o l l o w i n g e x p r e s s i o n : 1 2 1 2 1/? AE = ± e qQ(l + ± n ) 7 = A (2) q 2 3 = const, x q ( e l e c t r i c f i e l d g r a d i e n t ) x Q (nuclear quadrupole moment x n (asymmetry f a c t o r ) For a x i a l symmetry, n = 0, t h e r e f o r e AE = A = const, q . Q (3) q (See F i g u r e 5 ) . As can be seen from equation ( 3 ) , both the s i z e and the s i g n of A w i l l depend upon q, the nonvanishing e l e c t r i c f i e l d g r a d i e n t . For t i n ( I V ) compounds, i t i s g e n e r a l l y b e l i e v e d that q a r i s e s p r i m a r i l y C - 24 -Figure 5. Quadrupole Coupling A ( m m / s e c ) Absorpt ion % Veloc i ty in m m / s e c Exci ted state I = ^ 1 2 Ground i= ^ sstate T A m i 2 ± 1 Isomer shift Quadrupole coupling - 25 -from the imbalance i n the p o l a r i t y of a bonds.^»61 p r e v i 0 u s l y 62 63 h e l d views ' where an imbalance of TT donor p r o p e r t i e s of the l i g a n d s around t i n i n regard to a p o s t u l a t e d p?r dn i n t e r a c t i o n w i t h the 5d o r b i t a l s have been r e j e c t e d on the b a s i s of experimental data. The e l e c t r i c f i e l d g r a d i e n t g i v i n g r i s e to the quadrupole s p l i t t i n g w i l l be due to p r i n c i p a l l y two e f f e c t s : (a) charges on l i g a n d s and surrounding atoms [q ^^tl» (b) a n imbalance i n the d i s t r i -b u t i o n of valence s h e l l e l e c t r o n s on t i n [q .. ]. Both c o n t r i b u t i o n s n v a l have opposite s i g n s ^ but i t i s presumed^ and r e c e n t l y confirmed by e x p e r i m e n t ^ that q , » q, t and i s thus the dominant f a c t o r . r M v a l H l a t To i l l u s t r a t e the s i t u a t i o n , two examples of t e t r a h e d r a l l y coordinated t i n are quoted. For t e t r a m e t h y l t i n , SnCCH^)^, q and hence A w i l l be zero whereas f o r (CH^)^SnCF^, a s p l i t t i n g of 1.38 mm/sec ^ i s 68 observable. E l e c t r o n e g a t i v i t i e s or even b e t t e r , the T a f t c o n s t a n t s , * a , are u s e f u l guides i n e s t i m a t i n g bond p o l a r i t i e s . I t i s g e n e r a l l y * found t h a t d i f f e r e n c e s between groups of ^ 0.7 or l a r g e r i n t h e i r a values w i l l r e s u l t i n r e s o l v a b l e s p l i t t i n g s where the r e s o l u t i o n l i m i t i s taken as 0.5 mm/sec f o r the spectrometer. Below t h i s l i m i t , l i n e broadening e f f e c t s may be i n t e r p r e t e d i n terms of s m a l l u n r e s o l v a b l e quadrupole s p l i t t i n g s . Quadrupole s p l i t t i n g s f o r t e t r a h e d r a l l y coordinated t i n compounds are g e n e r a l l y found i n the range 0.5-2.5 mm/sec. S t r u c t u r a l e f f e c t s come i n t o p l a y when the c o o r d i n a t i o n number f o r t i n i s expanded to f i v e or more commonly to s i x . The most obvious examples i n organotin(IV) chemistry w i l l be of the types R.jSnX2 and R^SnX^ w i t h c i s and t r a n s isomers f o r the l a t t e r . Examples i n c l u d e the chain type polymers (CH.j),jSnF, the sheet type polymer 2- 2-( C H 3 ) 2 S n F 2 and anions such as ( C R ^ S n C l ^ or ( C H ^ S n F ^ . I t i s f o r these simple types that q u a n t i t a t i v e assessments of quadrupole s p l i t t i n g s have been made. Very few d e t a i l s are known f o r the s t r u c t u r a l types RSnX^Y, R^SnX^, R 2SnX 2Y 2 and R 3SnXY, the main reason being the l a c k of e s t a b l i s h e d examples f o r these r a r e r cases. This d i s c u s s i o n w i l l t h e r e f o r e center around the three above mentioned examples, namely R.SnX_, c i s R~SnX. and trans R-SnX.. The three con-3 2 2 4 2 4 f i g u r a t i o n s are shown below: X R An extremely u s e f u l approach i n the i n t e r p r e t a t i o n of quadrupole s p l i t t i n g v alues f o r organotin(IV) d e r i v a t i v e s has been the use of p o i n t charge c a l c u l a t i o n s . These were f i r s t i n troduced by Fitzsimmons et a l . extended by P a r i s h and P l a t t ^ ' ^ and by Debye and Zuckerman. 7^ The model has been employed f o r t e t r a h e d r a l molecules of the type R SnCl. , f o r t r i g o n a l b i p y r a m i d a l ones of the R SnX r type and f o r n 4-n' e n 5_ n - 27 -oct a h e d r a l molecules of the R SnX, type. The assumption made i s n 6-n y r that a l l r e s u l t i n g c o o r d i n a t i o n polyhedra have i d e a l symmetry, that i s that the asymmetry parameter, n , i s zero. The l i g a n d s are considered to be p o i n t charges and i n d i v i d u a l c o n t r i b u t i o n s to the t o t a l quadrupole s p l i t t i n g may be c a l c u l a t e d . As a r e s u l t of such c a l c u l a t i o n s i t can be shown t h a t t r a n s - o c t a h e d r a l molecules of type R 2SnX 4 w i l l have twice as h i g h a quadrupole s p l i t t i n g as w i l l a corresponding c i s form. By assuming or knowing a given c o n f i g u r a t i o n , quadrupole s p l i t t i n g s may be c a l c u l a t e d from the p a r t i a l s p l i t t i n g v a l u e s , [ L ] , f o r both R and X i n the above mentioned systems. Good agreement w i t h observed values i s found and A values as high as 5.5 mm/sec can be r a t i o n a l i z e d by the use of t h i s method. Some r e p r e s e n t a t i v e A values as w e l l as some [L] val u e s are l i s t e d below. Compound [L] (mm/sec) obs ^ c a l c (mm/sec) (mm/sec) ( E t ^ N ) [ S n C l 5 ] [Cl] = 0.63 0.77 0.63 ( E t 4 N ) [ M e 3 S n C l 2 ] [Cl] = 0.63 [Me] = -0.31 3.32 3.45 [Me 3SnF] [Me] = -0.31 [F] = 0.73 3.86 3.85 [Me 2SnF 2] [Me] = -0.31 [F] = 0.73 4.12 4.16 Whether s i m i l a r c a l c u l a t i o n s are f e a s i b l e f o r systems encountered here remains to be seen but some i n s i g h t i n t o the geometry must f i r s t be obtained. -, 28 -(c) Room temperature e f f e c t At room temperature, t i n compounds g e n e r a l l y r e c o i l when e m i t t i n g or absorbing r a d i a t i o n and s i n c e the Mossbauer e f f e c t depends upon r e c o i l -l e s s emission and a b s o r p t i o n , no s p e c t r a are produced. The f a c t that some t i n compounds do gi v e s p e c t r a at room temperature has been 71 72 a t t r i b u t e d to the polymeric nature of these compounds. ' Polymeric compounds w i l l have l e s s freedom to r e c o i l , thus, they w i l l e x h i b i t resonant a b s o r p t i o n at higher temperature than w i l l monomeric compounds. The e f f e c t i s o f t e n r e p o r t e d as the parameter R = e298°^ e78° w ^ e r e e i s the a b s o r p t i o n at the r e s p e c t i v e temperature. R w i l l be i n the range 0 to 1 although the lower l i m i t i s .03 as a r e s u l t of experimental c o n s i d e r a t i o n s , e.g. SnF^, R = 0.73; (CH^^SnF, R = 0.12; SnCl^, R = 0. 3. P e r t i n e n t Data Mossbauer parameters are p r e s e n t l y known f o r an ext e n s i v e number of. t i n compounds. Table 3 contains the parameters of the compounds of d i r e c t i n t e r e s t here as w e l l as those of some pentacoordinated a n i o n i c species and of some hexacoordinated molecular complexes. Some features of i n t e r e s t are i l l u s t r a t e d i n Table 3: (1) There are some r a t h e r e x t e n s i v e d i s c r e p a n c i e s i n 6 and A values i n some cases e.g., Me^SnF <S = 1.18-1.31 and A = 3.47-3.86. One o b v i o u s l y must be cautious when usin g some of these values i n p a r t i c u l a r the ones de r i v e d from o l d e r references where c a l i b r a t i o n and other t e c h n i c a l problems may have e x i s t e d however- the p r e c i s e reasons f o r the v a r i a t i o n s and a f u r t h e r d i s c u s s i o n of t h i s ' p o i n t are beyond the scope of t h i s t h e s i s . - 29 -TABLE 3 Mossbauer Parameters f or Some Methyltin(IV) Compounds and Tin(IV) Halides (6 r e l a t i v e to Sn0 2) Compound Temp. 6 A (°K) (mm/sec) (mm/sec) R Reference (CH 3) 4Sn (CH 3) 3SnCl ( C H 3 ) 2 S n C l 2 CCH 3) 2SnCl 2.2(CH 3) 2SO (CH 3) 2SnCl 2.2PY CCH 3) 3SnF (CH 3) 2SnF, SnCl, SnF. 78 1.20 0 0 57 78 1.29 0 0 60 80 1.59 0 0 73 78 1.44 3.67 — 57 80 1.41±0.09 3.41±0.09 - 74 80 1.44 3.50 - 75 78 1.40 3.09 - 76 80 1.43±0.03 3.32±0.03 - 77 77 1.54 3.55 34 78 1.60 3.52 - 64 80 1.52±0.09 3.62±0.09 - 74 78 1.53 3.41 . - 76 80 1.68 3.85 - 75 78 1.39 4.10 _ 72 77 1.40 4.16 - 78 80 1.37 3.83 - 73 78 1.26 3.77 0.12 71 298 1.2 3.60 71 80 1.28 3.86 - 73 78 1.18 3.47 - 76 80 1.31 3.79 - 79 298 1.24 3.71 - 79 78 — 4.12 _ 60 77 1.31 4.11 - 34 77 1.24 4.11 - 78 - - - .19 71 77 +0.78 0 _ 56 77 +0.85 0 - 57 77 +0.9 0 - 65 80 -0.25 1.75 57 78 -0.3 1.8 - 65 80 -0.26 1.80 - 76 - - - .73 71 - 30 -TABLE 3 (Continued) Compound Temp. (°K) 6 (mm/sec) A (mm/sec) R Reference (Et.N)(Me„SnCl„) 78 1.42 3.32 64 78 1.24 3.23 80 Cs0Me„SnCl, 2 2 4 78 1.63 4.32 64 K 2Me 2SnF 4 78 1.38 4.12 64 (2) The f l u o r i d e s are the only compounds which e x h i b i t an observable room temperature e f f e c t . This f e a t u r e i s i n d i c a t i v e of t h e i r polymeric s t r u c t u r e described e a r l i e r i n S e c t i o n D of t h i s I n t r o d u c t i o n . (2) The r e l a t i v e l y h i g h values f o r A of compounds l i k e Me^SnCl (^3.4) and M e 2 S n C l 2 (^3.6) i n d i c a t e that i n t e r m o l e c u l a r a s s o c i a t i o n may be f a i r l y e x t e n s i v e causing c o n s i d e r a b l e d i s t o r t i o n i n the s t r u c t u r e from f o u r - c o o r d i n a t e to higher c o o r d i n a t i o n around t i n . G. Summary The problem at hand was the s y n t h e s i s and s t r u c t u r a l c h a r a c t e r i z a t i o n of CH^SnF^ and some m e t h y l t i n ( I V ) c h l o r i d e - f l u o r i d e s . The c o n v e n t i o n a l l y used methods f o r the s y n t h e s i s of organotin(IV) h a l i d e s d i d not seem a p p l i c a b l e i n our case. S o l v o l y s i s i n hydrogen f l u o r i d e seemed to have promise as a m i l d f l u o r i n a t i n g agent s i n c e some sulp h o n i c a c i d s had been found to be s u c c e s s f u l i n c l e a v i n g both Sn-Cl and Sn-C bonds i n organotin(IV) c h l o r i d e s . S t r u c t u r a l p roposals f o r the new compounds to be prepared would be made using v i b r a t i o n a l spectroscopy and Mbssbauer spectroscopy. - 31 -I t was a l s o intended to extend the use of HF to the s o l v o l y s i s of other organotin(IV) compounds c o n t a i n i n g other organyl groups such as phenyl and v i n y l . A l s o , s o l v o l y s i s of compounds c o n t a i n i n g bromides and i o d i d e s could be considered. These extensions would depend upon the success of HF r e a c t i o n s w i t h the m e t h y l t i n ( I V ) c h l o r i d e s . - 32 -I I . EXPERIMENTAL A. P r e p a r a t i o n and Sources of S t a r t i n g M a t e r i a l s Anhydrous hydrogen f l u o r i d e (99.9%) was obtained from the Matheson Co. I t was contained i n t h e i r storage c y l i n d e r number 3L (9 l b ) and adapted w i t h non-automatic c o n t r o l no. 55 and connection no. 660. The gas. was vacuum d i s t i l l e d from the c y l i n d e r i n t o K el-F traps p r i o r to i t s t r a n s f e r i n t o a r e a c t o r . C h l o r i n e (99.9%) was a l s o obtained from Matheson and was used d i r e c t l y w i t h no f u r t h e r p u r i f i c a -t i o n . T r i c h l o r o f l u o r o m e t h a n e ( f r e o n 11) was obtained from Matheson, s t o r e d over molecular s i e v e s and vacuum d i s t i l l e d before being used. F l u o r i n e and sulphur t r i o x i d e were s u p p l i e d by A l l i e d Chemical Corp. L t d . C h l o r i n e monofluoride was a product of Ozark-Mahoning Co. and was used d i r e c t l y from the c y l i n d e r . Reagent grade bromine was obtained from B r i t i s h Drug Houses. Stannous f l u o r i d e was a Matheson, Coleman and B e l l product and s t a n n i c c h l o r i d e came from Baker and Adamson Co. The f o l l o w i n g t i n ( I V ) compounds were products of A l f a I n o r g a n i c s , Ventron: t e t r a m e t h y l t i n , t r i m e t h y l t i n c h l o r i d e , d i m e t h y l t d i c h l o r i d e , m e t h y l t i n t r i c h l o r i d e , d i m e t h y l t i n o x i d e , d i e t h y l t i n d i c h l o r i d e , d i p r o p y l t i n d i c h l o r i d e , d i b u t y l t i n d i c h l o r i d e , d i o c t y l t i n d i c h l o r i d e , d i p h e n y l t i n d i c h l o r i d e , d i b e n z y l t i n d i c h l o r i d e and t i n tetrabromide. These compounds were used d i r e c t l y as s u p p l i e d . - 33 -T e t r a v i n y l t i n was s u p p l i e d by Pen. Chem. Research (PCR Inc.) and aqueous hydrogen f l u o r i d e (48%) by F i s h e r S c i e n t i f i c . P e r o x y d i s u l p h u r y l d i f l u o r i d e (,S^O^F^) was prepared from f l u o r i n e 81 and sulphur t r i o x i d e according to the method of Dudley and Cady. C h l o r i n e monofluorosulphate (ClOSC^F) was prepared according to 82 G i l b r e a t h and Cady and bromine monofluorosulphate (BrOSO^F) usi n g 83 the method of Aubke and G i l l e s p i e . D i c h l o r o t i n b i s f l u o r o s u l p h a t e ( S n C ^ ^ O ^ F ^ ) was obtained from Mr. P.A. Yeats i n t h i s l a b o r a t o r y from an e a r l i e r p r e p a r a t i o n . " ^ Both d i v i n y l t i n d i c h l o r i d e and v i n y l t i n t r i c h l o r i d e were prepared from t e t r a v i n y l t i n and t i n t e t r a c h l o r i d e according to Rosenberg and 9 Gibbons. B. General Apparatus 1. Reaction V e s s e l s (a) Glass r e a c t o r s . Three types were used. ( i ) A two p a r t r e a c t o r c o n s i s t i n g of a 50 ml round bottom f l a s k equipped w i t h a B19 cone and a t e f l o n stopcock equipped w i t h a B19 socket f o r attachment to the f l a s k and a BIO cone f o r connection to a g l a s s vacuum m a n i f o l d . ( i i ) A one p a r t r e a c t o r c o n s i s t i n g of an erlenmeyer f l a s k w i t h a c a p a c i t y of about 100 ml f i t t e d at the top w i t h a B19 cone. A t e f l o n stopcock equipped w i t h a BIO cone was attached to the s i d e . S o l i d s could be added through the top and, a f t e r s e a l i n g t h i s p o r t i o n , v o l a t i l e substances could be d i s t i l l e d i n t o the f l a s k v i a the s i d e i n l e t . - 34 -( i i i ) Bromine monofluorosulphate was prepared i n a r e a c t o r constructed from a 100 ml round bottomed f l a s k w i t h a long neck of 100 mm and equipped w i t h a t e f l o n stopcock and BIO cone f o r vacuum l i n e connection. (b) Monel r e a c t o r s ( i ) C h l o r i n e monofluorosulphate was prepared i n a c y l i n d r i c a l one p a r t r e a c t o r w i t h a volume of about 125 ml. Three inches of 1/4" monel tub i n g was s o l d e r e d to the top of t h i s r e a c t o r which was then f i t t e d w i t h a Whitey v a l v e . ( i i ) Attempted r e a c t i o n s w i t h t i n tetrabromide were c a r r i e d out i n v e s s e l s c o n s i s t i n g of two p a r t s , the upper p a r t f i t t e d w i t h a Hoke v a l v e (No. 431) and a 1/4" Swagelock connector. The lower p a r t was a hollow c y l i n d r i c a l c o n t a i n e r approximately 100 ml i n content. A t i g h t s e a l was achieved w i t h t e f l o n r i n g s i n s e r t e d i n a groove. 2. Dry Box Water s e n s i t i v e samples were handled i n a dry box f i l l e d w i t h an i n e r t n i t r o g e n atmosphere. The dry box was s u p p l i e d by Vacuum Atmosphere C o r p o r a t i o n , Model HE-43-2 D r i Lab. The L grade n i t r o g e n was used as an i n e r t atmosphere and was c i r c u l a t e d through the D r i T r a i n Model HE-93B. Regeneration of the Linde molecular s i e v e s was done at r e g u l a r i n t e r v a l s to m a i n t a i n the dry atmosphere i n the box. 3. I n f r a r e d , Raman and Mossbauer C e l l s The i n f r a r e d s p e c t r a of a l l the s o l i d samples were taken using - 35 -C s l , AgCl or KRS-5 windows. The spectra were taken either on the neat ground powder or on a nujol mull of the sample. Thin films of the compounds or mulls were used between the plates. A l l water sensitive samples were mounted i n the dry box. The Raman c e l l s for the soli d s were made from 5 mm O . D . pyrex tubing with a f l a t bottom. The c e l l s were f i l l e d i n the dry box and flame sealed afterward. The two part Mo'ssbauer c e l l s were made of brass and were f i t t e d with mylar windows. They were c i r c u l a r being 29 mm i n diameter and 10 mm deep. Samples weighing approximately 70 mg were loaded inside a, t h i n t e f l o n ring CO.5 mm thick) contained i n the bottom part of the c e l l . The other half of the c e l l was then threaded into place sandwiching the sample between the windows. 4. Table of Suppliers Material Source Remarks Kel-F traps Kontes thermocouple gauge Hel i c o i d test gauge Swagelock and Cajon f i t t i n g s , Whitey valves Hoke valves Hot p l a t e - s t i r r e r Teflon coated s t i r r i n g bars I.R. c e l l windows Argonne National Labora-t o r i e s , Chicago, 111. Kontes of I l l i n o i s , Measures pressures Franklin Park, I l l i n o i s from 10~3 to 1 mm Hg American Chain and Cable Measures pressures Co., Bridgeport,New Jersey from 1 to 103 mm Hg Columbia Valves and F i t t -ings, Vancouver, B.C. Hoke Inc., C r e s k i l l , N.J. Fisher S c i e n t i f i c , Van. Canlab, Vancouver Harshaw Chemicals, Cleveland Ohio. - 36 -C. Anhydrous HF S o l v o l y s i s Apparatus The r e f l u x r e a c t o r i s shown i n Figure 6 and the monel ma n i f o l d i n F i g u r e 7. The r e a c t o r was normally charged i n the dry box and attached to the m a n i f o l d at A. Anhydrous HF was d i s t i l l e d from a K e l - F trap and CFCl^, i f necessary, from a g l a s s storage v e s s e l attached at B. Dry (L grade) n i t r o g e n was a l s o l a t e r admitted through B and a d r y i n g tube f i l l e d w i t h phosphorus pentoxide was attached at C. D. Reactions i n Anhydrous Hydrogen F l u o r i d e In a t y p i c a l r e a c t i o n , the f i r s t step was to vacuum d i s t i l l t r i -chlorofluoromethane, i f necessary, i n t o the r e a c t o r . The r e a c t o r was then allowed to warm to room temperature and the contents were s t i r r e d using an e x t e r n a l hot plate-magnetic s t i r r e r to achieve s o l u t i o n or d i s p e r s i o n of the s u b s t r a t e . The r e a c t o r was quenched i n l i q u i d n i t r o g e n and anhydrous HF was admitted. When s m a l l volumes were necessary, they were v i s u a l l y judged by d i s t i l l a t i o n from the t r a n s l u c e n t K e l - F t r a p s . At t h i s p o i n t , the r e f l u x dewar was f i l l e d w i t h a t r i -c h l o r o e t h y l e n e - d r y i c e mixture at about -78°C. The e n t i r e m a n i f o l d , e x c l u d i n g the r e a c t o r , was then f i l l e d w i t h dry N 2- The r e a c t o r would then be warmed to room temperature and higher i f necessary using an o i l bath on the hot p l a t e - s t i r r e r . The Whitey v a l v e on the r e a c t o r was opened and the cooled dewar prevented l o s s of HF or C F C l y Once the r e a c t o r was opened, pressures could be monitored u s i n g the H e l i c o i d t e s t gauge. The gases produced were allowed to pass out of the manifold v i a the d r y i n g tube and could be c h a r a c t e r i z e d as HC1 or hydrocarbon (CH^) at the e x i t . - A f t e r the r e a c t i o n was completed, a l l v o l a t i l e products were removed from the r e a c t o r by vacuum d i s t i l l a t i o n and pumping. Figure 6. H F Monel metal reflux reactor Whitey valve (IKS 4 ) Silvered dewar flask rubber stopper D e c o m p r e s s e d air cooling - Teflon gasket Two part monel metal reactor (Volume ^ 130 c c . ) F i g u r e 7. Monel V a c u u m Line. - to p u m p U g l a s s W w K1 w • w -U C a j o n g l a s s to m e t a l un ion W W h i t e y - v a l v e ( I K S 4 ) T C a j o n T - p i e c e K 1, K 2, K e l - F t u b e X C a j o n c r o s s p i e c e G H e l i c o i d t e s t g a u g e (1-tOOOmm) T G , T h e r m o c o u p l e g a u g e t u b e (1-1OOO/-0 D T o H F t a n k A , B , C , L i n e i n l e t - o u t l e t UJ 0 0 K 2 - 39 -The contents of the r e a c t o r were examined i n the dry box. E. Reactions i n Aqueous Hydrogen F l u o r i d e A simple 400 ml nalgene beaker was used as the r e a c t o r . The s u b s t r a t e was f i n e l y ground i n a mortar and p e s t l e and a f t e r being t r a n s f e r r e d to the beaker, aqueous HF was poured on u n t i l the sample was completely submerged. Methanol was added i n some cases to achieve b e t t e r " w e t t i n g " of the s u b s t r a t e . The beaker was placed on a hot p l a t e and the excess HF s l o w l y evaporated at a temperature of about 50°. The product was scraped out of the beaker and was subjected to f u r t h e r d r y i n g i n a 120° oven. F. F l u o r o s u l p h o n a t i n g Reactions The erlenmeyer r e a c t o r was used and was charged w i t h SnCl2F2 a n d a t e f l o n coated magnetic s t i r r e r i n the dry box. A f t e r removal from the dry box and subsequent flame s e a l i n g of the top i n l e t of the r e a c t o r , the erlenmeyer was attached to a vacuum l i n e . Excess ^£^6^2' C10S0 2F or BrOS0 2F was d i s t i l l e d onto the S n C ^ F ^ The r e a c t o r was c l o s e d and heated and s t i r r e d on an o i l bath over a hot p l a t e - s t i r r e r . V o l a t i l e m a t e r i a l s were then pumped o f f under vacuum and the r e a c t o r was opened i n the dry box f o r examination of products. G. P h y s i c a l Methods 1. I n f r a r e d spectroscopy I n f r a r e d s p e c t r a i n the range 3000 cm 1 to 250 cm 1 were obtained on a P e r k i n Elmer Model 457 g r a t i n g i n f r a r e d spectrophotometer. - 40 -2. Raman spectroscopy Raman s p e c t r a were recorded on a Cary model 81 spectrophotometer equipped w i t h a Spectra-physics model 125 He-Ne l a s e r as a source of o e x c i t i n g . l i g h t of wavelength 6328 A. 3. Mossbauer spectroscopy The Mossbauer s p e c t r a were obtained on a constant a c c e l e r a t i o n type spectrometer. I t c o n s i s t e d of an e l e c t r o m e c h a n i c a l v e l o c i t y transducer (TMC Model 305) d r i v e n at a constant a c c e l e r a t i o n by a TMC Model 306 wave-form generator and was phase-locked to a 400 channel 119m analyze r . The source (BaSnO^ enriched w i t h Sn) embedded i n a Pd m a t r i x was mounted on the transducer. A f t e r passing through the absorber, the y~ rays from the source were detected by a Reuter Stokes RSG-60 p r o p o r t i o n a l counter w i t h 1 atmosphere Xe/N^ as f i l l gas and fed i n t o the Nuclear Chicago 33-15 s i n g l e channel a n a l y z e r and then to the 400 channel memory. The spectrum could be seen on the o s c i l l o -scope (Hewlett Packard Model 120B) and was p r i n t e d out a f t e r completion on a t y p e w r i t e r (IBM model 44-16). The output data were f i t t e d onto L o r e n t z i a n curves by use of the 360/67 computer and the i n f o r m a t i o n about peak i n t e n s i t y , quadrupole s p l i t t i n g s and the isomer s h i f t could be obtained i n terms of channel numbers. The v e l o c i t y s c a l e s were c a l i b r a t e d w i t h N a t i o n a l Bureau of Standards (NBS) sodium n i t r o p r u s s i d e c r y s t a l absorber of 1.726 mm/sec. The isomer s h i f t s were c a l i b r a t e d 119 w i t h a Sn0 2 sample enriched i n Sn. Samples were placed i n the brass c e l l and the s p e c t r a were taken w i t h the c e l l at e i t h e r 77°K or 298°K. - A l -i i . A n a l y s i s and C h a r a c t e r i z a t i o n T i n and f l u o r i n e microanalyses were obtained from the A. Bernhardt M i c r o a n a l y t i c a l L a b o r a t o r i e s , Germany. Carbon and hydrogen micro-analyses were c a r r i e d out i n t h i s department by Mr. Peter Borda. C h l o r i n e was determined i n t h i s l a b by p o t e n t i o m e t r i c t i t r a t i o n . The f o l l o w i n g t a b l e summarizes the a n a l y s i s , m e l t i n g or decomposition p o i n t and other c h a r a c t e r i s t i c f e a t u r e s of the new compounds. Compound Analysis T h e o r e t i c a l Found H Sn Cl Sn Cl Melting or Decomposition Point Remarks CH 3SnF 3 6.30 1.59 62.23 - 29.88 6.30 1.80 62.34 - 29.96 327°d S l i g h t l y grey powder. Only very s l i g h t l y water s e n s i t i v e CH 3SnCl 2F 53.07 31.71 8.50 52.94 30.1 8.59 ^160°d White powder. S o l i d condenses i n upper regions of melting point tube at 160°. Hydrolyzes r e a d i l y . (CH 3) 2SnClF 11.82 2.96 58.42 17.45 9.35 11.88 2.88 58.32 17.2 9.45 ^155°d White powder. S o l i d condenses i n upper regions of melting point tube at 155°C. Hydrolyzes r e a d i l y . S n F 2 ( S 0 3 F ) 2 - 33.45 21.42 33.29 21.59 ^235°d S l i g h t l y pale yellow powder. Extremely water s e n s i t i v e . - 43 -I I I . RESULTS AND DISCUSSION A. Synthesis 1. Reactions i n Anhydrous HF (a) Apparatus The r e f l u x apparatus shown i n Figure 6 i n c o n j u n c t i o n w i t h the monel ma n i f o l d shown i n Figure 7 was found to be very s u i t a b l e f o r the s y n t h e s i s of m e t h y l t i n ( I V ) f l u o r i d e s and c h l o r i d e - f l u o r i d e s . The open r e f l u x apparatus was found to have s e v e r a l advantages over a c l o s e d monel r e a c t o r : (1) HF s o l v o l y s i s of SnCl^ i n a c l o s e d system d i d not y i e l d SnCl2F2 but r a t h e r gave a heterogeneous product of unknown composition. However, when SnCl^ was s o l v o l y z e d w i t h HF i n the r e f l u x apparatus, SnCl2p2 was r e a d i l y obtained as a white, homogeneous powder. (2) The r e f l u x apparatus, being open to the h e l i c o i d t e s t gauge, allowed one to monitor the pressure i n the r e a c t o r and thus gave an i n d i c a t i o n of whether any r e a c t i o n was o c c u r r i n g at a given temperature s i n c e the expected v o l a t i l e by-products, HC1 (b.p. -83.1°C) and/or CH^ (b.p. -161.5 PC), could pass out of the r e f l u x tube Ctemp. = -78°C). By u s i n g the pressure gauge as a r e a c t i o n i n d i c a t o r , temperatures could be e a s i l y adjusted u n t i l r e a c t i o n was apparent. The end of a r e a c t i o n could a l s o be determined e a s i l y t h i s way. (3) Since v o l a t i l e products (HC1 and/or CH^) were expected, a sudden p r e s s u r e , i n c r e a s e could occur at higher r e a c t i o n temperatures i n - 44 -a sealed v e s s e l . However, the r e f l u x apparatus could be heated to an o i l bath temperature of 120°C and any v o l a t l l e s produced could escape from the r e a c t o r i n t o the fume hood v i a the d r y i n g guard tube, thereby e l i m i n a t i n g the pressure problem. As w e l l as these advantages, at l e a s t two l i m i t a t i o n s of the apparatus were evident: (1) I f the o i l bath was heated to temperatures much above 120°C, the HF and CFCl^ would tend to escape from the r e a c t o r past the cooled r e f l u x tube. As a r e s u l t , t h i s temperature was not exceeded and f o r the work described here, i t was found to be a s u f f i c i e n t l y high temperature. However, i f higher temperatures would he needed, the r e f l u x system would have to be adapted by lengthening the r e f l u x tube and dewar. (2) For the higher temperature r e a c t i o n s , tedium was experienced by the n e c e s s i t y of adding dry i c e to the r e f l u x dewar at approximately f i v e minute i n t e r v a l s . However, i n s p i t e of these two minor l i m i t a t i o n s , the apparatus was found to f u n c t i o n e x c e l l e n t l y f o r the r e q u i r e d purposes. For a l l r e a c t i o n s , a t e f l o n coated magnetic s t i r r i n g bar was added i n t o the r e a c t o r which was then a c t i v a t e d e x t e r n a l l y w i t h a hot p l a t e - s t i r r e r . The s t i r r i n g allowed f o r i n t i m a t e mixing of the HF i n s o l u b l e s u b s t r a t e or CFCl^ i m m i s c i b l e s o l u t i o n of the s u b s t r a t e w i t h HF. (b) Reaction d e t a i l s and r e s u l t s The d e t a i l s of the i n d i v i d u a l s o l v o l y s i s r e a c t i o n s are summarized i n Table 4. The w e l l known compounds, ( C H ^ S n F and ( C H ^ S n F ^ were c h a r a c t e r i z e d from microanalyses and i . r . s p e c t r a . S e v e r a l c onclusions may be made upon examination of the r e s u l t s i n Table 4: - 45 -TABLE 4 Reactions of Various M e t h y l t i n ( I V ) Compounds and T i n T e t r a c h l o r i d e w i t h Anhydrous HF Substrate mmoles mmoles o i l bath r e a c t i o n HF temp(°C) time(hr) Reaction Products 1) (CH 3) 4Sn 5.6 ^1000 25 0.7 (CH 3) 3SnF + CH 4 2) (CH 3) 4Sn 7.0 -vlOOO 130 max 4.0 5.5 mmoles ( C H ^ S n F , 1.5 mmoles ( C H 3 ) 2 S n F 2 + CH, 3) ( C H 3 ) 3 S n C l 12.0 ^1000 130 max 15.0 ( C H 3 ) 2 S n F 2 + HC1 + CH 4 4) ( C H 3 ) 3 S n C l 74.0 26.0 25 2.0 (CH 3) 3SnF + HC1 + (CH 3) 3SnCl(unreacted) 5) ( C H 3 ) 2 S n C l 2 6) ( C H 3 ) 2 S n C l 2 41.0 25.0 5.9 -^1000 130 max 7.0 25 7.0 ( C H 3 ) 2 S n F 2 + HC1 (CH 3) 2SnClF + HC1 + (C H 3 ) 2 S n C l 2 ( u n r e a c t e d ) 7) (CH 3) 2Sn0 8) C H 3 S n C l 3 15.0 -^1000 130 max . 1.5 18.0 -vlOOO 130 max 18.0 ( C H 3 ) 2 S n F 2 + H 20 CH 3SnF 3 + HC1 9) C H 3 S n C l 3 10) SnCl. 11) SnCl. 15.0 200 92 15.0 25 4.0 250 65 max 7.0 50 25 4.5 CH 3SnCl 2F + HC1 + CH 3 S n C l 3 (unreacted) S n C l 2 F 2 + HC1 S n C l 2 F 2 + HC1 + S n C l 4 (unreacted) 50 ml CFC1 3 added; excess s u b s t r a t e removed from product by s u b l i m a t i o n under vacuum at 50°C max. - 46 -(1) As can be c l e a r l y seen, both the Sn-Cl and the Sn-CH^ bond can be cleaved. The order of bond cleavage i s Sn-Cl before Sn-C. This p o i n t can be concluded from the r e s u l t s f o r r e a c t i o n s 4-6 and 8-9. A l s o , i n the case of ( C H ^ S n C ^ and CH^SnCl.^, complete cleavage of Sn-Cl was p o s s i b l e under the r e a c t i o n c o n d i t i o n s employed whereas Sn-C cleavage d i d not occur. Reaction 7 i n d i c a t e s that Sn-0 bond cleavage a l s o occurs before Sn-C bond cleavage. The f a c t that the Sn-Cl bond i s more e a s i l y cleaved than the Sn-CH^ bond r e f l e c t s d i f f e r e n c e s i n bond p o l a r i t i e s as a consequence of e l e c t r o -n e g a t i v i t y d i f f e r e n c e s , however t h i s r a t i o n a l e does not e x p l a i n the 18 observations of Wang and Shreeve where r e l a t i v e l y weak p r o t o n i c a c i d s were used. (2) Stepwise cleavage may be achieved by c o n t r o l l i n g the r e a c t i o n temperature and the mole r a t i o s of s u b s t r a t e to a c i d . Thus, i n the case of (CH^^Sn, (CH 3) 3SnF r e s u l t s at room temperature whereas ( C H 3 ) 2 S n F 2 i s formed at h i g h temperature. (CH 3) 2SnClF i s formed at room temperature when the mole r a t i o of HF: ( C H 3 ) 2 S n C l 2 i s < 1, but ( C H 3 ) 2 S n F 2 i s formed at h i g h temperature w i t h a l a r g e excess of HF. F i n a l l y , CH 3SnF 3 forms from C H 3 S n C l 3 at h i g h temperature w i t h excess HF and CH 3SnCl 2F i s the product at room temperature w i t h the r e q u i r e d s t o i c h i o m e t r i c amount of HF. CH 3SnF 3 was not o b t a i n a b l e under i d e n t i c a l r e a c t i o n c o n d i t i o n s from ( C H ^ S n , (CH 3) 2SnO or e i t h e r of the other two m e t h y l t i n ( I V ) c h l o r i d e s , ( C H 3 ) 3 S n C l or ( C H 3 ) 2 S n C l 2 ( r e a c t i o n s 2, 3, 5 and 7) where ( C H 3 ) 2 S n F 2 appears to be the f i n a l product. I t can be argued, that i n t h i s 37 compound, the Sn-C bond i s e x c e p t i o n a l l y short and t h e r e f o r e more s t a b l e toward s o l v o l y s i s . The f a c t that a l l r e a c t i o n s seem to proceed i n a stepwise manner - 47 -makes r e a c t i o n s 6 and 9 extremely a t t r a c t i v e routes f o r the s y n t h e s i s of the h i t h e r t o unknown m e t h y l t i n ( I V ) c h l o r i d e - f l u o r i d e s . T h i s occurs because the i n i t i a l . c h l o r i d e - f l u o r i d e formed i s i n s o l u b l e i n CFCl-j and w i l l p r e c i p i t a t e out of s o l u t i o n thereby making f u r t h e r r e a c t i o n p o s s i b l e only by the heterogeneous contact of l i q u i d HF and the s o l i d . A s e p a r a t i o n of the new compounds from the excess ( C H ^ ^ S n C ^ or CH^SnCl^ i s e a s i l y accomplished e i t h e r by s u b l i m a t i o n or by s o l v e n t e x t r a c t i o n w i t h C C l ^ or CHC1 3. The i n s o l u b i l i t y of ( C H ^ S n C l F and CH^SnC^F i n these s o l v e n t s may be taken as i n i t i a l evidence f o r t h e i r polymeric or i o n i c nature. Only CH^SnCl^F was found to be n o t i c e a b l y sublimable at temperatures of ^90°C and a pressure of 10 mm Hg. The s u b l i m a t i o n i s found to be very slow but the compound can be p u r i f i e d t h i s way. A l l attempts to s y n t h e s i z e the l a s t m i s s i n g m e t h y l t i n ( I V ) c h l o r i d e -f l u o r i d e , CH 3SnClF2, i n a pure form were u n s u c c e s s f u l . Reactions between CH^SnCl^ and anhydrous HF i n a mole r a t i o of 1:1.5-2.0 r e s u l t e d i n the formation of products of roughly the r e q u i r e d composition ( C l a n a l y s i s ) 119 but both i n f r a r e d and Sn Mossbauer s p e c t r a i n d i c a t e d a mixture. I t appears that once CH^SnC^F i s formed, f u r t h e r s o l v o l y s i s does not proceed i n two d i s t i n c t steps. An attempt to o b t a i n CH 3SnClF2 by p y r o l y s i s of CH^SnC^F y i e l d e d a s i m i l a r r e s u l t . I t was noted that CH^SnC^F^ decomposed at ^ 160°C and one atmosphere pressure w i t h the r e l e a s e of CH^SnCl^, thus suggesting the p o s s i b l e r e a c t i o n : 2CH 3SnCl 2F 1 6 0 C • CH 3SnClF 2 + C H 3 S n C l 3 - 48 -However, a n a l y s i s i n d i c a t e d that a mixture of presumably CH^SnF^ and CH 3SnClF 2 was formed. The s o l v o l y s i s of the m e t h y l t i n ( I V ) c h l o r i d e s has t h e r e f o r e r e s u l t e d i n the s u c c e s s f u l p r e p a r a t i o n of CH 3SnF 3, ( C H ^ S n C l F and CH^SnCl^F. The r e a c t i o n route has a l s o provided an a l t e r n a t i v e method f o r o b t a i n i n g ( C H ^ S n F , CCR 3) 2SnF 2 and SnCl The s o l v o l y s i s of SnCl^ w i t h HF y i e l d e d a product i d e n t i c a l w i t h 48 S n F 2 C l 2 s y n t h e s i z e d by Dehnicke as evidenced by i t s m i c r o a n a l y s i s , decomposition p o i n t and i n f r a r e d spectrum. Samples obtained from HF s o l v o l y s i s were v e r y pure, whereas i n our experience, f l u o r i n a t i o n w i t h C1F o r , as recommended by Dehnicke, a C1F 3/C1 2 m i x t u r e , l e d very e a s i l y 119 to higher f l u o r i n a t e d products as was very apparent from the Sn Mossbauer s p e c t r a obtained on some of the samples. Attempts to o b t a i n a S n C l 3 F by r e a c t i n g an excess of SnCl^ w i t h HF ( r e a c t i o n 11) at room temperature r e s u l t e d i n the formation of S n C l 2 F 2 o n l y . P r e p a r a t i o n of ( C H 3 ) 2 S n F 2 and ( C H ^ S n F v i a s o l v o l y s i s of ( C H ^ S n , ( C H 3 ) 3 S n C l and ( C H 3 ) 2 S n C l 2 i n anhydrous HF does not appear to be e i t h e r a simple or p r a c t i c a l convenient route to these f l u o r i d e s . S o l v o l y s i s i n aqueous HF, as w i l l p r e s e n t l y be d i s c u s s e d , d i d provide a convenient route to these f l u o r i d e s . (c) Other attempted s o l v o l y s i s r e a c t i o n s ( i ) SnBr^ Numerous attempts to s o l v o l y z e SnBr^ w i t h HF y i e l d e d only unreacted SnBr. and no b r o m i d e - f l u o r i d e could be i s o l a t e d . 4 Reactions were c a r r i e d out i n both the r e f l u x r e a c t o r and c l o s e d two p a r t monel r e a c t o r s u s i n g v a r i o u s temperatures up to a maximum - 49 -of 130°. In the case of the r e f l u x r e a c t o r , the dewar was f i l l e d w i t h a CHCl^/dry i c e s l u s h (y -65°C) which provides a temperature above the normal b o i l i n g p o i n t of HBr (-67°C). ( i i ) ( C 6 H 5 ) 2 S n C l 2 An attempt to prepare CCgH.^)2SnClF i n a manner analogous to th a t f o r r e a c t i o n 6 i n Table 4 y i e l d e d , a f t e r e x t r a c t i o n of the excess (C,H C) ^ SnCl- w i t h CC1, , a c h l o r i d e f r e e product which o 5 I I 4 analyzed f o r C (22.45%), H (2.65%) where even CgH 5SnF 3 r e q u i r e s C (28.5%), H (1.98%). I t was concluded t h a t a p p r e c i a b l e Sn-C cleavage was o c c u r r i n g which i s c o n s i s t e n t w i t h the cleavage order C^H^ > CH^ shown on page 3. ( i i i ) V i n y l t i n ( I V ) d e r i v a t i v e s Attempts to prepare d i v i n y l t i n ( I V ) d i f l u o r i d e , v i n y l t i n ( I V ) t r i f l u o r i d e as w e l l as mixed v i n y l t i n ( I V ) c h l o r i d e - f l u o r i d e s were undertaken. In each case, the r e f l u x apparatus was used. The d e t a i l s of the r e a c t i o n s are summarized i n Table 5. As can be seen f o r r e a c t i o n s 1 to 4, the carbon a n a l y s i s found i s lower than the t h e o r e t i c a l one f o r ( C 2 H 3 ) 2 S n F 2 . Reaction 7, an attempt at C^^SnF^, shows an a n a l y s i s f a r removed from the t h e o r e t i c a l one f o r the t r i f l u o r i d e . Reactions 5 and 8, attempts at mixed c h l o r i d e - f l u o r i d e s , a l s o gave values f o r C and H a n a l y s i s which d i d not f i t w i t h any t h e o r e t i c a l p o s s i b i l i t y . Again, i t appears t h a t some Sn-C cleavage occurred and t h i s i s not too s u r p r i s i n g s i n c e v i n y l > methyl w i t h respect to ease of Sn-C cleavage as shown on page 3. - 50 -TABLE 5 S o l v o l y s i s Reactions of V i n y l t i n ( I V ) Compounds w i t h Anhydrous HF Substrate mmoles mmoles O i l bath Reaction S o l i d product a n a l y s i s ' HF temp(°C) time(hr) and gaseous products 1) ( C 2 H 3 ) 4 S n 2) ( C 2 H 3 ) 4 S n 3) ( C 2 H 3 ) 4 S n 4) ( C 2 H 3 ) 2 S n C l 2 7 ^1000 7 %1000 15 'vlOOO 30 30 25 2.0 2.0 'vlOOO 130 max 2.0 2.0 C 21.95; H 3.15 + C 2 H 4 b C 20.16; H 2.92 + C 2 H 4 b C 13.75; H 2.74 + C 2 H 4 b C 20.33; H 2.59; C l 0.00 + HC1 5) ( C 2 H 3 ) 2 S n C l 2 29 20 25 5.0 C 19.51; H 2.18; C l undetermined + HC1 6) C 2 H 3 S n C l 3 15 -vlOOO 25 5.5 C 10.50; H 1.57; C l 11.7 + HC1 7) C 2 H 3 S n C l 3 15 ^1000 110 10 C 3.67; H 1.53; C l 0.00 + HC1 8) C 2 a 3 S n C l 3 24 15 25 5.0 C 13.97; H 2.33; C l undetermined + HC1 ^50 ml CFC1 3 added. T h e o r e t i c a l C(%) H(%) C l ( % ) C 2 H 3 S n C l 2 F 10.19 1.28 30.09 C 2 H 3 S n C l F 2 10.96 ,1.38 16.17 C 2H 3SnF 3 11.85 1.49 -( C 2 H 3 ) 2 S n F 2 22.79 2.87 -( C 2 H 3 ) 2 S n C l F 21.14 2.66 15.60 c h a r a c t e r i z e d by i . r . 2. Reactions i n Aqueous (M8%) HF Aqueous HF was found to be a convenient f l u o r i n a t i n g agent and y i e l d e d the d i f l u o r i d e s of d i m e t h y l t i n , d i e t h y l t i n , d i p r o p y l t i n , d i b u t y l t i n and d i o c t y l t i n from t h e i r corresponding d i c h l o r i d e s . D i m e t h y l t i n oxide underwent s o l v o l y s i s to give d i m e t h y l t i n d i f l u o r i d e as i n the case of anhydrous HF s o l v o l y s i s . T e t r a m e t h y l t i n s o l v o l y z e d to y i e l d n e e d l e - l i k e c r y s t a l s of (CH^^SnF whereas (CH^^SnCl gave (CH^^SnF w i t h a powdery t e x t u r e . A l l the products are known compounds and were c h a r a c t e r i z e d by C and H microanalyses. C e r t a i n l y , t h i s s y n t h e t i c method f o r o b t a i n i n g f l u o r i d e s was found to be a simple one and c o n t r a s t s that of the i n v o l v e d anhydrous HF r e a c t i o n s . I t s v a l u e l i e s i n that i t g i v e s a f a s t method f o r o b t a i n i n g only the d i f l u o r i d e s (except f o r (CH^J^SnF) as the c h l o r i d e - f l u o r i d e s 44 are water s e n s i t i v e . Hobbs and Tobias mention the use of aqueous HF on d i m e t h y l t i n oxide to y i e l d d i m e t h y l t i n d i f l u o r i d e but no other s i m i l a r use of aqueous HF can be found i n the present l i t e r a t u r e . .Aqueous HF, l i k e anhydrous HF, cleaves both the Sn-Cl and Sn-0 bond p r i o r to the Sn-C bond although no Sn-C cleavage was observed w i t h aqueous HF except f o r the case of (CH^^Sn where an 11% y i e l d of (CH^^SnF was obtained i n the form of w e l l c r y s t a l l i z e d needles. Attempts to s o l v o l y z e CH^SnCl^ d i d not y i e l d the t r i f l u o r i d e presumably because of the hygroscopic nature of CH^SnCl^. Reactions of ^ 2 ^ ) 2SnCl2 a n d (^5^5) 2^Ti^2 w ^ t ^ a < l u e o u s HF again d i d not give the d e s i r e d d i f l u o r i d e s as was evident from the obtained C and H a n a l y s i s f o r the phenyl compound which showed values lower than those expected f o r d i p h e n y l t i n d i f l u o r i d e . D i v i n y l t i n ( I V ) d i c h l o r i d e presumably - 52 -84 gave the reported d i h y d r a t e upon a d d i t i o n of aqueous HF and d i d not seem to undergo a c l e a r - c u t c h l o r i d e exchange w i t h HF. D i b e n z y l t i n d i c h l o r i d e was reacted w i t h aqueous HF but the low C and H values obtained w i t h respect to the t h e o r e t i c a l values of the d i f l u o r i d e suggested once again that some Sn-C cleavage had occurred. 3. P r e p a r a t i o n of S n F 2 ( S 0 3 F ) 2 (a) From S n C l 2 F 2 A convenient route f o r the p r e p a r a t i o n of SnF 2(SO.jF) 2 was found i n the r e a c t i o n of SnCl„F„ w i t h e i t h e r excess S„0,F„ or C10S0 oF. / I 2. o z z Replacement of C l i n S n C l 2 F 2 was e a s i l y accomplished i n a r e a c t i o n l a s t i n g about 40 hours at a maximum temperature of 50°C i n an erlenmeyer r e a c t o r . A t e f l o n coated s t i r r i n g bar i n the r e a c t o r served the f u n c t i o n of m i x i n g the s o l i d s u b s t r a t e and l i q u i d f l u o r o s u l p h o n a t i n g reagent s i n c e the r e a c t i o n was apparently heterogeneous; The p h y s i c a l p r o p e r t i e s of SnF 2(S0.jF) 2 are comparable to the p r e v i o u s l y s y n t h e s i z e d SnCSO^F)^ and S n C l 2 ( S 0 3 F ) 2 . ~ ^ A l l are r e l a t i v e l y h i g h m e l t i n g , hygroscopic white s o l i d s which are i n s o l u b l e i n nonpolar s o l v e n t s and are only very s l i g h t l y s o l u b l e i n f l u o r o s u l p h u r i c a c i d (HS0 3F). (b) Other attempts ( i ) From S n C l 2 ( S 0 3 F > 2 An attempt to cleave the Sn-Cl bond i n t h i s compound usi n g anhydrous HF d i d not meet w i t h any success. The r e f l u x apparatus used i n the other anhydrous HF s o l v o l y s i s r e a c t i o n s was employed here. A f t e r repeated h e a t i n g of the r e a c t i o n m i x t u r e , c h l o r i d e was s t i l l found to be present i n the product. - 53 -Another attempt to cleave the Sn-Cl bond was made using a sealed two p a r t monel r e a c t o r which d i d not possess a r e f l u x tube. C h l o r i n e monofluoride was used as the f l u o r i n a t i n g agent i n t h i s case. Again the product formed was found to c o n t a i n c h l o r i n e even a f t e r repeated h e a t i n g . The i . r . spectrum a l s o i n d i c a t e d t h a t some breakdown of the SO^F bridged s t r u c t u r e had occurred. ( i i ) From SnF 2 Stannous f l u o r i d e was heated w i t h S_0,F o to a maximum tempera-/ o I t u r e of 100° i n an erlenmeyer r e a c t o r f o r 12 hours i n an attempt to o x i d i z e the SnF 2 to S n F 2 ( S 0 3 F ) 2 . However, v i r t u a l l y no weight i n c r e a s e was observed f o r the s o l i d r e s i d u e remaining a f t e r the heating p e r i o d . - 54 -B. V i b r a t i o n a l Spectra 1. Methyltin(IV) fluorocompounds. The v i b r a t i o n a l frequencies i n the range of 1000-250 cm ^ are l i s t e d i n Table 6 for a l l the methyltin(IV) f l u o r i n e d e r i v a t i v e s . The C-H s t r e t c h i n g modes (found at 2870-3000 cm ^) as w e l l as the bending modes (1420 and 1215 cm "*") were found to vary only very s l i g h t l y f o r a l l compounds, therefore i n t e r e s t i s d i r e c t e d toward the frequency range below 1000 cm ''"where the tin-carbon and tin-halogen s t r e t c h i n g modes are expected. 43 45 79 Agreement with previous reports on the spectra of (CH^^SnF * ' 44 and (CH 3) 2SnF2 i s good with respect to peak p o s i t i o n and assignment. 44 45 As found previously, ' no Raman absorption was noted i n the region of 340-360 cm where very strong and broad i n f r a r e d bands are found, due to the s t r e t c h i n g mode or modes i n v o l v i n g t i n and bri d g i n g f l u o r i n e . 36 37 As i s obvious from the Sn-F distances reported f o r both compounds, ' 37 the t i n - f l u o r i n e bond i s weak and very polar so that detection by Raman spectroscopy on s o l i d compounds becomes a d i f f i c u l t task. The same observation can be made for the new compounds. A l l have strong and broad i n f r a r e d bands i n the region of 365-425 cm ^ with no corresponding Raman bands. These bands are assigned to Sn-F bri d g i n g s t r e t c h i n g modes. Ca) CH 3SnF 3 For CH 3SnF 3 , (the i . r . spectrum i s shown i n Figure 8) an i n f r a r e d a c t i v e doublet at 646 and 629 cm ^ with only one counterpart i n the Raman spectrum (644 cm "*") i s assigned to a s t r e t c h i n g mode in v o l v i n g t i n and f l u o r i n e i n a terminal p o s i t i o n . The bands appear at a Table 6 Vi b r a t i o n a l Frequencies of Some Methyltin(IV)-Fluorine Compounds Compounds: (1) (2) (3) (4) (5) (CH 3) 3SnF (CH 3) 2SnF 2 CH 3SnF 3 ( C H ^ S n C l F CH 3SnCl 2F Assignment IR Raman IR Raman IR Raman IR Raman IR Raman [cm - 1]Int [cm _ 1]Int [cm~ 1]Int [cm - 1]Int [cm - 1]Int [cm _ 1]Int [cm - 1]Int [cm - 1]Int [cm - 1]Int [cm -l]Int 780 vs,b n.o. 788 vs,b n.o. 822 vs,b n.o. 796 vs,b n.o. 795 vs n.o. Sn-CH 3 rock f o n V S f 644 s Sn-F k s t r e t c h o29 s \ t 555 s n.o. 559w 598 vs n.o. 582 s 588 mw Sn-C s t r e t c h , S , R j asym. Z Z Z v s \ 544 vs 5 5 5 s 558ms Sn-C s t r e t c h 535 s i 521 s 536 528 ms 536 vs Sn-C s t r e t c h sym. 335 vs,b n.o. 360 vs,b n.o. 425 vs,b n.o. 365 vs,b n.o. 398 vs,b n.o. S n ~ F b s t r e t c h 385 s,sh 390 m Sn-Cl s t r e t c h , asym. 335 s 334 s Sn-Cl s t r e t c h 370 s 365 vs Sn-Cl s t r e t c h sym. 3 2 2 ™ S n - F t b e n d 7 Sn-C bend? -1 cm : 287 ms f 278 m j In a d d i t i o n to the l i s t e d bands, the following modes were observed: CH 3SnF 3: 2944, 2905, 2886, 1415 and 1212 (CH 3) 2SnClF: 2943, 2929, 2905, 2868, 1410, and 1212 cm - 1; CH 3SnCl 2F: 2944, 2906, 2872 and 1205. Explanation: vs=very strong, s=strong, m=»medium, w=weak, b=broad,sh=shoulder, n.o.=not observed, Int=intensity, asym=asymmetric, sym=symmetric, F =terminal f l u o r i n e , F =bridging f l u o r i n e . 1 t D - 56 -F i g u r e 8. Infrared S p e c t r u m of Mgthvlt in ( iv ) - t r i f luor ide from 1000 to 2 5 0 cm"' 4 2 5 I — 1 1 ' 1000 800 600 400 - 57 -s l i g h t l y higher value than that proposed i n the Introduction of t h i s t h e s i s f o r Sn-F t (y 600 cm "*") , however, the absorption bands are too intense to allow an i n t e r p r e t a t i o n as combination, summation or d i f f e r e n c e bands. The only other a l t e r n a t i v e , the i n t e r p r e t a t i o n as t i n -carbon stretches i s not very r e a l i s t i c e i t h e r as V g n ^ i s u n l i k e l y -1 3 to occur at frequencies higher than 580 cm The doublet at 548 and 535 cm "\ however i s very d e f i n i t e l y due to Sn-CH^ s t r e t c h i n g . Again, s p l i t t i n g i s observed only i n the i n f r a r e d spectrum. The Raman spectrum shows a s i n g l e absorption i n t h i s region at 544 cm 1 The s p l i t t i n g of the Sn-F t and Sn-CH^ modes i s unique to t h i s compound and has not been observed i n the v i b r a t i o n a l spectra of any other methyltin(IV) c h l o r i n e or f l u o r i n e compounds. Such an unprecedented observation requires some dis c u s s i o n . The two peaks i n the doublets can be i n t e r p r e t e d as being caused by a s p l i t t i n g of unique v i b r a t i o n a l modes rather than as being Independent v i b r a t i o n s (symmetric and asymmetric) f o r the following reasons: 1). Only one Sn-C s t r e t c h i n g band i s expected. The two bands at 548 cm 1 and 535 cm 1 cannot be assigned to asymmetric and symmetric Sn-C stretches r e s p e c t i v e l y i f a pentacoordinated structure i n v o l v i n g two F and one CH^ i n a plane with one F i n a bridging p o s i t i o n i s postulated. Such a structure could conceivably be used to i n t e r p r e t the bands at 646 cm 1 and 629 cm 1 as Sn-F t stretches (asymmetric and symmetric), however, the small separation between such modes i s d i f f i c u l t to j u s t i f y . A lso, the Mossbauer spectrum of the compound, which w i l l be presented i n the next s e c t i o n , i n d i c a t e s that the Sn i s i n one environ-ment only. Therefore a hexacoordinated structure i n v o l v i n g a l t e r n a t i n g - 58 -H^C-Sn-CH^ and F-Sn-F u n i t s bridged by f l u o r i n e i s not p o s s i b l e . Such a proposed s t r u c t u r e could g ive r i s e to two s t r e t c h i n g f r e q uencies f o r both Sn-F t and Sn-CH^ i n the i . r . spectrum i f n o n - l i n e a r F-Sn-F and H^C-Sn-CH^ u n i t s are present. 2.) The peak s e p a r a t i o n (y 15 cm 1 ) i n both doublets i s i d e n t i c a l w i t h i n the l i m i t s of e r r o r . This f a c t suggests that the same cause give s r i s e to the s p l i t t i n g of the two modes. V i b r a t i o n a l c o u p l i n g i n the o b v i o u s l y polymeric substance seems to be the most l i k e l y cause f o r the observed s p l i t t i n g . Other p o s s i b l e reasons f o r these s p l i t t i n g s such as f a c t o r group s p l i t t i n g , c r y s t a l l i n e £i.eld s p l i t t i n g , i s o t o p e s p l i t t i n g or c o u p l i n g of i n t e r n a l and e x t e r n a l modes appear to be l e s s l i k e l y i n t h i s case. The assignment of the lower frequency doublets as Sn-C and Sn-F t bending modes i s not supported by the Raman spectrum where no r e l i a b l e spectrum could be obtained i n t h i s low range. I t seems sa f e to conclude that CH^SnF^ contains f l u o r i n e i n both b r i d g i n g and t e r m i n a l p o s i t i o n s . Since no f u r t h e r a b s o r p t i o n i s found i n the Sn-F f c range, i t appears t h a t one f l u o r i n e i s i n the t e r m i n a l p o s i t i o n which leaves two f l u o r i n e s per formula u n i t i n b r i d g i n g p o s i t i o n s , r e s u l t i n g i n hex a c o o r d i n a t i o n around t i n . (b) CH 3SnCl 2F and ( C H ^ S n C l F . Only b r i d g i n g f l u o r i n e seems to be present i n CH^SnC^F and (CH^^SnClF. An assignment of the observed bands i s presented i n Table 6 and i n d i c a t e s that two Sn-Cl s t r e t c h e s are observed f o r the former and two Sn-C s t r e t c h e s f o r the l a t t e r compound. A l l are Raman and i n f r a r e d a c t i v e . I t must be concluded that the Cl- S n - C l and the C-Sn-C groups i n the r e s p e c t i v e compounds are not l i n e a r . The observed - 59 -t i n - c h l o r i n e s t r e t c h f o r (CH^^ShClF i s found i n the same r e g i o n as 46 i n (CH^^SnCl. Some weak c h l o r i n e b r i d g i n g , as was found r e c e n t l y 34 f o r ( C H ^ ^ S n C ^ i n a n x _ r a y d i f f r a c t i o n study, cannot be r u l e d out. An i n t e r e s t i n g aspect regarding the behaviour of (CH^^SnClF appeared w h i l e i . r . s p e c t r a of the compound were being taken. I n f r a r e d s p e c t r a of the product taken p r i o r to i t s s u b l i m a t i o n , necessary f o r the removal of the unreacted (CH^^SnC^, were found to be a b s o r p t i o n f r e e at 598 cm the band c h a r a c t e r i s t i c of the asymmetric Sn-C s t r e t c h i n g mode f o r (CH3)2SnF2« I t was apparent th a t a stepwise cleavage p a t t e r n of ( C H - ^ S n C ^ w a s p o s s i b l e . However s a f t e r the product had the excess ( C H ^ ^ S n C ^ removed by s u b l i m a t i o n -2 and was subjected to f u r t h e r pumping at a pressure of 10 mm Hg f o r ^ 12 hr at room temperature to ensure removal of a l l the d i c h l o r i d e , a small i . r . peak at 598 cm ^ became apparent. I t was concluded t h a t a d i s p r o p o r t i o n a t i o n of the type: 2 ( C H 3 ) 2 S n C l F ^ ( C H ^ S n C l ^ + ( C H 3 ) 2 S n F 2 was o c c u r r i n g . This hypothesis was f u r t h e r s u b s t a n t i a t e d by the f a c t t h a t s u b l i m a t i o n of the compound at room temperature w h i l e being pumped on y i e l d e d a compound c h a r a c t e r i z e d as (CH-j^SnC^ which p e r s i s t e n t l y condensed on the c o l d f i n g e r of the s u b l i m a t i o n apparatus even though no i . r . a b sorptions c h a r a c t e r i s t i c of (CH 3)2SnCl2 could be observed i n the m a t e r i a l p r i o r to i t s placement i n the s u b l i m a t i o n apparatus. - 60 -The s t r e t c h i n g frequencies f o r the t i n - c a r b o n bond have been found to r e s u l t i n extremely sharp a b s o r p t i o n bands, a l l o w i n g a r a t h e r accurate determination of the band p o s i t i o n . This f a c t can be u t i l i z e d i n the i d e n t i f i c a t i o n of the v a r i o u s m e t h y l t i n ( I V ) f l u o r i n e compounds. Fi g u r e 9 shows the band p o s i t i o n s and t h e i r occurrence i n i . r . and/or Raman s p e c t r a f o r the v a r i o u s compounds. These s t r e t c h i n g frequencies can be used to i n d i c a t e the presence of mixtures s i n c e a l l the compounds have Sn-C s t r e t c h e s i n s l i g h t l y d i f f e r e n t p o s i t i o n s . A case i n p o i n t i s the discovered d i s p r o p o r t i o n a t i o n behaviour of (CH 3) 2SnClF. A r a t h e r i n t e r e s t i n g trend i s observed f o r v„ „ . The r a t h e r ° Sn-F, D broad i n f r a r e d band s h i f t s g r a d u a l l y from i t s lowest p o s i t i o n a t 340 cm - 1, (CR 3) 3SnF, as CH 3 i s repl a c e d by C l or F. For CH 3SnF 3, t h i s band centers around 425 cm \ I t seems reasonable to assume that the bond p o l a r i t y of the Sn-F^ bond w i l l decrease and the covalent bond ch a r a c t e r i n c r e a s e when Sn i s coordinated to h i g h l y e l e c t r o n e g a t i v e l i g a n d s . V i b r a t i o n a l c o u p l i n g , as observed f o r CH 3SnF 3, appears to be absent f o r these compounds. 2. Ti n ( I V ) d i f l u o r o - b i s ( f l u o r o s u l p h a t e ) and T i n ( I V ) d i c h l o r o d i f l u o r i d e I t has been pointed out p r e v i o u s l y , 1 ^ 16,50,51 t n a t t ^ e Q symmetry of the f r e e SO-F i o n i s reduced to C when the group acts as a mono-j s dentate or b i d e n t a t e covalent group. A d i s t i n c t i o n between both conformations can be made on the b a s i s of the S-0 s t r e t c h i n g frequencies which are found i n d i f f e r e n t regions of the spectrum. -'OjSl Extensive Figure 9 . T in -Carbon stretching frequencies tor the Methyltin (iv) Fluorine Compounds A sym E C A s y m B s y m C C a s y m D E a s y m B a s y m 500 c m - ' 521 5 3 2 T r ~ 5 3 6 5 4 4 5 4 8 5 5 5 5 5 6 5 3 5 5 8 4 5 9 8 6 0 0 A - ( C H 3 ) 3 S n F B - ( C H s ) 2 S n F ^ C - C H , S n F ^ D - C H ^ S n C l ^ F E - ( C H J , S n C l F ' 3 '2 3 '2" i.r. active only "i.r. and R active R active only - 62 -information of the v i b r a t i o n a l frequencies for bridging SO^F groups has been obtained f o r a number of methyltin(IV) f l u o r o s u l f a t e s ^ and r e c e n t l y , confirmation from an X-ray d i f f r a c t i o n study of (CH 3) 2Sn(S0 3F) could be obtained. Since the i n f r a r e d spectrum of S n F 2 ( S 0 3 F ) 2 gave no i n d i c a t i o n of the c h a r a c t e r i s t i c absorption band f o r Sn-F bridge s t r e t c h i n g , commonly found at 350-450 cm 1 , the presence of b r i d g i n g SO^P groups was considered to be more l i k e l y . That bridging S0.jF groups are indeed present can be seen from Table 7 where the observed i n f r a r e d and Raman bands f o r S n F 2 ( S 0 3 F ) 2 are l i s t e d together with those f o r S n C l 2 ( S 0 3 F ) 2 , 5 0 ( C H 3 ) 2 S n ( S 0 3 F ) 2 , 1 6 86 and KS0 3F. As expected, the number of i n t e r n a l S0 3F v i b r a t i o n a l modes i s increased from 6 f o r S0 3F (3 A^ modes and 3 E modes) to 9 (3 A" modes and 6 A 1 modes). These can be described as 3 S0 3 s t r e t c h i n g modes, 1 SF s t r e t c h , 3 S0 3 bending modes and 2 S0 3 rocking and t o r s i o n a l modes. The two S0 3 s t r e t c h i n g modes at ^1400 and at ^1100 cm 1 can be thought to o r i g i n a t e from the s p l i t t i n g of the E mode at ^1285 cm 1 f o r the S0 3F ion. This s p l i t t i n g apparently increases from ^170 cm 1 to 225 cm - 1 to about 300 cm"1 i n the s e r i e s X 2 S n ( S 0 3 F ) 2 with X being CR^, C l and F r e s p e c t i v e l y . The t i n - S 0 3 F bond apparently becomes more coyalent, the observed trend i s obviously the same as that noted for the methyltin(IV) f l u o r i d e s where the Sn-F^ s t r e t c h was found to increase i n the same d i r e c t i o n . Some small s p l i t t i n g s of v i b r a t i o n a l modes are found i n the s t r e t c h -ing region. This can be explained e i t h e r by a strong v i b r a t i o n a l coupling i n the polymeric framework or by the presence of s l i g h t l y nonequivalent S0 3F groups. The s p l i t t i n g does not seem to be resolvable i n the range of deformation modes. Table 7 V i b r a t i o n a l Spectrum of S n F 2 ( S 0 3 F ) 2 and Related Compounds 1) SnF 2 ( S 0 3 F ) 2 Assignment 2) SnCl2(S03F)2a 3) ( C H 3 ) 2 S n ( S 0 3 F ) 2 D K S 0 3 F c Assignment IR [ c m _ 1 ] I n t Raman [ c m - M i n t IR [cm" 1] IR [cm-1] Raman [cm - 1] 1420m,sh j 1431ms j S 0 3 s t r e t c h (A") 1385 1350 1405vs ,b ) 1410m ) 1285 SO3 s t r e t c h asym (E) 1115vs,b ) 1108s ) S0 3 s t r e t c h (A') 1130 1180 1103s,sh ) 1093s ) 1070s,b 1068s 884vw S0o s t r e t c h (A') 1087 1072 1079 SOj s t r e t c h sym (A^) 855vs 862s SF s t r e t c h 864 827 745 SF s t r e t c h (A^) 691s n.o. n.o. 612vs SnF s t r e t c h asym SnF s t r e t c h sym 594 . 586/ S 0 3 bend asym (E) 628sm 630m S0 3 bend (A') 628 620 590s 590mw S0 3 bend (A") 586 590 570 S 0 3 bend sym (A^) 548vs 551m S0 3 bend (A') 555 554 430sm 437mw S0 3 rock (A") 446 417 407 S03F rock (E) 350m Sn-0 s t r e t c h 260w Sn-F bend 280m,sh 277ms S0 3F t o r s i o n (A') 312 304 3 Ref. 50, the Sn-Cl modes are omitted; ^  Ref. 16, the Sn-C and the CH 3 modes are c omitted; Ref. 86. - 64 -Assignment of the IR band at 691 cm 1 as the asymmetric Sn-F s t r e t c h and the Raman band at 612 cm 1 as the corresponding symmetric s t r e t c h i s i n good agreement w i t h the proposed assignment of vc „ i n CH_SnF_ at -1 b <v640 cm , and i s i n the accepted range f o r Sn-F t s t r e t c h i n g modes. Since mutual e x c l u s i o n f o r both s t r e t c h i n g modes i s found, one can conclude that the F-Sn-F group i s l i n e a r or 1 hearty l i n e a r i n t h i s compound. The same co n c l u s i o n s had been reached p r e v i o u s l y f o r the c h l o r i n e " ^ and 14 the methyl d e r i v a t i v e , thus i n d i c a t i n g that a l l three compounds have c l o s e l y r e l a t e d s t r u c t u r e s . The v i b r a t i o n a l frequencies f o r SnCl2F2 are l i s t e d i n Table 8 48 together w i t h the values and assignments reported by Dehnicke. Only two bands were found i n the Raman spectrum, at 370 and 415 cm 1 . This f a c t precludes any reasonable assignment, however some observations seem to c o n t r a d i c t the previous assignment. 1) The bands at 555 cm 1 and 495 cm 1 are d e c i d e d l y too low f o r Sn-F f c s t r e t c h e s . An average value of 525 cm 1 i s found, c o n s i d e r a b l y lower than that f o r e i t h e r v i n CH SnF_ or the bn—r 3 3 t _1 average of the Sn-F s t r e t c h i n g frequencies f o r SnF2(SO,jF)2> 652 cm I t seems u n l i k e l y t h a t the discrepancy can be accounted f o r by i n v o k i n g i n d u c t i v e e f f e c t s alone. In a d d i t i o n , the Band contours are extremely broad, q u i t e i n c o n t r a s t to that f o r the i n f r a r e d bands due to vc „ i n our compounds. The absence of pronounced Raman bands and the broadness of the IR peaks i s i n f a c t reminiscent of the s t r e t c h i n g modes due to b r i d g i n g f l u o r i n e even though the band p o s i t i o n i s r a t h e r high f o r the Sn-F^ s t r e t c h . Some a s s o c i a t i o n v i a f l u o r i n e b ridges can n e v e r t h e l e s s 34 e x i s t . The s o l i d s t a t e s t r u c t u r e of ( C H^^SnC^ may serve as an example, where the halogen i s p r e f e r e n t i a l l y bonded to one t i n atom and weakly bonded to another t i n atom. 2) The peak s e p a r a t i o n f o r the symmetric Table 8 V i b r a t i o n a l Frequencies of SnCl2F2 IR [cm - 1] I n t a -1 a Raman [cm ] Int IR [cm X ] I n t b Raman [cm ^ ] I n t b Assignment 555 vs,b 495 s,b 402 ms 392 s 278 ms 415 s 370 ms 555 vs 491 s 405 m 392 s 292 w 283 w 568 w 500 m 403 s 370 m 170 m 148 s SnF2 asym s t r e t c h SnF2 sym s t r e t c h SnCl2 sym s t r e t c h SnCl2 asym s t r e t c h SnF2 deformation SnCl2 deformation ON t h i s work b Ref. 48 - 66 -and asymmetric SnC]^ stretches increases from about 10 cm i n the infrared to 45 cm 1 in the Raman spectrum,assuming the proposed assign-48 ment. This i s rather unprecedented. 3) The physical properties are indicative of a polymeric substance not withstanding the reported molecular weight determinat ion in POCl^. The solvent i s an excellent 87 donor ligand, the 2:1 complex with SnCl^ has been well investigated Since SnF^ i s also known^9'^ to form coordination complexes with oxygen donor ligands, i t seems possible that SnCl2F2 might do the same thus rendering the molecular weight determination meaningless with respect to i t s structure in the solid state. On a l l these grounds, the postulated monomeric nature in the solid state and C2 v symmetry seem to be rather questionable. The structure is certainly more complex and a definite assignment based solely on the vibrational spectrum i s -^impossible. - 67 -C. Mossbauer Spectra 119 The Sn Mossbauer data f o r the m e t h y l t i n ( I V ) f l u o r i d e s and some r e l a t e d compounds of the type R^SnF^ w i t h R = C2 H5> n - C 3 H 7 ' n _ C 4 ^ 9 a n c* n-CgH^^ are l i s t e d i n Table 9. Agreement w i t h previous work on .34,78 (CH^^SnF 71-»73*76,79 ^ g ^ g np^ 34 s e r ^ e s £ s g e n e r a l l y q u i t e good. For the quadrupole s p l i t t i n g of (CH 3)2SnF2> Davies and co-workers" and P a r i s h and P l a t t ^ r e p o r t values of 4.11 and 4.12 mm/sec r e s p e c t i v e l y , 89 at l i q u i d n i t r o g e n temperature, whereas Herber and Chandra quote s p l i t t i n g s of 4.65 mm/sec (78°K) and 4.54 mm/sec (294°K). The data repo r t e d i n t h i s t h e s i s were obtained from four d i f f e r e n t samples obtained from v a r i o u s s o l v o l y s i s r e a c t i o n s i n anhydrous or aqueous HF and from a commercial sample. The composition was determined each time by a n a l y s i s and the A values were c o n s i s t e n t , l y i n g i n the range 4.50-4.58 mm/sec (80°K). To exclude a p o s s i b l e systematic i n s t r u m e n t a l e r r o r , 90 MOssbauer s p e c t r a of one of the samples were recorded by Dr. B.V. Liengme on a d i f f e r e n t spectrometer y i e l d i n g the values 4.50 mm/sec (80°K) and 4.48 mm/sec (295°K). A l l the a l k y l t i n ( I V ) f l u o r i d e s s t u d i e d give w e l l - r e s o l v e d MOssbauer s p e c t r a at room temperature, as i l l u s t r a t e d by F i g u r e 10, which shows a spectrum obtained f o r CH 3SnF 3 at 298°K. This can be taken as good evidence f o r polymeric s t r u c t u r e s i n these compounds, as suggested before from the v i b r a t i o n a l s p e c t r a . The Mossbauer s p e c t r a f o r the two new m e t h y l t i n ( I V ) c h l o r i d e f l u o r i d e s show that both are t r u e compounds w i t h t i n i n only one chemical environment. No d i s s o c i a t i o n i n t o the corresponding c h l o r i d e s and f l u o r i d e s seems to occur at ambient tempera-t u r e . The strong room temperature resonance absorptions observed are again I n d i c a t i v e of polymeric s t r u c t u r e s f o r these substances. - 68 -Table 9 Sn Mbssbauer Data of Some M e t h y l t i n ( I V ) F l u o r i d e s and D l a l k y l t i n ( I V ) D i f l u o r i d e s Compound Temperature [°K] 6 [mm/sec] A [mm/sec] r [mm/ sec] R (CH 3) 3SnF 80 298 1.27 1.26 3.90 4.01 1,21 1.08 1.23 1.19 ( C H 3 ) 2 S n F 2 80 298 1.23 1.20 4.52 4.47 1.08 0.87 1.20 0.83 CH 3SnF 3 80 298 .76 .74 3.24 3.24 1.70 1.20 1.81 1.24 0.74 CH 3SnCl 2F 80 298 1.08 1.03 2.69 2.65 1.30 1.03 1.25 1.00 0.50 (CH 3) 2SnClF 80 298 1.32 1.27 3.80 3.79 1.05 1.01 1.10 1.00 0.53 ( C 2 H 5 ) 2 S n F 2 80 1.40 4.43 1.21 1.19 0.37 (n-C 3H 7) 2'SnF 2 80 1.38 4.40 1.07 1.09 0.21 ( n - C 4 H g ) 2 S n F 2 80 1.42 4.48 1.05 1.12 . 0.16 ( n - C 8 H 1 7 ) 2 S n F 2 80 1.42 4.50 1.17 1.19 0.32 The Mossbauer data f o r S n F 2 ( S 0 3 F ) 2 and S n C l ^ are l i s t e d i n Table 10,together w i t h the parameters f o r some s t r u c t u r a l l y r e l a t e d compounds. Again, i n t e r m o l e c u l a r a s s o c i a t i o n i s i n d i c a t e d f o r both compounds even though only a weak room temperature e f f e c t i s found f o r S n C l 2 F 2 . 1. R 2SnF 2 compounds As can be seen from Table 9 and Fi g u r e 11, the isomer s h i f t values and quadrupole s p l i t t i n g values f o r t h i s c l a s s of f l u o r i d e s a l l f a l l w i t h i n a very narrow range (1.23 < 6 < 1.42; 4.40 < A < 4.52). Such a - 69 -Figure 1 0 . Sn Mossbauer Spectrum of C H 3 S n r f at 298 °K Doppler velocity ( m m / s e c ) - 70 -Figure 11. C O M P A R I S O N O F M O S S B A U E R P A R A M E T E R S O F D I A L K Y L T I N ( i v ) D I F L U O R I D E S , B I S - D I -F L U O R O P H O S P H A T E S , B I S - F L U O R O S U L P H A -T E S A N D B IS— T R I F L U O R O M E T H Y L S U L P H O -N A T E S . - 71 -Table 10 Sn Mossbauer Data of Some Tin ( I V ) F l u o r i n e - C h l o r i n e and F l u o r o s u l f a t e Compounds Compound Temperature [°K] 6 [mm/sec] A • ' [mm/sec] r [mm/sec] R S n F 2 ( S 0 3 F ) 2 80 298 -.23 -.26 1.96 1.99 1.07 1.22 1.02 .98 0.36 S n C l 2 F 2 80 +.19 1.50 1.16 1.20 a) S n C l , b ) 4 80 +.78 -S n F , c ) 4 80 -.26 1.80 0.73 S n C l 2 ( S 0 3 F ) 2 d ) 80 +.34 2.29 0.46 S n ( S 0 3 F ) 4 d ) 80 -.27 1.34 0.42 ( C H 3 ) 2 S n ( S 0 3 F ) 2 e ) 80 1.82 5.54 0.09 A s m a l l but n o t i c e a b l e e f f e c t was obtained at 298°K. Ref. 71 and r e f . 76. d ) Ref. 50. e ) Ref. 14. c o r r e l a t i o n i m p l i e s t h a t these compounds are i s o s t r u c t u r a l . A l s o , i t can be seen that the f l u o r i d e s conform to the same p a t t e r n as do the S0 3F, S0 3CF 3 and YO^F^ d e r i v a t i v e s which have been assigned s t r u c t u r e s i n which t i n i s i n a hexacoordinative environment w i t h the a l k y l groups i n t r a n s - t e r m i n a l p o s i t i o n s and the f l u o r o s u l p h a t e , t r i f l u o r o m e t h a n e -sulphonate and difluo r o p h o s p h a t e groups i n b r i d g i n g p o s i t i o n s . C e r t a i n l y 37 such s t r u c t u r e s have been unambiguously assigned to (CH»)9SnF„ and - 72 -( C H 3 ) 2 S n ( S 0 3 F ) 2 . The isomer s h i f t and quadrupole s p l i t t i n g s f o r the oxyacid d e r i v a t i v e s show the gene r a l order S0 3F ^ S0 3CF 3 > ^0^2 ^ n accordance w i t h the order of a c i d s t r e n g t h or proton donor a b i l i t y . The bonding i n the (CH 3) 2Sn p a r t approaches the i d e a l c o n f i g u r a t i o n , sp, w i t h a high 5s share f o r t i n the more p o l a r the Sn-0 bonds become, w i t h e l e c t r o n d e n s i t y d e l o c a l i z e d i n t o the S-0, S-F, P-0 and P-F r e g i o n . This f a c t i s very evident from the i n t e r a c t o m i c d i s t a n c e s f o r ( C H 3 ) 2 S n ( S 0 3 F ) 2 . The asymmetric e l e c t r o n d i s t r i b u t i o n produces the observed wide quadrupole s p l i t t i n g . The corresponding f l u o r i d e s cannot d e l o c a l i z e e l e c t r o n s i n a s i m i l a r manner, t h e r e f o r e , the observed 6 and A values are a p p r e c i a b l y lower. S u b s t i t u t i n g CH 3 by the higher a l k y l groups r e s u l t s i n a grea t e r 5s share f o r t i n , r e f l e c t i n g the s l i g h t l y b e t t e r e l e c t r o n donor p r o p e r t i e s of these groups, and subsequently a higher isomer s h i f t . The f a c t that A drops s l i g h t l y i s ex p l a i n e d by the suggestion t h a t some of the a d d i t i o n a l e l e c t r o n d e n s i t y i s d i s p e r s e d i n t o the Sn-0 and Sn-F bonding r e g i o n , r e s u l t i n g i n a s l i g h t l y reduced asymmetry i n the e l e c t r o n d i s t r i b u t i o n around t i n . 2. S n F 2 ( S 0 3 F ) 2 Table 10 i n d i c a t e s that the values of <5 and A f o r t h i s compound as w e l l as f o r SnF^ and S n ( S 0 3 F ) 4 are r e l a t i v e l y s i m i l a r and i t can be assumed, t h e r e f o r e , t h a t S n F 2 ( S 0 3 F ) 2 i s i s o s t r u c t u r a l w i t h these compounds. The v i b r a t i o n a l s p e c t r a a l s o i n d i c a t e d that the most l i k e l y s t r u c t u r e i s a hexacoordinate one w i t h t e r m i n a l f l u o r i n e and b r i d g i n g - 73 -f l u o r o s u l p h a t e groups. I t i s a l s o noteworthy that the s m a l l v a r i a t i o n i n the isomer s h i f t s of SnF 2(SC> 3F) 2, SnF^ and SnCSC^F)^ would prevent the use of 6 values i n the i d e n t i f i c a t i o n of these compounds i n a mixture. 3. CH 3SnF 3 V i b r a t i o n a l spectroscopy has already been used to suggest an o c t a h e d r a l s t r u c t u r e f o r t h i s m e t h y l t i n ( I V ) f l u o r i d e . Mbssbauer spectroscopy can be used to lend a d d i t i o n a l support to t h i s p r o p o s a l . At l e a s t two observations p o i n t to a trans arrangement of CH 3 and t e r m i n a l F w i t h b r i d g i n g F making up the s i x coordinate s t r u c t u r e : (1) Both ( C H 3 ) 2 S n F 2 and SnF^ are known to be polymeric w i t h t e r m i n a l CR 3 f o r the former and t e r m i n a l F f o r the l a t t e r . The average value of A f o r these species i s 3.15 mm/sec. The observed value (Table 9) i s 3.24 mm/sec. C e r t a i n l y , a s t r u c t u r e based on both t e r m i n a l F and CH 3 seems q u i t e p l a u s i b l e from t h i s o b s e r v a t i o n and the d i f f e r e n c e s between the averaged and found val u e could be e x p l a i n e d on the b a s i s of i n s t r u m e n t a l l i m i t a t i o n s or on the b a s i s of l i g a n d asymmetry which could s l i g h t l y d i s t u r b the s t r u c t u r e from t r u e a x i a l symmetry ( i . e . n 4 0) and thus e x p l a i n the s l i g h t v | discrepancy. A c i s - o c t a h e d r a l s t r u c t u r e cannot be conceived as the value of A should be about h a l f of t h a t observed as has been discussed i n the I n t r o d u c t i o n . (2) T a f t constants have been used to c o r r e l a t e quadrupole s p l i t t i n g s i n i s o s t r u c t u r a l species (see I n t r o d u c t i o n ) . Figure 12 shows a p l o t of quadrupole s p l i t t i n g v a l u e s versus the sum of the T a f t constants f o r the a x i a l l i g a n d s i n ( C H 3 ) 2 S n F 2 , CH 3FSnF 2(CH 3SnF 3), F 2 S n F 2 ( S n F 4 ) and S n C l ^ . Since CH 3SnF 3 l i e s almost along the s t r a i g h t l i n e j o i n i n g (CH„)„SnF9 w i t h SnF, i t i s ( C H 3 ) 2 S n r | Figure 12. Correlation between sums of "Taft constants and quadrupole splittings for Y 2 Snf^ where Y= C H 3 , C l or F - 75 -assumed that the three compounds are i s o s t r u c t u r a l . 5^:1^2 i s o b v i o u s l y removed from the l i n e and w i l l be discussed l a t e r i n t h i s s e c t i o n . The trend i n isomer s h i f t values i n going from (CH 3)2SnF2 to CH 3SnF 3 to SnF^ (1.23 to 0.76 to -0.26) i s e x p l a i n e d by the decrease i n s e l e c t r o n d e n s i t y at t i n as the e l e c t r o n donating methyl group i s r e p l a c e d by the e l e c t r o n withdrawing f l u o r i n e atom. 4. CH 3SnCl 2F and ( C H ^ S n C l F Mossbauer spectroscopy i n d i c a t e s , as does v i b r a t i o n a l spectroscopy, that a pentacoordinated s t r u c t u r e w i t h CH 3 and C l i n e q u a t o r i a l p o s i t i o n s and F i n b r i d g i n g p o s i t i o n i s most probable ( i . e . s i m i l a r to the s t r u c t u r e of ( C H 3) 3SnF). However, the quadrupole s p l i t t i n g values f o r these two compounds and (CH 3) 3SnF are not l i n e a r l y dependent upon * a summation of a v a l u e s , suggesting the p o s s i b i l i t y of s l i g h t s t r u c t u r a l v a r i a t i o n s w i t h i n t h i s group of compounds. In p a r t i c u l a r , the high A value found f o r (CH^^SnClF may be i n d i c a t i v e of some weak c h l o r i n e b r i d g i n g 34 as found f o r (CH 3)2SnCl2. The s t r o n g room temperature e f f e c t s and l a r g e quadrupole s p l i t t i n g s a r e , however, s u f f i c i e n t evidence to r u l e out t e t r a h e d r a l s t r u c t u r e s . 5. S n C l 2 F 2 Mossbauer spectroscopy does not l e a d one to make a d e f i n i t i v e c o n c l u s i o n regarding the s t r u c t u r e of t h i s s p e c i e s . C e r t a i n l y the room temperature e f f e c t i n d i c a t e s that some a s s o c i a t i o n v i a f l u o r i n e and/or c h l o r i n e b r i d g i n g i s present. However, Fi g u r e 12, shows that the s t r u c t u r e of the compound cannot be a t r u e o c t a h e d r a l one w i t h t r a n s - C l as the p o i n t f o r Cl2SnF2 l i e s w e l l o f f the l i n e . On the other hand, a 48 t e t r a h e d r a l s t r u c t u r e , as proposed by Dehnicke, seems u n l i k e l y as a - 76 -r e s u l t of the quadrupole s p l i t t i n g of 1.50 mm/sec which i s f a r too h i g h f o r a compound where d i f f e r e n c e s i n bond p o l a r i t i e s are expected to be s m a l l . Such a t e t r a h e d r a l s t r u c t u r e would give a quadrupole s p l i t t i n g which would probably be u n r e s o l v a b l e . A case i n p o i n t i s 57 ( C l C R ^ ^ S n ( C H ^ ^ where no quadrupole s p l i t t i n g i s observed. I t can only be concluded that the s t r u c t u r e of S n C ^ ^ * s n o t a t r u e o c t a h e d r a l one w i t h t r a n s - C l (as i s SnC^CSOgF^"^) nor i s i t a t e t r a h e d r a l one. A s s o c i a t i o n over F bridges occurs i n some f a s h i o n which must r e s u l t i n a s t r u c t u r e which i s i n t e r m e d i a t e between f o u r -and s i x - c o o r d i n a t e d t i n . The r e s u l t s f o r t h i s compound p o i n t to the l i m i t a t i o n s of v i b r a t i o n a l and Mossbauer spectroscopy as s t r u c t u r a l t o o l s f o r now i t would seem th a t only an X-ray d i f f r a c t i o n study could c l e a r up the problem. - 77 -D. General Conclusions As evidenced by t h e i r p h y s i c a l p r o p e r t i e s , the v i b r a t i o n a l and 119 the Sn Mossbauer s p e c t r a , the new compounds are a l l polymeric. The r e p e a t i n g u n i t s , showing the c o o r d i n a t i o n around the c e n t r a l t i n atoms are shown i n F i g u r e 13. The proposed c o n f i g u r a t i o n f o r CH^SnF^ i s 37 d e r i v e d from the known s t r u c t u r e of (CH.j)2SnF2 by s u b s t i t u t i n g a t e r m i n a l f l u o r i n e f o r one of the methyl groups. In the same way, the s t r u c t u r e s of the m e t h y l t i n ( I V ) c h l o r i d e f l u o r i d e s are d e r i v e d from a r a t h e r i d e a l i z e d s t r u c t u r e f o r (CH 3) 3SnF where j u s t one and then a second CH^ group i s r e p l a c e d by c h l o r i n e . Whether a l l these groups i n the e q u a t o r i a l plane are e x a c t l y coplanar and whether the b r i d g i n g f l u o r i n e are e q u i d i s t a n t from t i n i s i m p o s s i b l e to decide at present. 36 45 79 These p o i n t s apparently are not even s e t t l e d f o r (CH^^SnF. > > The suggested s t r u c t u r e f o r SnF2(S0.jF)2 has precedents i n the s t r u c t u r e s of ( C H 3 ) 2 S n ( S 0 3 F ) 2 8 5 and S n C l 2 ( S 0 3 F ) 2 ^° w i t h b r i d g i n g S0 3F groups r a t h e r than b r i d g i n g f l u o r i n e . Even though the present evidence does not i n d i c a t e a t e t r a h e d r a l l y 48 coordinated c o n f i g u r a t i o n w i t h symmetry as suggested e a r l i e r , the t r u e s t r u c t u r e of SnCl2F2 * s s t i l l very much i n doubt. A f i n a l d e c i s i o n w i l l have to be made from an X-ray study. I t now appears that the problem i n o b t a i n i n g any organotin(IV) t r i f l u o r i d e s or c h l o r i d e f l u o r i d e s i n the past has been the l a c k of a s u i t a b l e s y n t h e t i c method. The two c h l o r i d e f l u o r i d e s which were obtained have been shown to be d e f i n i t e unique compounds and cannot be r a t i o n a l i z e d as weak adducts such as ( C H 3 ) 2 S n F 2 . ( C H 3 ) 2 S n C l 2 i n the case o f , f o r example, ( C H ^ S n C l F . - 78 -F i g u r e 13. Suggested configurations around Tin for the Fluoro Derivatives. E x p l a n a t i o n : = F - a t o m in b r i d g i n g p o s i t i o n F = F — a t o m in t e r m i n a l p o s i t i o n (t) M 0^^= O - a t o m in b r i d g i n g p o s i t i o n O = O - a t o m in t e r m i n a l p o s i t i o n - 79 -I f such adducts were present, the Mossbauer spectrum would i n d i c a t e t h a t t i n i s present i n two environments and the v i b r a t i o n a l s p e c t r a would show c h a r a c t e r i s t i c bands f o r the two components, i n p a r t i c u l a r , the Sn-C s t r e t c h i n g modes would be most d i a g n o s t i c . A few suggestions can be made w i t h r e f e r e n c e to f u t u r e work: 1) S o l v o l y s i s w i t h HF (both anhydrous and aqueous) might be attempted w i t h other o r g a n o m e t a l l i c m o i e t i e s using the apparatus employed i n t h i s study. Since the use of anhydrous HF i n such systems has not been attempted p r i o r to t h i s work, such an e x t e n s i o n could l e a d t o new and i n t e r e s t i n g compounds. Suggested o r g a n o m e t a l l i c systems which could be i n v e s t i g a t e d i n p a r t i c u l a r are methyl c h l o r i d e s of l e a d , germanium as w e l l as antimony and bismuth and a l s o g a l l i u m and indium. 2) F u r t h e r HF s o l v o l y s i s of o r g a n o t i n ( I V ) compounds should be s t u d i e d , however, the l i m i t a t i o n here, as found from the r e s u l t s of the phenyl- and v i n y l t i n ( I V ) attempts, i m p l i e s that only the a l k y l groups to the r i g h t of the methyl group shown i n the s e r i e s on page 3 need be i n v e s t i g a t e d , i . e . e t h y l to o c t y l . Such a study could con-c e i v a b l y r e s u l t i n the s y n t h e s i s of some new a l k y l t i n ( I V ) c h l o r i d e - f l u o r i d e s . 3) Since t i n tetrabromide s o l v o l y s i s w i t h anhydrous HF was u n s u c c e s s f u l , perhaps some m e t h y l t i n ( I V ) bromides could be attempted as s u b s t r a t e s . Of course, e x t e n s i o n to the s o l v o l y s i s of higher a l k y l t i n ( I V ) bromides could a l s o be undertaken. 4) M e t h y l t i n ( I V ) t r i f l u o r i d e was obtained only a f t e r an extremely lengthy and tedious HF s o l v o l y s i s , t h e r e f o r e , the use of c o o r d i n a t i n g s o l v e n t s , such as POCl^, could be i n v e s t i g a t e d w i t h respect to shortening the r e a c t i o n time. Such a suggestion presupposes that the c o o r d i n a t i n g - 80 -s o l v e n t i s i n e r t w i t h respect to HF s o l v o l y s i s . 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