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Studies of group IV fluoroorganometallic derivatives Waldman, Mark Cyril 1969

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STUDIES OF GROUP IV FLUOROORGANOMETALLIC DERIVATIVES by MARK CYRIL WALDMAN B.Sc. (Hons.)/, University of British Columbia, 1965 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Chemistry We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October, 1969 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o lumbia, I agr e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and Study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Department or by h ils r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n ot be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f Chemistry  The U n i v e r s i t y o f B r i t i s h C olumbia Vancouver 8, Canada Da t e November 1 2 . 1969 To My Parents -• i -ABSTRACT The butyne, HC E C C F ( C F ^ ) 2> can be prepared v i a the dehydro-halogenation of I C H = C H C F ( C F 3 ) 2 , the o l e f i n i s produced by the u l t r a -v i o l e t i r r a d i a t i o n of mixtures of ( C F 3 ) 2 C F I and acetylene. Group I V p e r f l u o r o a l k y n y l d e r i v a t i v e s (CH 3) nM(CECR f)^_ n (n = 0 -> 3; M = S i , Ge, Sn; R f = C F 3 > CF(CF 3> 2) can be prepared by the r e a c t i o n of XMgCECR^ (X = Br, I) with the appropriate group IV organohalide. Some, but not a l l , of the combinations of n, M, and R f are described. The reaction of CH^SiCJ^ with IMgC=CCF3 produces (CH 3) 2Si(C=CCF 3) 2. . ' _ Difluorocarbene from (CH 3) 3SnCF 3 at 150° adds to the C=C bond of HC=CRf (R f = CF 3, C 2 F 5 , C F ( C F 3 ) 2 ) and some of the (CH 3) nM(CECR f) 4_ n d e r i v a t i v e s to give the corresponding cyclopropenes, HC=CR^(CF,,) and (CH 3) nM(C=CR f(CF 2))^_ n» r e s p e c t i v e l y . The s p e c t r a l properties of the group IV p e r f l u o r o a l k y n y l and cyclopropenyl derivatives e x h i b i t several novel trends. The difluorocarbene species from (CH-j) 3SnCF 3 i s e l e c t r o p h i l i c and i s i n a s i n g l e t state i n gas phase addi t i o n reactions to unsaturated bonds. The carbene adds s t e r e o s p e c i f i c a l l y to both c i s - and to trans-butene-2 to give the corresponding isomeric cyclopropanes. The carbene also i n s e r t s i n t o the Sn-H bond of (CH 3) 3SnH. The u l t r a v i o l e t i r r a d i a t i o n of mixtures of ( C F 3 ) 2 C F I and (CH-j) 3SnSn(CH 3) produces (CH 3) 3SnCF(CF 3) 2 . A s i m i l a r reaction i n v o l v i n g (CH 3) 3SnSn(CH 3) 3 and CF 2=CFI produces (CH 3) 3SnCF=CF 2 < None of the d e r i v a t i v e s , (CH 3) 3SnR f (R f = CF(CF 3> 2, CF=CF2> , produces a carbene upon pyrolysis. Bis(trifluoromethyl)diazomethane reacts with HC^CCF^ and with CF^C^CCF^ at oa. 150° to give a mixture of the corresponding isopyrazole, RC=C(CF3)N=N(C(CF^2>, and cyclopropene, RC=C(CF 3)(c(CF 3) 2) (R = H, CF 3). Similar reactions of the diazo compound with (CH3)3MC=CCF3 (M = Ge, Sn) produce (CH3) 3M£~=C (CFy (C(CF3) 2) derivatives. The reaction of bis(trifluoromethyl)diazirine and (CH3)3GeC=CCF3 also produces the cyclopropene. The diazo compound inserts CCCF-^^ i n t o the M-II bonds o f (CH3)3SnH and (CH^AsH and produces (CH ) 2AsCF(CF 3) 2'H and (CH3)2AsCF=CF2 upon reaction with (CH 3) 2AsAs(CH 3) 2. The diazo compound f a i l s to react however, with either (CH3)3MH (M = Si, Ge), (CH 3) 3GeBr, or (CKy GeGe(CH ) 3 < The Mossbauer spectra of the compounds (CH^^nR^ reveal that the quadrupole s p l i t t i n g in the Sn nucleus increases in the order Rf = CFH2 < CF2H < CF 3 < CH(CF 3) 2 < C 2F 5 < CF(CF 3) 2 which indicates the order of increasing electronegativity of the R^  groups. The order of electronegativity, CF 3 < C^F^ < CF(CF 3) 2 > is also supported by n.m.r. studies of the compounds HCHCR- and HC=CRf(CF2). As an Appendix the stereochemistry of the olefins produced by the ultraviolet irradiation of mixtures of R^I (R^ = CF3» C 2F^, CF(CF 3) 2) and acetylene i s described. Predominantly trans addition takes place. - i i i -TABLE OF CONTENTS Page ABSTRACT i LIST OF TABLES v i LIST OF FIGURES ix ACKNOWLEDGEMENTS x i GENERAL INTRODUCTION 1 CHAPTER 1. GROUP IV PERFLUOROALKYNYL DERIVATIVES 5 INTRODUCTION 5 EXPERIMENTAL 8 I. General Experimental: Apparatus and Techniques 8 II. Starting Materials 12 III. Preparation of Group IV Perfluoroalkynyl Derivatives 16 RESULTS AND DISCUSSION 34 I. The Fluoroalkynes 34 II. Perfluoroalkynyl Derivatives of Silicon Germanium and Tin 42 CHAPTER 2. DIFLUOROCARBENE 71 INTRODUCTION 71 EXPERIMENTAL 77 I. Starting Materials 77 - iv -Page II. Preparation of Perfluoroorganotrimethyltin Derivatives 78 III. Reactions of Trifluoromethyltrimethyltin ... 81 IV. Reactions of Some Other Perfluoroorgano-trimethyltin Compounds 97 RESULTS AND DISCUSSION 100 I. Difluorocarbene from Trifluoromethyltri-methyltin 100 II. Difluorocarbene: Multiplicity, Mechanism of Addition to Unsaturated Bonds, and Electro-p h i l i c i t y 124 III. Difluorocarbene Insertion into the Sn-H Bond 134 IV. Preparation and Pyrolysis of Other Perfluoro-organotrimethyltin Derivatives 137 CHAPTER 3. BIS(TRIFLUOROMETHYL)DIAZOMETHANE 144 INTRODUCTION 144 EXPERIMENTAL 150 I. Starting Materials 150 II. Reactions of Bis(trifluoromethyl)diazo-methane 151 RESULTS AND DISCUSSION 163 I. Addition Reactions of Bis(trifluoromethyl)-diazomethane to Fluoroalkynes and 3,3,3-Trifluoropropynyl Group IV Derivatives 163 - v -Page II. Reactions of Bis(trifluoromethyl)diazo-methane with M-H and M-M Bonds 177 CHAPTER 4. MOSSBAUER ABSORPTION SPECTRA OF SOME (CH 3) 3SnR f COMPOUNDS 182 INTRODUCTION 182 EXPERIMENTAL 189 I. Mb'ssbauer Spectrometer and Sample Prepara-tion 189 II. Preparation of Tin Compounds 189 RESULTS AND DISCUSSION 191 I. Fluoroalkyltrimethyltin Derivatives 191 II. Trifluorovinyltrimethyltin Derivatives 195 III. 3,3,3-Trifluoropropynyltin Derivatives I 9 7 APPENDIX 1. STEREOCHEMISTRY OF SOME OLEFINS RfCH=CHI 198 INTRODUCTION 198 EXPERIMENTAL 200 I. Preparation of the Olefins 200 RESULTS AND DISCUSSION 204 APPENDIX 2. ADDRESSES OF THE SUPPLIERS 209 REFERENCES 210 PREPARATIVE INDEX 224 - v i -LIST OF TABLES Page Table I. V.p.c. Columns 10 II. Characteristic Infrared Frequency of V(CEC) of Some Fluoroalkynes and Their Non-Fluorinated Analogs .... 36 III. Summary of Chemical Shifts of the Fluoroalkynes HC=CRf (R = CF 3, C 2F 5, CF(CF 3) 2) 39 IV. Group IV Perfluoroalkynyl Derivatives 45 V. Infrared Spectra (Main Bands in cm ^ ) of Some Fluoroalkynes and Perfluoroalkynyl Derivatives 48 VI. Summary of N.m.r. Parameters of Some Fluoroalkynes and Group IV Perfluoroalkynyl Derivatives 50 VII. v(CHC) of Some Non-Fluorinated Group IV Alkynyl Derivatives 61 VIII. Infrared Trend 1.1: v(C=C) (in cm"1) of (CH„) M(C=CR_). (where n and Rr are constant) 63 3 n f 4-n f IX. Infrared Trend 1.2: v(CHC) (in cm-1) of (CH„) M(C=CR,), (where M and n are constant) 64 3 n f 4-n X. Infrared Trend 1.3: v(C=C) (in cm"1) of (CH,.) 0M(CHCR£) . (where M and R^  are constant) 65 J j l H—n r 1 19 XI. N.m.r. Trend 1.1: H and F N.m.r. Chemical Shift Values (in p.p.m.) of (CH 3) nM(CECR f)^ (where n and Rj. are constant) 67 - v i i -Page Table XII. N.m.r. Trend 1.2: ^ and 1 9 F n.m.r. Chemical Shift Values (in p.p.m.) of (CH 3) nM(CECR f)^_ n (where M and R£ are constant) XIII. Perfluoroalky1-3,3-difluorocyclopropenes and Some of Their Group IV Derivatives XIV. Infrared Spectra (Main Bands Only (in cm ^)) of 68 102 Some Perfluoroalkyl-3,3-difluorocyclopropenes and Some of Their Group IV Derivatives. (All bands are high intensity absorptions except those at 3160 ± 5 cm"1) 103 XVA. 1H and 1 9 F N.m.r. Chemical Shifts (6) of Some Perfluoroalkyl-3,3-difluorocyclopropenes and Some of Their Group IV Derivatives -*-04 19 XVB. F N.m.r. Coupling Constants of Some Group IV Per-fluoroalkyl-3,3-difluorocyclopropenyl Derivatives ... 1^ 6 XVIA and XVIB. Double Bond Frequencies of Some Cyclo-propenes (in cm "'") XVII. Double Bond Frequency (in cm ^ ) of Some Group IV Cyclopropenyl Derivatives V2.7. XVIII. Some N.m.r. Parameters of Some (CH^^SnR^ Derivatives XIX. Infrared Spectra (Main Bands Only (in cm 1 ) ) of RC=C(CF 3)C(CF 3) 2 Derivatives .... • 1 6 4 XX. N.m.r. Parameters of Some RC=C(CF 3)C(CF 3) 2 and RC=C(CF3)N=NC(CF3)2 Derivatives 1 6 5 - v i i i -Page Table XXI. Isomer Shifts of Some Tin Compounds in Different Oxidation States 183 XXII. Some R^SnR' Compounds Which Show No Observable Quadrupole Splitting 186 XXIII. MOssbauer and N.m.r. Parameters of Some (CH^^SnR^ and Related Compounds 192 XXIV. 1:1 Adducts from R fI + HC=CH xV^fffcTA^ 2 0 3 XXV. Summary of Chemical Shifts of Some Olefins RfCH=CHI.. 205 - i x -LIST OF FIGURES Page Figure 1. S p e c i f i c a t i o n s f o r construction of system f o r handling re a c t i v e l i q u i d s during v.p.c. p u r i f i c a t i o n 8 2. F i t t i n g s for apparatus described i n Figure 1 8 3. Apparatus used i n Procedure A f o r the preparation of Group IV perfluoroalkynyl d e r i v a t i v e s 17 19 4. F N.m.r. spectrum of trif l u o r o m e t h y l - 3 , 3 - d i f l u o r o -cyclopropene 109 19 5. F N.m.r. spectrum of pentafluoroethyl-3,3-difluoro-cyclopropene 112 19 6. F N.m.r. spectrum of cis-1,1-difluoro-2,3-dimethyl-cyclopropane 129 7. Long-range s h i e l d i n g e f f e c t s i n 1,1-difluoro-2-methylcyclopropane 131 8. "*"H N.m.r. spectrum of 3 , 3 , 5 - t r i s ( t r i f l u o r o m e t h y l ) -isopyrazole 168 19 9. F N.m.r. spectrum of 1 , 3 , 3 - t r i s ( t r i f l u o r o m e t h y l ) -cyclopropene 169 19 10. F N.m.r. spectrum of 3 , 3 , 4 , 5 - t e t r a k i s ( t r i f l u o r o -methyl) isopyrazole 3-71 11. Radioactive decay scheme of ''""'"^ Sn v. 182 12a. Schematic Diagram showing o r i g i n of isomer s h i f t and quadrupole s p l i t t i n g i n Mossbauer absorption spectrum of ^ ^ S n compounds 185 - X -P a g e Figure 119 12b. Typical Mossbauer absorption spectrum for Sn compound showing a quadrupole splitting 185 13. Mossbauer absorption spectrum of (CH^^SnCFCCF^^ (6 = 1.32 mm/sec; A = 1.89 mm/sec ) 190 14. Correlation between quadrupole sp l i t t i n g and "4i n.m.r. chemical shift of the CH^ groups of (CH^)^SnR^ derivatives 196 - x i -ACKNOWLEDGEMENT S I would like to express my sincerest appreciation to Professor W.R. Cullen for guidance and encouragement during the course of this Thesis. My association with him has been, I believe, very rewarding. 1 would also like to thank Dr. D. McGreer for the assistance which he provided while Dr. Cullen was on Sabbatical (1966-67). Appreciation is extended to the following for reading parts of the manuscript and for their constructive comments: Professor W.R. Cullen, Dr. D. McGreer, Dr. F. Aubke, Dr. R. Pincock, Dr. J.A.J. Thompson, Mrs. K. O'Sullivan Mailer, and Mr. J.E.H. Ward. The financial assistance of the National Research Council of Canada who awarded me a Bursary (1965-66) and Studentships (1966-69) is also gratefully acknowledged. Finally, but not least, I would like to thank my family for their patient understanding and tolerance throughout the years of study. - 1 -GENERAL INTRODUCTION This Thesis describes, in general, investigations carried out in the f i e l d of fluoroorganometallic chemistry. Non-metallic fluorocarbon chemistry has been developed mostly in the last 30 years."*" Several short chain fluoroalkanes were prepared before 1940; however, the only notable development was 2 the preparation of CHFCtf^ which has found wide use as a non-toxic refrigerant. Today CHFCJ^ and similar compounds, such as CF2CJI2 and 3 CFC£ 3 > are also used as aerosol propellants. The biggest impetus to the study of fluorocarbons arose during World War II. It was found that the few perfluoroalkanes that were available at the time had the necessary physical properties for use as buffer gases, coolants, lubricants, and sealants in chemical plants concentrating 2 3 5 U for use in atomic bombs.^ The war and post-war research into methods of preparation of fluoroalkanes quickly led to the finding of various methods for the preparation of fluoroalkenes and fluoro-alkynes as well. Interest in fluorocarbons has been maintained u n t i l now because of their unusual properties, particularly those of fluoro-carbon polymers. Tetrafluoroethylene, for example, readily polymerizes to form long chain polymers which can be cross-linked. The unusual properties of this polymer, particularly i t s thermal and chemical s t a b i l i t y , make i t one of the most widely used polymers in the world today. - 2 -Organometallic compounds have been known for over 100 years. Notable ones, for the controversies which i n i t i a l l y surrounded them, are Ziese's salt,"' K^C^H^PtCJ!^) .^0, considered by some to be the f i r s t organometallic compound and tetramethyldiarsine, also known as "cacodyl", a constituent of "Cadet's fuming liquid".' 7 Present day interest in organometallic compounds was spawned largely by the discovery that lithium and aluminium alkyls catalyze the polymeriza-g tion of ethylene and by the findings of very thermally stable 9 10 silicones and metallocenes, e.g., ferrocene. Interest in fluoro-organometallics has arisen out of expectations of novel properties induced by the highly electronegative fluorine substituents. For example, perfluoroalkyl zinc halides, R^ZnX (X = usually I, also C£), resemble zinc halides rather than alkylzinc compounds in their behaviour towards oxygen and in their a b i l i t y to form stable 1:1 complexes with ethers and amines (e.g. dioxane 1 1 and pyridine1"*) . The term pseudohalide is often applied to a perfluoroalkyl group 12 because i t is so strongly electronegative. Intensive research in the f i e l d of fluoroorganometallic chemistry has, un t i l now, been concentrated on f l u o r o a l k y l 1 3 ' 1 4 ' 1 " ' and fluorovinyl d e r i v a t i v e s 1 3 ' 1 ^ The chemistry of organometallic fluoroalkynyls* has, by comparison, ft For the purposes of this thesis, an organometallic alkynyl compound is defined as either (a) a derivative in which a terminal alkyne is o-bonded to the metal or metalloid, that i s , M-C=CR, or (b) a iT-bonded derivative in which the alkyne is bonded to the metal or metalloid only by ir-type bonds involving -rr-electrons of the t r i p l e bond. - 3 -lagged behind in development. In particular, knowledge is lacking about the derivatives of group IV. Chapter 1 of this thesis describes some perfluoroalkynyl derivatives (CH3)nM(C=CR^)^ where M = Si, Ge, Sn; Rf =.CF3, CF 2CF 3, CF(CF 3) 2 and n = 3, 2, 1, 0. Some, but not a l l , of the combinations of M, R^ , and n are described. Chapter 2 of this thesis describes the preparation of a new class of organometallic compounds in which an organogermyl or - t i n moiety i s a-bonded to a cyclopropene at a vinylic position. The new compounds are prepared by the addition of difluorocarbene (from 16 (CH 3) 3SnCF 3 at 150° , to some of the group IV perfluoroalkynyl derivatives described in Chapter 1. Chapter 3 discusses the reactions of bis(trifluoromethyl)— diazomethane with some fluoroalkynes, a perfluoroalkynyl germanium and a t i n derivative from Chapter 1, and various other organometallic reagents. The electronegativity of CF 3 has been estimated to be intermediate between that of fluorine and chlorine"'"''' and i t i s expected that the reactivity and reactions of the diazo compound w i l l reflect the large inductive effect of the trifluoromethyl groups. Chapter 4 briefly considers the Mossbauer absorption spectra of some (CH3)3SnR^ derivatives and mainly those derivatives where R^  is a fluoroalkyl substituent. The discussion emphasizes the cause of the quadrupole splitting and the effect of the electronegativity of the R^  group on the magnitude of the sp l i t t i n g . As an appendix to this Thesis a study of the stereochemistry of the olefins, RfCH=CHI (R,. = CF,, C-F,., CF(CF )„), i s described. - 4 -These olefins are precursors to the corresponding fluoroalkynes, HC=CR_, of Chapter 1. CHAPTER 1 GROUP IV PERFLUOROALKYNYL DERIVATIVES INTRODUCTION The f i r s t organometallic alkynyl derivative, 18 (CH-^AsC^CAsCCH.^, was prepared in 1923 ; however, the majority of the research into the preparations and properties of alkynyl-metallic or -metalloid derivatives has been carried out in the last 20 years. The findings, at least with respect to non-fluorinated alkynes, have 19 been f a i r l y extensive. A recent review l i s t s over 300 a-bonded non-fluorinated alkynyl derivatives of the elements of the main groups II - V, excluding nitrogen. Included in the review are compounds like RNM(C=CR')m (M = metal or metalloid, R = usually alkyl or aryl, R' = a wide variety of organic substituents including C=CH) and several dimetallic substituted derivatives like (CHg^AsCECAsCCH^^ mentioned above. Recent research into alkynyl derivatives of the elements of the main groups has concentrated on preparing mixed 2 0 2 1 dimetalloid derivatives ' e.g. R M(CECM'R„). (M ± M' = Si, Ge, Sn, b n 3 4-n Pb, R = alkyl and/or aryl, n = 3, 2). Research into alkynyl derivatives of the transition metals 22 was, i n i t i a l l y , encouraged by the report of Reppe and Vetter in 1952 that acetylene is catalytically cyclized and carbonylated by iron pentacarbonyl to give, as the fi n a l product, hydroquinone. The suspicion that an organoiron intermediate was involved has led to a large body of experimental evidence relating to reactions of alkynes - 6 -23 wi t h t r a n s i t i o n metal complexes. Numerous a- and Tr-bonded non-2 A f l u o r i n a t e d t r a n s i t i o n metal d e r i v a t i v e s have been reported of 25 26 which (1) and (2) are examples. ( ( C 6 H 5 ) 3 P ) 2 P t ( C s C C 6 H 5 ) B r f 6 H 5 C (CO) 3 CoC. ^ Co(CO). 'C I C 6 H 5 CD (2) The chemistry of organometallic f l u o r o a l k y n y l d e r i v a t i v e s , by comparison w i t h the above, i s j u s t s t a r t i n g to develop. The com-97 28 9Q 97 pounds LiCECR f (R f = F, CF 3, and C ^ , and NaC=CF have been reported as w e l l as a few t r a n s i t i o n metal a-bonded d e r i v a t i v e s of HCECRf (R f = F 3 0 ' 3 1 , C F 3 2 9 ' 3 2 " 3 4 , C 2 F 5 , 3 5 CH 2CF 3, 3 6 C ^ 2 9 ) and 0 " 7 0 Q *^  Q / O TT-bonded d e r i v a t i v e s of RC^CR^ (R = H, R,. = CF„ ' ; R r = C,F_ ' : f t 3 r 6 5 39 41 42 43 43 R = R f = CF 3 ' ; R = R f = C & F 5 ; R = R f = 4-CH 30C 6F 4 ; R = 44 C,F C, R, = 4-C£C,F., 4-C,FcC,F., 4-C,H cC5CC,F / ). The d e r i v a t i v e s 6 5 ' f 6 4 6 5 6 4 6 5 6 4 R nMCECCF 3 (R nM = ( C H 3 ) 3 S i , (C 2H 5) 3Ge, (CH 3) 2As) and C H 3 A s ( C E C C F 3 ) 2 4 5 which r e s u l t e d from a p r e l i m i n a r y study conducted i n t h i s l a b o r a t o r y immediately p r i o r to the i n c e p t i o n of t h i s i n v e s t i g a t i o n have been reported; however, no systematic study of f l u o r o a l k y n y l d e r i v a t i v e s of the elements of the main groups I I I - V has been c a r r i e d out. I t there f o r e seemed t i m e l y to undertake such a study. The p e r f l u o r o a l k y n y l - 7 -derivatives of Si, Ge, and Sn were chosen as the basis for the study since many non-fluorinated analogs have been made and comparisons of properties would be possible. The fluoroalkynes HC=CR^  (Rf = CF 3, C^CF^) were chosen as the i n i t i a l starting alkynes since they are, reportedly, easily prepared in good yields'^'"^. It was also decided to attempt the preparation of HCsCCFCCF.^ and some of i t s group IV derivatives to widen the scope of the study. Besides expecting that the properties of the perfluoroalkynyl derivatives would reflect the presence of fluorine substituents, i t was hoped that some information might be gained concerning the effective electro-negativities of different perfluoroalkyl substituents. This latter subject has been relatively unexplored. Two methods of preparation have been used in the past in preparing the majority of the non-fluorinated alkynyl derivatives of 19 group IV. They include the reaction of a group IV metal halide with either (a) an a l k a l i metal (Na or Li) alkynyl compound, or (b) an alkynyl magnesium halide. The second method was chosen for the i n i t i a l attempts at preparation for three reasons: (a) i t is easier to carry 29 46 out experimentally, (b) XMgC=CCF.j (X = C&, Br) has been reported, ' 45 and (c) the preliminary investigation was successful using this method. - 8 -EXPERIMENTAL I . General Experimental: Apparatus and Techniques The f o l l o w i n g describes the apparatus and general techniques that were used f o r the experimental work i n t h i s T h e s i s . S p e c i f i c m o d i f i c a t i o n s are noted i n the body of the t e x t . standard vacuum techniques. To t h i s end a standard Pyrex vacuum system was constructed i n c o r p o r a t i n g mercury manometers, s e v e r a l l a r g e storage bu l b s , and stopcocks l u b r i c a t e d w i t h Apiezon grease. When necessary n o n - v o l a t i l e m a t e r i a l s were handled i n a n i t r o g e n - f i l l e d dry box. handling p o t e n t i a l l y a i r s e n s i t i v e , t o x i c , h i g h l y r e a c t i v e or low b o i l i n g compounds - p a r t i c u l a r l y during vapour phase chromatographic (v.p.c.) a n a l y s i s . The sample to be p u r i f i e d was condensed under vacuum i n t o the l a r g e r f i n g e r (Figure 1). The pressure over the sample V o l a t i l e reactants and products were manipulated using A s p e c i a l l y designed apparatus (Figures 1 and 2) was used i n B I O / 1 9 GLASS ROD FOR E X T R A SUPPORT (OPTIONAL) L MEASUREMENTS GIVEN CENTIMETERS! cations for construction of system for handling reactive liquids during vpc purification. Figure 1. (left) Specifl-Figure 2. (above) Fittings for the apparatus. I* 1 T E F L O N , „ / FERRULES SILICONE SEPTUM GLASS - 9 -was equalized by f i l l i n g the vacuum with nitrogen. Tipping the apparatus at right-angles allowed the liquid to run into the sampling finger. Standing the apparatus upright allowed the excess liquid to drain back into the larger finger and l e f t the sampling finger f u l l (ca. 1 ml). A sample could then be removed by using a v.p.c. syringe. Any suitable lubricant could be used for the stopcock. Stainless steel Swagelok fittings (Figure 2) were found to be the most inert. The Swagelok fittings (1/4 in. bore) had to be hollowed out slightly to accommodate the glass insert which was obtainable in metric sizes only. The Swagelok was attached to the glass with Teflon ferrules. The ferrules (1/4 in. I.D.) were slightly smaller than the glass O.D.; however, when heated slightly in an oven they fitted easily and formed an air-tight seal. V.p.c. silicone septums were air tight, permitted multiple injections, and were essentially chemically inert. Unless otherwise indicated reactions were carried out in thick-walled Pyrex "Carius" tubes. The C arius tubes, volatile reactants added, were attached to the vacuum system, cooled to -196°, and sealed off in vacuo. For reactions requiring temperatures > 20° the Carius tubes were heated in a specially designed tube furnace equipped with a hinged safety door. For reactions initiated by ultraviolet light the tubes were placed 20 - 30 cm from the light source. Pyrex effectively absorbs any ultraviolet irradiation below 2850 JL Two ultraviolet sources were used; either a 100-watt - 10 -(Hanovia lamp No. 608A-36) or a 450-watt source (Hanovia lamp No. 679A-36). The specific source used is noted in the text. Purifications were carried out using standard techniques: d i s t i l l a t i o n , vacuum trap-to-trap d i s t i l l a t i o n , sublimation, recrystallization, and vapour phase chromatographic (v.p.c.) techniques. V.p.c. separations were carried out using an Aerograph model A-90-P gas chromatograph equipped with a thermal conductivity detector and connected to a Honeywell recorder. The latter was equipped with a disc integrator. Table I l i s t s the chromatographic columns used including the mesh sizes of the stationary supports. (The column lengths and diameters are in brackets.) Table I V.p.c. Columns 1. 20% Silicone GE-SS-96 on 60/80 firebrick (10' x 1/4"). 2. 20% Dinonyl phthalate on 60/80 chromosorb W (10' x 3/8"). 3. 20% SF-96 on 60/80 chromosorb W (10' x 3/8"). 4. 20% Kel-F grease on 60/80 chromosorb W (10' x 1/4"). 5. 20% SE-30 on 60/80 chromosorb P (5' x 1/4"). 6. Apiezon J on 60/80 regular firebrick (5' x 1/4"). 7. 20% SF-96 on 60/80 regular firebrick (10' x 1/4"). T 11 -Either helium or nitrogen was used as the carrier gas with flow rates varying from 2 - 1 5 cc/min. Separations were carried out with the injector approximately 25° above, and the detector 35° above, the column temperature. Molecular weights were determined by Regnault's method. Micro boiling points were determined using Siwoloboff's 47 method and are reported at atmospheric pressure (atm). Melting points were determined using either a hot-stage microscope or a capillary-holding (Gallenkamp) apparatus. Vapour pressure measurements on compounds with boiling points greater than 75° were made using an isotenoscope. Lower boiling liquids were attached directly to the vacuum line. In both cases the pressures were read from mercury manometers by means of a cathetometer and boiling points were determined by extrapolation of the plot of log p (vapour 3 -1 pressure) against (10 /T °K ). Infrared spectra reported in cm 1 were obtained using Perkin-Elmer models 21 and 457 instruments. Those spectra which are reported in microns (u) were obtained using a calibrated Perkin-Elmer model 137 instrument. The nature of the sample, that i s , vapour, film, or mull, i s reported in the text. The "*"H nuclear magnetic resonance (n.m.r.) spectra were obtained using either Varian A-60 or Jeolco C-60 H instruments both 19 operating at 60 Mc. The F n.m.r. spectra were obtained using a Varian HA-100 spectrometer operating at 94.07 Mc. The "*"H n.m.r. - 12 -spectra are reported in parts-per-million (p.p.m.) relative to external 19 (CH 3)^Si and the F n.m.r. spectra, in p.p.m. relative to either internal or external CFC&3 (negative values being to low f i e l d in both cases). The external CFCJl^ standard, when used, was present ' as a CFCJl^ f i l l e d capillary in the n.m.r. tube. Elemental analyses were carried out by Mr. P. Borda, Department of Chemistry, University of British Columbia; Drs. F. and E. Pascher, Mikroanalytisches Laboratorium, Bonn, Buchstrasse 54, Germany; Schwarzkopf Microanalytical Laboratory, 59-19 37th Avenue, Woodside 77, New York; and Dr. Alfred Bernhardt, Mikroanalytisches Laboratorium, 5251 Elbach Uber Engelskirchen, Fritz-Pregl-Strasse 14-16, West Germany. II. Starting Materials The following chemicals were purchased (supplier in brackets") and used as received: CF^I (Peninsular Chemresearch, Inc.); C 2F 5I (Peninsular); (CF^CFI (Peninsular); CF 3CC£=CC£ 2 (Columbia Organic Chemicals, Ltd.); (CH 3) 2SiC£ 2 (Dow-Corning Chemicals, Inc.); CH 3SiC£ 3 (Dow-Corning); GeCJ^ (Peninsular); (CH 3) 2GeC£ 2 (Alfa Inorganics, Inc.); CH^ GeCJ!^  (Alfa); (CH 3) 2SnC£ 2 (Alfa); and SnC^ (Alfa). Of the above compounds, those which showed an n.m.r. spectrum were found to be at least 99% pure except (CH 3) 2GeC£ 2 which showed, in addition to the main peak at -1.30 p.p.m., a small peak (15% of For the addresses of the suppliers - see Appendix 2. - 13 -main peak) at -1.78 p.p.m. This peak was probably due to CH^ GeCft which also absorbs at -1.78 p.p.m.; however, the' (CH^^GeC^ w a s used without further purification. Acetylene was purchased from Matheson of Canada Ltd. and the acetone solvent was removed by trap-to-trap d i s t i l l a t i o n . A. Fluoroalkynes 1. Preparation of 3,3,3-Trifluoropropyne 1,2,2-Trichloro-3,3,3-trifluoropropene was dehalogenated 34 according to the method of Finnegan and Norris with two slight modifications. The amount of fused zinc chloride was increased from 0.025 to 0.3 moles and the reaction temperature was maintained at 140° - 150° instead of 100° during the addition of the propene. Using these modifications a 77% yield of the propyne was obtained. 2. Preparation of 3,3,4,4,4-Pentafluorobutyne 35 Using the procedure of Haszeldine and Leedham, the olefin, 3,3,4,4,4-pentafluoro-l-iodobutene, which resulted from the ultra-violet irradiation of pentafluoroethyl iodide with acetylene (see also Appendix 1 of this Thesis) was added to a large excess of finely powdered KOH and heated under reflux (1 hr.). The resulting 3,3,4,4,4-pentafluorobutyne (51% yield) was collected in^trap cooled to -78° and purified by trap-to-trap d i s t i l l a t i o n . The purity of the butyne was checked by i t s "*"H n.m.r. spectrum which showed a tripl e t of quartets centred at -2.23 p.p.m. Urv „ = 5.3 cps; 19 JC~F -H = C P S ) • T n e F spectrum (external CFCJ^) showed two absorptions: a quartet of doublets at 105.9 p.p.m. (-CF^-) and a t r i p l e t of doublets at 88.7 p.p.m. (-CF0) ( J _ = 3.6 cps). j r —r 3. Preparation of 3,4,4,4-Tetrafluoro-3-trifluoromethylbutyne The butyne was prepared using Haszeldine's method for the 35 preparation of 3,3,4,4,4-pentafluorobutyne. In two separate experiments, 3,4,4,4-tetrafluoro-3-trifluoromethyl-l-iodobutene, prepared by the u l t r a v i o l e t i r r a d i a t i o n of heptafluoroisopropyl iodide with acetylene (see Appendix 1, p. 201) was added to a large excess of f i n e l y powdered KOH and heated under re f l u x (1 h r . ) . The resulting alkyne, 3,4,4,4-tetrafluoro-3-trifluoromethylbutyne, was collected i n a trap cooled to -78°, pu r i f i e d by trap-to-trap d i s t i l l a t i o n , and dried for one day over KOH (42% y i e l d ) . Anal. Found: C, 30.71; H, 0.60%. Calc. for C5H7H: C, 30.92; H, 0.52%. Infrared spectrum (vapour): 3340 (m), 2155 (w), 1795 (vw), 1629 (vw), 1395 (w), 1319 (s), 1282 (s) , 1259 (vs), 1209 (m), 1189 (m), 1160 (s), 1079 (s) , 1056 (m), 990 ( s ) , 950 (vw), 850 ( w ) , 732 (m), 700 (w), and 677 (w) cm"1. The "4 n.m.r. spectrum showed a doublet of septets centred at -2.35 p.p.m. C J ^ ^ p ^ p ^ 19 3 2 = 6 cps; J n-n/n-n \ ~ 0.6 cps). The F n.m.r. spectrum (external n—Or(Or 3^2 CFC£3) showed a doublet of doublets centred at 90.7 (-CF^) and a doublet of septets centred at 171.8 (=CF) p.p.m. ( J „ „ = 9.9 cps). - 15 -The following vapour pressure data were obtained for the butyne: T(°K) 103/T(°K 1) P (cm) log p 1 209.0 4.785 0.869 - 0.061 2 227.8 4.390 3.358 0.526 3 236.1 4.255 5.854 0.768 4 250.1 4.000 12.243 1.088 5 273.0 3.663 38.070 1.595 6 297.0 3.36 66.25 1.821 The plot of log p against 10 /T( b .p. = Latent Heat of _ Vapourization:L r v Trouton's const. = K ) gave the following results: 23° (760 mm) 6.28 kcal/mole 21.2 e.u. B. Group IV halides 1. Preparation of Trimethylgermanium Bromide Tetramethylgermane, prepared by the reaction of methyl-48 magnesium iodide with germanium tetrachloride, and bromine (0.05 49 molar excess) were shaken at 20° for 10 days. The excess bromine was removed by shaking with mercury while keeping the reaction flask in an ice-water bath. D i s t i l l a t i o n at atmospheric pressure yielded - 16 -trimethylgermanium bromide, b.p. 116° - 118° (atm) ( l i t . value: 113.7° (760 mm)~*^ . Its purity was checked by ''"H n.m.r. spectroscopy which showed a single peak at -0.79 p.p.m. 2. Preparation of Trimethyltin chloride Trimethyltin chloride was prepared according to the method given by van der Kerk and Luij ten"?"*" A stoichiometric 1:3 mixture of tin tetrachloride and tetramethyltin were heated at 134° for three hours. The product d i s t i l l e d at 146° - 152° (atm). I l l . Preparation of Group IV Perfluoroalkynyl Derivatives A. General Experimental Procedures A l l group IV perfluoroalkynyl derivatives were prepared by the reaction of a fluoroalkynyl Grignard reagent with the appropriate metal halide. The fluoroalkynyl Grignard reagent was prepared by displacing either an alkyl or aryl group from the corresponding alkyl or aryl magnesium halide by a terminal alkyne. Reaction with a metal halide then produced the metal alkyne. Two quite different experimental procedures were used. They are described f i r s t as general procedures and are referred to in the text. Procedure A. The appropriate fluoroalkyne was condensed into a Carius tube containing a diethyl ether solution of a slight molar excess of either an alkyl or aryl magnesium halide. The tube was sealed, allowed to warm slowly to room temperature (behind a safety shield), and then shaken at 20° for 24 hours. The contents of the tube were then added in small quantities using either a right-angled adapter (Figure 3) or a syringe, to the appropriate metal halide dissolved in a small quantity of ether in a 250 ml flask. The flask was to portable trap at -78° reagent Figure 3. Apparatus used in Procedure A for the preparation of Group IV perfluoroalkynyl derivatives. equipped with a magnetic stirrer and was either (a) connected to a vacuum line leading to a mercury manometer via an in-line trap cooled to -78°, or (b) equipped with a water-cooled condenser leading to a paraffin o i l bubbler and with an in-line portable trap cooled to -78°. When the addition of the fluoroalkynyl Grignard - 18 -reagent was complete the mixture was refluxed with the portable trap s t i l l attached. (The refluxing time is specified for each reaction.) After refluxing the in-line trap was examined for starting fluoro-alkyne. The majority of the ether solvent was removed under atmospheric pressure and the remaining volatiles were removed under vacuum with heating. Further d i s t i l l a t i o n and v.p.c. purification, or, in the cases of solids^ recrystallization, yielded the metal perfluoroalkynyl product. Procedure B. A 250 ml flask was equipped with a magnetic stirr e r , a bubbler which extended to the bottom of the flask, a dropping funnel with pressure equalizing arm, and a low-temperature condenser cooled to -78°. A portable trap, also cooled to -78°, was connected i n -line between the low temperature condenser and a paraffin-oil bubbler. The fluoroalkyne, contained in a Carius tube equipped with a screw-down Teflon valve, was bubbled into the flask which contained a slight molar excess of a diethyl ether solution of an alkyl magnesium halide. The fluoroalkyne was added at a rate slow enough so that the displaced gaseous alkane (usually CH^) did not overly agitate the bubbler when venting into the atmosphere. Furthermore, when necessary, extra diethyl ether was added to the flask so that the level of the liquid was well above the bubbler exit. The solution was stirred for 10 minutes after the addition of the fluoroalkyne was complete. The low-temperature condenser - 19 -was then replaced by a water-cooled condenser and the mixture was heated under reflux for 5 - 1 0 minutes. The flask was then allowed to cool to room temperature and the appropriate metal halide dissolved in a small quantity of ether was added with vigorous st i r r i n g . The mixture was then refluxed. (The refluxing time i s specified for each reaction.) After refluxing the contents of the portable trap were examined for unreacted fluoroalkyne. The majority of the ether was removed directly at atmospheric pressure and the remaining volatiles were removed under vacuum with heating. Further d i s t i l l a t i o n and v.p.c. purification or recrystallization yielded the metal alkynyl product. In certain cases, in both procedures A and B, the Grignard complex was decomposed using a saturated aqueous solution of ammonium chloride. When this was done, the ethereal solution was dried over calcium chloride for at least three hours before d i s t i l l a t i o n . B. Group IV Derivatives of 3,3,3-Trifluoropropyne 1. Preparation of Bis(3,3,3-trifluoropropynyl)dimethylsilane Using procedure B (p. 18) 3,3,3-trifluoropropyne (5.3 g, 56.5 mmoles) was bubbled into a solution containing the Grignard reagent prepared from magnesium and methyl iodide (10.6 g, 74.8 mmoles). Dimethylsilicon dichloride (6.0 g, 46.5 mmoles) was added over 45 minutes. The mixture was refluxed for 15 hours. Examination of the contents of the portable trap showed only a trace of the parent propyne. V.p.c. purification (20% silicone GE-SS-96 at 55°) of the d i s t i l l a t i o n fraction b.p. 82° - 102° (atm) gave bis(3,3,3-trifluoropropynyl)— dimethylsilane CO.7 g, 11% yield), micro, b.p. 111° (atm). - 20 -Anal. Found: C, 39.19; H, 2.28; F, 46.41%. Calc. for C 0H,F,Si: O D D C, 39.35; H, 2.48; F, 46.68%. Infrared spectrum (vapour): 2990 (w), 2910 (w), 2221 (w), 1261 (s), 1250 (vs), 1222 (s), 1179 (vs), 1140 (w) , 1078 (w), 885 (m), 841 (w), 821 Cm), 800 (m) cm"1. The 1H n.m.r. and 19 F (external CFC£^) n.m.r. spectra both showed singlets at -0.10 and 53.41 p.p.m., respectively. In a second reaction when an attempt was made to decompose the excess Grignard reagent with a saturated aqueous solution of ammonium chloride there was complete decomposition of the s i l i c o n -propyne product and the starting propyne was recovered quantitatively. The dimethylsilicon propynyl derivative could be stored at room temp-erature and exposed to the atmosphere without visi b l y decomposing. 2. Attempted preparation of Tris(3,3,3-trifluoropropynyl)methylsilane. Using procedure B (p. 18) 3,3,3-trifluoropropyne (9.10 g, 96.9 mmoles) was bubbled into a solution of the Grignard reagent made from methyl iodide (17.82 g, 125.5 mmoles) and magnesium. Methyl-silicon trichloride (7.20 g, 48.1 mmoles) in anhydrous ether was added over 30 minutes and the reaction mixture was stirred without heating for 16.5 hours. D i s t i l l a t i o n gave a major fraction, b.p. 107 - 108° (atm), which was purified by v.p.c. (20% silicone GE-SS-96 at 60°) and identified as bis(3,3,3-trifluoropropynyl)dimethylsilane (see 1 above). Anal. Found: C, 39.30; H, 2.76%. Calc. for CgHgFgSi: C, 39.35; H, 2.48%. - 21 -3a. Preparation of 3,3,3-Trifluoropropynyltrimethylgermane. Using procedure B (p. 18) the fluoropropynyl Grignard was made from 3,3,3-trifluoropropyne (9.0 g, 95.8 mmoles), magnesium, and methyl iodide (15 g, 105.5 mmoles). Trimethylgermanium bromide (12 g, 60.8 mmoles) was added over 15 minutes and the reaction mixture was refluxed for 3 hours. The excess Grignard reagent was decomposed with a saturated aqueous solution of ammonium chloride. No free propyne was detected in the portable trap. D i s t i l l a t i o n gave the 3,3,3-trifluoropropynyltrimethylgermane (1.9 g, 14.5% yield), micro b.p. 94° (atm), which turned slightly yellow on standing. An analytical sample was obtained by v.p.c. (20% SE-30 at 103° or 20% dinonyl phthalate at 85°). Anal. Found: C, 33.83; H, 4.35%. Calc. for CgHgF^Ge: C, 34.19; H, 4.28%. Infrared spectrum (vapour): 2995 (w), 2910 (w), 2201 (w), 1261 (s), 1219 (m), 1163 (s), 1129 (vw), 839 (m), -1 1 19 770 (w) cm . The H and F (external CFC£ 3) n.m.r. spectra both showed singlets at -0.17 and 51.35 p.p.m., respectively. The same reactions when carried out using procedure A but omitting the hydrolysis with ammonium chloride gave a 13% yield of the germanium propynyl product. 3b. Attempted hydrolysis of 3,3,3-Trifluoropropyryltrimethylgermane. 3,3,3-Trifluoropropynyltrimethylgermane (0.315 g, 1.49 mmoles) and water (ca. 2 g, 111 mmoles) were immiscible at 20°C. After three months at room temperature only a trace of the parent acetylene, 3,3,3-trifluoropropyne, the expected hydrolysis product, - 22 -was detected. 4a. Preparation of Bis(3,3,3-trifluoropropynyl)dimethylgermane. Using procedure A (p. 16) 3,3,3-trifluoropropynyl magnesium bromide from 3,3,3-trifluoropropyne (15.55 g, 165.5 mmoles), ethyl bromide (18.0 g, 165.5 mmoles) and magnesium. Dimethylgermanium dichloride (20 g, 115.0 mmoles) in ether (100 ml) was added over 15 minutes. After refluxing for three hours a small amount of starting propyne (< 0.5 g) was isolated from the contents of the i n -line trap. D i s t i l l a t i o n gave two main fractions b.p. 118° - 125° (atm) and 137° - 138° (atm). These were separated by v.p.c. according to the following scheme to give bis(3,3,3-trifluoropropynyl)dimethyl-Fr.#l' Discarded Fr.//2' Discarded b.p. 118° - 125° Apiezon-J at 120° Fr.//2 Dinonyl Phthalate at 125° Fr.#3 Fr.#4 Discarded Fr.//2" Unknown A Fr.#5 b.p. 137° - 138 - 23 -germane (1.03 g, 10% yield), micro b.p. 126° Catm). Anal. Found: C, 33.22%; H, 2.41; F, 40.23%. Calc. for CgR^FgGe: C, 33.31; H, 2.09; F, 39.5%. Infrared spectrum (vapour): 2999 (w), 2923 (vw), 2208 (m), 1266 (s), 1251 (vs), 1221 (m), 1179 (vs), 853 (m), 829 (s), -1 1 19 778 (m) cm . The H and F (external CFCl^) n.m.r. spectra both showed singlets at -0.39 and 52.6 ppm, respectively. Of the remaining v.p.c. fractions only those which are labelled Unknown A and Unknown B were kept. The others, including fractions labelled 1', 2', 3, 4, 5, 6, and 8, were discarded on the basis that (a) they a l l showed more than two peaks in their "'"H n.m.r. spectra which did not integrate in small whole-number ratios, and (b) they were a l l < 0.1 g and i t was not feasible to attempt further separation. The two fractions, Unknowns A and B, both showed only one peak in their n.m.r. spectra. They could not however, be identified. Data on these two fractions includes: Unknown A: Anal. Found: C, 21.66; H, 2.32; Cl, 13.00; F, 27.14%. Infrared spectrum (vapour): 2990 (vw), 2900 (vw), 2200 (w), 1412 (vw), 1253 (s(br)), 1218 (s), 1170 (s), 1137 (w), 848 (m), 825 (s), 767 (w) cm"1. The """H and 1 9 F (external CFCl^) n.m.r. spectra of Unknown A both showed singlets at -1.0 and 51.7 p.p.m., respectively. Unknown B: Anal. Found: C, 13.04; H, 3.8; Cl 13.00%. Infrared spectrum (film): 1404 (m), 1239 (m), 852 (s) , 825 (s), 772 (m) cm 1 . The "'"H n.m.r. spectrum showed a singlet at -1.79 p.p.m. There were no fluorine atoms in the sample. - 24 -4b. Attempted hydrolysis of Bis(3,3,3-trIfluoropropynyl)dimettrylgermane. Bis(3,3,3-trifluoropropynyl)dimethylgermane (0.216 g, 0.75 mmoles) and water (ca. 1 g, 55.5 mmoles) were immiscible at 20°. After four months at 20° only a trace of 3,3,3-trifluoropropyne was detected. The reactants were recombined and heated at 150° for 24 hours. Again, however, only a trace of propyne was detected. 5. Preparation of Tris(3,3,3-trifluoropropynyl)methylgermane. Using procedure B (p. 18) 3,3,3-trifluoropropynyl magnesium iodide was prepared from 3,3,3-trifluoropropyne (11.1 g, 118 mmoles), methyl iodide (16.8 g, 118.5 mmoles), and magnesium. Methylgermanium trichloride (6.5 g, 35.3 mmoles) in ether (30 ml) was added to the Grignard solution. After refluxing for three hours a very small amount of unreacted propyne (< 0.1 g) was detected. The volatiles were removed under high vacuum with heating and then d i s t i l l e d to give a major fraction, b.p. 132° - 133.5° (atm), which was slightly reddish. The red colour was removed by shaking with mercury. The d i s t i l l a t e s o l i d i f i e d upon standing at room temperature. Purification was affected by vacuum sublimation onto a cold finger cooled to -78°C followed by recrystallization from hot hexane. This gave white crystals of tris(3,3,3-trifluoropropynyl)methylgermane (0.9 g, 7.0% t yield),*, m.p. 47°. Anal. Found: C, 32.99; H, 0.99; F, 46.^0%. The yield was probably considerably higher since a large amount of product was lost through an unfortunate accident during the work-up. - 25 -Calc. for C H^Ge: C, 32.75; H, 0.82; F, 46.63%. Infrared spectrum (Nujol mull): 2223 (m), 1241 (vs), 1218 (s) , 1166 (vs), 851 (m), -1 1 19 831 (m) cm . The H and F (internal CFC£ 3) n.m.r. spectra (CDC£3 solution) both showed singlets at -1.07 and 52.85 p.p.m., respectively. The germanium propynyl product was stable in air at 20°. 6. Preparation of Tetrakis(3,3,3-trifluoropropynyl)germane. Using procedure B (p. 18) the fluoropropynyl Grignard reagent was prepared from 3,3,3-trifluoropropyne (10.0 g, 106 mmoles), methyl iodide (16.5 g, 106 mmoles), and magnesium. The Grignard solution was refluxed for 45 minutes after the addition of the propyne. Germanium tetrachloride (4.84 g, 22.5 mmoles) in ether (40 ml) was added over 5 minutes. The reaction was exothermic. The mixture was refluxed for three hours. A small amount of 3,3,3-trifluoropropyne was detected in the portable trap. The high boiling volatiles and some ether were removed under high vacuum while heating the flask with a bunsen burner. A solid product was separated from the ether solvent by vacuum sublimation onto a cold finger cooled to -78°. The sublimed product was then taken up in hot hexane, decolourized with mercury and activated charcoal, and recrystallized to give white crystals of tetrakis(3,3,3-trifluoropropynyl)germane (1.0 g, 10.0% yield), m.p. 101.5° - 102.5° (sealed capillary). Anal. Found: C, 32.60; F, 51.00%. Calc. for C^F^Ge: C, 32.41; F, 51.26%. Infrared spectrum (Nujol mull): 2225 (w), 1241 (vs), 1219 (s), -1 19 1155 (vs), 925 (w), 858 (m) cm . The F spectrum (internal CFC£ , • - 26 -CDC&3 solution) showed a singlet at 53.35 p.p.m. 7a. Preparation of 3,3,3-Trifluoropropynyltrimethyltin. Using procedure A (p. 16 ) the fluoropropynyl Grignard reagent, prepared from 3,3,3-trifluoropropyne (8.04 g, 85.6 mmole), methyl iodide (18 g, 127 mmoles), and magnesium, was added over 20 minutes to trimethyltin chloride (28.04 g, 141 mmoles) in ether (50 ml). The mixture was refluxed for three hours. No free propyne was detected in the portable trap after refluxing. D i s t i l l a t i o n under nitrogen gave 3,3,3-trifluoropropynyltrimethyltin (14.0 g, 64% yield), micro b.p. 125° (atm). Anal. Found: C, 28.22; H, 3.82; F, 22.2: Sn, 46.09%, Calc. for C 6H gF 3Sn: C, 28.06; H, 3.53; F, 22.19; Sn, 46.21%. Infra-red spectrum (vapour) : 3020 (TO), 2960 (vw), 2188 (m), 1252 (vs), -1 1 1219 (s), 1164 (vs), 785 (m), cm . The H n.m.r. showed a singlet at -0.26 p.p.m. with t i n s a t e l l i t e peaks ( J i i 7 c m , = 58.2 cps; £>n— 19 J i l 9 c ^„ = 61.0 cps). The F n.m.r. spectrum (external CFC&,) an—t/H^ J showed a singlet at 50.25 p.p.m. A higher boiling fraction, b.p. 167° - 170° (760 mm),was identified as trimethyltin iodide (9.78 g, b.p. l i t . value: 170° (760mm) 5 2). Anal. Found: C, 12.22; H, 3.09; I, 43.41%. Calc. for C ^ I S n : C, 12.40; H, 3.12; I, 43.65%. Attempted preparations using procedure A, and either benzyl or ethyl bromides in preparing the i n i t i a l Grignard reagent gave lower yields; furthermore, the propynyltin compound was more d i f f i c u l t to purify when either C^Hj-Br or C~Hj.Br were used in place of C1L.I. - 27 -7b. Hydrolysis of 3,3,3-Trifluoropropynyltrimethyltin. 3,3,3-Trifluoropropynyltrimethyltin CO.341 g, 1.33 mmoles) and water (ca. 1 g, 55 mmoles) reacted immediately upon warming to room temperature. A gas was produced. After 24 hours at room temp-erature a yellow solution and some white precipitate had formed. Trap-to-trap d i s t i l l a t i o n of the volatiles yielded 3,3,3-trifluoro-propyne (0.122 g, 98% yield) identified by i t s known infrared spectrum and molecular weight of 95.2 (Calc. for C^F^H^). 8a. Preparation of Bis(3,3,3-trifluoropropynyl)dimethyltin. Using procedure A (p. 16 ) the fluoropropynyl Grignard reagent was made from 3,3,3-trifluoropropyne (12.0 g, 128 mmoles), ethyl bromide (21.0 g, 193 mmoles), and magnesium. The Grignard reagent was added over 15 minutes to dimethyltin dichloride (41.44 g, 189 mmoles) in anhydrous ether (50 ml). The reaction was slightly exothermic. The mixture was stirred for five hours and then refluxed for 1.5 hours. No starting propyne was detected in the portable trap. D i s t i l l a t i o n under nitrogen gave a major fraction^b.p.,149° - 156° (atm). V.p.c. purification of this fraction (20% silicone GE-SS-96 at 158°) gave bis(3,3,3-trifluoropropynyl)dimethyltin (9.05 g, 21.2% yield), micro b.p. 156° (atm). Anal. Found: C, 28.55; H, 1.85; F, 33.81; Sn, 35.51%. Calc. for CgHgFgSn: C, 28.67; H, 1.81, F, 34.05; Sn, 35.45%. Infrared spectrum (vapour): 3008 (vw), 2915 (vw), 2195 (m), 1242 (vw), 1220 (s), 1172 (vs), 779 (m) cm"1. The "'"H n.m.r. spectrum showed a single peak at -0.49 p.p.m. with t i n - 28 -satellites C J i i 7 g n _ C H =68.6 cps; J H 9 S N _ C H = 7 2 - 7 cps). The F n.m.r. spectrum (external CFC^) showed a singlet at 51.54 p.p.m. Other attempted preparations using procedure A and either benzyl bromide or benzyl iodide as sources for the i n i t i a l Grignard reagent were unsuccessful. The bis(propynyl)tin compound was produced in very small yields and could not be separated from substituted benzene by-products. The bis(propynyl)tin compound was very unstable and decomposed rapidly under vacuum at room temperature yielding a white precipitate and HC^CCF^. The latter was identified by i t s infrared spectrum. The bis(propynyl)tin compound could only be stored under vacuum and at 0°. 8b. Hydrolysis of Bis(3,3,3-trifluoropropynyl)dimethyltin. Bis(3,3,3-trifluoropropynyl)dimethyltin (0.601 g, 1.8 mmoles) and water (ca. 1 g, 55 mmoles) were immiscible but reacted after several minutes at room temperature. After 24 hours some white precipitate had formed. Trap-to-trap d i s t i l l a t i o n yielded 3,3,3-trifluoropropyne (0.244 g, 76% yield) identified by i t s known infra-red spectrum and molecular weight of 97.2 (calc. for C.jF3H:94). No remaining.bis(propynyl)dimethyltin was detected. - 29 -C_. Group IV Derivatives of 3,3,4,4,4-Pentafluorobutyne. 1. Preparation of 3,3,4,4,4-Pentafluorobutynyltrimethylgermane. Using procedure B (p. 18) trimethylgermanium bromide (10.5 g, 53.2 mmoles) was added over 30 minutes to the fluorobutynyl Grignard reagent prepared from 3,3,4,4,4-pentafluorobutyne (4.94 g, 34.7 mmoles), methyl iodide (7.4 g, 52 mmoles),and magnesium. The reaction was slightly exothermic. After refluxing for three hours the excess Grignard reagent was decomposed with a saturated aqueous solution of ammonium chloride. No starting butyne was detected in the portable trap. V.p.c. purification (20% Kel-F grease at 85°) of the major d i s t i l l a t i o n fraction, b.p. 99° - 106° (atm), gave a compound identified as 3,3,4,4,4-pentafluorobutynyltrimethylgermane (6.66 g, 74% yield), micro b.p.: 104° (atm). Infrared spectrum (vapour): 2980 (TO), 2900 (vw), 2195 (vw), 1339 (w), 1225 (s), 1200 (s), 1130 (m), 1050 (m), 835 (m) cm The "*"H n.m.r. showed a singlet at -0.16 p.p.m. 19 The F n.m.r. spectrum (external CFCii^) showed a t r i p l e t centred at 86.65 p.p.m. (-CF^) and a quartet centred at 101.9 p.p.m. ( - C F 2 - ) (J = 4.1 cps). An analytically pure sample could not be obtained r —r although a v.p.c. investigation showed only a single peak with a l l available columns (Table I, p. 10 ). The butynylgermanium derivative was clear upon d i s t i l l a t i o n but turned yellow upon standing; i t was both hydrolytically and thermally stable in air at 20°. - 30 -2 . Preparation of Bis (3,3,4,4 ,4-pentaf luorobutynypdimethylgermane. Using procedure B (p. 18) 3,3,4,4,4-pentafluorobutynyl magnesium iodide was prepared from 3,3,4,4,4-pentafluorobutyne (5.09 g, 34.6 mmoles), methyl iodide (7.4 g, 52 mmoles), and magnesium. Dimethylgermanium dichloride (4.5 g, 26 mmoles) in anhydrous ether (30 ml) was added to the Grignard solution over 15 minutes. After refluxing for three hours the excess Grignard reagent was decomposed with a saturated aqueous solution of ammonium chloride. No starting butyne was detected in the portable trap. D i s t i l l a t i o n under nitrogen gave a fraction, b.p. 130° - 142° (atm), which was purified by v.p.c. (using two columns in series and collecting only the major fraction from each column: 20% Kel-F grease at 115° followed by 20% silicone GE-SS-96 at 110°) and identified as bis(3,3,4,4,4-pentafluorobutynyl)-dimethylgermane (4.61 g, 67% yield), micro b.p. 138° (atm). Anal. Found: C, 30.69; H, 1.55%. Calc. for C ^ K ^ ^ G e : C, 30.90; H, 1.56%. Infrared spectrum (vapour): 3000 (vw), 2910 (vw), 2200 (vw), 1340 (m), 1226 (s), 1207 (s(br)),1137 (m), 1051 (s), 850 (w), 825 (m), 787 (w), 705 (w) cm The n.m.r. spectrum showed a singlet at 19 -0.47 p.p.m. The F spectrum (external CFC^) showed a t r i p l e t at 86.9 p.p.m. (-CF3) and a quartet at 103.7 p.p.m. (-CF2~) (Jp_ F = 3.8 cps) . The bis(butynyl)germane turned pink upon standing at 20°. It was both hydrolytically and thermally stable in air at 20°. - 31 -3a. Preparation of 3,3,4,4,4-pentafluorobutynyltrimethyltin. Using procedure B (p. 18), the fluorobutynyl Grignard reagent was prepared from 3,3,4,4,4-pentafluorobutyne (5.15 g, 34.7 mmoles), methyl iodide (7.35 g, 52 mmoles), and magnesium. Trimethyl-t i n chloride (10.4 g, 52 mmoles) in ether (30 ml) was added to the fluorobutynyl Grignard solution over 20 minutes. The solution was refluxed for three hours. No starting butyne was detected. D i s t i l l a t i o n under a nitrogen atmosphere at atmospheric pressure gave three fractions, b.p. 38° - 120°, 120° - 132°, and 160° - 172°. V.p.c. purification (20% silicone GE-SS-96 at 75°) of the fraction b.p. 38° - 120° gave a small quantity of tetramethyltin (0.114 g) and 3,3,4,4,4-pentafluorobutynyltrimethyltin (2.13 g, 20% yield), micro b.p. 130.5° - 131° (atm). Anal. Found: C, 27.42; H, 3.10; F, 30.69%. Calc. for C-^F^n: C, 27.40; H, 2.96; F, 30.96%. Infrared spectrum (vapour): 3005 (w), 2938 (vw), 2182 (w), 1346 (m), 1231 (s), 1208 (s), 1133 (s), 1172 (vw), 1054 (s), 781 Cm), 699 (w) cm The "*"H n.m.r. spectrum showed a single peak at -0.22 p.p.m. with t i n s a t e l l i t e " ( J i 1 7 0 ^ T 7 = 59.0 cps; J u s - „„ = 61.7 cps). bn—On, bn—On, 19 The F n.m.r. spectrum (internal CFCiLj) showed two sets of peaks, one, a t r i p l e t centred at 86.43 p.p.m. (-CF^), and the other, a quartet centred at 101.1 p.p.m. (-CF2~) C J p _ F = 4.1 cps). The third fraction, b.p. 160° - 172° was identified as trimethyltin iodide by comparison 1 of i t s b.p. and H n.m.r. spectrum with the corresponding values of 52 a known sample C b . p . l i t value: 170° ). - 32 -3b. Hydrolysis of 3,3,4.4,4~Pentafluorobutynyltrimethyltin. 3,3,4,4,4-Pentafluorobutynyltrimethyltin (1.360 g, 1.20 mmoles) and water (0.7 g, 39 mmoles) were immiscible but reacted after five minutes at room temperature. A gas was produced. After 12 hours some white precipitate had formed., After one month at room temperature 3,3,4,4,4-pentafluorobutyne (0.141 g, 72% yield) was isolated by trap-to-trap d i s t i l l a t i o n and identified by i t s known infrared spectrum and molecular weight of 143 (calc. for C4F^H:144). D_. Group IVA Derivative of 3 ,4 ,4 ,4-Tetraf luoro-3-trif luoromethylbutyne. 1. Preparation of 3,4,4,4-Tetrafluoro-3-trifluoromethylbutynyl-trimethylgermane. Using procedure B (p. 18 ) the fluorobutynyl Grignard reagent was prepared from 3 ,4,4,4-tetrafluoro-3-trifluoromethylbutyne (8.35 g, 43 mmoles), methyl iodide (7.5 g, 53 mmoles), and magnesium. Trimethylgermanium bromide (8.5 g, 43 mmoles) in ether (30 ml) was added over 20 minutes. After refluxing for three hours the excess Grignard reagent was decomposed with a saturated aqueous solution of ammonium chloride. No starting butyne was detected in the portable trap. D i s t i l l a t i o n at atmospheric pressure gave a fraction, b.p. 112° - 114°, which was purified by v.p.c. (20% Kel-F grease at 80°) and identified as 3,4,4,4-tetrafluoro-3-trifluoromethylbutynyl-trimethylgermane (7.09 g, 77% yield), micro b.p. 113.1° (atm). Anal. Found: C, 30.89; H, 2.91; F, 42.90; Ge, 23.13%. Calc. for - 33 -CcHnF^Ge: C, 30.93; H, 2.91, F, 42.79; Ge, 23.36%. Infrared spectrum o y / (vapour): 2989 (w), 2920 (w), 2182 (vw), 1419 (vw), 1312 (s), 1272 (s), 1245 (vs), 1182 (m), 1158 (vs), 1077 (s), 978 (s), 840 (m), 772 (m), 725 (m) cm The n.m.r. spectrum showed a singlet at -0.18 p.p.m. 19 The F n.m.r. spectrum (internal CFCl^) showed a doublet centred at 73.0 p.p.m. (-CF^) and a septet centred at 166.0 p.p.m. (=CF) (Jp_p = 10.6 cps). This butynyl germanium compound did not discolour upon standing but remained colourless unlike the other fluoroalkynyl germanium derivatives. It was both hydrolytically and thermally stable in air at 20°. - 34 -RESULTS AND DISCUSSION I. The Fluoroalkynes A. Preparation of 3,4,4,4-Tetrafluoro-3-trifluoromethylbutyne. The alkyne, HCSCCF(CF3>2, is conveniently prepared in 42% yield by the dehydroiodination of 3,4,4,4-tetrafluoro-3-trifluoro-methyl-l-iodobutene with finely powdered KOH. The butene precursor, i t s e l f , is prepared by the ultraviolet-induced addition of hepta-fluoroisopropyl iodide to acetylene. ICF(CF )_ + HC=CH — -> IHC=CHCF(CF ) [1.1] J A > 2850A J KOH IHC=CHCF(CF3)2 > HCHCCF(CF3)2 [1.2] (See Appendix 1 for a discussion of the trans:cis isomer ratio produced by eq. [1.2]). Similar preparations of HC=CCF3 and 32 35 HC=CCF2CF3 via CF 3I and C^^I, respectively, have been reported. ' The structure of HCECCF(CF3)2 (b.p. 23°C) is deduced from i t s infrared (Table V, p. 48 ) and n.m.r. (Table VI, p. 50 ) spectra and confirmed by elemental analysis. The infrared spectrum includes bands at 3340 cm and 2155 cm which are due to the C-H and CEC stretching vibrations. The "'"H n.m.r. spectrum shows the expected doublet (J , « =6 cps) and each peak is broadened by coupling H—Or (Lb 3) 2 with the t r i f luoromethyl groups although J„ \ i-s n o t discernible. This latter coupling constant is clearly resolved in 19 the F n.m.r. spectrum and the set of peaks due to the trifluoromethyl - 35 -groups is displayed as a doublet of doublets at 90.7 p.p.m. (J = F-~F 9.9 cps; = 0.6 cps). The fluoromethyne group absorbs at 3 19 higher f i e l d (171.8 p.p.m.) in the F n.m.r. spectrum as the expected doublet of septets. 53 Dear and Gilbert have attempted the preparation of this butyne by reacting SF^ with 4,4,4-trifluoro-3-trifluoromethyl-3-hydroxybutyne but obtained only 1-fluoro-3,3-bis(trifluoromethyl)allene. (CF3)2CC=CH + SF 4 > (CF3)2C=C=CFH [1.3] OH The 1-chlorobutyne derivative can be prepared however, by a similar 53 ^ reaction, that i s , (CF3)2CCECC£ + SF^ > (CF3)?CFC=CC£ [1.4] OH B. Comparison of Characteristic Infrared Frequencies. The C=C stretching frequencies of the fluoroalkynes are a l l higher than the corresponding frequencies of their non-fluorinated 54 analogs. This i s shown in Table II. For two reasons, this finding is the opposite of what is expected. The frequency of the C=C stretching vibration in HC=C-Z, in general, has been calculated to decrease as the mass of the atom Z directly bonded to the C=C bond 55 increases, assuming that the force constant, k r 7 , is constant. V< Li - 36 -Table II Characteristic Infrared Frequency of v(CHC) (in cm ^ ) of Some 54 Fluoroalkynes and Their Non-Fluorinated Analogs. HC=CR V(CEC) R = CF 3 2165 CH0 2150 R = CF 2CF 3 2160 CH2CH3 2120a CF(CF 3) 2 2155 CH(CH 3) 2 2135 a -1 This value is only approximate. The value 2120 cm is probably closer to 2140 cm by interpolation between the corresponding values for HC=CCH3 (2150 cm"1) and HCECCH(CH3)2 (2135 cm"1) and by analogy with the trend in the fluoroalkynes. The decrease i s caused by the fact that the observed frequency does not result from an isolated C^ C bond vibration but rather from a coupling of the vibrations of the C=C bond and the adjacent bonds. Increasing the mass of the adjacent atoms reduces the frequency of the bond joing i t to the C=C bond and leads to less vibrational coupling * - 37 -and a lower observed frequency for v(C=C). Thus, the frequency of V(C=C) is expected to be lower in the compounds HC=CR^  than in the non-fluorinated alkynes due to the increased mass of the substituent group caused by the presence of fluorine atoms instead of hydrogen atoms. It is to be noted that this expectation is based on the assumption that the force constant of the bond joining the substituent group to the C=C bond is the same in both fluorinated and non-fluorinated alkynes. An alternative reason for expecting a lower frequency for V(C=C) in the fluoroalkynes is that the high electro-negativity of the fluorine substituents is expected to reduce; the electron density of the triple bond, thereby reducing the force constant and V(C=C). The observed higher frequency of v(C=C) in the spectra of fluorinated alkynes relative to the frequency observed in the non-fluorinated analogs may be related to the observed frequency of V(C=C) in the compounds HC=C-X which increases in the order X = I < Br < Cl < 56 F ; this order is the opposite of what is expected. However, in the case of the haloacetylides, the force constants, k v , are not the L—X 56 same, but increase also in the order X = I < B r < C J £ < F . Thus, in the two classes of alkynes, HC=CRf and HC=CR, i t appears that the force constant k may be larger in the former than in the latter and that the subsequent effect of the apparently larger constant, ^-Q_Q> i - n increasing the frequency of V(C=C) in HC=CR^  compounds is greater than the predicted decreasing effects caused by either the increased mass - 38 -or electronegativity of the groups. It is to be noted that the relationship between the force constant k in HC=C-X and the C — A frequency of V(C=C) is not understood."^ The observed frequency of the C=C bond stretching vibration decreases within each of the fluorinated and non-fluorinated alkyne classes as the mass of the substituent group increases. (This is seen in Table II). If i t is assumed that the force constant, 1*-Q_Q> although different in each class of alkynes as deduced above, is the same within each class, then the decrease in the frequency of v(CEC) as the mass of the substituent group increases may be related to the decrease in v(C=C) in HCEC-Z which, as described above, is calculated to decrease as the mass of the atom Z increases, assuming that k^ ,_^  i s constant. C. Comparison of Some N.m.r. Parameters. The n.m.r. parameters of HCECCF2CF.J have not been previously recorded. The "'"H n.m.r. spectrum shows the expected t r i p l e t at -2.23 p.p.m. ( J j T _ r j - p Q p =5.3 cps) and the peaks are somewhat broadened by ~ 2 3 1 9 coupling with the CF^ groups. The F n.m.r. spectrum displays the expected t r i p l e t of doublets centred at 88.7 p.p.m. and quartet of-doublets centred at 105.9 p.p.m. due to splitting of the CF^ and CF^ groups, respectively ( J F _ F = 3.6 cps; J H _ C F C F =0.5 cps). The chemical shift data and coupling constants for the three fluoroalkynes HCECRf (Rf = CF 3, C ^ , CF(CF 3) 2) are summarized in Table III and in (3)-(5) below. - 39 -Table III Summary of Chemical S h i f t s a of the Fluoroalkynes HC=CRf (Rf = CF 3 > C 2F 5, CF(CF 3) 2). HCECRf 1 9 F =CH CF 3 CF 2 CF -1.88 55.55 -2.23 88.7 105.9 -2.35 90.7 171.8 HC=CCF3 (2) HCECCF2CF3(4) HC=CCF(CF3)2(5) a 1 1 9 In p.p.m. relative to external (CH^^Si ( H) and external CFC&3 ( F) 3.5 5.3 3.6 6 9.9 HC=CCF3 HCECCF 2 CF 3 HC=CCF(CF 3 ) 2 0.5 0.6 (1) (4) (5) A trend in the J u „ coupling constant is noticeable in (3)-rl—r — (5). The J coupling in HC=CCF„ (3) is 3.5 cps* and the analogous rl—Cr3 J coupling constant increases in HC=CCF„CF„ (4) (J =5.3 cps) Beisner et a l , also report a value of 3.5 cps; however, Cullen 45 and Leeder report a value of 3.7 cps. - 40 -and HCECCF(CF3)2 (5) ( J H _ C F ( C F ) = 6 cps). Abraham and C a v a l l i 5 8 . 3 2 have found that the vicinal J coupling constant in substituted ti— t ethanes increases with decreasing total electronegativity of the f i r s t atoms of the substituent groups, e.g., F3C-CF F^C-CF CF 3 F The trend observed in the fluoroalkynes (3)-(5) may have a similar explanation. In Table III i t can be seen that the chemical shift value of the acetylenic hydrogen increases as the size of the group increases. This shift to lower f i e l d may be interpreted as being due to increased deshielding of the hydrogen caused by an increase in the effective electronegativity of the R^  substituents, that i s ; C F 3 < C2 F5 < C F ( C F 3 ) 2 * T h e d i a m a g n e t i c anisotropic effect of the C-CF3 bond on the resonance positions of the hydrogens is not expected to be important at these large distances. Nothing conclusive has yet been reported about the order of the effective electronegativities of perfluoroalkyl groups. The order which is suggested by the n.m.r. results is the opposite to that which has been predicted by Powell and Lagowski. "^'^ Lagowski has estimated the effective group electronegativity of the CF 3 group to 17 be intermediate between that of F and Cil. Powell and Lagowski took this estimate (based on bond dissociation energies) and reasoned that - 41 -replacing a fluorine atom by a less electronegative CF^ group should produce an overall decrease in the inductive effect of CF^CF^ and a further decrease in CF(CF 3) 2. 0 n e might also argue hoxv-ever, that the electron-withdrawing effect of R^  groups should increase as the number of fluorine substituents increases. Powell and Lagowski, i n support of their prediction, have reported estimates of the electronegativities of various R^  groups in R^ HgX including C^HgX, (CF^CFHgX and CF3CF2CF2HgX (X = OH, Cl, Br, and 1 ) . ^ The average electronegativity estimates and error factors for the three R^  groups are (using CF^ =3.3 as a basis): C 2F^ = 3.23 ± 0.6 CF(CF 3) 2 = 3.375 ± 0.3, and CFCF 2CF 3 = 2.97 ± 0.48. Thus no firm conclusion regarding the order of the electronegativities can be drawn from these results. 61 One group of workers, from some approximate (their term) pKa values for the alcohols RfCH(R)0H (Rf = n - C ^ , R = or n-C 3F 7 > pKa = 11.4; R = CF(CF 3) 2, R = n-CgF pKQ = 12.6) have reached conclusions regarding the effective electronegativity of R^  groups that are in harmony with the prediction of Powell and Lagowski. Their term "approximate" is noteworthy. As we shall see i n Chapter 2, the chemical shift of the T r hydrogen atoms the cj'clopropenes HC=CR^(CF2) move to lower f i e l d as the size of the R^  group increases. Furthermore, we shall see i n Chapter 4 that the numerical value of the quadrupole s p l i t t i n g in the MSssbauer absorption spectra of the - 42 -compounds (CHO^SnR^ increases in the order = CF^ < C^CF^ < CFCCF^^- Thus n.m.r. and Mossbauer results, together, form a good basis for concluding that the electronegativity order is CF„ < CF„CF„ < II. Perfluoroalkynyl Derivatives of Silicon, Germanium, and Tin. Group IV perfluoroalkynyl derivatives can be prepared by the reaction of a perfluoroalkynyl Grignard reagent with the appropriate group IV metal halide. The perfluoroalkynyl Grignard reagents are discussed f i r s t . A. Perfluoroalkynyl Magnesium Halides. The compound XMgC=CCF3 (X = Br, I) can be prepared by the reaction of HCECCF3 with C^MgBr or C ^ M g l . Preparation of this propynyl Grignard reagent via CH^Mgl or C2H^MgBr have been previously 29 45 46 reported. ' ' The acetylenic hydrogens of the fluoroalkynes, HCECCF2CF3 and HCECCF(CF3)2, like that of HC=CCF3, are also sufficiently acidic to react with CH3MgI and form the corresponding Grignard reagents IMgCHCRf. Eqs. [1.5] and [1.6] summarize the above reactions: CF(CF„) VI' RX + Mg -> RMgX [1.5] RMgX + HC5CRf [1-6] The perfluoroalkynyl magnesium halides produced by eq. [1.6] are a l l stable in refluxing diethyl ether. This s t a b i l i t y is notable since - 43 -61 62 the corresponding perfluoroisopropyl and perfluoropropyl Grignard reagents decompose at room temperature. The reaction described by eq. [1.6] can be carried out in a sealed Carius tube (diethyl ether solution) or by bubbling the fluoroalkyne in a diethyl ether solution of RMgX. Both procedures yield XMgC=CCF3 although only the latter method was used in making IMgC=CR^  (R = C2F5> C F ( C F 3 ) 2 ) . The latter method is preferred when CH^Mgl or C2H^MgBr is used since the large quantities of evolved methane and ethane, respectively, produce dangerously high pressures when contained as in a sealed Carius tube. B. Preparation of Group IV Perfluoroalkynyl Derivatives. The perfluoroalkynyl magnesium halides from eq. [1.6] react smoothly with various group IV halides to give group IV a-bonded perfluoroalkynyl derivatives. A similar reaction has been used to 13 63 65 prepare perfluoroalkyl and perfluorovinyl Group IV derivatives, e.g. BrMgCF(CF3)2 + (CH^SiCJl > (CH 3) 3SiCF(CF 3) 2 + MgBrCil [1.7] BrMgCF=CF2 + R 3SnC£ > R3SnCF=CF2 + MgBrCS, [1.8] With the exception of (CH 3) 2Si(C=CCF 3) 2 derived from CH 3SiC£ 3, the following general equation describes the preparation of the perfluoro-alkynyl derivatives listed in Table IV, p. 45 . - 44 -(CH 3) nMX 4_ n + (4-n)XMgCSCRf > (CH 3)nM(CECR f>4_n + (4-n)MgX2 [1.9] (X = usually CX,, also Br; M = Si, Ge, or Sn; R = CF„, C„F C, or f 3 2 5 CF(CF 3) 2). Also included in Table IV is the starting halide RX which is used or the halide which gives the best overall results in terms of (a) yield and ease of purification of the metal-alkynyl product, and (b) fewest by-products. Methyl iodide is the best starting halide in these terms. Ethyl bromide when used to prepare (CrL^GeCC^CCF,^),, gives many by-products and the purification of (CH 3) 2Ge(CSCCF 3) 2 is d i f f i c u l t -even by v.p.c. techniques. Similarly, use of ethyl bromide and benzyl bromide make (CH 3) 3SnCsCCF 3 d i f f i c u l t to purify as well as leading to very low yields of this t i n compound. Use of either benzyl bromide or iodide produce very small yields of (CH 3) 2Sn(C=CCF 3) 2 which cannot be purified from by-products. 1. Derivatives of 3,3,3-Trifluoropropyne. Reaction of XMgC=CCF3 (X = I or Br) with (CH^SiCJ^, (CH3)3GeBr, (CH^GeC^, CH^GeCJ^, GeC£ 4, (CH3)3SnC£, and (CH^SnC^ gives the corresponding metal 3,3,3-trifluoropropynyl derivative (CH 3) 2Si(C=CCF 3) 2, (CH3)3GeCECCF3, (CH 3) 2Ge(C=CCF 3) 2, CH^Ge(C=CCF3) , Ge(C=CCF0),, (CH0)0SnCECCF0, and (CH0)„Sn(CECCFj_, respectively, j 4 3 J J O Z J Z according to eq. [1.9]. The reaction involving CH3SiC&3 gives (CH 3) 2Si(C5CCF 3) 2 and w i l l be discussed later. The proposed structures of the metal perfluoroalkynyl products are based on their infrared and Table IV Group IV Perfluoroalkynyl Derivatives Starting Perfluoroalkynyl Metal > Metal Perfluoro- a B.p.°C (atm) % Yield Halide (RX) Grignard Rgt. Halide Alkynyl Deriv. (m.p.°C) 1. Derivatives of HCECCF A. CH 3I IMgC=CCF3 + (CH 3) 2SiCJl 2 - > (CH 3) 2Si(CECCF 3) 2 111 11 B. CH3I IMgCECCF3 + CH3SiC£3 > (CH 3) 2Si(CECCF 3) 2 111 ~5 C. CH3I IMgCECCF3 + (CH3)3GeCJl - > (CH3)3GeCECCF3 94 14.5 D. • C 2H 5Br BrMgC=CCF3 + (CH 3) 2GeC£ 2 - > (CH 3) 2Ge(CECCF 3) 2 126 10 E. " ' C H 3 I IMgCECCF3 + CH3GeC£3 > CH 3Ge(CECCF 3) 3 (47) 7 F. CH3I IMgCECCF3 + GeCJl, -4 > Ge(CECCF 3) 4 (101.5-102.5) 10 G. C H 3 I IMgCECCF3 + (CH3)3SnCj> - > (CH3)3SnCECCF3 125 64 b' d H. C 2H 5Br BrMgCECCF3 + (CH 3) 2SnC£ 2 - > (CH 3) 2Sn(CECCF 3) 2 156 21 c 2. Derivatives ; of HCECCF2CF3 A. CH3I IMgCECCF2CF3 + (CH 3) 3GeB r > (CH 3) 3GeCECCF 2CF 3 104 74 B. CH3I IMgCECCF2CF3 + (CH 3) 2GeCJl 2 - > (CH 3) 2Ge(CECF 2CF 3) 2 138 67 C. CH3I IMgCECCF2CF3 + (CH3)3SnC£ - > (CH 3) 3SnCECCF 2CF 3 131 20 Table IV (continued) 3. Derivative of H C E C C F ' ( C F 3 ) 2 A. CH3I IMgCECCF(CF3)2 + (CH^GeBr > (CH ) 3GeCECCF(CF3) 2 113.1 77 Only one product isolated and identified in each reaction.. C2H^Br and C^H^Br both gave much lower yields ~ 5%. CgH^Br and CgH^I both gave much lower yields and the products could not be separated. Best yield of 3 attempts using CH,I. Other yields: 10% and 13%. - 47 -n.m.r. spectra. Formulae of a l l the compounds are confirmed by elemental analysis for at least two elements. The main bands in the infrared spectra of the derivatives (Table V, p. 48 ) can a l l be assigned. The absorption at 2225 -2201 cm 1 is due to the C=C stretching vibration. It is notable that, although the intensity of the band due to the C=C increases in 66 R Si(C=CH), as n decreases (3 -*• 0) , the opposite trend is evident n 4-n in the spectra of the compounds (CH 3)nM(CECR f)^_ n (Rf = CF^, M = Ge, n = 3,2; R = CF 3, M = Sn, n = 3,2; Rf = C ^ , M = Ge, n = 3,2). The strong bands at 1250 ± 1 1 cm 1 and 1157 ± 22 cm 1 can be assigned to the approximately fundamental C-F symmetric and asymmetric stretching modes, respectively. The corresponding bands in the spectrum of —1 67 HCECCF3 occur at 1254 and 1182 cm . The medium intensity absorption at 1218 ± 4 cm 1 is probably an overtone. The only medium intensity band in this region in the spectrum of HCECCF3 occurs at 1222 cm 1 is assigned to an overtone of the fundamental mode associated with the CF3~deformation which occurs at 611 cm . The remaining lower frequency absorptions in the region 885 - 729 cm 1 are due to metal-CH3 rocking modes.^9'7^ Not included in Table V is a weak doublet in the region 3020 - 2885 cm 1 which is present in the spectra of a l l the derivatives that contain one or more methyl groups. The high and low frequency absorptions in the doublet are due to the C-H symmetric and asymmetric 71 stretching vibrations, respectively, of the C-H bonds. Table V Infrared Spectra (Main Bands in cm "*") of Some Fluoroalkynes and Perfluoroalkynyl Derivatives. HCECCF 3 a > C 3330 2165 1254 1222 1182 (CH 3) 3SiCECCF 3 a' d 2205 1262 1222 1165 (CH 3) 2Si(CECCF 3) 2 a 2221 1250 1222 1179 885 821 800 (CH 3) 3GeCECCF 3 a 2201 1261 1219 1163 839 771 (CH 3) ?Ge(CHCCF 3) 2 a 2208 1251 1221 1179 829 778 CH 3Ge(C=CCF 3) 3 b 2223 1241 1218 1166 831 Ge(CECCF 3) 4 b 2225 1241 1219 1155 858 (CH 3) 3Sn(CECCF 3) a 2188 1252 1219 1164 785 (CH 3) 2Sn(CHCCF 3) 2 a 2195 1242 1220 1172 779 HCHCCF2CF3a 3339 2160 1348 1237 1205 1150 1052 690 (CH 3) 3GeCECCF 2CF 3 a 2195 1339 1225 1200 1130 1050 835 (CH 3) 2Ge(CECCF 2CF 3) 2 a 2200 1340 1226 1207 1137 1051 825 (CH 3) 3SnCECCF 2CF 3 a 2182 1346 1231 1208 1133 1054 781 HCECCF(CF 3) 9 a 3340 2155 1319 1282 1259 1189 1160 1079 1056 990 732 (CH ) GeCHCCF.(CF3)9a 2182 1312 1272 1245 1182 1158 1077 978 722 725 840 3 Vapour b Mull Berney et a l . (ref. 67) ^ Cullen and Leeder (ref. 45) i I Table VI Summary of N.m.r. Parameters of Some Fluoroalkynes and Group IV Perfl u o r o a l k y n y l Derivatives. i a,f f S W J1"S„-CH 3 J"' S n-CH 3 S C C F 3 > ^ S < C F ) J " V - „ V-H HCHCCF3 -1.88 55.55 b 3.5 (CH 3) 3SiCECCF 3 +0.20 49.95 e ( C H 3 ) 2 S i ( C H C C F 3 ) 2 -0.10 53.41 b (CH 3) 3GeC-CCF 3 -0.17 51.35 b (CH 3) 2Ge(CECCF 3) 2 -0.39 52.6 b (CH 3)Ge(CECCF 3) 3 -1.07 52.85 C' d Ge(C=CCF 3) 4 . 53.35 C , d (CH 3) 3SnCECCF 3 -0.26 58.2 61.0 50.25 b (CH 3) 9Sn(C=CCF 3) 2 -0.4 9. 68.6 72./7 51.54 b HC=CCF 2CF 3 -2.23 88.7 b 105.9 3.6 5.3 0.5 (CH 3) 3GeC=CCF 2CF 3 -0.16 86.65 b 101.9 4.1 (CH 3) 2Ge(CECCF 2CF 3) 2 -0.47 86.9 b 103.7 3.8 (CH 3) 3SnCHCCF 2CF 3 -0.22 59.0 61.7 86.43 101.1 4.1 Table VI (continued) a,f 19, 6 ( H ) J117 J119 Sn-CH3 . Sn-CH3 6(CF 3) 6(CF 2) 6(CF) J p _ p J p a _ H HCECCF(CF 3)2 -2.35 (CH 3) 3GeC5CCF(CF 3) 2 -0.18 90.7 73.0 171.8 9.9 166.0 10.6 6.0 0.4 Chemical sh i f t , 6, in p.p.m. with respect to external (CH^^Si. b Chemical s h i f t , 6, in p.p.m. with respect to external CFC&3 (capillary). Chemical shift, 6, in p.p.m. with respect to internal CFC£ in solution with sample. d CDC£ 3 solution. e 19 W.R. Cullen and W.R. Leeder, ref. 45. The F n.m.r. spectrum of this compound was originally obtained on an HR-60 Spectrometer operating at 56.4 Mc/s and with CF3C00H as an external reference. The original value of -26.6 p.p.m. downfield from CF3C00H has been converted to a chemical shift relative to CFC£ 3 by using 6(CF3C00H) = +76.6 p.p.m. upfield from CFC£ 3 > ^ Coupling constants J in cps. - 52 -The "*"H n.m.r. spectra (Table VI, p. 50 ) of the perf luoro-alkynyl derivatives containing a methyl group show, as expected, a single main peak at high f i e l d (-1.07 to -0.10 p.p.m.). The spectra of the t i n derivatives show, in addition, two low intensity doublets which are symmetric about the main peak. These doublets are due to 117 coupling of the methyl hydrogens with the two t i n isotopes Sn and 119 Sn. The isotopes both have a nuclear spin of 1/2 and occur in < 10% natural abundance. 19 • The F spectra (Table VI, p. 50) of a l l the,perfluoropropynyl derivatives show, as expected, a single peak in the range 50.25 to 53.41 p.p.m. , Only one metal perfluoropropynyl product was isolated and identified from each of the reactions of the various group IV halides with XMgCSCCF3. The reactions involving CH 3SiC£ 3 and (CH 3) 2GeC£ 2 however, are worthy of further comment. The reaction of CH 3SiC£ 3 and IMgCECCF3 (prepared via CE^Mgl) gives a small yield of (CH 3) 2Si(C=CCF 3) 2. None of the expected product, CH resulted from the reaction of (CH 3) 2SiC£ 2 with IMgCECCF3. Theoretically 3Si(C=CCF 3) 3, was isolated. It is not l i k e l y that the (CH 3) 2Si(C=CCF 3) 2 CH3SiC&3 can thermally redistribute according to the equation; 2CH 3SiC£ 3 > (CH 3) 2SiC£ 2 + SiC&4 [1.10] however, this redistribution probably did not take place in the present case for two reasons. First, the presence of chlorine substituents on - 53 -72 sil i c o n is known to inhibit the migration of alkyl groups. Second, the thermally induced redistributions of chlorosilanes that have been studied have been found to take place at very elevated temperatures 7 3 7 4 (> 450°) ' ; the temperature in the present reaction did not exceed 108°. The (CH 3) 2Si(CECCF 3) 2 product probably resulted from one of the following reactions: (a) a redistribution between CH 3SiC£ 3 and CH 3Si (C5CCF 3) 3, or (b) a peroxide catalyzed redistribution of CH 3Si(CECCF 3) 3, or (c) a thermal induced redistribution of CH 3Si(CECCF 3) 3. Of these three possibilities the last, reaction (c), is the most lik e l y . Reaction (a) is rejected on the basis that thermal redistribution of trichlorosilanes and tetraalkyl- or -arylsilanes are not known to give rise to R 2SiR 2 products, , e.g., C-H cSi(CH_) 0 + HSiC£0 > C,H cSiC£ 0 + (CH„)QSiH [1.11] Reaction (b) is also unlikely. The diethyl ether solvent was used as i t was received from the supplier without purification or treatment and may have contained small amounts of peroxide. However, in those peroxide catalyzed systems that have been studied only aryl 77 but not alkyl groups have been found to migrate. The migration of a methyl group is necessary in the present case. The most reasonable possibility is reaction (c). The tetra-organosilanes C ^ S i C C H ^ and C ^ S i C C g H ^ both thermally - 54 -78 disproportionate to give (C^Hj-^SiR^ products. 2 C 2 H 5 S i ( C H 3 ) 3 > ( C 2 H 5 ) 2 S i ( C H 3 ) 2 + ( C H 3 ) 4 S i [1.12] 2 C 2 H 5 S i ( C 6 H 5 ) 3 > ( C 2 H 5 ) 2 S i ( C 6 H 5 ) 2 + ( C g H ^ S i [1.13] The expected product, CH 3Si(C=CCF 3) 3 may disproportionate s i m i l a r l y . C H 3 S i ( C 5 C C F 3 ) 3 > (CH 3) 2Si(C=CCF 3) 2 + ( C E C C F ^ S i [1.14] The compound (C=CCF 3) 4Si i s expected to be a s o l i d by analogy with 19 other t e t r a a l k y n y l s i l a n e s and would not be i s o l a t e d during the present method of i s o l a t i o n and p u r i f i c a t i o n . It should be mentioned that the C 2H^Si(CH 3) 3 and C 2H,-Si(C 3H,-) 3 r e d i s t r i b u t i o n reactions were ca r r i e d out at 300° and under hydrogen at 100 atm. No such extreme conditions were used i n the present case; however, the ease of migration of the CF 3CEC-group and the e f f e c t of the CF 3CEC-group on the migratory a b i l i t y of the methyl groups are unknown. The reaction of ( C H ^ G e C ^ with BrMgC=CCF3 (prepared v i a C^H^Br) gives, i n addition to (CH 3) 2Ge(CECCF 3) 2, a large number of by-products. The two largest by-products were i s o l a t e d by v.p.c. 1 19 One of them (A), shows single peaks i n both H and F n.m.r. spectra. The in f r a r e d absorption spectrum of (A) i s very s i m i l a r to that of (CH 3) 2Ge(CECCF 3) 2 including bands assignable to C-H stretching v i b r a t i o n s (2990 and 2900 cm"1) , C=C stretching v i b r a t i o n (2200 cm 1 ) , C-F v i b r a t i o n s (1253 and 1170 cm CF 3~deformation overtone (1218 cm , - 55 -and methyl-germanium rocking mode (825 cm^) . The elemental analysis shows the presence of chlorine and the compound may be, on the basis of the above, (CH3)2Ge(C&)CECCF3 ^but the compounds analyzes for the ratio C:H:C£:F = 5:10L:4 (Calc. C:H:C£:F = 5:6:1:3). The other large by-product (B) , shows a single peak in i t s "'"H n.m.r. spectrum, contains chlorine but no fluorine, and analyzes for the ratio C:H:C£ = 1:4:1. Germanium may also be present by virtue of the infrared bands at 852 and 825 cm 1 which may be CH^-Ge rocking modes. 2. Derivatives of 3 ,3,4 ,4 ,4-Pentafluorobutyne. The Group IV halides (CH^GeBr, (CH3)2GeC&2, and (CH 3) 3SnC£ when treated with IMgCECC2F^ (prepared via CH3MgI) give the perfluoro-butynyl derivatives (CH 3) 3GeCECC 2F 5, (CH 3) 2Ge(CECC 2F 5) 2, and (CH3)3SnC=CC2Fr-, respectively. Only one metal-butynyl derivative was isolated and identified from each reaction. The products are character-ized on the basis of their infrared (Table V, p. 48 ) and n.m.r. (Table VI, p. 50) spectra, and elemental analysis. Included, as expected, in the infrared spectra of a l l three derivatives i s a band in the region 2200 - 2182 cm 1 due to the C=C stretching vibration. The five main bands in the region 1346 - 1050 cm 1 occur at frequencies similar to those of the main bands in the spectrum of the parent fluoroalkyne, HCECC,-^. They are undoubtedly associated with the C^F^ group; however, there i s a large amount of coupling in this region between the C-F and C-C vibrations and a complete assignment of the bands is d i f f i c u l t . The two bands at 1344 ± 4 cm 1 and 1231 ± 6 cm \ - 56 -including those of HC^CC^F^, are probably due to the C-F symmetric and asymmetric stretching modes. Similar assignments have been made for -1 -1 79 the bands at 1339 cm and 1240 cm in the spectrum of CF 3CF 2Br. -1 The low frequency bands in the region 835 - 781 cm are due. to methyl-metal rocking modes. The "^H n.m.r. spectra of a l l three of these group IV penta-fluoro butynyl derivatives shows a single main peak (-0.47 p.p.m. to -0.16 p.p.m.) due to the methyl hydrogen atoms. The spectrum of (CH-j)3SnC=CCF2CF3 also shows two low intensity doublets symmetrically placed about the main peak and due to coupling of the methyl hydrogens 117 119 with the t i n isotopes Sn and Sn. 19 The F n.m.r. spectra show, as expected, two absorptions: a t r i p l e t (86.65 ± 0.25 p.p.m.) and a quartet (102.4 ± 1.3 p.p.m.) due to the CF, and CF 0 groups, respectively (J = 3.9 ±.& cps). Elemental analysis failed to confirm the proposed structure of (CH3)3GeC=CCF2CF3; however, confirmation is obtained by the complete characterization, including an elemental analysis, of the cyclopropene, (CH3)3GeC=CCF2CF3(CF2) which results from the addition of difluoro-carbene to the t r i p l e bond of (CH3)3GeC=CCF2CF3 (Chapter 2, p. 90). 3. Derivative of 3-Trifluoromethyl-3,4,4,4-tetrafluorobutyne. The reaction of IMgCSCCF(CF3)2 (prepared via CH3MgI) and (CH3)3GeBr gives (CH 3) 3GeC=CCF(CF 3) 2. The ' \ spectrum (Table VI, p. 50) 19 shows a single peak (-0.18 p.p.m.) and the F spectrum (Table VI), a doublet (73.0 p.p.m.) and a septet (166.0 p.p.m.) due to the CF 3 group - 57 -and the fluoromethyne group, respectively (J = 1 0 . 6 cps). The r —F infrared spectrum (Table V, p. 48 ) shows a band at 2 1 8 2 cm 1 (CEC stretch) and the remaining absorption pattern is similar to that of the parent fluoroalkyne, HCECCF(^3)2• Further absorption assign-ments are not immediately possible because of the complexity of the 6 1 spectrum; however, Chambers et a l . , have divided the infrared absorptions associated with the CF(CF^)^ group in the spectra of some perfluoroisopropyl, compounds into the following regions: C-F stretching vibrations, 1 2 9 9 - 1 1 2 6 cm"1; CF3-CF deformation, 7 5 9 - 7 1 3 cm"1; and C-F deformation, 9 7 0 - 8 9 2 cm 1 . A similar division may apply in the present case. C. Hydrolysis with Saturated Aqueous Ammonium Chloride Solution. A useful procedure in reactions involving Grignard reagents is hydrolysis of the reaction mixture with a saturated aqueous ammonium 8 0 chloride solution. This causes the magnesium salts to precipitate out of solution and leaves the product in the organic layer from which i t is easily obtained. This procedure can be used in the preparation of a l l the germanium alkynyl derivatives (Table IV, p. 45 ) but not in the preparation of either the sili c o n or t i n derivatives. When the Grignard intermediate formed in the preparation of (CH^^Si^SCCF^^ via (CH 3) 2SiC&2 and IMgCECCF^, is treated with a saturated aqueous ammonium chloride solution, the intermediate complex is decomposed and the starting propyne, HCECCF^, is recovered quantitatively. The intermediate Grignard complex involving the t i n perfluoroalkynyl - 58 -derivatives cannot be treated with aqueous ammonium chloride due to the hydrolytic instability of the tin derivatives (to be discussed in the next section). Both the silicon and t i n perfluoroalkynyl products are obtained from the Grignard intermediate by removing the ether solvent. D. Stability of the Group IV Perfluoroalkynyl Derivatives. Although the carbanion CF^CEC is expected to be unusually stable in keeping with high acidity of alkynes and the large s t a b i l i z -ing effect of the very electronegative fluorine atoms, only the t i n perfluoroalkynyl derivatives are unusually unstable with respect to hydrolysis. The silicon derivative, (CH^^Si^ECCF^^, is both hydro-l y t i c a l l y and thermally stable in air at 20°. The s t a b i l i t y of other s i l i c o n alkynyls varies although most are cleaved by strong nucleophilic agents. Water alone has been claimed to cleave the Si-C bond in (HC=C)3SiOSi(CECH)3 and (C 2H 50) 2Si(C=CC 6H 5) 2 and liberate 82 the alkyne, although the latter has been denied. It is particularly interesting that the analogous compound (CH 3) 2Si(C=CCgH,j) 2 is stable 83 to hot water. It has been implied that aqueous cleavage, even with dilute aqueous a l k a l i , is d i f f i c u l t due to the insolubility of organo-82 sil i c o n compounds. This may be true since in homogeneous solutions of water-methanol the compound (CH3) .^ SiC^ CC^ -H^ , for example, is -2 84 cleaved readily at 25° by 10 M a l k a l i . A l l the germanium derivatives are both hydrolytically and thermally stable at 20°. In addition, the compound (CH 3) 2Ge(C=CCF 3) 2 - 59 -yields only a trace of propyne after heating with water for 24 hours at 150°. This stability is in keeping with the s t a b i l i t y of tetraalkyl-and tetraarylgermanes which are stable in air even at quite high temp-85 eratures. By comparison, the compound (C^H^) ^ GeC^CGeCC^H,.)3 is reported to undergo slow decomposition on exposure to the atmosphere,^ but whether the decomposition involves hydrolysis, oxidation, or polymerization is not clear; nor is i t known whether i t is the Ge-C bond that is undergoing a change. The solid germanes, CH^GeCCECCF^)^ and GeCCECCF^)^ are both stable to impact and rapid heating. The stability of the tetrasubstituted derivative contrasts with that of Ge(C=CH)4 which 87 detonates explosively on impact. The tin derivatives (CH3) 3SnCECRf (Rf = CF3» and (CH3)2Sn(CECCF3)2 are a l l both hydrolytically and thermally unstable. Furthermore, relative to each other, their s t a b i l i t y i s found to decrease as the size of the R^  group increases and as the number of perfluoroalkynyl substituents increases. Thus, (CH3)3SnC=CCF3 is thermally stable in the absence of air at 20°, (CH3)3SnCECCF2CF3 under the same conditions is stable only at 0°, and (C H 3)2Sn(C=CCF 3)^ under the same conditions , decomposes at 0°. A l l three t i n compounds are readily cleaved by water at 25° to give the starting fluoroalkyne quantitatively. The order of increasing ease of hydrolysis is the same as the order of decreasing thermal s t a b i l i t y . This neutral hydrolysis is rather surprising in 88 view of the reaction, 2R'C=CH + R3SnOSnR3 > 2R'C5CSnR3 + B^ O [1.15] (R' = C 6H 5, CH30, CH2 = CH, NC-C=C; R = C 2H 5, C 4H g, or C&H ) - 60 -The anomaly may be explained on the basis of the effect of the fluorine atoms, which, being highly electronegative, shift the electron density along the internuclear axis and leave a polarized tin-carbon bond. 6- 6+ CF3CEC <— Sn(CH 3) 3 The electron shift makes the t i n atom sufficiently electrophilic to undergo attack by the electron pairs of the water molecule. :0Ho (CH3)3Sn-CECCF3 + :QH2 > (CHg)3Sn-CECCF3 (6) (CH3)3SnOH + HCECCF3 [1.16] The intermediate (6) is reasonable since i t is known that t i n compounds are very susceptible to nucleophilic attack and further, that t i n 89 90 compounds form five coordinate complexes. ' (See also Chapter 3 for a discussion of a five-coordinate t i n complex involving a diazo compound). E. Trends and Correlations involving v(CEC) and N.m.r. Parameters  of the Group IV Perfluoroalkynyl Derivatives. Several comments have already been made above concerning the relative positions of v(C=C) in fluorinated and non-fluorinated alkynes and concerning band assignments in the infrared absorption - 61 -spectra of group IV perfluoroalkynyl derivatives. This section elaborates on these. The C=C bond stretching frequencies (Table V, p. 48 ) in the group IV perfluoroalkynyl derivatives occur in the region 2225 - 2182 cm ^ . These frequencies are higher, in general, than those of V(C=C) in either the parent fluoroalkynes (2165 - 2155 cm or the non-fluorinated group IV alkynyl derivatives (Table VII). Table VII V(C=C) of Some Non-fluorinated Group IV Alkynyl Derivatives V(C=C)(Phase) Reference (CH3)3SiC=C-C=C(CH2)2CH2 2145(film) (CH3)3SnCECCH3 2165 (CC.^) 91 n-(C 4H 9) 3GeCSCn-C 3H 7 2169(film) 92 93 (C6H5)3SnC=CCH3 2163(KBr) 93 The frequency of v(CSC) in mono-substituted alkynes (HCSCR) is known to be lower than the corresponding frequency in disubstituted alkynes (RC=CR') . The shift to lower frequencies in HC=CR type compounds is due to strong coupling between the C-H and C=C vibrations. Strongly coupled oscillators vibrate at frequencies - 62 -5 6 farther apart than when not coupled. The extreme of such C-H — G -1 54 C=C coupling occurs in H^CH where v(C=C) is at 1974 cm (vapour). Since l i t t l e such coupling exists in disubstituted acetylenes V(CEC) occurs at a higher frequency. The higher frequency, generally found for v(C^C) in the group IV perfluoroalkynyl derivatives relative to the non-fluorinated analogs is not expected. Similarly, i t has been noted that the frequency of v(CEC) in the fluoroalkynes occurs at higher frequencies than those in the non-fluorinated alkynes. It was suggested earlier (p. 37) that the apparent anomally in the positions of v(C=C) in these two classes of alkynes is related to the force constant, k , of the bond joining the group to the C=C bond which is apparently larger than of the same bond in non-f luorinated alkynes. A similar explanation probably applies in explaining the present observation of higher frequencies of v(C=C) in group IV perfluoroalkynyl derivatives relative to the non-fluorinated analogs. There are three trends in the relative positions of v(C=C) in the group IV perfluoroalkynyl derivatives studied in this investiga-tion. Using the general formula (CH„) M(C=CR^). as a basis, the 3 n f 4-n following are observed: - 63 -I n f r a r e d Trend 1.1. In those compounds where n and are constantsV(C^C) decreases as M changes from S i to Ge to Sn. Table V I I I I n f r a r e d Trend 1.1 v(CEC) ( i n cm"1) of (CH ) M(CECR ). (where n and R are constant) v(CEC) (CH 3) 3SiCHCCF 3 (CH 3) 3GeCECCF 3 (CH 3) 3SnCECCF 3 2205 2201 2188 ( C H 3 ) 2 S i ( C E C C F 3 ) 2 2221 (CH 3) 2Ge(CECCF 3) 2 2208 ( C H 3 ) 2 S n ( C E C C F 3 ) 2 2195 (CH 3) 3GeC=CCF 2CF 2 2195 (CH 3) 3SnCECCF 2CF 3 2182 - 64 -Infrared Trend 1.2. In those compounds where M and n are constants, v(CEC) decreases as the size of the group increases. Table IX Infrared Trend 1". 2. V(C=C) (in cm"1) of (CHQ) M(CECRC). (where M and n are constant) o n f 4-n v(CEC) (CH3)3GeCECCF3 2201 (CH3)3GeCECCF2CF3 2195 (CH 3) 3GeCECCF(CF 3) 2 2182 (CH3)3SnCECCF3 2188 (CH 3) 3SnCECCF 2CF 3 2182 (CH 3) 2Ge(CECCF 3) 2 2208 (CH 3) 2Ge(CECCF 2CF 3) 2 2200 - 65 -Infrared Trend 1.3. In those compounds where M and are constants, v(C=C) increases as n decreases. Table X Infrared Trend 1.3. V(C=C) (in cm 1) of (CH„) M(C=CR,). (where M and R,. are constant) J n t q-n 1 V(CSC) (CH 3) 3SiCSCCF 3 2205 (CH 3) 2Si(CECCF 3) 2 2221 (CH3)3GeCECCF3 2201 (CH 3) 2Ge(CECCF 3) 2 2208 CH 3Ge(CECCF 3) 3 2223 Ge(CECCF 3) 4 2225 (CH3)3SnCECCF3 (CH 3) 2Sn(CECCF 3) 2 2188 2195 - 66 -A decrease in the frequency of v(C=C) similar to infrared 94 Trend 1.1 has been observed by Gastilovich et^ a l . for the series (CH^) 3MC=CH, the frequency decreasing in the order M = Si > Ge > Sn > Pb. This group of workers studied the vapour phase spectra (as in the present case) and found that the observed decrease in the frequency of v(C=C) is greater than the decrease calculated on the basis of. the increasing mass of M and suggested that dr^P71 bonding might be involved but did not explain how d_7T-p_n interactions would affect the frequency of v(CHC). Other investigators have reported quite convincing 95 evidence for drT-pjr bonding in ethynyl silanes. Furthermore, i t has been suggested that d7T-p_7r interactions between group IV metal d-°rkit.a;Ls and IT-electrons of unsaturated ligands decrease in the order Si > Ge > Sn > 96 Pb, an order however, which ought to result in an increase in v(C=C) in the compounds (CH^^MCECR, in general, as the atomic number of M is increased. The decreasing frequency of v(C=C) as the metal changes from Si to Ge to Sn may be partly related to drr-pjr bonding but the nature of the relationship is not immediately obvious. The decrease in v(C=C) as the size of the group increases when M and n are constant (Infrared Trend 1.2) i s probably caused by the increas-ing mass of the R^ group in a similar way, as explained above (p. 36), that the frequency of v(C=C) decreases in both fluorinated and non-fluorinated alkynes (HC=CR) decreases as the size of the substituent group increases. - 67 -The cause of Infrared Trend 1.3, the increase in v(CEC) when M and are constant and n decreases (3 -*- 0) , i s , at this point not understood. As we shall see in Chapter 2 the corresponding trend in the group IV cyclopropenyl derivatives in the opposite to what is observed for V(CEC); that i s , in the compounds (CH 3) nM(C=CR f(CF 2)> 4_ n V(C=C) decreases when M & Rf are constant and n decreases (3 -> 2). Several trends in the chemical shift values in the "'"H and 19 F n.m.r. spectra of the group IV perfluoroalkynyl derivative are also observed. Using, as above, the general formula (CH3)nM(CECR^) as a basis, the following are observed. N.m.r. Trend 1.1. In those compounds where n and R^  are constant, both the chemical shift values of the hydrogen and the fluorine atoms successively shift to lower f i e l d as M changes from Si to Ge to Sn. Table XI N.m.r. Trend 1.1 1 19 H and F n.m.r. Chemical Shift Values (in p.p.m.) of. (CH-) M(C=CRi.). r 3 n f 4-n (where n and R^  are constants). «S(CH3) 6(CF 3) 6(CF 2) (CH3)3GeCECCF3 -0.17 51.35 (CH3)3SnCECCF3 -0.26 50.25 (CH 3) 2Si(CECCF 3) 2 -0.10 53.41 (CH 3) 2Ge(CECCF 3) 2 -0.39 52.6 (CH 3) 2Sn(CECCF 3) 2 -0.49 51.54 ,/cont'd - 68 -Table XI (cont'd) <5(CH3) 6(CF3) 6(CF 2) (CH3)3GeC=CCF CF 3 -0.16 86.65 101.9 (CH 3) 3SnCECCF 2CF 3 -0.22 . 86.43 101.1 N.m.r. Trend 1.2. In those compounds where M and R^  are constant the chemical shift values of the hydrogens shift downfield and those of the fluorines shift upfield as n decreases (3 -> 0). Table XII N.m.r. Trend 1.2 1 19 H and F n.m.r. Chemical Shift Values (in p.p.m.) of (CH3)nM(CECRf) (where M and R^  are constant) <5(CH3) 6(CF3) <5(CF2) (CH3)3GeCECCF3 -0.17 51.35 ( C H 3 ) 2 G e ( C 5 C C F 3 ) 2 -0.39 52.6 CH 3Ge(CECCF 3) 3 -1.07 52.85 Ge(CECCF 3) 4 53.35 r ( C H 3 ) 3 S n C 5 C C F 3 -0.26 50.25 (CH 3) 2Sn(CECCF 3) 2 -0.49 51.54 (CH3)3GeCECCF2CF3 -0.16 86.65 101.9 (CH 3) 2Ge(CECCF 2CF 3) 2 -0.47 86.9 103.7 - 69 -The decrease in 6(CH.j) in N.m.r. Trend 1 J L may be related to the increasing electropositive character of the metal and/or to the decreasing du -pTT bonding, noted above, in moving from Si to Ge to Sn; however, the origin of the relationship is not immediately obvious. The decrease in 6 ( 0 ^ ) noted in N.m.r. Trend 1.2 is suggested to result from the additivity of the electron withdrawing effect of the alkynyl substituents in deshielding the methyl hydrogens. A similar decrease 97 in 6(CH0) has been noted for the series (CH,,) ml, (M = Si, Ge) . 3 3 n 4-n The changes in the chemical shift of the fluorines included in n.m.r. trends 1.1 and 1.2 are apparently related to the changes in v(CEC) as described by infrared trends 1.1 and 1. 3, respectively. The decrease in the chemical shifts of the fluorine atoms described by n.m.r. trend 1.1 parallels the decrease in the frequency of V(CEC) described by infrared trend 1 . 1 for the same series of compounds. Similarly, the chemical shifts of the fluorine atoms and the frequency of v(CEC) both increase in the same series of compounds in n.m.r. trend 1.2 and in infrared trend 1 . 3 , respectively. The apparent relationships may be explained in the following way. If a change in the observed frequency of v(C=C) is accompanied by a similar change in the electron density of the C=C bond than i t is reasonable to expect that the magnitude of the paramagnetic anisotropic effect exerted by the CEC bond on the CF^ groups w i l l also change since the magnitude of the paramagnetic anisotropy is expected to be proportional to the C=C bond electron density. In particular, - 70 -when v(C=C) decreases (infrared trend 1.1) the shielding effect on the fluorine atoms caused by the paramagnetic anisotropy of the C=C bond also decreases and thus a decrease in the chemical shift of fluorine atoms is observed (N.m.r. trend 1.1). Similar considerations apply in explaining the relationship between infrared trend 1.Sand n.m.r. trend 1.2. - 71 -CHAPTER 2  DIFLUOROCARBENE . INTRODUCTION A carbene5'' is a carbon-centred (usually) } short lived species containing two substituents and two unshared electrons, :CRR', where the substituent groups R and/or R' can be any combination of hydrogen, alkyl, aryl, alkenyl, carboalkoxy, keto or halogen groups. A very wide variety of carbenes from an almost equally wide variety of sources u u - A - A 98-103 have been studied. , Carbenes undergo two basic types of reactions (a) insertion reactions into single bonds (insertions into C-H bonds have been the most studied (eq. [2.1])) and (b) addition reactions to unsaturated bonds (additions to C=C have been studied the most (eq. [2.2])). The term "carbene" conflicts with the nomenclature suggested by the " International Union of Pure and Applied Chemistry (IUPAC) Organic 98 Nomenclature Committee. It has been suggested that the ending for =C: be -ylidene, e.g. CF2=difluoroylidene. This system has failed to gain popularity however, and the term carbene i s most widely used, e.g. CF 2 = difluorocarbene. For the purposes of this thesis a l l CR2 species, with the exception of CH2, w i l l be named using carbene as the basis. CH„ w i l l be called "methylene". - 72 -i n s e r t i o n •CRR' + C-H -> CCRR'H [2.1] addition tCRR' + ^ C K T C / \ R' Although t r i p l e bonds are, i n general, less reactive than double bonds towards carbenes"^^' the addition of carbenes to the t r i p l e bonds of the compounds described i n Chapter 1 to form cyclopropenes was of i n t e r e s t . The formation of a few cyclopropenes v i a addition of a 10 6"" 129 carbene to a C=C bond have already been reported. Cyclopropene from methylene and acetylene i s unstable and , 106-108 „ . , , J,, - 1, - o 1 0 9 decomposes. However, methylene has been added to butyne-2. CH, C H 2 + CH 3CECCH 3 ^ C I L [2.3] E t h y l diazoacetate reacts with a number of alkynes to give i i A • 110-112 . _ A . • -, cyclopropenyl derxvatives. The xntermedxate isopyrazoles are more l i k e l y to occur i n thermal reactions with polar t r i p l e bonds ([2.4b]) whereas u l t r a v i o l e t i r r a d i a t i o n at low temperature generally proceeds v i a eq. [2.4a]. N 2CHC0 2C 2H 5 C 0 2 C 2 H 5 [2.4] C 0 2 C 2 H 5 - 73 -Phenylchlorocarbenes generated from benzal chloride and potassium t^-butoxide have been added to a l k y n e s ; 1 1 3 ' 1 1 ^ however, 6+ 6-because of the highly polarized C-Ci bond, the i n i t i a l carbene adduct is converted under the experimental conditons to a 3-phenyl-3-t_-butoxycyclopropene derivative. C,H -CHCJL + t-BuOK + R-CSC-R 6 5 2 — t-BuO K + C,H, t-BuO 6 5 — [2.5] The reaction given by eq. [2.5] can be carried out using either alkyl or aryl substituted acetylenes, 1 1"' 1 1 ^ and substituted benzal chlorides (X-C,H.-CHCJL) 6 4 2 117 Chlorocarbene generated by the action of methyl lithium on methylene chloride has been added to butyne-2. The intermediate chloro-cyclopropene is not isolated since the chlorine exchanges with methyl lithium to give 1,2,3-trimethylcyclopropene as the f i n a l product; 118 however, the chlorocyclopropene is probably an intermediate. - 74 -CH 3Li + CH 2C£ 2 + CH3CECCH3 CH CH 3Li 3 \ [2.6] H CHo The addition of dihalocarbene to acetylenes is an inter-mediate step in the preparation of cyclopropenones 115, 119-122 CX 2 + RC=C-R [2.7] X X The intermediate dihalocyclopropene is not isolated but is hydrolyzed under the experimental conditions to the corresponding cyclopropeneone. The dihalocarbenes can be generated either from haloforms with potassium 113 12 A _t-butoxide or from methyltrichloroacetate and sodium methoxide. Difluorocarbene generated by the thermal decomposition of 125 126 chlorodifluoroacetic acid in diglyme ' has been added to the 127 17a-acetylenic side chain of ethynylestradiol-3-methyl ester. * It is interesting to note that 17a-ethynylestradiol is a main 128 structural component of oral contraceptives. Interest in fluorinated derivativeshas arisen from the finding that halogenated derivatives, in general, are more potent. Certainly this area of chemistry is pregnant with possibilities for fluorocarbon chemists. - 75 -CH„0 OAc OAc - -T. r.H A second molecule of CF,, w i l l add across the double of the cyclopropene in (7) to form the bicyclobutane derivative. Difluorocarbene from (CY^^PF^ at 100° adds in the gas phase to hexafluorobutyne-2 129 Further reaction results in addition of a second molecule of CF 2 to form the bicyclobutane. C F 2 + C F 3 C E E C C F 3 CF 3 [2.9] 2 r2 Difluorocarbene i s also produced by the thermal decomposition of trifluoromethyltrimethyltin (T^MTMT). Evidence for the formation of difluorocarbene comes from the pyrolysis of T^ MTM with CF2=CF2 at 150°. The main product is perfluorocyclopropene formed by addition of 16 CF 2 across the C=C bond. (CH 3) 3SnCF 3 + CF2=CF2 + (CH 3) 3SnF [2.10] Only one report had appeared at the time of the inception of this Thesis concerning reactions of CF 9 from T,MTMT. Cullen and Leeder - 76 -describe the addit i o n of CF„ across the t r i p l e bonds of R MC=CCF~ 2 r n 3 (RnM = ( C H 3 ) 3 S i , (C 2H 5) 3Ge, ( C H ^ A s ) to form the cyclopropenyl 45 d e r i v a t i v e s . Part I of t h i s Chapter i s an extension of t h i s work and describes the thermally induced reactions of T^MTMT with the fluoroalkynes and some of the group IV perfluoroalkynyl d e r i v a t i v e s described i n Chapter 1. A discussion of the m u l t i p l i c i t y and e l e c t r o -p h i l i c i t y of the difluorocarbene intermediate i s included. Part II of t h i s Chapter describes the preparation and p y r o l y s i s of other perfluoroorganotrimethyltin compounds i n e f f o r t s to obtain other perfluorocarbenes v i a an a-elimination mechanism s i m i l a r to that which y i e l d s CF 2 from T^MTMT. We were encouraged i n these 130-132 e f f o r t s by the reports by Haszeldine et_ a l . that CHFC£SiC£ 3 and CFC£ 2CF 2SiC£ 3 both thermally decompose, p r i m a r i l y , v i a a-elimination to give an intermediate carbene. 250° CHFC£CF 2SiC£ 3 — > CHFC£CF: + SiFC£ 3 [2.11] CFC£ 2CFSiC£ 3 2 5 ° ° > CFC^CF: + SiFC£ 3 [2.12] This l i n e of i n v e s t i g a t i o n was also encouraged by the f i n d i n g that the presence of f l u o r i n e atoms a to the s i l i c o n atom aids, i n general, 132 the decomposition of f l u o r o a l k y l substituted s i l a n e s . - 77 -EXPERIMENTAL The general experimental apparatus and techniques have been described in Chapter 1, p. 8. I. Starting Materials. The perfluoroalkyl iodides, trifluoromethyl, pentafluoroethyl, and heptafluoroisopropyl iodide, were a l l purchased from Peninsular Chemresearch, Inc.* Trifluorovinyl iodide was obtained from Columbia Organic Chemicals Ltd., Hexamethylditin was purchased from Alfa Inorganics, Inc. and also from Peninsular; i t s purity was checked by i t s "*"H n.m.r. spectrum which showed a single peak at -0.33 p.p.m. with t i n sate l l i t e s . Trimethyltin hydride was prepared by the reduction of trimethyl-tin chloride with sodium borohydride in predried bis(2-methoxylethyl)-.v. 1 3 3 ether. Cis- and trans-butene-2 were both 99% pure according to the manufacturer's label (Phillip's Co., Ltd.) and were used without further purification. The butenes were both gifts from Dr.E.A. Ogryzlo of this Chemistry Department. The fluoroolefins, RfCH=CHI (RfCH=CHI (Rf = CF 3, C ^ , and C(CF 3) 2) ,were prepared by the ultraviolet irradiation of a mixture of acetylene and the appropriate perfluoroalkyl iodide (see Appendix 1). J L for the addresses of the suppliers - see Appendix 2. - 78 -A l l the fluoroalkynes and perfluoroalkynyl derivatives were prepared as described in Chapter 1 of this thesis. 2-Trifluoromethyl-3,3-difluorocyclopropenyltriethylgermane was a g i f t from Dr. W.R. Cullen. II. Preparation of Perfluoroorganotrimethyltin Derivatives. A. Preparation of Trifluoromethyltrimethyltin (TfMTMT). Trifluoromethyltrimethyltin was prepared by the U.V. irradiation (100 watt U.V. source) of hexamethylditin and excess CF^I 134 for 24 hours. It was purified by d i s t i l l a t i o n under nitrogen, b.p. 101° - 102° (atm) (b.p. l i t . value: 100° - 101° (760 mm)16) and i t s purity was checked by means of i t s n.m.r. spectrum which showed one peak at -0.30 p.p.m. with t i n s a t e l l i t e s . B. Preparation of Pentafluoroethyltrimethyltin (PfETMT). 136 Following the procedure of Kaesz et a l . hexamethylditin (27.00 g, 82.5 mmoles) and pentafluoroethyl iodide (30.41 g, 124 mmoles) were irradiated for 24 hours (450 watt U.V. source). Pentafluoroethane (6.94 g) which was not condensed by a trap at -95° was isolated and identified by i t s known infrared spectrum and molecular weight of 121.9 (Calc. for C2F^H:121). D i s t i l l a t i o n under nitrogen of the remaining vol a t i l e material gave two fractions: b.p. 99° - 109° (atm) and 93° - 150° (70 mm). The f i r s t fraction was separated by v.p.c. (20% Kel-F at 85°) into tetramethyltin (1.206 g), identified by i t s known infrared and ''"H n.m.r. spectra and molecular weight of 178 (Calc. for - 79 -C^rL^Sn: 178.7), and pentafluoroethyltrimethyltin (3.908 g, 17% yield). 136 micro b.p. 106.5 (atm) ( l i t . value: 107° (760 mm). Anal. Found: C, 21.00; H, 3.09; F, 33.3%. Calc. for C 5H gF 5Sn: C, 21.45; H, 3.18; F, 33.61%. Infrared spectrum (vapour): 3002 (w), 2918 (w), 1329 (s), 1300 (m), 1202 (s), 1105 (s), 1070 (s), 941 (s), 788 (s) cm"1. The "'"H n.m.r. spectrum showed a singlet at -0.23 p.p.m. with t i n sa t e l l i t e 19 peaks ( J H 7 S n _ C H = 55.6 cps, J H 9 S n _ C H ~ 5 8 - 2 cps). The F n.m.r. (CFCJig internal) spectrum show two resonances, a quartet centred at 113.2 p.p.m. with J satellites peaks (-CF0-) (J„ „ = 1.4 cps, on—r / r —r J i i 7 c T-, = 208.0 cps, J i i 9 c = 217.8 cps) and a very broad singlet bn-r bn—r at 84.90 p.p.m. (-CFD (width at base of peak = 8 cps). The higher boiling fraction was identified as (CHLp^Snl (26.66 g) by i t s known infrared and 1H n.m.r. spectra. tr. C. Preparation of Heptafluoroisoprop^tin (H^i-PTMT) . A mixture of hexamethylditin (15.05 g, 46.0 mmoles) and heptafluoroisopropyl Iodide (20.45 g, 69.1 mmoles) was irradiated for 24 hours (100 watt U.V. source). The reaction mixture was yellow and contained a yellow precipitate after irradiation. D i s t i l l a t i o n under nitrogen gave the following fractions: b.p. 102° - 104° (457 mm), b.p. 117° (156 mm), and b.p. 103° (93 mm). The f i r s t pt fraction was identified as he^afluoroisopropyltrimethyltin (6.65 g, 42% yield). An analytical sample was obtained by v.p.c. (20% silicone GE-SS-96 at 100°). Anal. Found: C, 21.48; H, 2.86; F, 39.67%. Calc. for C 5H gF 7Sn: C, 21.64; H, 2.71; F,'39.97%. Infrared spectrum - 80 -(vapour): 2990 (w), 2938 (w), 1302 Cs) , 1282 Cs), 1221 Cs), 1211 CsCsh)), 1150 Cm), 1071 (m), 950 Cm), 915 Cw), 784 Cm), 745 Cw), 701 (s) cm"1. The 1H n.m.r. spectrum showed a singlet at -0.33 p.p.m. with t i n 19 satellites ( J H 7 S n _ C H = 5 6 - 8 cps; J H 9 S n _ C H = 5?.8 cps). The F n.m.r. (CFCil^ internal) spectrum showed two absorptions: one was.a doublet of septets at 71.1 p.p.m. (-CF„) (J_ _ = 12.4 cps; J„ „ = 0.1 cps) j r — r H—r and the other, a well defined septet at 211.4 p.p.m. (=CF) with t i n sa t e l l i t e peaks ( J i i 7 c „ = 160.5 cps; J i i 9 0 _ = 167.5 cps). on—r bn—r The higher boiling fractions were identified as trimethyltin iodide, by i t s known "'"H n.m.r. spectrum. D. Preparation of Trifluorovinyltrimethyltin (TfVTMT). A mixture of hexamethylditin (20.53 g, 62.7 mmoles) and t r i -fluorovinyl iodide (17.77 g, 85.5 mmoles) were irradiated for 24 hours (100 watt U.V. source). A l l volatiles with a vapour pressure greater than 1 cm were passed through -63.5°, -78°, and -95° baths. The contents of the three baths were identified as slightly impure trifluorovinyl iodide (1.37 g). The material that passed through the -95° bath was identified as trifluoroethylene (< 0.5 g) by i t s known infrared spectrum. D i s t i l l a -tion under nitrogen of the less volatile material gave two fractions. The f i r s t , b.p. 120° - 135° (atm), was separated by v.p.c. (20% silicone GE-SS-96 at 100°) into tetramethyltin (0.58 g) and t r i f l u o r o v i n y l t r i -methyltin (3.70 g, 23.3% yield). Anal. Found: C, 24.53; H, 3.57; F, 23.41%. Calc. for CgH FgSn: C, 24.52; H, 3.68; F, 24.23%. The "'"H n.m.r. spectrum shox^ ed a singlet at -0.20 p.p.m. with t i n s a t e l l i t e - 81 -peaks C J i i 7 S n _ C H = 5 6 - 8 C P S 5 J l l 9Sn-CH = 5 9 , 2 CP S) • T h e second fraction, b.p. 74° - 77° (14 mm) was identified as trimethyltin iodide by i t s known n.m.r. spectrum. III. Reactions of Trifluoromethyltrimethyltin (T£MTMT). In a l l the following reactions TFMTMT was present in excess. Products from the thermal decomposition of TFMTMT were always found, including (in varying amounts) (CH-p^SnF, SiF^, c-C^Fg, CHF^ and in some cases CF2 =CF2. The latter four products were always found among the most volatile products. Trimethyltin fluoride was observed as white crystals on the tube walls. A. Reactions of T^ MTMT with Some Fluoroalkynes and Group IV Perfluoro- alkynyl Derivatives. 1. Reaction of TfMTMT with 3,3,3-Trifluoropropyne. 3,3,3-Trifluoropropyne (1.119 g, 1.19 mmoles) and TfMTMT (2.63 g, 11.3 mmoles) were heated at 143° for 24 hours. Trifluoro-methyl-3,3-difluorocyclopropene (0.250 g, 15% yield) condensed at -78° but could not be separated from trace impurities. Infrared spectrum (vapour): 3115 (vw), 1730 (m), 1353 (s), 1264 (s), 1189 (s), 1113 (s), -1 1 967 (w), 880 (m), 815 (w), 765 (w) cm . The H n.m.r. spectrum showed 19 a multiplet of at least 10 peaks at -7.37 p.p.m. The F n.m.r. spectrum showed a quartet of doublets centred at 102.8 p.p.m. (-CF2-) (J =1.3 cps, J = 2.8 cps) and a tr i p l e t of doublets centred at F—H F—F 63 ,3 p.p.m. ("CF3) ( J p _ H = 0.4 cps), - 82 -2a. Reaction of TFMTMT with 3,3,3-Trifluoropropynyltrimethylgermane• 3,3,3-Trifluoropropynyltrimethylgermane (1.062 g, 5.08 mmoles) and TfMTMT (1.723 g, 7.4 mmoles) were heated at 145° for 21 hours. The major product 2-trifluoromethyl-3,3-difluorocyclopropenyl-trimethylgermane (1.095 g, 84% yield) condensed at -78° and was purified by v.p.c. (20% silicone GE-SS-96 at 105°), Anal. Found: C, 32.43; H, 3.41; F, 36.10; Ge, 27.86%. Calc. for C^HgF^Ge: C, 32.31; H, 3.45; F, 36.45; Ge, 27.86%. Infrared spectrum (vapour): 2979 (w), 2900 (w), 1752 (m), 1344 (s), 1285 ,(s) , 1178 (s), 1095 (s), 843 (m), 772 (w) cm"1. 1 19 The H n.m.r. spectrum showed a singlet at -0.20 p.p.m. The F n.m.r. spectrum (external CFCiJ.^ ) showed a tr i p l e t at 63.25 p.p.m. (CF^) and a quartet at 103.4 p.p.m. (-CF0) (J„ „ = 3.6 cps). The fraction which passed through the -78° bath included HCECCF^ and TfMTMT thermal decomposition products. The following vapour pressure data were obtained for the cyclopropene: T(°K) 10 3/T(°K" 1) p (cm) log p 1 308.8 3.240 - 7.207 0.858 2 316.3 3.161 11.143 1.047 3 319.1 3.135 12.381 1.093 4 325.4 3.072 15.719 1.197 5 330.2 3.029 19.396 • 1.288 6 337.3 2.965 26.027 1.416 7 344.0 2.907 34.243 1.535 .../cont'd - 83 -cont'd T(°K) 10 3/T(°K _ 1) p (cm) log p 2.861 41.712 1.620 2.830 49.155 1.692 2.805 66.25 1.821 The extrapolated linear plot of log p versus 10J/T(°K x) gave b.p. = 93.2 ± 0.5 (760 mm) 2b. Hydrolysis of 2-Trifluoromethyl-3,3-difluorocyclopropenyltrimethyl- germane. The germane (0.233 g, 0.90 mmoles) and water (1.1 g, 61.2 mmoles) were immiscible at 20°. After six months at 20° an infrared examination of the volatile material showed that no reaction had taken place. 3. Reaction of TFMTMT with Bis(3,3,3-trifluoropropynyl)dimethylgermane. Bis(3,3,3-trifluoropropynyl)dimethylgermane (0.390 g, 1.35 mmoles) and TfMTMT (0.628 g, 2.81 mmoles) were heated together at 145° for 20 hours. Some 3,3,3-trifluoropropyne was detected. V.p.c. separation (20% silicone GE-SS-96 at 75°) of the volatile fraction which condensed at -78° showed 4 components; however, only the last two could be collected. The third component analyzed for C, 30.23; F, 15.15%. Infrared spectrum (vapour): 2201 (vw), 1751 (w), 1344 (w), 1285 (m), 8 349 .4 9 353 .6 10 356 .7 - 84 -1254 (s), 1244 Cw), 1175 (s), 1105 (m), 853 (w) , 826 (m), 772 (vw) cm 1. The fourth component was identified as bis(2-trifluoromethyl)-3,3-3,3-difluorocyclopropenyl)dimethylgermane (0.199 g, 38% yield). Anal. Found: C, 30.90; H, 1.71; F, 48.51%. Calc. for C^HgF^Ge: C, 30.86; H, 1.54; F, 48.86%. Infrared spectrum (vapour): 2999 (vw), 2905 (vw), 1749 (w), 1342 (s), 1280 (s), 1183 (vs), 1090 (s) cm"1. The XH n.m.r. 19 spectrum showed a singlet at -0.15 p.p.m. The F n.m.r. spectrum (internal CFC&O showed a tr i p l e t at 63.9 p.p.m. (-CF^) and a quartet at 102.8 p.p.m. (-CF0-) (J_ _ = 3.9 cps). Z r —r 4a. Reaction of TFMTMT with 3,3,3-Trifluoropropynyltrimethyltin. 3,3,3-Trifluoropropynyltrimethyltin (1.000 g, 3.89 mmoles) and TfMTMT (1.256 g, 5.41 mmoles) were heated at 143° for 20 hours. The volatiles were fractionated through a -78° bath. Some HCECCF^ anc HC=CCF.j(CF2) were detected by infrared spectroscopy. The main product, 2-trifluoromethyl-3,3-difluorocyclopropenyltrimethyltin, (0.468 g, 39% yield) condensed at -78° and was purified by v.p.c. (20% silicone GE-SS-96 at 100°). Anal. Found: C, 27.38; H, 2.91; F, 30.39; Sn, 38.88%. Calc. for C 7H gF 5Sn: C, 27.40; H, 2.76; F, 30.98; Sn, 38.72%. Infrared spectrum (vapour): 3000 (vw), 2935 (vw). 1741 (m), 1344 (s), 1285 (s), 1192 (s), 1179 (s), 1096 (s), 843 (w) cm"3 The "'"H n.m.r. spectrum showed a singlet at -0.21 p.p.m. with t i n sat e l l i t e peaks ( J i i 7 P = CHQ = 57.8 cps; J119., = 60.3 cps). on—L.ri„ J bn—\->ti~ 19 The F n.m.r. spectrum (external CFCJc^) showed two sets of peaks, one, a tri p l e t at 63.5 p.p. . and the other a quartet 0 ^ ) at 101.3 p.p. m. ( J p _ F =3.75 cps). - 85 -The following vapour pressure data were obtained for the tin cyclopropene: T°K 103/T(°K 1) P (cm) log p 1 301.35 3.318 1.136 0.053 2 310.95 3.216 1.265 0.102 3 316.70 3.158 2.054 0.313 4 321.15 3.113 2.491 0.396 5 329.15 3.038 3.113 0.493 6 336.35 2.973 4.363 0.640 7 343.15 2.914 5.812 0.764 8 354.95 2.817 9.309 0.969 9 359.95 2.778 11.431 1.058 10 364.15 2.746 13.334 1.125 11 373.25 2.679 18.301 1.263 12 383.35 2.608 26.172 1.418 13 391.75 2.551 34.535 1.538 14 398.75 2.508 43.206 1.636 15 403.65 2.477 50.242 1.701 16 409.15 2.444 58.750 1.769 A l l the points except nos. 1, 3,and 4 fitted a perfect linear plot of 3 -1 log p versus 10 /T(°K ). The extrapolated plot gave: b.p. = 135.0 ± 0.5°C (760 mm) L =9.85 kcal/mole v Trouton's const. = 23.5 e.u. - 86 -The t i n cyclopropene seemed unstable - at least, in the presence of small impurities at higher temperatures. The vapour pressure data as presented was obtained after several attempts where the sample became cloudy at about 323°K (50°C), and, as a result, a discontinuity was obtained in the plot. The isotenoscope had to be scrupulously clean and dry to prevent "clouding". 4b. Hydrolysis of 2-Trifluoromethyl-3,3-difluorocyclopropenyltri- methyltin. The cyclopropenyltin derivative (0.056 g, 0.180 mmoles) and water (ca. 2 g, 110 mmoles) reacted immediately upon warming to room temperature and a gas was produced. After three days a flaky white precipitate had formed and the solution was yellow. Trifluoromethyl-3,3-difluorocyclopropene (0.018 g, 71% yield) was recovered and identified by i t s known infrared spectrum. 4c. Pyrolysis of 2-Trifluoromethyl-3,3-difluorocyclopropenyltri- methyltin. The t i n compound (0.220 g, 0.72 mmoles) was heated at 150° for 25 hours. A few white crystals were formed' however, the tin compound was recovered essentially quantitatively (0.202 g, 92% recovery). 5. Reaction of TFMTMT with Bis(3,3,3-trifluoropropynyl)dimethyltin. Bis(3,3,3-trifluoropropynyl)dimethyltin (0.648 g, 1.94 mmoles) and TfMTMT (0.710 g, 3.19 mmoles) were heated at 145° for 20 hours. The addi-tion product, bis(2-trifluoromethyl-3,3-difluorocyclopropenyl)dimethyltin - 87 -was the major product and condensed i n a trap cooled to -78°. It was purified by v.p.c. (20% silicone GE-SS-96 at 100°C). Anal. Found: C, 27.96; F, 43.5%. Calc. for C i nH,F i nSn: C, 27.61; F, 43.71%. 10 6 10 Infrared spectrum: 2988 (vw), 2900 (vw), 1729 (m), 1339 (s) , 1280 (s), 1192 (s), 1181 (s), 1090 (s), 842 (w) cm"1. The 1H n.m.r. spectrum showed a singlet at -0.2 p.p.m. with tin satellites (Jii7„ n v = Sn—Cn„ 19 57.6 cps; Jn9g n_Qj = 61.6 cps). The F n.m.r. spectrum (internal CFC&3) showed a tr i p l e t at 63.4 p.p.m. (~CF3) and a quartet at 101.3 p.p.m. (-CF0-) (J„ = 3.75 cps). The bis(cyclopropenyl)tin compound was very thermally unstable and decomposed at room temperature while in CFC£ 3 solution. No vapour pressure measurements were possible. 6. Reaction of TfMTMT with 3,3,4,4,4-Pentafluorobutyne. 3,3,4,4,4-pentafluorobutyne (0.830 g, 5.75 mmoles) and TfMTMT (1.952 g, 8.35 mmoles) were heated at 150° for 24 hours. The major product, pentafluoroethyl-3,3 -difluorocyclopropene (0.25 g, 23% yield), condensed at -78°; however, trace impurities could not be removed by further trap-to-trap d i s t i l l a t i o n and an elemental analysis was not attempted. Infrared spectrum (vapour): 3165 (vw), 1737 (m), 1347 (s(br)), 1231 (vs), 1172 (s), 1126 (s), 1076 (m), 1046 (m), 955 (w), 841 (m), 820 (w), 761 (w) cm"1. The 1H n.m.r. spectrum 19 showed a narrow, undefined, multiplet at -7.80 p.p.m. The F n.m.r. spectrum (internal CFC£3) showed three well defined multiplets with some second-order splittings. First-order analysis gave the following: a tr i p l e t of triplets centred at 85.85 p.p.m. (~CF„C_F,), a multiplet -88 -of 18 peaks centred at 104.6 p.p.m. (-C¥^-(bridge)), and an overlapping set of 16 peaks centred at 115.8 p.p.m. (-CF„-CF„) (J„_, __ = 2.55 cps, JCF 2(bridge)-CF 2CF 3 = 5 , 2 C p s ; JCF_ 2(bridge)-CF^ = °" 9 C p S ; JH-CF 2CF 3 = °' 3 5 C P S ; JH-CF 2(bridge) = 1 ' 2 C p s ) ' The remaining volatiles included the starting butyne and decomposition products derived from TFMTMT. 7. Reaction of TFMTMT with 3,3,4,4,4-Pentafluorobutynyltrimethylgermane. 3,3,4,4,4-Pentafluorobutynyltrimethylgermane (0.765 g, 2.94 mmole) and TfMTMT (1.007 g, 4.32 mmoles) were heated at 150° for 24 hours. The fraction which passed through a -63.5° bath consisted of decomposition products including (CH^^Ge and HCSCC2F^. The -63.5° fraction was separated by v.p.c. into three main components. They are described in the order of their elution. The f i r s t and second were identified as tetramethylgermanium (0.020 g) and the starting butynyl-germane (0.053 g), respectively, by means of their known infrared spectra. The third fraction was identified as 2-pentafluoroethyl-3,3-difluorocyclopropenyltrimethylgermane, (0.253 g, 31% yield), micro b.p. 128° - 128.5° (atm). Anal. Found: C, 31.03; H, 2.84%. Calc. for C gH gF 7Ge: C, 30.90; H, 2.95%). Infrared spectrum: 3000 (w), 2935 (w), 1748 (m), 1349 (m), 1340 (m), 1330 (m), 1260 (m), 1230 (s), 1158 (m), 1122 (s), 1100 (s), 1010 (m), 845 (m), 780 (w), 762 (w), 619 (m) cm The ''"H n.m.r. spectrum showed a singlet at -0.34 p.p.m. 19 The F n.m.r. spectrum (internal CFCi^) showed three well defined multiplets: a t r i p l e t of triplets at 85.79 p.p.m. ( - C F p C F , ^ ) , a t r i p l e t - 89 -of quartets at 103.6 p.p.m. (-CF,,-(bridge)), and a slightly overlapping tri p l e t of quartets at 115.0 p.p.m. (-CF2CF3) (J^p ^p =2.75 cps; JCF 2(bridge)-CF 2CF 3 = 6 - 4 C p S ; JCF_ 2(bridge)-CF^ = °" 9 c p s ) ' 8. Reaction of T£MTMT with Bis(3,3,4,4,4-pentafluorobutynyl)dimethyl- germane . Bis(3,3,4,4,4-pentafluorobutynyl)dimethylgermane (0.750 g, 1.93 mmoles) and TfMTMT (1.442 g, 6.2 mmoles) were heated at 150° for 24 hours. The fraction which condensed at -78° was examined by v.p.c. (20% Kel-F grease at 110°) and found to consist of six minor and one major component. Only one minor component could be identified. It was characterized by infrared spectroscopy as slightly impure bis(butynyl) germane starting material (0.010 g). The major component was identified as bis(2-pentafluoroethyl-3,3-difluoropropynyl)dimethylgermane (64% yield, v.p.c. integrator extrapolation). Anal. Found: C, 29.72; H, 1.42; F, 54.11 . Calc. for C^HgF^Ge: C, 29.45, H, 1.23, F. 54.45%. Infrared spectrum (vapour): 3000 (vw), 2950 (vw), 1737 (w(br)), 1733 (m(br)), 1224 (s), 1155 (m), 1117 (m), 1000 (m(br)), 827 (m(br)) cm"1. The 1H n.m.r. 19 spectrum showed a singlet at -0.7 p.p.m. The F spectrum (internal CFCi^) showed a triplet of triplets at 85.6 p.p.m. (-CF2C_F_3) , a poorly defined tri p l e t of quartets at 103.3 p.p.m. (-CF,,-(bridge)), and another poorly defined t r i p l e t of quartets at 115.2 p.p.m. (-CJ^CF^) (J^p _^ p = 2.2 cps) JCF 2(bridge)-CF 2CF 3 = 6 C p S ; JCF_ 2(bridge)-CF^ = °' 8 C p s ) ' It i s to be noted that the bis(cyclopropenyl)germanium compound was extremely thermally unstable and decomposed at room temperature even - 90 -under vacuum. Except when absolutely e s s e n t i a l the compound was kept under vacuum and at -78°. The f r a c t i o n which passed through the -78° bath was found by in f r a r e d spectroscopy to be decomposition products in c l u d i n g HCECC^F;-and (CH 3) 4Ge. 9. Reaction of T£MTMT with 3,3,4,4,4-pentafluorobutynyltrimethyltin. 3,3,4,4,4-Pentafluorobutynyltrimethyltin (0.697 g, 2.27 mmoles) and TfMTMT (0.908 g, 3.90 mmoles) were heated at 150° f o r 12 hours. Trap-to-trap d i s t i l l a t i o n was very slow and was not allowed to proceed to completion. The f r a c t i o n which condensed at -78° and the u n d i s t i l l e d m a t e r i a l was examined by v.p.c. (20% s i l i c o n e GE-SS-96 at 120°) and found to consist of four components, three minor and one major. Only two of the three minor components were characterized. They are described i n the order of t h e i r e l u t i o n . The f i r s t and second minor components were pentafluoroethy1-3,3-difluorocyclopropene (0.010 g) and the b u t y n y l t r i m e t h y l t i n s t a r t i n g material (0.042 g), both i d e n t i f i e d by t h e i r known i n f r a r e d spectra. The t h i r d minor component showed absorp-tions at 3.38 (w), 3.47 (w), 5.70 (vw), 7.56 (m), 8.19 ( s ) , 8.63 (w), 8.90 (m); and 13.0 y. The l a s t eluted and major component was i d e n t i f i e d as the addi t i o n product, 2-pentafluoroethyl-3,3-difluorocyclopropenyl-t r i m e t h y l t i n (0.291 g, 36% y i e l d ) . Anal. Found: C, 27.18; H, 2.64%. Calc. for CgHgF^Sn: C, 26.90; H, 2.52%. Infrared spectrum (vapour): 3012 (vw), 2921 (vw), 1733 (m), 1342 (m(br)), 1258 (m(sh)), 1227 ( s ) , 1159 (w), 1120 (m), 1099 (m), 1047 (w), 1009 (m), 840 (w), 760 (w), 725 (w) cm \ The n.m.r. spectrum showed a s i n g l e t at -0.30 p.p.m. - 91 -with t i n s a t e l l i t e peaks ( J n ? „„ = 57.8 cps; J u g . _TT = 60.3 cps). bn—Uri„ bn—Orl_ 19 The F n.m.r. spectrum ( i n t e r n a l C F C J ^ ) showed a t r i p l e t of t r i p l e t s centred at 85.61 p.p.m. (CF Q C F - J , a t r i p l e t of quartets centred at 102.0 p.p.m. ( C F 2 ( b r i d g e ) ) , and a s l i g h t l y overlapping t r i p l e t of quartets centred at 115.4 p.p.m. ( - C F 0 C F ) (J =2.8 cps; / j 2~" 3 J C F 2 ( b r i d g e ) - C F 2 C F 3 = 6 ' 5 C P S ; J C F _ 2 ( b r i d g e ) - C F ^ = °- 9 C P S ) * T H E cyclopropenyltin compound was very thermally unstable. I t had completely decomposed a f t e r two weeks at 0°. 10. Reaction of TfMTMT with 3,4,4,4-Tetrafluoro-3-trifluoromethylbutyne,. 3,4,4,4-Tetrafluoro-3-trifluoromethylbutyne (0.683 g, 3.52 mmoles) and TfMTMT (1.142 g, 4.91 mmoles) were heated at 150° f o r 24 hours. The ad d i t i o n product, heptafluoroisopropyl-3,3-difluorocyclo-propene (0.071 g, 8% y i e l d ) condensed at the -78°; however, further trap-to-trap d i s t i l l a t i o n f a i l e d to remove trace impurities and a micro-analysis was not attempted. Infrared spectrum (vapour): 3162 (vw), 1732 (m), 1360 ( s ) , 1318 (vs), 2187 ( s ( b r ) ) , 1252 (vs), 1190 ( s ) , 1125 (s). 1075 (m), 1059 (m), 992 ( s ) , 949 (w), 840 (m), 825 (m), 805 (vw), 765 (w), 728 (m) cm ^. The "*"R n.m.r. spectrum showed two overlapping t r i p l e t s at -7.95 p.p.m. < J H ^ F ( b r ± d g e ) - 1.4 cps; J H - C F ( C F J 9 = 1 > 4 C P S ) " 19 z . i i The F n.m.r. spectrum ( i n t e r n a l C F C £ 3 ) showed three sets of peaks: one, a doublet of t r i p l e t s centred at 77.05 p.p.m. ( - C F ( C F _ 3 ) 2 , the second, a complex but w e l l defined m u l t i p l e t of 28 peaks centred at 104.9 p.p.m. ( - C F 2 ~ ( b r i d g e ) ) , and the t h i r d , a septet centred at 182.2 p.p.m. ( - C F ( C F 3 ) 2 ) , with each peak being further s p l i t many times, - 92 -( JCF 2(bridge)-CF(CF 3) 2 6 ' 8 C p S ; JCF_ 2(bridge)-CF(CF3) 2 °' 9 CP S' J C F - ( C F 3 ) 2 = 9 - 2 C P S ) -A fraction which passed through the -78° bath and stopped at -111.5° was identified as the butyne starting material (0.542 g) by i t s known infrared spectrum and molecular weight of 196 (Calc. for C^H^H: 194). The material which passed through the -111.5° bath was found to be TFMTMT decomposition products. 11. Reaction of TfMTMT with 3,4,4,4-Tetrafluoro-3-trifluoromethyl- butynylt rimethylgermane. 3,4,4,4-Tetrafluoro-3-trifluoromethylbutynyltrimethylgermane 6.85 mmoles) were heated at 150° for 44 hours. The fraction which stopped at -78° was separated by v.p.c. into four components (20% Kel-F grease at 90°). Three of the four components were identified. The f i r s t and third eluted fractions were tetramethylgermanium (0.073 g) and the butynyltrimethylgermane starting material (0.108 g), both identified by their known infrared spectra. The fourth eluted fraction was the major product, 2-heptafluoroisopropyl-3,3-difluorocyclopropenyl-trimethylgermane (0.120 g, 38% yield), micro b.p. 138.5° (760 mm). Anal. Found: C, 30.22; H, 2.62; F, 47.08%. Calc. for CgH^FgGe: C, 29.97; H, 2.49; F, 47.37%. Infrared spectrum (vapour): 2995 (w), 2918 (w), 1738 (m), 1686 (w), 1410 (w), 1338 (m), 1319 (s), 1280 (m), 1259 (s), 1244 (s), 1204 (m), 1183 (m), 1120 (m), 1093 (s), 1009 (m), 985 (m), 838 (m), 775 (w) , 760 (w) , 729 (m) cm"1. The """H n.m.r. spectrum showed a singlet at -0.35 p.p.m. The 1 9 F n.m.r. spectrum (internal CFCZ^) showed three sets of peaks: a doublet of triplets - 93 -centred at 79.35 p.p.m. (-CF(CF 3) 2, a doublet of septets centred at 104.2 p.p.m. (-CF 2-(bridge)), and a septet, with each peak being further s p l i t , centred at 181.1 p.p.m. (-CF(CF 3) 2) ( J c p _ ( C F ) =9.6 cps; J C F 2 (bridge)-CF(CF 3) 2 = 8 ' 6 C p S ; JCF_ 2 (bridge)-(-CF(CF_ 3) 2 = 1 ' ° C p s ) ' The f r a c t i o n which passed through the -78° bath was i d e n t i f i e d by i n f r a r e d spectroscopy as predominantly £^-C^F^. B. Reactions of TfMTMT with A c y c l i c O l e f i n s . 1. Reaction of TfMTMT with Trans-butene-2. Trans-butene-2 (0.538 g, 9.61 mmoles) and TfMTMT (1.258 g, 5.4 mmole) were heated at 150° f o r 22.5 hours. The v o l a t i l e s were passed twice through a -78° bath and once through a -83.6° bath. V.p.c. analyses of the combined fr a c t i o n s (20% SF-96 at 112°) showed a sing l e major product with ca. 2% impurity. The major-product was i d e n t i f i e d as trans-1,1-difluoro-2,3 -dimethylcyclopropene (0.522 g, 91% y i e l d ) . Anal. Found: C, 56.35; H, 7.64%. Calc. for C CH 0F 0: C, 56.60; H, 5.75%. J o Z Molecular weight found: 106.9 (Calc. f o r C ^ g F ^ 106). Infrared spectrum (vapour) 3022 (m), 2975 (m), 2940 (m), 2887 (m), 1479 ( s ( b r ) ) , 1330 (m), 1325 (m), 1268 ( s ) , 1219 ( s ) , 1162 (m), 1067 (m), 1032 ( s ) , 979 (m), 936 (m), 888 (m), 811 (m) cm"1. The 1H n.m.r. spectrum showed three multiplets at ca. -0.83 to -0.93 p.p.m. that were complicated by 19 v i r t u a l s p l i t t i n g s . The F n.m.r. spectrum (external CFC£ 3) showed an unsymmetrical multiplet of at least 30 peaks centred at 142.3 p.p.m. The following vapour pressure data were obtained for the cyclopropane. - 9 4 -T ( ° K ) I O - V T C K - 1 ) p(cm) log p 1 2 2 7 .8 4 . 3 9 0 0 . 7 7 5 - 0 . 1 1 0 2 2 3 7 . 1 4 . 2 1 7 1 . 4 7 5 0 . 1 6 9 3 2 4 7 . 2 4 . 0 4 6 3 . 0 0 9 0 . 4 7 8 4 2 7 3 . 3 3 . 6 5 9 1 0 . 7 6 1 . 0 3 2 5 2 9 9 . 8 3 . 3 3 4 3 1 . 0 3 2 1 . 4 9 2 6 3 0 0 . 5 3 . 3 2 7 3 2 . 5 6 6 1 . 5 1 3 The plot of log p versus 1 0 3 / T ( ° K _ 1 ) was linear over the whole range of temperatures. The extrapolated curve gave the following data: b.p. (760 mm) = 52.5° ± 1°C (760 mm) L =6.9 Kcal/mole v Trouton's const. = 21.2 e.u. The fraction which passed through the -83.6° bath was identified as trans-butene-2. 2. Reaction of TFMTMT with Cis-Butene-2. Cis-butene-2 (0.51 g, 9.25 mmoles) and TfMTMT (0.786 g, 3.37 mmoles) were heated for 22.5 hours at 150°. Cis-butene-2 (0.324 g) which passed through a -83.6° bath was recovered. The majority of the contents of the -83.6° bath were identified as cis-1,1-difluoro-2,3-dimethylcyclopropane (0.333 g, 93.5% yield). An analytical sample was obtained by v.p.c. (20% SF-96 at 115°). Molecular weight found: 109 (Calc. for C H F • 106). Anal. Found: 56.63; H, 7.37%. Calc. for - 95 -C 5 H 8 F 2 : C ' 5 6 ' 6 0 ' H» 7.55%. Infrared spectrum (vapour): 3040 (m), 2989 (m), 2940 (m) , 2985 (m), 1481 (s), 1455 (m) , 1295 (s), 1210 (s) , 1120 (m), 1018 (m), 911 (m), 905 (m(sh)) cm"1. The "Hi n.m.r. spectrum showed an AB pattern with resonances centred at 128.1 and 157 .2 p.p.m. ( J p _ F = : 156 cps; J F-H(cis) = 14.0 cps; JF-H(trans) 0 ; J F - CH 3(cis) 0.125 cps); J_ _ u , . = F-CH„(trans) 0.3 cps) and were assigned to the fluorine atoms cis and trans to the methyl groups , respectively. The following vapour pressure data were obtained for the cyclopropane: °K 103/T(°K 1) P (cm) log p 1 228 4.386 0.762 -0.118 2 237 4.219 1.333 0.125 3 248.2 4.029 2.800 0.447 4 273.8 3.653 9.163 0.957 5 ' 297 3.367 22.243 1.347 From the extrapolated plot of log p versus 10 /T(°K ) the following data was obtained: b.p. = 59.7° ± 2° (760 mm) L ° =6.59 Kcal/mole v Trouton's const. = 19.8 e.u. 3. Reaction of TFMTMT with the Fluoroolefins, R,CH=CHI (R^ = CF„, —. f 1—f >_f 3 > C 2F 5, and CF(CFj . Difluorocarbene from TFMTMT failed to add to any of the fluoro-olefins RfCH=CHI (Rf = CF,, C ^ F r , or i~C,F 7) to give the expected cyclo-- 96 -propane when a mixture of the particular olefin and TFMTMT were heated at 150° for 24 hours. 4. Reaction of TFMTMT with Vinyltrimethylsilane. Vinyltrimethylsilane (0.912 g, 9.12 mmoles) and TfMTMT (3.13 g, 13.5 mmoles) were heated at 130° for 21.5 hours. V.p.c. purification (20% silicone GE-SS-96 at 75°) of the -63.5° fraction.collected after three passes, yielded 2,2-difluorocyclopropyltrimethylsilane (0.30 g, 41%). Anal. Found: C, 48.22; H, 7.83; F, 25.12%. Calc. for CgH^FjSi: C, 48.0; H, 8.0; F, 25.3%. The lower boiling fraction consisted of TFMTMT decomposition products. C. Reactions of TFMTMT with Group IV Cyclopropenes. 1. Reaction of TFMTMT with 2-Trifluoromethyl-3,3-difluorocyclopropenyl- trimethylgermane. The cyclopropenylgermane (0.578 g, 2.12 mmoles) and TfMTMT (1.243 g, 5.35 mmoles) were heated together for 20 hours at 145°. TFMTMT (0.005 g) and the cyclopropenylgermane starting material (0.236 g, 41% recovery) were recovered in a -78°C bath and separated by v.p.c. (20% silicone GE-SS-96 at 50°). The fraction which passed through the -78° bath was identified as a mixture of decomposition products. There was no sign of a carbene-olefin adduct. 2. Reaction of TfMTMT with 2-Trifluoromethyl-3,3-difluorocyclopropenyl- triethylgermane. In two separate reactions, the germanium compound and an excess of T,MTMT were heated for 24 hours at 144° and 201°. In neither - 97 -reaction was there any sign of a bicyclobutane product. D. A Reaction of TfMTMT with a Compound Containing the Sn-H Bond. 1. Reaction of TfMTMT with Trimethyltin hydride. Trimethyltin hydride ( 2 . 1 9 4 g, 1 3 . 3 mmoles) and TfMTMT ( 1 . 0 9 3 g, 4.7 mmoles) were heated at 1 5 0 ° for 24 hours. After heating, the tube walls and the trimethyltin fluoride crystals were coloured gray. V.p.c. separation ( 2 0 % Kel-F grease at 95°J of the - 7 8 ° fraction yielded tetramethyltin ( 0 . 3 3 6 g) , identified by i t s known infrared and "'"H n.m.r. spectra and molecular weight of 1 7 7 . 6 (Calc. for C^H^Sii: 1 7 8 . 7 ) , and difluoromethyltrimethyltin(0.635 g, 6 3 % yield), micro b.p. 1 1 1 . 5 ° ( 7 6 0 mm), Mol. wt. found 2 0 9 . 5 (Calc. for C ^ ^ S n : 2 1 4 . 7 ) . Anal. Found: C, 2 2 . 4 8 ; H, 4 . 7 7 ; F, 1 7 . 5 1 % . Calc. for C 4H 1 ( )F 2Sn: C, 2 2 . 3 8 ; H, 4.66; F, 1 7 . 7 1 % . Infrared spectrum (vapour): 3 0 4 3 (w), 2 9 9 3 (w), 2 9 1 0 (m), 1 2 8 2 (m), 1 2 0 0 (w), 1 1 2 0 (w), 1 0 8 5 (w), 1 0 5 2 (s), 1 0 0 9 (s), 775 (s) cm - 1. The 1H n.m.r. spectrum showed a singlet at - 0 . 1 8 p.p.m. (-CH^ ) with tin s a t e l l i t e peaks ( J i i 7 c ~ 5 3 . 5 4 cps; J U J . n u = 5 5 . 9 2 cps) and a o n — O n , o n — O H , 1 9 t r i p l e t centred at - 6 . 2 5 p.p.m. ( J „ „ = 4 5 . 5 cps). The F n.m.r. Jt1— ti spectrum (internal CFCJcV^ ) showed a doublet centred at 127 p.p.m. ( J „ „ = 4 5 . 0 cps) with t i n s a t e l l i t e peaks ( J i i 7 c „ = 2 5 4 . 5 cps; r — ti on—r J l l 9 S n - F = 2 6 5 , 5 C P S ) • IV« Reactions of Some other Perfluoroorganotrimethyltin Compounds. A. Pentafluoroethyltrimethyltin (P£ETMT). I. Pyrolysis of P ETMT. PfETMT ( 0 . 8 4 6 g, 3.0 mmoles) was heated at 2 0 0 ° for 72 hours, - 98 -A small amount of white precipitate formed. There was a minimum of charring. P£ETMT (0.766 g, 91% recovery) was recovered as well as a small amount of pentafluoroethane (0.026 g). 2. Reaction of P£ETMT with Cyclohexene. Cyclohexene (1.451 g, 1.78 mmoles) and PfETMT (1.044 g, 3.7 mmoles) were combined and heated at 200° for 72 hours. The fraction which passed through a -78° bath was identified as pentafluoroethane (6.030 g). The ''"H n.m.r. spectrum of the -78° fraction showed peaks due to cyclohexene and P£ETMT only. B. Heptafluoroisopropyltrimethyltin (H£i-PTMT). 1. Pyrolysis of H£i-PTMT. The t i n compound (0.858 g, 2.58 mmoles) was heated at 150° for 24 hours. There was l i t t l e evidence of decomposition and the tube was heated for a further 40 hours at 150°. H£i-PTMT (0.46 g, 54% recovery) was recovered in a -78° bath after two passes. Perfluoropropene (0.097 g, 56% based on H£i-PTMT consumed) was also recovered. The white crystals which formed on the side of the tube were identified as trimethyltin fluoride. Anal. Found: C, 19.94; H, 5.09%. Calc. for C^FSn: C, 19.71; H, 4.93%. 2. Reaction of H£i-PTMT with Cyclohexene. Cyclohexene (0.800 g, 9.75 mmoles) and H£i-PTMT (0.744 g, 2.24 mmoles) were heated at 250° for 123 hours. Some white crystals had formed. Perfluoropropene (0.233 g) was recovered. The "hi n.m.r. - 99 -spectrum of the remaining volatiles showed peaks due to cyclohexene and a small peak at 0.2 p.p.m. with t i n satellites which may have been due either to the remaining H£i-PTMT or tetramethyltin. The peak at 0.2 p.p.m. integrated as less than 10% of the total number of protons. 3. Reaction of H£i-PTMT with 3,3,3-Trifluoropropynyltrimethylgermane. A mixture of the propynylgermanium (0.779 g, 3.69 mmoles) and H i-PTMT (1.107 g, 3.32 mmoles) were heated at 150° for 64 hours. V.p.c. analysis (20% silicone GE-SS-96 at 95°) of the -78° fraction yielded the starting propynylgermane (0.640 g, 82% recovery) and Hfi-PTMT (0.24 g). Perfluoropropene was isolated in the -196° bath. C. Trifluorovinyltrimethyltin (T£VTMT). 1. Pyrolysis of TfVTMT. TfVTMT (0.711 g, 2.91 mmoles) was heated at 200° for 147 hours. A ''"H n.m.r. spectrum of the volatiles showed peaks at -0.2 and +0.12 p.p.m. which were assigned to T£VTMT and tetramethyltin (area ratio = 5.3:1). On this basis 73% of the TfVTMT was recovered. In another reaction TfVTMT was heated at 300° for 168 hours. There was extensive charring. Small quantities of SiF^ (0.071 g) and tetramethyltin (0.038 g) were recovered. - 100 -RESULTS AND DISCUSSION I. Difluorocarbene from Trifluoromethyltrimethyltin (TFMTMT). A. Preparation of Perfluoroalky1-3,3-difluorocyclopropenes and Group IV Derivatives. The novel class of organometallic compounds in which a group IV element, other than carbon, is a-bonded to a cyclopropene ring at a vinylic position can be prepared, in general, by the reaction of TFMTMT in the gas phase at ca_. 150° with the group IV perfluoroalkynyl derivatives described in Chapter 1. The reaction proceeds by f i r s t thermally inducing the elimination of difluorocarbene CF 2, from TFMTMT; the carbene then adds across the tri p l e bond to form the cyclopropene. The reactions which produce the parent cyclopropene and the group IV cyclopropenyl derivatives are given by eq. [2.13] and [2.14], respectively. [2.13] 4-n [2.14] (R = CH3; M = Ge or Sn; Rf = CF 3, C ^ , CF(CF 3) 2; n = 2,3) - 101 -,Not a l l combinations of M, R^ , and n were explored in the reaction given by eq. [2.14]. The cyclopropenes and cyclopropenyl derivatives that were prepared are listed in Table XIII, p. 102. The compounds list e d were characterized by their infrared and n.m.r. spectra and, with the exceptions of the cyclopropene products of eq. [2.13], also by elemental analysis. Seyferth et_ a l . have obtained gem-difluorocyclopropane products by the reaction, in solution, of TFMTMT with a number of olefins 137-139 including some group IV vinylic derivatives. The effectiveness of the gas-phase CF 2 addition versus Seyferth's solution technique w i l l be discussed later. The individual reactions generalized by eq. [2.14] and [2.15] and explanation of the structural assignments of the cyclo-propenyl products are described in the next three sections. The reactions are divided according to the kind of perfluoroalkyl substituent on the cyclopropene ring. 1. Trifluoromethyl-3,3-difluorocyclopropene and some of i t ' s Group IV  Derivatives. Difluorocarbene from TfMTMT adds to the tr i p l e bonds of HCECCF3 and (CH0) M(CECCF-). (M = Ge, Sn, n = 2,3) to give HC=CCFQ(CF0) and 3 n 3 4-n 3 2 (CH 3) nM(C=CCF 3(CF 2))^_ n» respectively. The cyclopropenyl products are characterized by five strong bands in their infrared spectra in the region 1752 - 1090 cm"1. (Table XIV, p. 103). The bands are at 1740 ± 12 cm"1, 1346 ± 7 cm"1, 1276 ± 12 cm"1, 1286 ± 7 cm"1 and 1102 ± 12 cm"1. HC=CRF or ( C H , ) M ( C = C R J . 3 n f 4-n Table XIII Perfluoroalkyl-3,3-difluorocyclopropenes and Some of Their Group IV Derivatives. H — > (Reaction Time) (4-n)(CH 3) 3SnCF 3 Reaction Temp.°C ? (CF2Source) R (CHo) n or 1. Rf = CF 3 A. HCECCF3 -j- CF 2 B. (CH3)3GeCECCF3 + CF, C. (CH 3) 2Ge(C=CCF 3) 2 + 2CF2 D. (CH3)3SnCECCF3 + CF, E. (CH 3) 2 Sn(C=CCF3)2 + 2CF2 2. Rf = CF 2CF 3 A. HCECCF2CF3 + CF, B. (CH3)3GeC5CCF2CF3 + CF, C. (CH 3) 2Ge(CECCF 2CF 3) 2 + 2CF2 D. (CH 3) 3SnCECCF 2CF 3 CF, 3. Rf - CF(CF 3) 2 A. HCECCF(CF3) 2 ; + CF 2 B. (CH 3) 3GeCECCF(CF 3) 2 + CF, 143° (24 hr) 145° (21 hr) 145° (21 hr) 143° (20 hr) 145° (20 hr) > 150° (24 hr) 150° (24 hr) 150° (24 hr) 150° (24 hr) 150° (24 hr) 150° (44 hr) F 2 4-n B.p.°C Yield % (atm) HC=CCF3(CF2) (CH3)3GeC=CCF3(CF2) (CH 3) 2Ge(C=CCF 3(CF 2)) 2 93.2 (CH ),Sn C=CCF„(CF„) 135-0 3 y3 (CH 3) 2Sn(C=CCF 3(CF 2)) 2 HC=CCF2CF3(CF2) (CH 3) 3GeC=CCF 2CF 3(CF 2) (CH 3) 2Ge(C=CCF 2CF 3(CF 2)) 2 (CH 3) 3SnC=CCF 2CF 3(CF 2) HC=CCF(CF3)2(CF2) 128.5 (CH 3) 3GeC=CCF(CF 3) 2(CF 2) 138.5 15 84 low 39 low 23 31 64 36 8 38 o Table XIV Infrared Spectra (Main Bonds Only (in cm 1 ) ) of Some Perfluoroalkyl-3,3-difluorocyclopropenes and Some of Their Group IV Derivatives (All bands are HC=CCF 3(CF 2) a (CH 3) 3GeC=CCF 3(CF 2) 3 (CH3)2Ge(C=CCF3(CF2) ) * (CH Q) 0SnC=CCF 3(CF 2) a y 3 (CH 3) 2Sn (C=CCF 3(CF 2)) 2 a HC=CCF 2CF 3(CF 2) a (CH 3) 3GeC=CCF 2CF 3(CF 2) 3 (CH 3) 2Ge(C=CCF 2CF 3(CF 2)) 2 a (CH 3) 3SnC=CCF 2CF 3(CF 2) a HC=CCF(CF 3) 2(CF 2) a (CH 3) 3GeC=CCF(CF 3) 2(CF 2) a 3115 3165 3162 ; except those at 316C 1 ± 5 cm" 1730 1353 1264 1189 1113 1752 1344 1285 1178 1095 1749 1342 1280 1183 1090 -1741 1344 1285 1179 1096 1729 1339 1280 1192 1090 1737 1347 1231 1172 1126 1046 1748 1340 1260- 1230 1158 1122 1100 1010 1737 1333 1253 1224 1155 1117 1000 1733 1342 1258 1227 1159 1120 1099 1009 1732 1360 1318 1287 1252 1190 1125 1059 992 728 1738 1338 1319 1280 1259 1204 1120 1009 838 1—1 o 1244 1093 985 729 Vapour Table XVA "Ti and F N.m.r. Chemical Shifts (6) of Some Perfluoroalkyl-3,3-difluorocyclopropenes and Some of Their Group IV Derivatives. Cyclopropene or Derivative l R a 19, HC=CCF3(CF2) (CH3)GeC=CCF3(CF2) (CH3)2Ge(C=CCF3(CF2) ) 2 (CH )3SnC=CCF3(CF2) (CH 3) 2SnC=CCF 3(CF 2)) 2 CCF 2CF 3(CF 2) (CH3)3GeC=CCF2CF3(CF2) (CH 3) 2Ge(C=CCF 2CF 3(CF 2) (CH 3) 3SnC=CCF 2CF 3(CF 2) HC=CCF(CF3), (CH.)„GeC=CCF(CF„)„(CF0) ,2"SF2) 3'3 3'2 6(HCH) 6(CH3) 6(CF 2(bridge)) 6(CF 3) 6(CF 2) -7.376 102.8°' e 63.3 -0.20d 103.4b'd 63.25 -0.15d 102.8 b' e 63.90 -0.21d 101.3 C' e 63.50 -0.2£d 101.3 b' d 63.4 -7.806 104.6°' e 85.85 115.8 -0.346 103.6 c , e 85.79 115.0 -0.76 103.3 C' £ 85.60 115.2 -0.3£ 102.0 C' e 85.61 115.4 -7.95e 104.9°' e 77.05 -0.356 104.2C'6 79.35 6(CF) o 182.2 181.1 With respect to external (CH^^Sn With respect to external CFCH^ With respect to internal CFCJi^ Neat CFC£ n solution Table XVB F N.m.r. Coupling Constants of Some Group IV P e r f l u o r o a l k y l -3,3-difluorocyclopropenyl D e r i v a t i v e s . CCH3) M/ V v J \ Fo A-n J C F 2 ( b r i d g e ) - C F 3 J C F 2 ( b r i d g e ) - C F 2 J C F 2 ( b r i d g e ) - C F J C F 2 ~ C F 3 JCF-CF 3 iC=CCF„(CI (CH 3) 3GeC F 3 CF 2) (CH 3) 2Ge(C=CCF 3(CF 2)) 2 (CH 3) 3SnC=CCF 3(CF 2) (CH 3) 2Sn(C=CCF 3(CF 2)) 2 3.6 3.9 3.75 3.6 o (CH 3) 3GeC=CCF 2CF 3(CF 2) (CH 3) 2Ge(C=CCF 2CF 3(CF 2) ) 2 (CH 3) 3SnC=CCF 2CF 3(CF 2) 0.9 0.8 0.9 6.4 6.0 6.5 2.75 2.2 2.8 (CH 3) 3GeC=CCF(CF 3) 2(CF 2) 1.0 8.6 9.6 - 107 -The band at 1740 ± 12 cm 1 is due to the vibrational mode associated with the C=C stretching mode. (The frequency dependence of this band on substituents attached to the cyclopropene ring w i l l be discussed later i n this Chapter.) The remaining four bands are a l l probably associated with C-F stretching vibrations. The infrared spectra of the germanium and t i n analogs display, in addition to the main bands list e d above and in Table XIV, a weak doublet at ca. 3000 - 2900 cm 1 due to the methyl groups' C-H symmetric and asymmetric stretching vibrations and lower frequency (880 - 750 cm )^ metal-methyl rocking modes. The ''"H n.m.r. spectra (Table XVA, p. 104) of the germanium and t i n derivatives a l l show, as expected, a single main peak at high f i e l d (-0.21 to -0.15 p.p.m.); the spectra of the t i n compounds also contain s a t e l l i t e peaks as described in Chapter 1, p. 52. The 19 corresponding F n.m.r. spectra (Table XVA, p. 104 and Table XVB, p. 106) are a l l very similar and display a t r i p l e t at 63.6 ±0.3 p.p.m. and a quartet at 102.3 ± 1.0 p.p.m. due to the CF^ and bridging CF, groups, respectively (J„„ „ „ / , . , \ — 3.75 — 0.15 cps). The chemical shift CF^CF, (bridge) values of the bridging CF, groups are expected to be higher than those of the CF^ groups since the bridging CF, group are perpendicular to the double bond and experience a shielding effect caused by the induced magnetic anisotropy of the unsaturated bond. The CF^ groups, on the other hand, experience a deshielding e f f e c t . 1 4 ^ - 108 -5 Elemental analysis data was not obtainable for the parent cyclopropene HC=CCF3(CF,); however, the observed spectral paramete leave no doubt concerning i t s structural assignment. Its infrared spectra contains in addition to the five characteristic bands mentioned above, including a C=C stretching vibration at 1730 cm \ a weak band at 3115 cm 1 due to the C-H stretching vibration. The n.m.r. spectrum shows a complex singlet at -7.37 p.p.m. that is d i f f i c u l t to 19 resolve; however, the s p l i t t i n g patterns in the F n.m.r. spectrum (Figure 4, p. 109) are well resolved and are consistent with the proposed structure. Furthermore, the chemical shift values of the low and high f i e l d CF^ and bridging CF, groups, respectively, are similar to those of the corresponding values of the well characterized germanium and tin analogs. Only one group IV cyclopropenyl derivative was isolated and identified i n a l l the reactions involving difluorocarbene and each of the group IV 3,3,3-trifluoropropynyl derivatives; however, several other products that were detected and are worthy of comment. Small amounts of HC=CCF3 and HC=CCF3(CF,) are isolated from the product mixture resulting from the reaction of (CH 3) 3SnCECCF 3 < The parent cyclopropene probably results from addition of CF, to HCSCCF3> the latter being formed by decomposition of the t i n alkynyl derivative. This conclusion i s supported by the finding that the t i n cyclopropenyl derivative i s stable under the reaction conditions. - 110 -In addition to the bis(cyclopropenyl)germane that is obtained from the reaction of CF 2 and (CH^^GeCCECCF^),,, a compound is isolated which shows an infrared spectrum that appears to be a combination of the spectra of (CH3)3GeCECCF3 and (CH3)3GeC=CCF3(CF2) including bands at 2201 and 1751 cm 1 which can be assigned the vibrations involving a CEC bond and a C=C bond, respectively. The compound may be (CH3)2Ge(CECCF3) (C=C^F3"(CF2)) resulting from the addition of only one molecule of CF 2 to the bis(alkynyl)germane; however, elemental analysis shows that the ratio C:F = 3:1 (Calc. C:F = 9:8). 2. Pentafluoroethyl-3,3-difluorocyclopropane and Group IV Derivatives. Difluorocarbene adds to the t r i p l e bonds of HCECCF2CF3 and (CH_) M(CECCF„CF„), (n = 3, M = Ge, Sn; n = 2, M = Ge) to give the 3 n 2 3 4-n corresponding cyclopropenes HC=CCF2CF3(CF2) and (CH 3) nM(C=CCF 2CF 3(CF 2)) 4_ n, respectively. The cyclopropenes are characterized by five main bands at similar frequencies in their infrared spectra (Table XIV, p. 103). The five main bands are at 1740 ± 8 cm"1, 1340 ± 7 cm"1, 1229 ± 2 cm"1, 1164 ± 9 cm"1, and 1122 ± 5 cm"1. The band at 1740 + 8 cm"1 is due to the vibrational motion including v(C=C); the rest are probably due to C-F stretching and CF 3 deformation vibrations. The germanium and t i n analogs also show a characteristic band at 1005 ± 6 cm 1 that is not present in HC=CCF2CF3(CF2) as well as a weak doublet at ca. 3000 -2900 cm 1 due to the C-H symmetric and asymmetric stretching vibrations in the methyl groups and low frequency (845 - 760 cm 1) metal-methyl rocking vibrations. The n.m.r. spectra (Table XVA, p. 104) of the - I l l -group IV derivatives a l l show, as expected, a single main peak at high f i e l d (-0.7 to -0.3 p.p.m.); the spectrum of the ti n derivative also shows s a t e l l i t e peaks due to coupling with the n.m.r. active tin 19 isotopes as previously described. The F n.m.r. spectra of the group IV derivatives (Tables XVA and XVB) a l l show three sets of peaks due to the inequivalence of the three groups of fluorine atoms which couple with each other. The chemical shift values of each of the three fluorine groups are similar in a l l three compounds. The low f i e l d t r i p l e t of triplets (85.7 ±.1 p.p.m.) ( ^ ( ^ i ^ ) . ^ - 0.9 ±.1 cps; J ^ . ^ = 2.5 ±.3 cps). The tr i p l e t of quartets (102.8 ± 0.8 p.p.m.) is due to the bridging CF 0 group (J . = 6.25 ± 0.25 cps), and the 2 r CF,(bridge)-CF, r 5 high f i e l d (115.2 ± 0.2 p.p.m.) tr i p l e t of quartets assigned to the CF, groups of the CF,CF3 moiety. An elemental analysis could not be obtained for the parent cyclopropene HC=CCF,CF2(CF,); however, i t s n.m.r. spectral parameters confirm the structure based on i t s infrared spectrums. The infrared spectrum contains in addition the characteristic set of five bands mentioned above, including a vibration at 1737 cm 1 due to (C=C), a v?eak band at 3165 cm due to the C-H stretching vibration. The n.m.r. spectrum shows a narrow multiplet at low f i e l d (-7.80 p.p.m.) as expected for a vinylic hydrogen; however, the spl i t t i n g pattern 19 cannot be resolved. The spl i t t i n g patterns in the F n.m.r. spectrum (Figure 5, p. 112) is clearly resolved and is consistent with the proposed structure. The chemical shift values and the J coupling r—F 19 constants are of similar numerical value to those i n F n.m.r. spectra - 113 -of the group IV cyclopropenyl derivatives discussed above (Table XVA, p. 104). Small amounts of germanium and t i n butynyl starting material were isolated from the appropriate reaction mixtures. Some (CH^^Ge and HCECCF2CF3 was detected in the reaction involving (CH3)3GeCECCF2CFj, arising apparently from thermal decomposition. Furthermore, a small amount of Hc"=CCF2CF3(CF2) was identified in the product mixture of the reaction involving the tin butynyl derivative. It is not possible to differentiate whether the cyclopropene results from addition of CF, to HC=CCF2CF3 from the decomposition of (CH3) 3SnC=CCF^Cli~(CF2) , or from a combination of both these processes since both the perfluoropropynyl and cyclopropenyl- tin derivatives are thermally unstable. 3. Perfluoroisopropyl-3,3-difluorocyclopropene and a Germanium Derivative. Difluorocarbene adds to the triple bonds of both H C E C C F ( C F 3 ) 2 and (CH 3) 3GeCECCF(CF 3) 2 to give HC=CCF(CF3)2(CF£) and (CHg)3GeC=CCF(CF3) (CF2>, respectively. The infrared spectra (Table XIV, p. 103) of both cyclo-propenes show what appears to be seven characteristic bands including a bands including a band at 1735 ± 3 cm 1 due to the vibrational mode associated with the C=C stretching mode. The spectrum of the parent cyclo-propene also shows a band at 3162 due to the C-H stretching vibration while the germanium derivative shows weak bands at 2995 cm 1 and 2918 cm 1 due to the C-H vibrations of the methyl group and a low frequency (828 cm ^) band due to the germanium methyl rocking modes. The 1H n.m.r. spectrum (Tables XVA and XVB, p. 104 ff.) of the ger-19 manium derivative shows a single high f i e l d peak and i t s F n.m.r. spectrum - 114 -shows, as expected, three sets of peaks: a doublet of triplets at 79.35 p.p.m. (CF3) ( J ^ ^ ^ ^ ^ - LO cps; J ^ ^ ^ = 9 ' 6 CPS>> a doublet of septets at 104.2 p.p.m. < C F 2 ( b r i d g e ) ) ( ^ ( b r i d g e ) ^ ^ ^ 8.6 cps) and a septet at 181.1 p.p.m. with broad peaks due to the fluoromethyne group. The broadening is caused by unresolved coupling with the bridging C F ^ group, The X H n.m.r. spectrum of H C = C C F ( C F 3 ) 2 ( C F 2 ) shows two overlapping triplets <JH-CF(CF 3) = 1 ' 4 C P S ' JH-CF 2(bridge) = 1 A C p s ) 3 n d t h e ^ n.m.r. spectrum is similar to that described above in terms of chemical shift values and the three inequivalent fluorine groups and J„ coupling constants with the splitting patterns of the bridging C F 2 group and fluoromethyne groups being further s p l i t into a doublet by the vinylic hydrogen atom. The n.m.r. parameters of this cyclopropene are summarized in Table XVA, p.104 and in the diagram below. C F ( C F 3 ) 2 - 115 -B. Stability of the Group IV Perfluoroalky1-3,3-difluorocyclopropenyl  Derivatives. The trimethylgermanyl derivatives (CH ) GeC=CRf(CF2) (Rf = CF 3, CF 2CF 3, CF(CF 3) 2 are a l l both thermally and hydrolytically stable at 20° and can be stored for long periods without apparent v. decomposition although some discolouration from an originally clear to a yellow coloured liquid does take place. The bis(cyclopropenyl) germanium derivatives (CH 3) 2Ge(C=CR f(CF,)) 2 (Rf = CF 2 > CF 2CF 3), on the other hand, decompose at room temperature. These observations contrast with those described in the previous chapter where both the mono-and bis(alkynyl)germanium derivatives are stable to heat. Of the three t i n cyclopropenyl derivatives only (CH3)3SnC=CCF3(CF2) is thermally stable, even at 150°. The other two cyclopropenyl t i n derivatives (CH 3) 2Sn(C=CCF 3(CF 2)), and (CH 3) 3SnC=CCF 2CF 3(CF 2), both decompose at 20°. This order of thermal s t a b i l i t y is similar to the order of thermal decomposition established i n the last chapter for the t i n perfluoroalky1 derivatives, that i s , the thermal s t a b i l i t y decreases as the number of fluorocarbon substituents bonded to t i n increase and as the size of the R£ group attached to the unsaturated bond increases. The derivative (CH3)3SnC=CCF3(CF2) is quantitatively hydrolyzed at room temperature to give HC=CCF3(CF2). The other t i n derivatives, are presumably hydrolyzed in a similar way. This apparent hydrolytic i n s t a b i l i t y means that the corresponding cyclopropenone derivatives of ti n cannot be prepared by the hydrolytic methods mentioned in the Introduction to this Chapter (eq. [2.7]). - 116 -C. Trends in the Double Bond Stretching Frequency of the Cyclopropenyl  Derivatives. Before discussing the trends in the observed double bond stretching frequency for some substituted cyclopropenes, the origin of the vibration i s worth noting. The concept of an isolated double bond vibration, applicable in an acyclic olefin, f a i l s completely when applied to a cyclopropene. In the cyclopropene ring the double bond vibration represents a coupling of either (or both) of two symmetrical normal skeletal modes of vibrations, (8) and (9), involving a substantial component of the (8) (9) 142 C=C stretching motion with other vibrations involving the substit-uents The position of the double bond frequency in a cyclopropene is remarkably dependent on the number and kinds of substituents and the positions of the substituents on the ring. Tables XVIA and XVIB, p. 117, l i s t the frequency of the double bond vibration observed for a number of cyclopropenes containing only a combination of H, CH3, CF and/or F substituents. - 117 -Tables XVIA and XVIB Double Bond Frequency of Some Cyclopropenes (in cm "*")a Table XVIA C H ^ 1877 ^ (10) CH3 CH3 H \ 1768 /CH, (13) CH3 CH3 C H3\^1880- r^ C H3 (11) H CH, H CH, H CH, increasing frequency H H H H H H Table XVIB H 3 A o c cr CJ u (50 C •H CO cS cu u o c F F CF 3 \^_1820_^ CF 3 (20) A CF„ ^ 1919 / CF 0 J > — r 3 (21) CF 3 CF 3 CF 3 CF 3 o QJ d cr co u 60 a •H CO CO cu u a •H - 118 -The double bond frequencies in the two tables are taken from the following sources: (10), (15), and (16) - ref. 142; (11), (14), and (17) - ref. 118; (12) - ref. 109; (13) - ref. 143; (18) -ref. 144; (19) - ref. 145; (20) - ref. 129; (21) and (23) -Chapter 3 of this Thesis; (22) - Chapter 2 of this Thesis; (24) - ref. 146. - 119 -Careful examination of the double bond frequencies i n Tables XVIA and XVIB reveals the following two orders of substituent dependence. (i) substituents at a v i n y l i c p o s i t i o n cause an increase i n the frequency of v(C=C) i n the order H < CH^ < CF 3 < F. The order H < CH 3 i s evident from Table XVIA. The order CH3 < CF 3 i s obtained by comparing the frequency of (24) with that of (21) and the order CF 3 < F i s taken from (19) and (20) i n Table XVIB. ( i i ) substituents at a 3-position cause an increase i n the frequency of v(C=C) i n the order F < C F 3 < CH 3 < H which i s the opposite order to ( i ) . The fact that the CF 3 group has a greater e f f e c t than F i s evident i n Table XVIB. The order CF 3 < CH 3 i s obtained by comparing (24) i n Table XVIB with (10) i n Table XVIA. The order CH 3 < H i s indicated i n Table XVIA. It i s i n t e r e s t i n g to compare the above substituent e f f e c t s on the frequency of the double bond i n cyclopropenyl derivatives with those i n 1,2-substituted a c y c l i c o l e f i n s with s i m i l a r substituents. - I 1 4 7 Ethylene, CR^CH,, has a C=C bond absorption at 1621 cm and su b s t i t u t i o n of methyl groups does ra i s e the frequency but not as dramatically as i n cyclopropenes, e.g. CR^CR^CH, (1647 cm "*")-^ and -1 54 cis-CH3CH=CHCH3 (1660 cm ). Methyl s u b s t i t u t i o n on the carbon atom adjacent to the double bond i s about as e f f e c t i v e i n lowering the frequency of v(C=C) as i s CH 3 s u b s t i t u t i o n at a 3-position i n cyclopropenes. e.g. CR^CR^CR^CH, (1645 cm" 1) 5 4 and cis-CH 3CH 2CH= CHCH2CH3 (1653 cm" 1). 5 4 Fluorine s u b s t i t u t i o n i n CH2=CH2 (1621 cm"1) - 120 -has a greater effect in raising the frequency of v(C=C) than does methyl substitution, e.g. CH2=CF2 (1730 cm"1) and CFH=CF2 (1780 cm" 1) 3; 4 8 but the frequency shift is less dramatic than in cyclopropenes. The influence of fluorine atoms on v(C=C) when not directly attached to 149 the double bond is negligible. The larger increases in the frequency of v(C=C) in both the acyclic olefins and the cyclopropenes when F rather than H or CH^ is attached to the double bond is probably due to a larger force constant of the C-F bond than that of either the C-H or C-CH^ bonds. As mentioned in the last Chapter an unusually large force constant has been found for the C-F bond in HCEC-F and the frequency of this acetylene is also unusually high."*^ The substantial effect of CF^ substitution at a vinylic position in raising the frequency of v(C=C) in cyclopropenes but no corresponding effect in acyclic olefins may be related to the fact that the CF^ group is more in-line with the C=C bond in cyclopropenes due to large exocyclic angle (ca. 150°) than in acyclic olefins where the angle is ^ a. 120°. This co-linearity favours coupling between the C-CF^ bond and the skeletal mode associated with the C=C stretching bond. This co-linearity may also be related to the reason why F substitution at a vinylic position in cyclopropenes causes a larger increase in the frequency of v(C=C) than does similar substitution in acyclic olefins. It i s not clear why Asubstxtutxon Aat a 3-posxtxon xs opposite to the order observed when the same substituents are attached - 121 -at a vinylic position. Table XVII shows the double bond frequencies of the group IV perfluoroalkyl-3,3-difluorocyclopropenyl derivatives as well as the frequencies of two 3,3-bis(trifluoromethyl) derivatives that w i l l be described in Chapter 3. In keeping with the order of substituent effects, observed above, when substitution takes place at a 3-position, the 3,3-bis(trifluoromethyl) derivatives show a higher C=C bond infrared frequency than their 3,3-difluoro analogs. Also seen in Table XVII are some trends in the frequency of v(C=C) that are similar to those described i n Chapter 1 for the frequency changes in v(CEC) in the group IV perfluoroalkynyl derivatives. In particular, by using the formula (CH^^Mf^CR^C^)^_ nl a s a basis, the following are observed: Infrared Trend 2.1: In those compounds where n and R£ are constant v(C=C) decreases as M changes from Si to Ge. Infrared Trend 2.2: In those compounds where M and n are constant v(C=C) decreases as the size of the R£ group increases. Infrared Trend 2.3: In those compounds where M and R£ are constant v(C=C) decreases as n decreases. Infrared trend 2.1 corresponds with infrared trend 1.1 described i n the last chapter and similar considerations regarding dTT-p_7T bonding may apply in explaining the frequency changes. Livshits and Chumaevskii1"^ have found a trend similar to infrared trend 2.1 in the C=C bond stretching' vibrations in the series of compounds - 122 -Table XVII -1, Double Bond Frequency (in cm ) of Some (CH 3) 3S Group IV Cyclopropenyl Derivatives H 3 S n ^ 1820 ±Z^1/ C F3 LK 1752 (CH 3) 3 (CH 3) 3 F F F F (CH 3) 2 (CH 3) 2Sn^/ 1 7 2 9 ^ \ Ge CF 3\ >F F (CH 3) 3 (CH3) 3Sn 1733 ^ - C 2 F5 Ge \ 1748 / C 2 F 5 F F F F a a a) 3 cr cu u LW 60 C •H cn crj a) o C •rl (CH 3) 3Ge^ 1 7 3 8 ^ C F ( C F 3 ) 2 F F increasing frequency - 123 -(CH3)3MCH=CH2 (Si = 1600 cm"1; Ge = 1590 cm 1; Sn = 1583). The successive decreases in the frequency of v(C=C) are greater than those calculated for the increase of the mass of M and d.TT-pjrr interactions were suggested as the cause. However, as discussed in Chapter 1, d_7T-p_7T bonding provides a poor explanation for the decreasing frequency of V(CEC) in (CH„) M(CECRJ. (M = Si, Ge, Sn; = CF„, CF 0CF„; 3 n f 4-n ' f 3 2 3 when n and R£ are constant and the atomic number of M increases. For similar reasons djT-p_7T bonding is also a poor rational for the decrease in V(C=C) noted by Livshits and Chumaevskii 1 5^ and by infrared trend 2.1. Infrared trend 2.2 corresponds with infrared trend 1.2described in the last chapter and the considerations applied in understanding infrared trend 1.2 also apply in explaining infrared trend 2.2. Infrared trend 2.3 which is observed for v(C=C) is the opposite to the corresponding trend, infrared trend 1.3, for v(CEC) in (CH„) M(CECRJ.) . described in Chapter 1. In both cases M and R,. are 3 n f 4-n r f constant and n decreases; however, explanations for each of these trends are not immediately obvious. D. Trends in N.m.r. Parameters. The chemical shift value of the hydrogen atom in the parent cyclopropenes, HC=CR^(CF2), decreases as the size of the R£ group increases: R£ = CF^, 6 = -7.37 p.p.m.; R£ = CF^F^, 6 =—7.80 p.p.m.; R£ = CF(CF 3) 2, 6 = -7.95 p.p.m. This successive shift to lower f i e l d may be due to increased deshielding of the hydrogen atom caused by an increase in the effective electronegativities of the Rf groups, - 1 2 4 -that i s , CF 3 < CF 2CF 3 < CF(CF 3) 2. This same order of electro-negativities is more fully discussed in Chapter 1. 1 1 9 No trends in either the H or F n.m.r. chemical shift values of the group IV cyclopropenyl derivatives are readily obvious. However, i t is of interest to consider the trend in the coupling constant between the bridging CF 2 group and the fluorine atoms nearest to the ring of the perfluoroalkyl group. CF= As is evident from Table XVB, p. 1 0 6 , this coupling increases as the size of R£ group in -C=CR^(CF2) increases, that i s , R£ = CF 3 ( JCF 2(bridge)-CF 3 = 3 " 7 5 * °' 1 5 C p s ) > R f = C F 2 C F 3 ( J C F 2 ( b r i d g e ) - C F ^ = 6.25 ± 0.25 cps), and Rf = CF(CF 3) 2 ( J C F 2 ( b r l d g e ) _ c F ( C F 3 ) 2 = 8 ' 6 C p s ) ' A similar trend in J__ in the fluoroalkynes HC=CR (R = CF 0 ( J u = H—r t t j ri—r 3 . 5 ) , C F 2 C F 3 ( J H _ ^ C F 3 - 5.3 cps), CF(CF 3) 2 ( J H ^ ^ ^ - 6 cps) has been noted in Chapter 1 and the present observation may have a related explanation. II. Difluorocarbene: Multiplicity, Mechanism of Addition to Unsaturated Bonds, and Electrophilicity. A carbene can be of either singlet or tr i p l e t multiplicity. 1 5 1 These terms arise in the following way. The spin-angular-momentum of - 125 -an electron has two eigenvalues: m = + and m = - ^ . The two values S 2 S 2 are commonly called the "spin" of an electron. The total-spin-angular-momentum of an electronic state consisting of a number of electrons depends only on the number of unpaired electrons since £mg = 0 for two paired electrons; furthermore, the total-spin-angular-momentum eigenvalues are ~^ms> ~ I m s + x > •••» ^, . . . +£ m g - 1> + £ m s* The eigenvalues can be found by f i r s t summing only m = + for each s 2 unpaired electron. In a carbene species, :CR,, there are two unshaired electrons. Thus, those carbenes which have unshared electrons with spins-paired, [ffis = 0, have only one total spin-angular-momentum eigenvalue and are called singlets; those carbenes in which the spins of the unshaired electrons are not paired, [mg = 1, have three total-spin-angular-momentum eigenvalues and are called t r i p l e t s . The multiplicity of a carbene species can be determined by 99 various spectroscopic techniques; furthermore, i t has been concluded that, in general, the multiplicity of a carbene species can be deduced from the stereochemistry of the cyclopropane products formed by the addition of a carbene across the C=C bond of an olefin of known stereo-chemistry."'" 5 2' 1 5 3 In particular, stereospecific addition is considered to involve a singlet carbene and concerted bond formation via a three-centred transition state in which molecular rotation about a C-C single bond cannot take place (eq. [2.15]). Conversely, i t is reasoned that - 126 -R. R 2 / \ R 4 + :CR 2 R, R. R 3 R, R 4 [2.15] . R' addition of a tr i p l e t carbene to a C=C bond takes place more as a free radical process. That i s , since the spins of the unshared electrons of a tr i p l e t carbene are parallel, two separate bond formation processes take place with an intermediate diradical in which spin inversion of one of the electrons of the diradical must occur before the second bond can be formed and ring closure completed. Since the rate of spin inversion is considered to be slow relative to the rate of molecular rotation about a C-C single bond, the biradical intermediate loses some of i t s stereochemical character and gives rise to a mixture of isomers. - 127 -[2.16] In the present case, CF, from TFMTMT adds stereospecifically In the gas phase at 150° to c i s - and trans-butene-2 to give c i s - and trans-1,1-difluoro-2,3-dimethylcyclopane, respectively. The yield of [2.17] [2.18] F - 128 -the cyclopropane products i s >90% in each case and contamination of one isomeric cyclopropane by the other is not detected in either reaction. On this basis, and in terms of the above discussion, i t can be concluded that i s in a singlet state in gas-phase addition reactions to cis — and trans-butene-2 and probably also in a singlet state in the addition reactions to the CEC bonds given by eqs. [2.13] and [2.14]. The cyclopropane products in the reactions given by eqs. [2.17] and [2.18] were characterized by elemental analysis for carbon and 19 19 hydrogen and by F n.m.r. spectroscopy. The F n.m.r. spectrum of cis-1,1-difluoro-2,3-dimethylcyclopropane i s shown in Figure 6, p. 129. An AB (J = 156 cps) pattern is displayed due to the inequivalence of r — r the fluorine atoms on the different sides of the ring. The spli t t i n g 154 patterns are centred at 128.1 and 157.2 p.p.m. Mitch obtained a 19 similar F n.m.r. spectrum for the cyclopropane product derived from difluorodiazirine and cis-butene-2 with absorptions displayed at 127.8 and 157.1 p.p.m. and with J = 157.6 cps. The low and high f i e l d r — r fluorine absorptions are assigned to the fluorine atoms cis and trans to the methyl groups, respectively. This assignment i s based upon the now well established rule that, in fluorinated cyclopropanes the numerical order of the vic i n a l fluorine-hydrogen coupling is J„ „, . x > 0 F-H(cis) J„ u / „ \ In the present case J „. . . = 14.1 cps and J . F-H(trans) ^ F-H(cxs) F-H(trans) 0 cps. The coupling constants of the fluorines with the methyl groups are also discernible (J„ . . . =0.13 cps: J„ tl_ N = 0.3 cps). F-CH 0(cis) F-CH„(trans) r 19 ' The F n.m.r. spectrum of the trans-1,1-difluoro2,3-dimethylcyclo-- 130 -propane consists of a broad multiplet (31 cps) centred at 142.3 p.p.m. 154 This chemical shift value i s the same as that reported by Mitch for 19 the F n.m.r. signal of the adduct obtained by adding CF, from difluorodiazirene to the double bond of trans-butene-2. The single absorption results from the equivalent nature of the two fluorine atoms; however, virtual couplings preclude spectral analysis on a f i r s t order basis. There appears to be another, independent method, of deducing the configurations of isomeric cyclopropanes based on the chemical shift values of the fluorine atoms. It is well known that the cyclo-propyl hydrogen atoms at a 1-position are shielded by cis-methyl groups and deshielded by trans-methyl groups when the methyl groups are sub-stituted at 2 and/or 3-positions. 1 5 6 The observations that axial hydrogen and fluorine substituents in cyclohexanes occur at higher fi e l d in n.m.r. spectra than equatorial hydrogens or fluorines are 157 158 examples of the same phenomenon. ' The shielding and/or deshielding of the particular hydrogen or fluorine atom in question is caused by the long range shielding effects associated with the diamagnetic anisotropy of the carbon-carbon single bonds that are " a l l y l i c " to the particular n.m.r. active nucleus. It seems reasonable that similar shielding and deshielding effects may be exerted on the fluorine atoms in cis-1,1-difluoro2,3-dimethylcyclopropane. Support for this assumption comes from studying a model of 1,1-difluoro-2-methylcyclo-propane. - 131 -Figure 7 Long-range sh i e l d i n g e f f e c t s i n 1,1-difluoro-2-methylcyclopropane. The average diamagnetic anisotropy (^^Q) f ° r a n a x i a l l y symmetric group (the C-C bond) has been derived by McConnel 1^ and i s written as (3 cos 26-l)(x L-X T) °AVG = 71 3r where a n ^ are the l o n g i t u d i n a l and tranverse diamagnetic suscept-i b i l i t i e s , r i s the distance from the f l u o r i n e atom i n question to the centre of e l e c t r i c a l gravity of the carbon-carbon bond ( i n t h i s case a r b i t r a r i l y chosen as the mid-point of the C-C bond since the discussion i s q u a l i t a t i v e ) , and 9 i s the acute angle r makes with the C-C bond. From the equation i t can be derived that acute angles 8 > 55°40' predict s h i e l d i n g of the f l u o r i n e by the C-CH^ bond while 0 < 55°40' predict deshielding. Thus, the chemical s h i f t values 128.1 and - 132 -157.2 p.p.m. of the cis-difluorocyclopropane are caused by deshielding and shielding, respectively, whereas the single chemical shift (142.3 p.p.m.) value of the trans-difluorocyclopropane represents an averaging of the deshielding and shielding effects. It is notable in connection with the concept of averaging that the absolute values of the differences between the chemical shift of the trans isomer and low and high chemical shifts of the cis isomer are 14.2 and 14.9 p.p.m., respectively. Similar considerations of the shielding and deshielding effects of C-CH-j bonds on the fluorine chemical shift have been applied 19 by Moss and Gerstl in discussing the F n.m.r. spectra of cis-and 159 trans-1-fluoro-l-chloro-2,3-dimethylcyclopropane. The conclusion that CF 2 is in a singlet state in the gas-phase addition reactions given by equations [2.13], [2.14], [2.17], and r o i o n • • i . • u n- u 161,162 163 [2.18] is xn harmony wxth the other reports, except one, which described the multiplicity of CF 2, even from different sources, as a singlet. Only Heicklen et^ a l . have reported evidence indicating 163 ' the transient existence of tr i p l e t CF 2 < The conclusion that CF 2 from TFMTMT is in a singlet state is also in harmony with the finding that, in general, other halo- and dihalocarbenes are in singlet states 164 (based on stereochmistry of addition reactions to olefins). Since CF 2 > in the present case, i s in a singlet state, i t follows, based on the theory outlined above, that the addition of CF 2 to the C=C and C=C bonds takes place via a three-centred transition - 133 -state (eq. [2.15]) with concerted formation of both bonds during forma-tion of the cyclopropanes (from the butenes) or cyclopropenes (from the alkynyls). From relative rate studies on the addition of dihalocarbenes to olefins, 1 6 4'"'" 6 5 dihalocarbenes have been found to be electrophilic and their relative order of electrophilicity has been established as: 164 CCA, < CBr, < CF,. The electrophilic nature of the CF, species from TFMTMT studied in this investigation i s shown by i t s failure to produce the expected cyclopropanes in reactions with the olefins RfCH=CHI (Rf = CF 3, C,F5, CF(CF 3),). The combined electron withdrawing effect of the particular R^  group and the iodine atom on the electron density of the C=C bond is considered to be the main cause of the lack of reaction. Steric interactions between the carbene and the substit-uents on the C=C are not considered to be important due to the relatively 45 small size of the fluorine atoms of the carbene. Cullen and Leeder have succeeded in adding CF, from TFMTMT under the same reaction condi-tions as those used in this investigation (150°; gas phase) to the C=C bond of 2-dimethylarsino-l,l,l,4,4,4-hexafluorobutyne but not to the C=C bond the analogous trimethylsilyl derivative. The presence of the arsenic lone pair of electrons may be significant. Difluorocarbene from TFMTMT also does not add to the double bond of the cyclopropenes, R^eC^CCF^CF,) (R = CH3, C,H5) in the gas phase at 150°. As mentioned in the Introduction two published reports describe addition of CF, (from sources other than TFMTMT) to the double - 134 -127 129 bond of a cyclopropenyl derivative. ' The failure to produce a bicyclobutane product in the present case may be related to (a) the method of generation of the carbene since i t is known that different sources of the same carbene produce carbene species of different r e a c t i v i t y , 1 6 6 , 1 6 7 or (b) the electrophilic character of CF, and the reduced electron density of the C=C caused by some form of p_7T-d.1T 168 bonding between the C=C and the germanium d_ orbitals. Seyferth et a l . have utilized TFMTMT as a source of CF, in reactions, in solution, with various olefins and group IV vinylic compounds and have found that vinylsilanes were less reactive towards CF, than similar unsubstituted olefins. The reduced reactivity has been attributed to reduced electron density in the vinyl silanes caused by d T T - p j T interactions. Both the gas-phase method of CF, transfer from TFMTMT used in this investigation and the solution method employed by Seyferth 169 et_ a__. seem equally good as sources of CF,. Seyferth et_ al_. obtained a 52% yield of (C,H5) SiCH-CH,(CF,) from (C,!^)3SiCH=CH, and TfMTMT in solution while a 44% of (CH^)^SiCH-CH,(CF,) was obtained during this investigation from (CH3)3SiCH=CH, and CF, from TfMTMT in the gas phase at 150°. III. Difluorocarbene Insertion Into Sn-H Bond. The reaction of TFMTMT and trimethyltin hydride in the gas phase at 150° gives, as the major product, difluoromethyltrimethyltin (b.p. 111.5; 63% yield). A small amount of tetramethyltin is also (CH3)3SnH + (CH 3) 3SnCF 3 > (CH^SnCF^ [2.19] - 135 -isolated. The formulation and structure of the insertion-like product is based upon i t s molecular weight (found 209.5; calc. 214.7), elemental analysis for C, H, and F, and spectral data. The presence of CH^-Sn bonds is shown in the infrared spectrum by the characteristic methyl-tin rocking frequency at 775 cm A CH^-Sn grouping is also indicated by the n.m.r. spectrum which shows a high f i e l d singlet (-.18 p.p.m.) flanked by two symmetrically placed doublets. The doublets arise from coupling of the methyl hydrogen atoms with the 117 119 1 n.m.r. active t i n isotopes, Sn and Sn. The H n.m.r. spectrum also shows a tr i p l e t (J = 45.5 cps) at lower f i e l d (-6.25 p.p.m.) F—H due to the CHF2 proton. (Area ratio: singlet:triplet = 10.65:1; 19 calc. 9:1). The F n.m.r. spectrum shows the expected doublet, centred at 127.0 p.p.m., as well as tin s a t e l l i t e peaks due to coupling of the fluorine atoms with the n.m.r. active t i n isotopes. Furthermore, the observed J coupling constant is of similar magnitude to that r —ri observed in the n.m.r. spectrum of (CH-p^SnCr^F (Jp_jj = 48 c p s ) . 1 7 ^ Similar reactions of tin hydrides with dihalocarbene . precursors have been described; however, only Tseng et al. 3"^ 3" have isolated a product resulting from apparent carbene insertion into the Sn-H bond. R3Sn-H + C£ 3C0 2Na -^-> R3SnCC&2H (R = n-C^Hg) [2.20] Seyferth et al_. have inserted CX^ (X = Cl, Br) into Si-H bonding using as carbene sources NaOC(0)CC£ 3 1 7 2 and C6H5HgCX2Br (X = Cl, B r ) 1 7 3 and 173 CC&2 into Ge-H bonds using C^H^HgCCil2Br as the source, but the - 136 -reaction between R^SnH (R = n-C^Hg, C 6 H 5 ) a n d C6H5HgCX3 (X 3 = C£ 2Br, C£Br2> Br 3) gives only products arising from the reduction of the 173 mercury compound by the t i n hydride. R3SnIi + C6H5HgCX3 > C^HgCX^ + R-^ SnBr [2.21] (R = n-C4H?, C 6H 5; X 3 = C£ 2Br, C£Br 2, Br3> In the present case (CH3)^SnCF2H may have been formed either by reduction of one of the fluorine atoms of TFMTMT by the t i n hydride or by insertion of a molecule of CF 2 into the Sn-H bond. Product forma-tion via insertion i s favoured. This conclusion is most l i k e l y since, although reduction of C-Br bonds by a t i n hydride can be effected 174 below 40°, reduction of C-C£ bonds requires temperatures of ca. 1 4 0 ° 1 7 4 and thus, reduction of C-F bonds is not expected at 150°. Assuming that insertion of CF 2 into the Sn-H bond does take place in the present case, the mechanism probably involves a three-centred transition state with CF 2 i n i t s singlet state. (CH 3) 3Si^ -7 H V / V CF„ It has already been shown that CF 2 from TfMTMT exists in i t s singlet state in the gas phase at 150° and the electrophilic nature of this carbene, shown earlier, precludes nucleophilic proton abstraction - 137 -followed by recombination. Seyferth et a l / ^ have studied the mechanism of the insertion of CC£, from CgH^HgCCJ^Br into the Si-H bond of aryldimethylsilanes and have concluded that insertion takes place via a three-centred transition state involving electrophilic 176 attack of CCA,. Sommer e_t a l . have reached similar conclusions from studies of the insertion of CX, (X = Cl, Br) from C^H^HgCX^ into the Sn-H bond of optically active 2-naphthyphenylmethylsilane. IV. Preparation and Pyrolysis of Other Perfluoroorganotrimethyltin  Derivatives. The ultra-violet induced reactions of heptafluofoisopropyl iodide and trifluorovinyl iodide with hexamethylditin give a 42% yield of hexafluoroisopropyltrimethyltin and a 23% yield of trifluorovinyl-trimethyltin, respectively. Trimethyltin iodide i s also isolated from both reaction mixtures as well as small amounts of (CH^^Sn and CF2=CFH from the reaction involving CF2=CFI. Similar preparations of (CH 3) 3SnR f (Rf = CF 3, CF 2CF 3 and CF=CF2> via CF 3I, CFpCF-jI, and 177-179 CF£=CFBr have been previously reported. The reaction involving G^Fi-I was also found, during the course of this investigation, to produce a large amount of G^F^H. Eq. [2.22] summarizes the major t i n products from the reactions that involve the perfluoroorgano iodides. R fI + (CH3)6Sn2- X > 2 8 5 0 K (CH 3) 3SnR f + (C H ^ S n l [2.22] (Rf = CF 3, CF 2CF 3, CF(CF 3) 2, CF=CF2) - 138 -Table XVIII l i s t s the n.m.r. parameters of the (CH^) SnR£ derivatives prepared via the reaction given by eq. [2.22] as well as other fluoroalkyl trimethyltin derivatives described in this Thesis. Table XVIII Some N.m.r. Parameters of Some (CH^)^SnR£ Derivatives l R a 19Fb,c CH3 F" F P JF-F or JF-H JCH 3-F' (CH 3) 3SnCF 2H -0.18 127.0 45 (CH 3) 3SnCF 3 -0.30 46.5 (CH 3) 3SnCF 2CF 3 -0.23 113.2 84.90d .1.4 ca.O.l' (CH ) 3SnCH(CF 3) 2 -0.3 56.1 11.5 0.5 (CH 3) 3SnCF(CF 3) 2 -0.33 211.4 71.1 12.4 0.1 • a 1 H chemical shifts in p.p.m. with respect to external (CH^^Si. b 19 F chemical shifts in p.p.m. with respect to CFC^3 internal. J xn cps. d broad singlet - width at base: 8 cps. 19 The chemical shifts in the F n.m.r. spectrum of (CH 3) 3SnCF 2CF 3 are 19 similar to the chemical shifts in the F spectra of other derivatives 180 containing a -CF 2CF 3 group bonded to a metal or metalloid. It i s - 139 -notable that i n the f l u o r o a l k y l t r i m e t h y l t i n compounds coupling takes place between the methyl hydrogens and a f l u o r i n e atom on the carbon that i s 3 to the t i n but, that no coupling takes place between the hydrogens and the f l u o r i n e s attached to the carbon atom that i s a to the t i n atom. This long-range coupling explains why the CF^ group i n (CH^) .jSnG^CFg i s displayed as a broad s i n g l e t rather than as the expected quartet. An explanation for the presence of J $ but not rl— r J u a i s not immediately evident but may involve "through-space" e f f e c t s . n—r 177 Chambers e_t a l . have discussed the mechanism of the reaction involving CF^I i n eq. [2.21] and have proposed a r a d i c a l mechanism involving i n i t i a l homolytic cleavage of the Sn-Sn bond. (CH 3) 3SnSn(CH 3) 3 A > 2850 A > 2(CH 3) 3Sn* [2.23] (CH 3) 3Sn + CF 3I > (CH 3) 3SnCF 3 +1* [2.24] I"+ (CH 3) 3SnSn(CH 3) 3 > ( C H ^ S n l + ( C H ^ S n etc. ... [2.25] According to the proponents of t h i s mechanism supporting evidence can be found i n the u l t r a - v i o l e t induced reactions of hexamethylditin with the o l e f i n s CF 2=CF 2, CF 3CF=CF 2, CFH=CF2, and CH 2=CF 2, the products of which, i t i s claimed, can only be c o n s i s t e n t l y explained by a r a d i c a l 179 mechanism that involves i n i t i a l homolytic f i s s i o n of the t i n - t i n bond. This mechanism may not be correct for the following reasons. - 140 -A l l of the reactions of hexamethylditin with the various olefins, mentioned above, were carried out in S i l i c a tubes ( A > 2000 A), whereas those reactions involving hexamethylditin and a fluoroorgano 177-179 iodide that have been reported and those carried out during this investigation, were carried out in Pyrex tubes ( A > 2850 A). The ?179 ultraviolet absorption maximum of hexamethylditin occurs at < 2100 A ; 1 RI those of CF 3I and C ^ I occur at 2680 A and that of CF=CFI is at 182 2580 A. The longer wavelength absorption limits of CF^I and C^F^I 181 are at ca. 3170 A and 3270 A, respectively and although the ultra-violet absorption spectrum of (CF^^CFI has not been recorded i t is expected to be similar to those of CF^I and C^F^I. On the basis of the ultraviolet absorption maxima of (CH^)^SnSnCCH^)3 and the fluoroorgano iodides, and further, on the basis that a l l four of the iodides are known to undergo radical reactions under the influence of light of wavelength A > 2850 A, (see Appendix 1 of this Thesis), a mechanism involving i n i t i a l homolytic cleavage of the C-I bond of the fluoroorgano iodides seems more reasonable than the i n i t i a l cleavage of the t i n - t i n bond previously proposed. R £I A > 2 8 5 0 1 > R' + L [2.26] Rf- + (CH 3) 3SnSn(CH 3) 3 > (CH 3) 3SnR f + (CH^Sn- [2.27] or I- + (CH 3) 3SnSn(CH 3) 3 > (CH^Snl, + (CH^Sn* [2.28] - 141 -(CH3)3Sn- + R fI > (CH 3) 3SnR f +1- [2.29] or (CH3)3Sn- + R fI > (CH^Snl + R^  [2.30] The mechanism involving i n i t i a l cleavage of the t i n - t i n bond in the reactions involving hexamethylditin and the fluoroolefins may be correct since the wavelength of light that was used, X > 2000 A, and the absorption o maximum of hexamethylditin, X < 2100 A, coincide. B. Pyrolyses of the Compounds (CH 3) 3SnR f (Rf = C 2 F5' CF(CF 3) 2 > CF=CF2). Pyrolysis of pentafluoroethyltrimethyltin (PfETMT) at 200° for 72 hours either by i t s e l f or with cyclohexene f a i l s to give any products resulting from the predicted carbene CF3CF. PfETMT is 91% recovered when heated alone and i t s observed sta b i l i t y contrasts with an earlier report that PFETMT is extensively decomposed at temperatures 178 > 180°. The small amounts of C2F,-H detected i n both reactions suggest that PFETMT is thermally decomposed by homolytic fission of the Sn-C bond rather than by either a or 6 fluorine elimination. Heptafluoroisopropyltrimethyltin decomposes at 150° (64 hr.) to give trimethyltin fluoride and hexafluoropropene. The propene may arise from rearrangement of the carbene C(CF 3) 2; however, thermally induced decompositions of the tin compound in the presence of 3,3,3-trifluoropropynyltrimethylgermane (150°, 64 hr.) or cyclohexene (250°, 123 hr.) f a i l s to give either the cyclopropene or cyclopropane. - 142 -Products which could have been produced by a carbene insertion reaction were also not detected. As we shall see in Chapter 3, the carbene, C(CF 3) 2 > produced by the pyrolysis of bis ( t r i f luoromethyl)diazomethane does add to the CHC bond the propynyl germane. The isopropyltin compound may decompose via a-elimination to give the carbene which, because of the method of generation, lacks sufficient energy to undergo the addition reaction and rearranges to form hexafluoropropene. (CH 3) 3SnC(CF 3) 2 > (CH3) 3SnF + C(CF 3) 2 [2.31] T I CF2=CFCF3 However, the decomposition probably takes place via a g-elimination to give hexafluoropropene directly. (CH ) 3Sn-rCFCF 3 > (CH^SnF + CF2=CFCF3 [2.32] F-CF2 The latter mechanism is supported by the failure to detect t e t r a k i s — (trifluoromethyl)ethylene, the expected product from coupling of two C(CF 3) 2 carbenes. g-Elimination in fluoroalkylsilanes has been reported. CHF - CH2 . f i n o | | — — > CHF=CF + SiF,. [2.33] F - SiF 3 - 143 -Trifluorovinyltrimethyltin is partly decomposed at 200° after 147 hr. (73% recovery) and completely decomposed at 300° after 168 hr. Small amounts of tetramethyltin are detected in each reaction as well as some SiF^ in the product mixture of the reaction at 300°. No other volatile fluorine containing products are isolated after heating at 300°. - 144 -CHAPTER 3 BIS(TRIFLUOROMETHYL)DIAZ (METHANE INTRODUCTION Bis(trifluoromethyl)diazoraethane (25) has recently been _ ,183 , , , * A - A 183-187 reported and a few of i t s reactions have been studied. Those reactions that have been investigated have been interpreted in three ways: (a) as attack by the diazo compound acting as a 1,3-dipolar . 184,186,187 ... • • i • u- i+ <-u i \ u 183,184, reagent, (bj as involving bis(trifluoromethyl)carbene, 186,187 main intermediate in both the thermal and photolytic decompositions of (25), or (c) as radical attack on the terminal nitrogen 185 of (25). The diazo compound was of primary interest in the present investigation as a 1,3-dipolar reagent and as a source of the carbene C(CF 3) 2. The 1,3-dipolar nature of diazo compounds, in general, and of (25) in particular, arises from the fact that the structure of a diazo compound is best represented as a number of canonical forms, (26)-(29). CF, CF, CF, CF, C-N=N: < > C-N=N: < > C-N=N: < > C=N=N 3 CF 3 CF 3 CF 3 (26) (27) (28) (29) In the case of (25) i t is predicted that the canonical forms (27) and (28) w i l l predominate due to the stabilizing effect of the strongly - 145 -electron-withdrawing trifluoromethyl groups. Numerous investigations of 1 , 3-dipolar additions of diazo 18 8 compounds to alkynes have been reported ; however, only one reaction 1 8 4 of ( 2 5 ) with an alkyne has been described. CH (CF 3) 2CN 2 + CH3CECCH3 -> CF [ 3 . 1 ] The isopyrazole* eliminates nitrogen at 4 0 0 ° to give the cyclopropene according to [ 3 . 2 ] The ring structure II \ has the parent name "pyrazole"; however, no septematic nomenclature has yet been accepted for the ring structure / \ j . This latter structure has been n A A ! > 3 , 1 9 5 - . 1 9 0 . B . 1 8 4 , called A pyrazole, pyrazolemne, 3-H-pyrazole, and 189 isopyrazole. In this Thesis the parent name isopyrazole w i l l be used. - 146 -The carbene C ( C F 3 ) 2 was of interest in keeping with the investigations of Chapter 2. The electronegativity of the tr i f l u o r o -methyl group has been estimated to be intermediate between that of fluorine and chlorine 1 7; however, bis(trifluoromethyl)carbene is expected to be more reactive than either difluoro- or dichlorocarbene since the resonance stabilization that reduces the electrophilicity of the dihalocarbenes is not expected to occur in CCCF^),-+ F - C < > F = C < > F - C F+ Several reactions involving (25) have produced products corresponding to the addition or insertion of a C ( C F 3 ) 2 moiety. Trans-butene-2 and (25) give the corresponding trans-cyclopropane only; CH, C H ' ( C F 0 ) 0 C N 0 + 3y2 2 \ / X ^ " x ' [3.3] :H3 I' I. 3 however, the reaction involving cis-butene gives a mixture of products including both the c i s - and the trans-cyclopropane isomers and the olefin (CF 3) 2C=C(CH 3)CH 2CH 3. 1 8 4 These two reactions have been interpreted as involving a triplet carbene and a diradical intermediate. Reaction of (25) with cis, cis-1,5-octadiene produces only the carbene JJ. • i 184 addition product. - 1 4 7 -+ (CF 3) 2CN 2' [ 3 . 4 ] Reactions of (25) involving cyclohexene or benzene both produce a 1 8 4 mixture of carbene addition and insertion products. + (CF 3) 2CN 2 kJ1 + (CF 3) 2CN 2 <TF3 C-H CF 3 [ 3 . 6 ] (25) reacts with the iron-iron bond of bis(cyclopentadienyl) iron dicarbonyl at room temperature in tetrahydrafuran but not i n i, A u i A- 1 8 6 , 1 8 7 hydrocarbon solvents according to: 0 C . / \ Fe Fe / v \ CO 0 CO C(CF 3) 2H + (CF 3) 2CN 2 Fe [ 3 . 7 ] CO CO - 148 -(25) also reacts with CO (CO)0 and (CO) ,-MnH at room temperature and with ((C 2H 5) 3P) 2PtHC£ at 120° to give (31), (32), and (33), _ , 186,187 respectively. (CF 3) 2 ( C 0 ) 3 C o ^ - -=aCo(C0) 3 (CO)5MnC(CF3)2H C 0 (31) (32) ( C 2 H 5 ) 3 P \ Pt ( C 2 H 5 ) 3 P ^ X v C ( C F 3 ) 2 H (33) The formation of (30), (31), and (32) are considered to involve direct attack by (25) as a 1,3-dipolar reagent; furthermore, i t i s suggested that, in the formation of (30), an intermediate 186 187 perhaps analogous to (31) abstracts hydrogen from tetrahydrofuran. ' The formation of the platinum complex (33) is suggested to result from attack by the carbene, (CF 3) 2C, on the platinum to form an unstable five-coordinate carbene (C2H,.) 3P) 2Pt (H)C£ (C(CF3) 2) which rearranges 186 187 to give (33). ' Evidence has been given for the formation of a 187 five coordinate iridium complex (34) from (25) and (C6rL-)2CH3P)Ir(C£)CO. - 149 -CF CF C ^ Ir (C 6H 5) 2CH 3P j \ ^ C 0 C l PCH 3(C 6H 5) 2 (34) Part I of this chapter discusses, in the main, the reactions of (25) with some fluoroalkynes and some 3,3,3-trifluoropropynyl group IV derivatives from Chapter 1. Both 1,3-dipolar and carbene addition reactions are considered. The stereochemistry of the 1,3-dipolar addition reactions was of particular interest. Part II of this chapter considers the reactions of (25) with some group IV and V hydrides and related compounds. Insertion of a C(CF 3) 2 group into, particularly, M-H bonds was expected. The insertion of CX2 (X = F, Cl, Br) into group IV M-H bonds has already been discussed in Chapter 2. Reactions of (25) with metal-metal bonds of involving group IV and V elements are also described in part II of this chapter. Recently, the insertion of C C l ^ into the ti n - t i n bond of hexamethylditin - 191 has been reported. - 150 -EXPERIMENTAL The general experimental apparatus and techniques have been described in Chapter 1, p. 8. I. Starting Materials. The following chemicals were purchased (supplier i n brackets*): (CF3)2C=NH (Hynes Chemical Research), C F 3 C E C C F 3 (Peninsular), and (CH 3) 3SiH (Peninsular). 3,3,3-Trifluoropropyne and the 3,3,3-trifluoropropynyl group IV derivatives were prepared as described in Chapter 1. The preparation of trimethyltin hydride has also been described in Chapter 1. Dimethylarsine and tetramethyldiarsine were gifts from Dr. W.R. Cullen. 1. Preparation of Bis(trifluoromethyl)diazomethane. Bis(trifluoromethyl)diazomethane was prepared according to 184 the method described by Gale e_t a l . Hexafluoroacetone amine was condensed onto anhydrous hydrazine (prepared by sti r r i n g hydrazine hydrate 192. with KOH for 24 hours )• The mixture was then d i s t i l l e d over P,0^ t o give hexafluoroacetone hydrazone. Oxidation of the hydrazone by lead tetraacetate in benzonitrile gave the diazo compound. Its purity was checked by infrared spectroscopy and by i t s molecular weight of 177 (Calc. for C 3F 6N 2: 178). For the addresses of the suppliers - see Appendix 2. - 151 -2. Preparation of Bis(trifluoromethyl)diazirine. Bis(trifluoromethyl)diazirine was prepared by a four step 184 procedure given by Gale et^ a l . 2-Aminohexafluoroisopropyl azide, prepared from hexafluoroacetone imine and sodium azide in acidic dimethylformamide, was heated for 7 days to give solid 3,3-bis(trifluoromethyl)diaziridine. The diaziridine was then oxidized by lead tetraacetate in a 10:90 acetic acid:benzonitrile solution to give the diazirine. The diazirine was found to be only 95% pure by 19 F n.m.r. spectrum but was used without further purification. 3. Preparation of Trimethylgermane. Trimethylgermane was prepared by reducing trimethylgermanium bromide in 1 molar hydrobromic acid with an aqueous solution of sodium 193 borohydride. 4. Preparation of Hexamethyldigermane. Hexamethyldigermane was prepared by refluxing trimethylgermanium 49 bromide for eight hours with molten potassium. The purity of the 49 d i s t i l l e d product, b.p. 138° - 140° (atm) ( l i t . value: 138° (750 mm) ), was checked by i t s "'"H n.m.r. spectrum which showed a single peak at -0.06 p.p.m. II. Reactions of Bis(trifluoromethyl)diazomethane. A. Reactions of Bis(trifluoromethyl)diazomethane with Some Fluoroalkynes and 3,3,3-Trifluoropropynyl Group IV Derivatives. 1. Reaction with 3,3,3-Trifluoropropyne. 3,3,3-Trifluoropropyne (1.395 g, 14.8 mmoles) and - 152 -bis(trifluoromethyl)diazomethane (1.187 g, 6.66 mmoles) were heated for 20 hours at 150°. V.p.c. separation (20% SE-30 at 55°) of the volatile fraction which condensed at -78° showed five components but only the second and third fractions could be collected and identified. The f i r s t eluted major component was identified as 3,3,5-tris(trifluoro-methyl) isopyrazole (0.776 g), micro b.p. 52° (atm). Anal. Found: C, 26.58; H, 0.43; F, 62.50%. Calc. for C^HF^N,: C, 26.45; H, 0.37; F, 62.90%. Infrared spectrum (vapour): 3060 (w), 2009 (w), 1738 (vw) , 1323 (m), 1300 (m) , 1281 (s), 1271 (s) , 1231 (w), 1200 (s) , 1180 (m) , 1120 (m), 978 (m) , 973 (m) , 852 (w) , 805 (vw) cm"1. The 1H n.m.r. spectrum showed a complex but well defined multiplet at -5.99 p.p.m. 19 The F n.m.r. spectrum (internal CFCJJ,^ ) showed two peaks, each a doublet, centred at 61.39 (=CCF„) (J„ u = 5.7 cps) and 61.81 p.p.m. (-C^F^),) (Jp_rr = 2.4 cps) which integrated i n the ratio 1:2, respectively (Calc. 1:2). The second component was identified as 1,3,3-tris(trifluoro-methyl) cyclopropene (0.201 g),micro b.p. 56.9° (atm). Anal. Found: C, 29.55; H, 0.62; F, 69.66%. Calc. for C 6HF g: C, 29.53; H, 0.41; F, 70.01%. Infrared spectrum: 3185 (w), 1814 (w), 1321 (s), 1291 (m), 1262 (s), 1246 (m(sh)), 1215 (s), 1195 (s), 1005 (w), 961 (m), 772 (w), 708 (m) cm The "''H n.m.r. spectrum showed a poorly defined complex 19 multiplet at -7.02 p.p.m. The F n.m.r. spectrum showed two multiplets centred at 62.0 p.p.m. (=CCF„) (J = 1.3 cps; J = 1.22 cps) and j r — i i r — r 67.65 p.p.m. (-C(CF,)0) (J = 1.5 cps) and which integrated in the J £- rj—H ratio 1:2, respectively (Calc. 1:2). - 153 -The fraction which passed through the -78° bath was identified as slightly impure 3,3,3-trifluoropropyne (0.728 g). In another reaction, the trifluoropropyne and the diazo compound were heated at 150° for 21 hours and then examined to determine the ratio of the products. From the v.p.c. and "''H n.m.r. integrations of the -78° fraction, i t was determined that the isopyrazole and the cyclo-propene together comprised 30% of the products based on propyne consumed, and that the ratio isopyrazole:cyclopropene was 2.45:1. When the reaction was carried out under ultraviolet light (450 watt U.V. source) for 21 hours i t was found by n.m.r. that the iso-pyrazole and cyclopropene comprised 65.5% of the products, based on propyne consumed, and that the ratio isopyrazole:cyclopropene was 2.04:1. 2a. Reaction with Hexafluorobutyne-2. Hexafluorobutyne-2 (0.424 g, 2.66 mmoles) and bis(trifluoromethyl)-diazomethane (0.466 g, 2.62 mmoles) were heated at 150° for 20 hours. A small amount of the starting butyne (0.086 g) was recovered. The fraction which condensed at -78° was separated by v.p.c. into 5 components (20% s i l i cone GE—SS—96 at 51°). Only the f i r s t and third eluted fractions were identified. The f i r s t (~ .07 g) was identified as tetrakis-(trifluoromethyl)cyclopropene (see 2b below). The second fraction was identified as 3,3,4,5-tetrakis-(trifluoromethyl)isopyrazole (0.262 g, 35% yield) micro b.p. 81° (atm). Anal. Found: C, 24.92; F, 66.6%. Calc. for C ?F 1 2N 2: C, 24.72; H, 67.04%. - 154 -Infrared spectrum (vapour): 2392 (vw), 1672 (vw), 1356 (s), 1302 (s) , 1269 (vw), 1227 (vw), 1197 (vs), 1149 (m), 1050 (w), 1004 (w), 980 (m), 952 (s), 941 (w), 772 (w), 755 (vw), 737 (m), 672 (w) cm"1. The 1 9 F n.m.r. spectrum (internal CFCJc^) showed an A^ M^ X^  pattern where A was the 4-position CF^ group (6(A) = 56.2 p.p.m.), M was the 5-position CF^ group (6(M) = 63.25 p.p.m.), and X was the two, 3-position CF^ groups (6(X) = 64.45 p.p.m.) ( J A _ M = 8.5 cps; J" A_ X = 6 cps). 2b. Pyrolysis of 3,3,4,5-Tetrakis(trifluoromethyl)pyrazole. The pyrazole (0.903 g, 2.68 mmoles) was heated at 300° for 72 hours. The product, tetrakis(trifluoromethyl)cyclopropene (0.764 g, 92% yield), was purified by repeated passes through a -78° bath (molecular wt. found: 308; Calc. for CyF^ 2 : 312). Anal. Found: C, 27.23; F, 72.60%. Calc. for C yF 1 2: C, 26.93; F, 72.90% . Infrared spectrum: 1919 (w), 1321 (s), 1303 (s(sh)), 1246 (s), 1225 (s), 1200 (s), 1030 (m), 961 (m), 765 (vw), 709 (m), 666 (m), 641 (w) cm"1. The 1 9 F n.m.r. spectrum (internal CFCJl^) showed two septets at 61.2 p.p.m. (CF3C=CCF_3) and 67.5 p.p.m. (-C(CF 3) 2) ( J F_ F = !-15 cps). The following vapour pressure data were obtained for the cyclo-propene : T(°K) 103/T(°K 1) p(cm) log p 1 227.2 4.403 0.726 -0.139 2 236.2 4.234 1.519 0.182 3 246.2 4.013 3.609 0.557 4 274.0 3.663 14.315 1.156 5 298.5 3.350 31.220 1.495 - 155 -The plot of log p against 10 /T(°K ) gave a straight line over a l l the temperatures except the last 298.5°K). From the extrapolated plot the b.p. was found to be 34.9° (760 mm). 3. Reactions with 3,3,3-Trifluoropropynyltrimethylgermane. 3,3,3-Trifluoropropynyltrimethylgermane (0.779 g, 3.69 mmoles) and bis(trifluoromethyl)diazomethane (1.076 g, 6.05 mmoles) were heated at 150° for 29 hours. A non-condensible gas, presumably nitrogen, was produced. The fraction which condensed at -78° was examined by v.p.c. (20% Kel-F grease at 72°). The two major components were identified as, in order of their elution: 3,3,5-tris(trifluoromethyl)isopyrazole, of known infrared spectrum (see 1 above) and 2,3,3-tris(trifluoromethyl)-cyclopropenyltrimethylgermane (0.179 g, 12.3% yield), micro b.p. 124.5° (atm). Anal. Found: C, 29.37; H, 2.46% Calc. for CgHgGe: C, 29.95; H, 2.50%. Infrared spectrum (vapour): 2995 (w), 2915 (w), 1837 (w), 1420 (vw), 1358 (w), 1320 (vs), 1295 (s), 1269 (vs), 1228 (s(sh)), 1209 (vs), 1183 (vs), 1163 (s(sh)), 1104 (vw), 1080 (vw), 997 (w), 958 (s), 841 (s), 841 (m), 768 (w), 710 (m) cm The "*"H n.m.r. spectrum showed 19 a singlet at -0.35 p.p.m. The F (internal CFCJi^) n.m.r. spectrum showed a septet and quartet centred at 62.0 p.p.m. and 66.9 p.p.m. with J = 1.2 cps in both splitting patterns. The area ratio of the low f i e l d : high f i e l d absorptions was 1:2 (Calc. 1:2). - 156 -4. Reactions with 3,3,3-Trifluoropropynyltrimethyltin. 3,3,3-Trifluoropropynyltrimethyltin (1.178 g, 4.59 mmoles) and bis(trifluoromethyl)diazomethane (1.424 g, 8.02 mmoles) were heated for 29 hours. There was considerable decomposition. No free propyne was detected but a non-condensible gas, presumably nitrogen, was produced. Only the last eluted component i n the v.p.c. separation (20% K e l - F grease at 110°) of the -78° fraction could be collected as a single, uncontaminated product. It was identified as 2,3,3-tris(trifluoromethyl)cyclopropenyltrimethyltin (0.140 g, 7% yield). Infrared spectrum (vapour): 3000 (vw), 2925 (vw), 1820 (w), 1358 (w), 1321 (s), 1290 (m), 1266 (s), 1209 (s), 1181 (s), 1000 (vw), 982 (vw), -1 1 958 (m), 788 (vw), 763 (vw) cm ). The H n.m.r. spectrum showed a singlet at -0.3 p.p.m. with t i n s a t e l l i t e peaks (Jll7g n_cg = 19 3 58.2 cps; J 1 1 9 S n _ C H = 6 1 « 0 cps). The F (internal C F C J t ^ ) n.m.r. spectrum showed two sets of peaks: a septet at 62.55 p.p.m. (-CF^) and a quartet at 66.9 p.p.m. (-C^CF-j^) (Jp_ F = 1.25 cps), (Area ratio septet-quartet = 1:2 (Calc. 1:2)). - 157 -In another experiment the tin compound (0.579 g, 2.16 mmoles) and bis(trifluoromethyl)diazomethane (0.541 g, 3.04 mmoles) were combined and heated at 150° for 20 hours. A non-condensible gas, presumably nitrogen, was again produced. V.p.c. separation (20% silicone GE-SS-96 at 75°) of the volatile fraction that condensed at -78° showed only one major component; however, the compound had decomposed (to be further described) before sufficient data could be obtained for properly basing a structural assigned. The following vapour pressure data were obtained for the tin compound. T(°K) 10 3/T(°K _ 1) p(cm) log p 1 293.95 3.401 2.311 0.364 2 302.65 3.304 3.772 0.577 3 313.95 3.185 6.419 0.808 4 323.35 3.092 10.675 1.028 5 332.45 3.007 15.900 1.201 6 337.65 2.962 20.100 1.303 When the isotenoscope o i l bath was ca. 67° extensive decomposition of the sample in the glass isotenoscope occurred. However, from the vapour 3 -1 pressure data a perfectly linear plot of log p versus 10 /T(K ) was obtained and the b.p. was established: b.p. = 98.7° (760 mm). - 158 -B. Reaction of Bis(trifluoromethyl)diazirine with 3,3,3-Trifluoro- propynyltrimethylgermane. Bis(trifluoromethyl)diazirine (0.924 g, 5.17 mmoles) and 3,3,3-trifluoropropynyltrimethylgermane (0.683 g, 3.24 mmoles) were heated at 165° for 13 hours. The fraction of the reaction mixture which condensed at -78° was examined by v.p.c. (20% Kel-F grease at 12°). The major component was identified as 2,3,3-tris(trifluoromethyl)-cyclopropenyltrimethylgermane (0.241 g, 20% yield) by i t s infrared spectrum (see Section 3 above). A small amount of 3,3,5-tris(trifluoromethyl)isopyrazole was also identified by i t s known infra-red spectrum (see 1 above). C. Reactions of Bis(trifluoromethyl)diazomethane with Other Organo- metallic Compounds. 1. Reaction with Trimethylsilane. Trimethylsilane (0.40 g, 5.4 mmoles) and bis(trifluoromethyl)-diazomethane (0.250 g, 1.4 mmoles) did not appear to react after one day at 20°. The mixture was heated at 100° for 72 hours after which the volatiles were examined by "'"H n.m.r. spectroscopy. The spectrum showed only a multiplet at -3.25 p.p.m. (J = 3.7 cps) which corresponded with the original trimethylsilane. 2. Reaction with Trimethylgermane. Trimethylgermane (0.356 g, 3.0 mmoles) and bis(trifluoromethyl)-diazomethane (0.761 g, 4.27 mmoles) were combined. No reaction was observed after one day at 20°. The mixture was heated at 135° for 50 - 159 -hours. The H n.m.r. spectrum of the volatiles showed three high f i e l d absorptions and a septet centred at -2.64 p.p.m. (J = 9.5 cps). However, ~4i n.m.r. spectra of the major v.p.c. separated products (20% Kel-F grease at 90°) showed that the septet was due to a compound which did not have any high f i e l d methyl absorptions and thus, not due to (CH^)3GeC(CF3)^H. The v.p.c. separated products were not further studied. 3. Reaction with Trimethyltin Hydride. Trimethyltin hydride (0.633 g, 4.0 mmoles) and bi s ( t r i f l u o r o -methyl) diazomethane (0.741 g, 4.2 mmoles) reacted upon warming to 20° with evolution of gas and loss of colour. A white precipitate had formed after 2 hours. After 3 days a brown decomposition product was observed. After 3 weeks at 20° the volatiles were fractionated by trap-to-trap d i s t i l l a t i o n . The fraction which condensed at -78° was purified by v.p.c. (20% Kel-F grease at 95°) and identified as 1,1,1, 3,3,3-hexafluoroisopropyltrimethyltin (0.611 g, 51% yield), micro b.p. 129.5° (atm). Anal. Found: C, 23.06; H, 3.20; F, 35.91%. Calc. for C 6H gF ?Sn: C, 22.89; H, 3.20; F, 36.21%. Infrared spectrum (vapour): 3000 (w), 2939 (w), 1766 (w), 1363 (s), 1282 (vs), 1250 (m), 1220 (vs(br)), 1195 (s), 1130 (w), 1079 (m), 1050 (m), 970 (vw), 900 (w), 870 (w), 787 (m), 674 (w) cm 1. The "*"H n.m.r. spectrum showed a singlet at -0.30 p.p.m. (-CH„) with t i n s a t e l l i t e peaks (J117 = 51.5 cps; J Sn—CH^ « J i i 9 n _ r H = 56.5 cps) and a septet at -2.54 p.p.m. (-CH(CF„)9) - 160 -(J„ „ = 11.5 cps). The two absorptions integrated in the ratio 9.3:1, 19 respectively. (Calc. 9:1). The F n.m.r. spectrum showed a doublet of septets centred at 56.1 p.p.m. (J„ n T ! = 0.5 cps). r - L.h.3 The material which passed through the -78° bath was identified as mostly perfluoropropene by i t s known infrared spectrum. 4. Reaction with Trimethylgermanium Bromide. Trimethylgermanium bromide (0.713 g, 3.60 mmoles) and bis(trifluoromethyl)diazomethane were miscible at 20°. The mixture was opaque after one day. After 48 hours at 100° a brown decomposition product had formed. A small amount of perfluoropropene (< 0.1 g) was isolated. The fraction which condensed at -78° was separated into two major components by v.p.c. (20% silicone GE-SS-96 at 90°). The f i r s t fraction (0.110 g) showed infrared absorptions at 7.9, 8.05, and 13.81 u . It was not identified. The second component was identified as trimethyl-germanium bromide (0.278 g) by comparison of i t s infrared and ^E spectra with that of a known sample. 5. Reaction with Dimethylarsine. Dimethylarsine (0.374 g, 3.54 mmoles) and bis(trifluoromethyl)-diazomethane (0.799 g, 4.48 mmoles) were miscible at 20°. No evidence of reaction was observed after two days. After 48 hours at 100° a brown decomposition product had formed. The fraction which condensed at -78° was purified by v.p.c. (20% Kel-F grease at 95°) and identified as the insertion product, 1,1,1,3,3,3-hexafluoroisopropyldimethylarsine - 161 -(0.605 g, 67% yield), micro b.p. 110.5° (atm). Anal. Found: C, 23.63; H, 2.84; F, 44.22%. Calc. for C^FgAs: C, 23.45; H, 2.75; F, 44.52%. Infrared spectrum (vapour): 3025 (w), 3000 (w), 2939 (w) , 1424 (w(br)), 1358 (s), 1296 (vs), 1241 (vs), 1213 (s), 1142 (m), 1090 (s), 1075 (s(sh)), 909 (m), 975 (w), 960 (w), 679 (m) cm"1. The XH n.m.r. spectrum showed a broad singlet and a septet at -1.0 p.p.m. (CH^) and -2.67 p.p.m. 19 (-CH_(CF3)> respectively. (Jp_^ = cps). The F n.m.r. spectrum displayed a doublet of septets centred at 55.90 p.p.m. (J = 0.95 cps). 3 The lower boiling fraction was identified by infrared spectroscopy as a mixture of starting diazo compound and perfluoropropene. 6. Reaction with Hexamethyldigermane. Hexamethyldigermane (0.726 g, 3.09 mmoles) and b i s ( t r i f l u o r o -methyl) diazomethane (0.742 g, 4.17 mmoles) were miscible at 20°. There was no visible evidence of any reaction after one day at 20°. The mixture was heated at 100° for 24 hours. The fraction which condensed at -78° was examined by v.p.c. (20% silicone GE-SS-96 at 132°), and found to be 82% hexamethyldigermane. Anal. Found: C, 30.63; H, 7.65%. Calc. for C^H^gGe: C, 30.85; H, 7.72%. The fraction which passed through the -78° bath was found by i t s infrared spectrum to be a mixture of tetra-methylgermane, perfluoropropene, and the starting diazo compound. 7. Reaction with Tetramethyldiarsine. Tetramethyldiarsine (0.940 g, 4.5 mmoles) and b i s ( t r i f l u o r o -methyl) diazomethane (0.893 g, 5.0 mmoles) were miscible at 20°. No - 162 -evidence of reaction was observed after two days at 20°. The mixture was heated at 100° for 48 hours. The volatile fractions which condensed at -36.5°, -45.2°, and -63° were combined and separated by v.p.c. (20% Kel-F grease at 100°). The two major components were identified as, in order of their elution: trifluorovinyldimethylarsine (0.164 g), (Anal. Found: C, 25.74; H, 3.63; F, 30.20%. Calc. for C^H^As: C, 25.83; H, 3.25; F, 30.64%), and 1,1,1,3,3,3-hexafluoroisopropyl-dimethylarsine. The latter was characterized by comparing i t s infrared spectrum with that of a known sample (see 5 above). - 163 -RESULTS AND DISCUSSION I. Addition Reactions of Bis(trifluoromethyl)diazomethane (25)to Fluoroalkynes and 3,3,3-Trifluoropropynyl Group IV Der i v a t i v e s . A. Fluoroalkynes. Bis(trifluoromethyl)diazomethane reacts with 3 , 3 , 3 - t r i f l u o r o -propyne ei t h e r at 150° (20 hr.) or under the influence of u l t r a v i o l e t l i g h t (A > 2850 A; 20 hr.) to give as the major products: 3,3,5-t r i s ( t r i f l u o r o m e t h y l ) i s o p y r a z o l e (35) and 1 , 3 , 3 - t r i s ( t r i f l u o r o m e t h y l ) -cyclopropane (36). When the reactants are heated at 150° (35) and (36) together comprise 30% of the products based on propyne consumed and are i n the r a t i o (35):(36) = 2.45:1. Under p h o t o l y t i c conditions a s l i g h t l y lower r a t i o , (35):(36) = 2.04:1, i s obtained^ however, the o v e r a l l y i e l d of (35) + (36) i s higher, namely, 65.5%. The proposed structure of (35) i s based on elemental analysis for carbon and f l u o r i n e and on the observed i n f r a r e d and n.m.r. spectra. The i n f r a r e d spectrum (Table XIX, p. 164) shows weak absorptions at 3006, 2009, and 1775 cm"1 due to the C-H, N=N, and C=C st r e t c h i n g Table XIX I i,ln Infrared Spectra (Main Bands Only (in cm - 1) of RC=C(CF»)C(CF0) y v yi Derivatives. H\ ^ CF, 3185 1814 1321 1262 1215 1195 1005. 961 772 708 CF 3 ^CF3 C F 3 \ JF3 CF 3 CF 3 1919 1321 1246 1225 1200 1030 961 1303 709 666 (CH 3) 3 G l CF, CF 3 ^CF3 1837 1320 1269 1209 1183 997 958 841 710 (CH 3) 3Sn CF, CF 3 ^CF 3 1820 1321 1266 1209 1181 958 Table XX N.m.r. Parameters of Some RC=(CF 3)C(CF 3) 2 and RC=C(CF3)N=N(C(CF3)2) Derivatives, V 1 9 F t t I. Cyclopropenes 6 <5(Fa) 6(F b) 6(F C) J F a _ R J pb_ H J ^ b J. Fb_F c H- .CF, CF 3 CF 3 -7.02 62.0 67.65 1.3 1.0 1.2 ON CF, CF, CF 3 CF 3 (CH3)3Ge CF, CF 3 CF 3 61.2 67.5 -0.35 62.0 66.9 1.15 1.2 (CH ) 3 S n \ / CF -0.30 62.55 66.9 1.25 l H t 19 Ftt II. Isopyrazole 6 6(F a) 6(F b) -5.99 61.39 63.25 56.2 in p.p.m. with respect to external (CHo^Si t t in p.p.m. with respect to internal CFC£» V - H J F b - H J F a - F b ' J F b - F C 61.81 5.7 2.4 as 64.45 8.5 6 - 167 -vibrations, respectively. The F n.m.r. spectrum (Table XX, p. 165) shows two doublets that integrate in the ratio 1:2. The smaller doublet occurs at lower f i e l d , consistent with the deshielding effect of the double bond on the CF^ group in the 5-position. By using the coupling 19 constants derived from the F n.m.r. spectrum the peaks in the very complex singlet displayed in the XH n.m.r. spectrum (Figure 8, p. 168) can be assigned. The cyclopropene structure, (36), is deduced in a similar way. The- compound analyzes correctly for C, H, and F. The infrared spectrum (Table XIX, p. 164) includes absorptions at 3185 and 1814 cm - 1 due to the C-H and the C=C stretching vibrations, respectively. (See also Chapter 2, p. 116 , for a discussion on the substituent dependency of the C=C frequency in cyclopropenes.) The XH n.m.r. spectrum shows a single peak which although too narrow and complex to be resolved has a chemical shift value (-7.02 p.p.m.) similar to that of HC=CCF3(CF2) (-7.37 p.p.m.). A small upfield shift might be expected in the present case since two groups of fluorine atoms are no longer vinylic but rather a l l y l i c to the hydrogen and thus their deshielding effect on the hydrogen via electron 19 withdrawal is reduced. The F n.m.r. spectrum (Figure, p. 169) shows two sets of peaks. The coupling constants can a l l be assigned on a f i r s t order basis and are consistent with the proposed structure. At 150° (25) and hexafluorobutyne-2 give 3,3,4,5-tetrakis-(trifluoromethyl)isopyrazole (37) and a small amount of tetrakis-(trifluoromethyl)cyclopropene (38). - 168 -- 170 -Under the conditions studied, (37) and (38) comprise 50% of the products (based on butyne consumed) and are in the ratio ca. (37):(38) = 3.8 :1. As in eq. [3.2] (37) looses nitrogen (300°) to give the cyclopropene (38). 19 The structure of (37) is shown immediately by i t s F n.m.r. spectrum (Figure 10 , p. 171) and confirmed by elemental analysis for carbon and 19 fluorine. The three peaks in the F n.m.r. spectra integrate in the ratio 1:1:2, as expected, and the splitting patterns can be completely analyzed on a f i r s t order basis. The structural proof of the cyclo-19 propene (38) is provided by i t s F n.m.r. spectrum which shows two septets (J = 1.15 cps) of equal intensity at chemical shift values similar to those of the cyclopropene (36) produced in eq. [3.7] (Table XX, p. 165). The infrared frequency associated with the C=C stretching vibration occurs at 1914 cm X and is the second highest recorded C=C frequency of a cyclo-propene. The highest frequency, 1945 cm X, occurs in perfluorocyclo-145 propene. This point i s further discussed in Chapter 2. B. Mechanisms. 194 Huisgen has c r i t i c a l l y reviewed the available information on 1,3-dipolar additions and has concluded that such addition reactions Figure 10. F N.m.r. spectrum of 3,3,4,5-tetrakis(trifluoromethyl)isopyrazole. Curve 2 is an expansion of the multiplet centred at 56.2 p.p.m. - 172 -take place by a concerted process involving formation of both o-bonds at the same time. The intermediate in the formation of the isopyrazoles in the present case are shown in (39). R ' tF-> o = = c ' C F3 (39) This intermediate (39) when R = H occurs in the reaction given by eq. [3.8] and is reasonable since (a) canonical forms (27) and (28) in which the central carbon atom of (25) possesses a formal negative are 46 predicted to predominate and (b) i t is known that the propyne is 6+ 6-polarized in the direction HCHC^-CF^ SO that the terminal carbon atom is the most susceptible to nucleophilic attack. It is interesting to compare the reaction involving (25) and 195 HC=CCF3 with that involving 2,2,2-trifluorodiazoethane and HCsCCF^ CF3CH-N=N + HC=CCF3 > _J[ ^ + N{/ \ ^ [3.10] (40) .(41) - 173 -Pyrazole derivatives are obtained in the reaction involving CF^CHN, since proton migration is possible but not in the case of (25). The interesting observation however, is the formation of a small amount of 3,4-bis(trifluoromethyl)pyrazole (41) in addition to the major and expected adduct (40)• The analogous compound in the reaction involving (25) would be 3,3,4-tris(trifluoromethyl)isopyrazole (42) but i t was not detected. The reasons for this difference between the reaction of (25) and that of CF^CHN, with HC^CCF^ are both electronic and steric. (a) Electronic - As mentioned earlier (25) probably exists predominantly as either canonical form (27) or (28) and presumably, mostly as (28), based on the intermediate (39), in 1,3-dipolar addition reactions. The diazo compound CF^CHN, probably also predominantly exists in a form similar to (28) ; however, the nucleophilicity of (25) is probably less than that of CF^CHN, due to the stabilizing effect of the second trifluoromethyl group. This reduced reactivity results in the production only of the isopyrazole that arises from nucleophilic attack by (25) at the most electrophilic site of HCECCF^, that i s , the terminal carbon atom. In contrast, CF^CHN,, because i t is more reactive, can attack as a nucleophile, both the terminal and the central carbon atoms of the propynt* (although terminal attack is s t i l l preferential). (b) Steric - Addition of diphenyldiazomethane to methylphenyl-propiolate gives (43). Only this isomer is produced because - 174 -C,H_ C0oCHo 6 5 «, / 2 3 N C,EL 6 5 (C,HC)0C-N=N + C,HcC=CC0oCHo ' \ - C * H * [3.11] 6 5 2 6 5 2 3 (43) the spatial requirements of the phenyl group are greater than those of the ester function. The similar reaction involving phenyldiazomethane however, gives both isomers, although the sterically favoured isomer 194 (44) is s t i l l the major one. C0oCH„ C,HC CO„CH„ 2 3 6 5 2 3 C6H5CH-N=N + C6H5C=CC02CH3 > ^(/ \ + 1 , „ [3.12] (44) The isopyrazoles that are produced in the reactions given by eqs. [3.11] and [3.12] directly parallel those produced in the reactions given by eqs. [3.7] and [3.10], respectively. The production of (41) in eq. [3.10] but none of the corresponding isomer in eq. [3.7] i s , therefore, also related to the smaller steric interaction between the CF^ groups of the reactants in eq. [3.10] relative to the same interactions in eq. [3.7]. The reaction of (25) with the group IV trifluoropropynyl derivatives at 165° (29 hr) gives the corresponding group IV 2,3,3-- 175 -tris(trifluoromethyl)cyclopropenyl derivative. - + (CF3)2C-N=N + (CH3)3MCECRf (M = Ge, Sn) CF 3 [3.13] (45) A small amount of (35) is also produced in the reaction involving the propynyl germanium derivative. (35) probably results from the reaction of (25) with HCECCF3. The latter was detected in the reaction mixture resulting from the reaction of TfMTMT and (CH3)3GeCECCF3 at 150° (Chapter 2). based primarily on the similarity of their observed infrared and n.m.r. p. 164 and Table XX, p. 165). Analytical data for the germanium compound is somewhat over the margin of experimental error. The proposed structure is confirmed by the finding that the infrared spectrum of the major product of the reaction of (CH_3) 3GeC=CCF3 and bis ( t r i f luoromethyl)-diazirine at 165° (12 hr) is identical with the spectrum of the germanium derivative produced in the reaction given by eq. [3.13]. Thermal decomposition of the diazirine at temperatures > 150° is known 184 to produce only C(CF,) as a reactive species and thus (CH3)3GeC=CCF3(C (CF 3) 2) is the expected product. It is notable that some of the isopyrazole, (35), is also produced in the reaction of (M = Ge, Sn) are spectra of the two derivatives to those o - 176 -(CH^)^GeCHCCF^ with the diazirine. This is surprising since the diazirine is not expected to produce isopyrazole products; however, the diazirine used was only 95% pure and the impurities may have been (25). The cyclopropenes (36), (38)? and (45) produced in the reactions given by eqs. [3.8], [3.9], and [3.13], respectively, could have been formed either by elimination of nitrogen from the corresponding isopyrazoles or by the direct addition of C(CF.j)2 to the C=C bonds. Formation of (36) and (38) via carbene addition is implied by the ratios of the isopyrazole:cyclopropene products produced in the two reactions given by eqs. [3.8] and [3.9]. To reiterate, the ratios are (for the thermally induced reactions) (a) eq. [3.8], (35):(36) = 2.45:1 (b) eq. [3.9], (37):(38) = 3.8 :1. It is known that the presence of trifluoromethyl groups on the tri p l e bond enhances the triple bond's reactivity towards 1,3-dipolar addition reactions and at the same time reduces the tri p l e bond's reactivity towards electrophilic carbene attack. These two trends are both a consequence of the electron withdrawing effect of the trifluoromethyl groups. From the ratios of the products of the two reactions i t i s immediately obvious that these two opposing trends are exhibited and that the suggestion that the cyclopropenes (36) and (38) are formed via carbene addition is valid. The cyclo-propenes, (45), were probably also formed by the direct addition of C(CF.j)2 since the same reaction conditions were used. It is to be noted however, that the formation of any of the cyclopropenes by elimination of nitrogen cannot be completely excluded at this point. - 177 -It i s interesting that the ratio of the products in eq. [3.8] is lower in the reaction induced photolytically ((35):(36) = 2.04:1) than that in the reaction induced thermally (2.45:1). It might be concluded that either (a) a more active carbene is produced photolytically than is produced thermally, or (b) the 1,3-dipolar addition reaction i s temperature dependent but no differentiation between these two possi-b i l i t i e s i s possible at this time. II. Reactions of Bis(trifluoromethyl)diazomethane with M-H and M-M Bonds. This section i s divided into three parts: (a) reactions involving a Group IV M-H and related bonds, (b) reactions of the arsenic hydride bond, and (c) reactions involving metal-metal bonds. A. Group IV M-H and Related Bonds. 1. Results. The XH n.m.r. spectra of the reaction products involving either trimethylsilane or trimethylgermane and (25) showed that no insertion of a CiCF^)^ moiety into either the Si-H or Ge-H bonds takes place at 100° and 135°, respectively. The reaction of (25) with trimethylgermanium bromide at 110° also f a i l s to insert C(CF 3) 2 into the Ge-Br bond. The reaction of (25) and trimethyltin hydride however, gives the insertion product, 1,1,1,3,3,3-hexafluoroisopropyltrimethyltinjat room temperature. The reaction seems to take place almost immediately although the mixture was l e f t for three weeks before separation. (CF 3) 2CN 2 + (CH3)3SnH -> (CH3>3SnC(CF3)2H + [3.14] (46) - 178 -The structure of the insertion product (46) is based on elemental analysis for C, H, and F and n.m.r. data. The "*"H n.m.r. spectrum shows two sets of peaks: a singlet with t i n satellites at high f i e l d due to the methyl groups, and a low f i e l d septet (J = 11.5 cps) due to the isopropyl hydrogen. The main high f i e l d peaks are slightly broadened by coupling with the fluorines but the spli t t i n g is not resolved. The 19 F n.m.r. spectrum shows a doublet of septets. This long range coupling has been discussed in Chapter 2, part IV. Already mentioned in Chapter 2 and in the Introduction to this Chapter are the insertions of CX^ (X = F, C£, Br) into group IV M-H (M = Si, Ge, Sn) bonds. The reaction of diazomethane and MC£^ (M = Si, Ge, Sn) also gives products corresponding insertion of CH^ into M-C£ bonds. 1 9 6 An explanation for the observed reactivities of (25) with the group IV hydrides can be found by f i r s t considering the proposed mechanism of insertion of CH„ from diazomethane into the M-C£ bonds of MC£. I 4 (M = Si, Ge, Sn). The ease of successive insertions of CH^ into the M-C£ bonds of a particular MC£^ compound increases as M is changed fr om Si to Ge to Sn. For example, at the limits, no (CH^C^^Si can be prepared even by reacting SiC&4 with a large excess of diazomethane; however, a 57% yield of (CH^CJO^Sn can be obtained from SnCJi^ and excess diazomethane. To account for these contrasting results Seyferth proposed a polar mechanism involving nucleophilic attack by diazomethane to form a five-coordinate intermediate (47) followed by loss of nitrogen and - 179 -rearrangement. C9J C iL C & i - + i + ^ i C£ 3M <- CH2-N=N--> C£ 3M-CH 2-N=N->C£ 3M-CH 2 + N2~> C£ 3MCH 2C£ [3.15] (47) Seyferth reasoned that the five-coordinate intermediate is plausible since the elements Si, Ge, and Sn have available d. orbitals, and further, 6+ 6-that the increasing polarity of the M-C bonds as the atomic number of M increases explains the apparent successive ease of methylene insertion since nucleophilic attack is the f i r s t step. A similar mechanism and considerations of bond polarity apply in explaining the reactivity of (25) with the group IV hydrides. It is to be noted that, assuming a polar mechanism, canonical forms (27) and (28) predominate as predicted earlier and as concluded on the basis of the stereochemistry of the products resulting from the 1,3-dipolar addition of (25) to HCECCF3. B. Reactions with a Compound Containing an As-H Bond. The reaction of (25) with dimethylarsine at 100° (48 hr.) gives a good yield (67%) of the product, 1,1,1,3,3,3-hexafluoroisopropyldi-methylarsine . (CF 3) 2CN 2 + (CH3)2AsH + (CH 3) 2AsC(CF 3) 2H + N 2 [3.16] (48) The structure of (48) is suggested by i t s n.m.r. spectrum and elemental analysis confirms the assigned formula. The XH n.m.r. spectrum - 180 -displays a broadened singlet at -1.0 p.p.m. due to the methyl hydrogens and a septet centred at -2.67 p.p.m. due to the isopropyl hydrogen atom (J = 10 cps). The area ratio, singlet:septet, is ca.. 7:1. (Calc. 6:1). The broadening of the singlet is caused by the unresolved long-range 19 J coupling. This coupling is clearly displayed in the F n.m.r. CH3-CF3 spectrum which shows a doublet of septets at 55.90 p.p.m. (Jnv „ = 0.95 cps). Long-range J„ couplings have been noted by other 3 ( C H 3 } 2 A s \ 45 investigators in compounds containing a C= group. CF 3 The mechanism of the reaction given by eq. [3.16] is probably different from that involving the group IV hydrides. The diazo com-pound (25) reacts with phosphorous and nitrogen nucleophilic reagents 184 to give linear adducts and a similar linear adduct resulting from CF 3 (C6H5)3P=N-N=C(CF3)2 { }J-N=N-C-H nucleophilic attack of the arsenic lone pair onto the terminal nitrogen atom of (25) may exist as an intermediate in the present case. It is suggested that the diazo compound exists mainly as canonical form (28). H CF„ H CF_ I + _ / . 3 | _ / 3 (CH 0) 0As > N=N-CV > (CH0)0As-N=N-C. 3 2 X C F 3 3 2 + X C F 3 [3.17] CF„ CF 0 I 3 | 3 -> (CH3)2As-N=N-C-H —> (CH3)2AsC-H + N 2 CF„ CF, 3 : - 181 -C. Reactions with Metal-Metal Bonds. The lack of reaction between (25) and hexamethyldigermane is in keeping with the polar mechanism suggested earlier for the reaction of (25) with group IV hydrides. Neither the germanium atoms nor the Ge-Ge bond are sufficiently electrophilic to undergo nucleophilic attack by (25) nor sufficiently nucleophilic to attack the terminal nitrogen as in the case of dimethylarsine (eq. [3.17]). At the low temperature (100°) at which the reaction was carried out carbene forma-184 tion i s minimal ; however, i f the reaction were to be carried out at higher temperatures (> 150°) when the rate of formation and the energy 184 of C(CF^)2 a r e both faster and higher, respectively, electrophilic attack by the carbene may take place. (25) reacts with the As-As bond of tetramethyldiarsine at 100° and two products are formed: 1,1,1,3,3,3-hexafluoroisopropyldimethy1-arsine and trifluorovinylarsine. The reaction temperature suggests that the mechanism involves i n i t i a l nucleophilic attack by the arsenic lone-pair onto the terminal nitrogen atom as in the reaction of (25) with (CH,)9AsH (eq. [3.17]) rather than i n i t i a l carbene attack. - 182 -CHAPTER 4 MOSSBAUER ABSORPTION SPECTRA OF SOME (CH0KSnR^ COMPOUNDS Jr-J——I INTRODUCTION The Mb'ssbauer effect is the recoilless emission and resonant 119 absorption of y - r a d i a t i o n . In Sn Mossbauer spectroscopy the source is X X^Sn in a metastable state, e.g. X x 9 mSn-enriched BaSnO^ or SnO,, which emits a y-ray in decaying from i t s f i r s t excited state to i t s 119 ground state. This radiation then excites a Sn atom in the absorbing sample to the excited state. 119m Sn Y=65.66 Kev 1st Excited State 1=3/2—^ Ground State 1=1/2 Y=23.875 Kev (Mossbauer y-ray) 119 Sn Figure 11 Radioactive Decay scheme of X x 9 m S n J I is the spin of the nuclear state. The energy of the nuclear ground and excited states of an atom depends on the s_-electron density at nucleus. This density changes as the oxidation state and substituents around the atom are changed. Thus, the energy difference between the ground state and the excited state - 183 -w i l l be slightly different in the absorber than i n the source. To bring the absorber and the source into resonance, the frequency of the y-radiation is altered by the doppler effect. The isomer shift measured in mm/sec is the source velocity causing the necessary doppler effect needed to effect absorption of y-rays by a particular sample. The dependence of the isomer s h i f t , 6, on the ^-electron densities at the source and the absorber is given by 6 = constant _^r $\i> (o) | 2 [4.1] r where 6 = r - r , is the difference in the nuclear r a d i i of the r ex gd excited (ex) and ground (ed) states and 6 (o) 2 = [lib (o)| 2 , s 1 1 s 1 Absorber |il> (o) I 2 ] is the difference in the electron density of the Mossbauer 1 s 1 Source J nucleus in going from the source to the absorber. Since <5 > 0 and 119 1 9 7 constant for Sn the isomer shift of t i n compounds w i l l increase with increasing ^-electron density at the absorbing tin nucleus relative to some standard source. This is dramatically displayed in the increasing isomer shift in going from ionic Sn (5s ) to ionic Sn (5s ) compounds. Table XXI Isomer Shift of Some Tin Compounds in Different Oxidation States. (5 in mm/sec relative to Sn02) ionic covalent metallic covalent ionic t i n 4+ IV o II 2+ Oxidation state Sn Sn Sn Sn Sn Isomer shift -0.0 -1.3 -2.1 -3.5 >3.7 Electron config. 5s^ (Ss^p3) Ss^p 3 5s 2(+p X) 5s 2 - 184 -A quadrupole spl i t t i n g (also measured in mm/sec) of the Mossbauer absorption line arises from the interaction of the nuclear quadrupole moment of the nucleus in question with an electric f i e l d gradient in the neighbourhood of the nucleus. A l l nucleii with spin 1 > 1/2 have quadrupole moments. This includes the f i r s t excited 119 state of Sn which has I = 3/2. When the t i n nucleus is in an asymmetric electronic environment the quadrupole interaction l i f t s the degeneracy of the excited state and absorption takes place to each of the excited states, I = ±3/2 and ±1/2, (Figure 12a). The spectrum 119 observed is a doublet (Figure 12b) . The quadrupole s p l i t t i n g for Sn , 199 is given by A = \ e Q V z z ( 1 + 3 ~ ) 1 / 2 [ 4 > 2 ] where A is the quadrupole splitti n g , e i s the coulombic charge of an 119 electron, Q is the quadrupole moment of the Sn excited nucleus and is a constant, V is the electric f i e l d gradient in the z direction z z ( 9 V / 9 Z ) , and n is the asymmetry parameter (V - V /V ). For x,y xx yy 'Zi'z* s t r i c t l y axially symmetric R^SnR1 compounds ( C 3 v symmetry) the , asymmetry parameter ( n ) is zero and A=|eQV z z. [4.3] One would expect, therefore, a quadrupole spl i t t i n g in the Mossbauer spectra of a l l R^SnR' compounds due to the electronegativity difference - 185 -Q u a d r u p o l e C o u p l i n g A ( m m / s e c ) Exc i ted T _ 3 state 2 Ground . _ i _ state 1 ~ 2' 1 A ±1 - 2 - 2 Isomer shif t (6) Quadrupole coupl ing (A) Figure 12a. Schematic diagram showing origin of isomer shift and quadrupole spl i t t i n g in Mossbauer absorption spectrum of 119 Sn compounds, M o s s b a u e r s p e c t r u m o Velocity in m m /sec Figure 12b. Typical Mossbauer absorption spectrum for a 1 1 9 S n containing compound which shows a quadrupole splitting. - 186 -between R & R', however, spl i t t i n g is not observed in many cases even where the difference is considered relatively large, e.g. (C^ H^ .) 3SnLi. Table XXIllist some other R-jSnR' compounds which show no observable quadrupole s p l i t t i n g . Table XXII Some R^SnR' Compounds Which Show No Observable Si Quadrupole Splitting. Reference CR3SnH3 200 (CH3)3SnH 200 (n-C 4H 9)SnH 3 200 H0Sn n-C.H_ 200 3 — 4 9 (CgH") 3SnLi 199 (CH3)3SnNa 201 Minimum observable linewidth in a l l of the Mossbauer spectra of these compounds was > 0.90 mm/sec and small splittings may not have been resolved. The quadrupole s p l i t t i n g that has been observed i n the Mossbauer spectr of R3SnR' compounds has been attributed to effects other than electro-negativity differences. For example, Greenwood et a l , suggested, on 202 203 the basis of the evidence available at the time, ' that quadrupole - 187 -splitting in R^SnR" compounds would only be observed when either the R' group or a l l three R groups were bonded to the ti n atoms via an atom which possessed a non-bonding pair of valence electrons (e.g. F, C£, Br, I, 0, S, N). Unsaturated substituents were also included, e.g. R^SnCECH (R = alkyl) in this prediction. It was reasoned that the imbalance in p T r - d i r interactions between the non-bonding or fr-pairs of electrons and the tin 5d_ orbitals leads to a distortion of the tin bonding orbitals and an electric f i e l d gradient near the t i n nucleus. 204 More recent evidence has indicated however, that, at least for R3SnX (R = alkyl; X = F, CSL, Br, I), the sp l i t t i n g results from intermolecular five-coordinate structures with halogen bridges.. Gassenheimer and Herber have suggested similar bridges to account for 205 the sp l i t t i n g in the spectra R-SnCN and R„SnSCN compounds. Khrapov e_t. a l . have suggested intramolecular five coordination for R R R3SnC(0)CH3 (R = CH 3 > C ^ ) 170 derivatives. -.188 -Very recently there have appeared some reports of quadrupole splitting of R^SnR' compounds which appear to be caused, at least in the main, by differences in a-bonding, that i s , electronegativity 20 A differences between R and R*. Parish and Piatt report a quadrupole splitting for (CH^^SnCF^ (A = 1.38 mm/sec) and slightly smaller but well resolved splittings for R^SnR' (R = CH3 or R' = or CgC£j.) . The spli t t i n g in the R^SnC^F^ compounds is probably due to electronegativity differences since n.m.r. shows no rr-donation from the C 6F 5 group to ( C H ^ S n . 2 0 6 The investigation of the Mossbauer absorption spectra of the fluoroalkyltrimethyltin derivatives, prepared during the course of this Thesis, was undertaken to further explore the causes of quadrupole spli t t i n g in R^SnR' compounds, particularly electronegativity induced splitt i n g . It was also of interest, assuming that (CH^)^SnR^ (R^ = fluoroalkyl) compounds are axially symmetric and that they display a quadrupole spl i t t i n g in their Mossbauer spectrum caused primarily by electronegativity differences, to see i f the magnitudes of the quadrupole splittings was indicative of the effective electronegativity of the R^  groups (eq. [4.3]). The spectra of trifluorovinyltrimethyltin and some of the perfluoroalkynyl derivatives described earlier also seemed of interest. - 189 -EXPERIMENTAL I. Mossbauer Spectrometer and Sample Preparation. The Mossbauer spectrometer consisted of a TMC Model 306 wave form generator which drove a TMC Model 305 velocity transducer at a constant acceleration. The generator also synchronized the analyzer which operated in the time mode. The transmitted Y -radiation was detected by a Reuter-Stokes RSG-30A proportional counter, fed into a Nuclear Chicago Model 33-15 single channel analyzer, and then stored in a 400-channel analyzer. The output was printed on a model 44-16 IBM typewriter and subsequently fitted to a Lorentzian curve on an IBM 360 computer. The samples were a l l liquid at room temperature and were frozen as glasses onto Mylar windows in a brass c e l l at 77°K. A l l spectra were obtained with the c e l l at 77°K and isomer shifts are reported relative to SnO^ at 77°K. The source, "'""'"^Sn-enriched barium 119 stannate, contained Sn in a metastable excited state which emitted a Y~ray of 23.8 kev on decay from the f i r s t excited to the ground state. II. Preparation of Tin Compounds. The preparations of a l l the t i n compounds are reported in this Thesis. The reader is referred to the Preparative Index, p. 223 , at the end of this Thesis. Doppler Velocity (mm/sec.) Figure 13. Mossb auer absorption spectrum of (CH^)^SnCFCCF^), (<5 = 1.32 mm/sec; A = 1.89 mm/sec.). - 191 -RESULTS AND DISCUSSION Figure 13 shows the Mossbauer absorption spectrum of (CH 3) 3SnCF(CF 3) . It is typical of a l l the spectra obtained. The solid curve represents a least squares computer f i t to a Lorentzian line shape. Table XXIII, p. 192includes the Mossbauer and n.m.r. parameters of both the compounds studied and some related compounds. The results are subdivided according to the type of R£ group in (CH 3) 3SnR £. Each subdivision is discussed separately. I. Fluoroalkyltrimethyltin Derivatives. The isomer shifts of the (CH^-jSnR^ compounds studied are identical, within the experimental limits of spectrometer (± 0.03 mm/sec), and i t can be concluded that the electron densities at the tin atoms of the compounds studied is constant. Also, from a comparison of the observed isomer shift values with the isomer shift observed for 204 (CH3)^Sn (1.29 mm/sec) i t can be concluded that the (CH3>3SnRf compounds studied in this investigation a l l have a tetrahedral environ-ment about the t i n atom. The above conclusions may also be applied to (CH^^SnC^F since the reported experimental error i n the isomer shift determination is ± 0.08 mm/sec. The quadrupole sp l i t t i n g of a l l the (CH 3) 3SnR £ derivatives list e d in Table XXIII increases with increasing fluorine substitution on, and increasing size and chain branching of, the R£ group.* It seems * 119m The spectrum of (CH3)3SnCH2F was obtained using Sn-enriched SnO^ as the source. Sn02 has a very large y-ray linewidth (1.5 ±0.2 mm/sec)2^ and thus a small quadrupole splitting may not have been resolved. - 192 -Table XXIII Mossbauer and N.m.r. Parameters of Some (CH^^SnR and Related Compounds -Mossbauer Data H n.m.r. Data 6" A F l F2 J119 Sn-CH (Ref.) "3 A. R£ = Fluoroalkyl • (CH3) ^ Sn 1.29 0.00 0.81 - - 54.0 (204)f (CH3) 3SnCH2F 1.38 0.00 - -. +7.5 (170)g (CH 3) 3SnCHF 2 1.28 0.94 0.81 0.67 11. B 55.92 e (CH 3) 3SnCF 3 1.31 1.38 0.92 0.92 - 60.9 (204) 1.31 1.57 0.71 0.71 -18 58.6 e (CH 3) 3SnCF 2CF 3 1.30 1.63 0.85 0.77 -13. 8 58.2 e (CH3) SnCF(CF 3) 2 1.32 1.89 0.89 0.87 -19.8 57.8 e (CH 3) 3SnCH(CF 3) 2 1.30 1.57 0.78 0.77 -18 56.5 e B. R£ = Trifluorovinyl (CH3)3SnCH=CH2 1.30 (fc.OO (199)g (CH3)3SnCF=CF2 1.30 1.41 - - 59. 2 d e (C6H5)3SnCH=CH2 1.28 0.00 0.96 - (204)f C. R£ = 3,3,3-Trifluoropropynyl (CH3)3SnC=CC6H5 1.23 1.17 0.92 0.76 60.3 (204)f (CH3)3SnCECCF3 1.25 1.77 1.25 1.39 61.0 b,e (CH 3) 2Sn(CECCF 3) 2 1.19 1.95 1.17 1.12 72.7 b,e - 193 -6 = isomer shift relative to SnO, at 77°K and A = quadrupole sp l i t t i n g . For this work both 6 and A are accurate to within ± 0.03 mm/sec. and at the widths at half-height of the absorptions at lower and higher velocities respectively and are accurate to within ± 0.05 mm/sec. Spectrum obtained using Pd(Sn) sourceI therefore, r's are not really comparable. Obtained by use of a Varian A-60 n.m.r. spectrometer operating at 60 Megacycles/sec. Negative values to low f i e l d relative to external (CH 3) 4Si. J 1,Q =60.5 cps has been reported (reference 207). Sn-CH3 This work Source: Pd(Sn) at room temperature. Isomer shift i s relative to SnO, at room temperature. Source: SnO, at room temperature. Isomer shift is relative to SnO, at room temperature. - 194 -reasonable to assume that these compounds are axially symmetric and that eq. [4.3] describes the quadrupole s p l i t t i n g . The magnitude of the quadrupole s p l i t t i n g of the (CHp^SnR^ compounds therefore, may indicate the electronegativity of the R£ groups, that i s : CH2F < CHF2 < CF 3 < CH(CF 3) 2< < CF(CF 3> 2 (A) (B) (C) (D) (E) (F) The order of increasing electronegativity of the groups (A)-(C) is expected on the basis of the number of fluorine atoms. The magnitude of the quadrupole s p l i t t i n g observed for the compounds (CH 3) 3SnR f(CF 3 < C ^ < CF(CF 3) 2) is predictable on the basis of the order of effective electronegativities which was established in Chapter 1. However, the equivalence of the quadrupole sp l i t t i n g observed for (CH 3) 3SnCF 3 and (CH 3) 3SnCH(CF 3) 2 implies that the electro-negativities of CF 3 and CH(CF 3) 2 are the same. The equivalence is surprising since the effective electronegativity of hydrogen has been 208 estimated to be considerably less than that of fluorine. It therefore appears that there i s another affect causing an electric f i e l d gradient in (CH 3) 3SnCH(CF 3) 2- The similarity of the observed isomer shift between (CH3) 3SnCH(CF3) 2 (1. 30 mm/sec) and (CH^Sn (1.29 mm/sec) is good evidence for tetrahedral coordination; however, there may be an interaction between the fluorine atoms of the CH(CF 3) 2 group and the CH3 groups of an adjacent molecules which leads to a non-vanishing asymmetry parameter and a larger observed quadrupole - 195 -splitting without noticably affecting the isomer sh i f t . Similar distortions may occur in (CH^) ^ SnG^ F,. and (CH^^SnCFCCF^),; however, assuming that the inductive effects of £2^5 an<^ c^(^-^2 a r e x a r 8 e r than CF^, then the observed quadrupole splitting for ( C H 3 ) ^ S n G ^ F ^ and (CH^)^SnCFCCF^)2 is expected to increase in the order = CF^ < C^F^ < CFCCF^), notwithstanding distortion effects. Several authors have found correlations between the Mossbauer A A , * A 170,205,209a,,, . , c 209a, and n.m.r. data of tin compounds. Chivers and Sams have recently found a correlation between the observed quadrupole s p l i t t i n g and Jii9„ „„ in (CH0)0SnX (X = polyhaloaryl) compounds. This same on—Crl^ j J correlation has not been found in the present investigation as seen from Table XXIII; however,the quadrupole spl i t t i n g of fluoroalkyltri-methyltin derivatives does appear to correlate with the n.m.r. chemical shift of the methyl hydrogens (Figure, p. 196). This correlation must be viewed with caution since both the abscissa and ordinate have small ranges; however, i t may be interpreted as resulting from the increasing electronegativity of the R^  groups and the subsequent deshielding effect on the methyl hydrogens. II Trifluorovinyltrimethyltin. 0 The constant isomer shift (A = 1.29 ± 0^ 1 mm/sec) of a l l the vinyltin derivatives (TableXXIII)lmplies a constant electron density at the t i n nucleii. The quadrupole splitting observed in the spectrum of (CH^) ^ SnG^CF, (A = 1.41 mm/sec) is probably due to the electronegativity effect of the fluorocarbon group rather than Tr-bonding interactions since no quadrupole splitting is observed in the Mossbauer spectra of - 196 -— 2.0 -10 0 6((CH3)(cps)(60 M cps XH n.m.r.) Figure 14. Correlation between quadrupole splitting and H n.m.r. chemical shift of the CH3 groups of (CH3) SnRf Derivatives. - 197 -(CH3)3SnCH=CH2, or ( C ^ ) 3SnCH=CH2, TT-Bonding effects however, cannot be rigorously excluded at this time. III. 3,3,3-Trifluoropropynyltin Derivatives. The quadrupole splitting observed in the spectrum of (CH3)SnCECCF3 (A = 1.77 mm/sec) is larger than that observed in 204 (CH3)3SnC=CCgH^ (A = 1.17 mm/sec). This increase might be explained by the larger inductive effect of CF 3 relative to the C^H^ ring. The s t i l l larger s p l i t t i n g observed for (CH 3) 3Sn(CECCF3> 2 (A = 1.95 mm/sec) may be due to both the increased total electronegativity effect on the electric f i e l d gradient caused by the addition of a second propynyl group and the fact that the asymmetry parameter, n, (eq. [4.2]) is now non-vanishing. It cannot be stated, at this time, which mechanism has the greatest influence. - 198 -APPENDIX 1 STEREOCHEMISTRY OF SOME OLEFINS RfCH=CHI INTRODUCTION The light induced free radical addition of perfluoroalkyl iodides to acetylenes has been reported by several authors. RCECH + R I > RCI=CHRf [Al.l] R = H, R = C F 3 2 0 9 b , C 2F 5(35); R = CH3, R = C F ^ 1 0 ' 2 1 1 ; R = CF 3, Rf = CF 3, C 2F 5, n-C 3F 7 2 1°; R = C ^ , Rf = C F ^ 1 2 ; R = CD 3 > Rf = C F 3 2 1 3 ; R = CH2OH, Rf = CF 3 > n - C ^ 2 1 4 . Trifluoroiodomethane also adds to hexafluorobut-2-yne and NN-bistrifluoro-methylamine under the influence of heat, probably by a radical , . 215,216 mechanism. CF 3I + CF3C=CCF3 > (CF 3) 2C=CICF 3 [A1.2] CF 3I + (CF3)2NCECCH > (CF3)2NCI=CHCF3 [A1.3] Stereochemical information about the vinyl iodide products is limited. The zinc-hydrochloric acid reduction of trans-1,1,1,4,4,4-hexafluoro-2-iodobut-2-ene produced a 70% yield of trans-1,1,1,4,4,4-hexafluorobut-2-ene; and a similar reduction using magnesium gave a 78% 210 yield of the same butene. These reduction techniques are considered stereospecific and the trans nature of the iodobutene (implying cis - 199 -addition) was inferred from these results. The zinc-ethanol reduction 214 of 4,4,4-trifluoro-2-iodobut-2-ene gave a trans:cis = 2:3 mixture of 4,4,4-trifluoro-but-2-enol. Predominantly trans addition of the alkyl iodide is implied although the stereospecificity of this reduction technique i s not known. The product of eq. [A1.3] was found by v.p.c. to u > i i * . 216 be a trans:cis =1:1 mixture of isomers. In the course of preparing 3,3,4,4,4-pentafluorobutyne and 3,4,4,4-tetrafluoro-3-trifluoromethylbutyne for studies on sigma bonded fluoroalkynyl derivatives of the Group IV elements (Chapter I) the inter-mediate vinyl iodides produced by the radical addition of C^F^I a n d ^ F3^2^ F x t 0 a c e t y ± e n e (e9« [Al.l] were isolated and their stereochemistry was studied. The stereochemistry of the olefin CF^CR^CRT produced by the radical addition of CF,I to acetylene^^was also studied. - 200 -EXPERIMENTAL The general experimental technique and apparatus have been previously described in Chapter 1. The perfluoroalkyl iodides were obtained from Peninsular Chem Research, Inc.*. Acetylene was purchased from Matheson of Canada Ltd. and the acetone solvent was removed by trap-to-trap d i s t i l l a t i o n . I. Preparation of the Olefins RfCH=CHI. 1. Preparation of 3,3,3-Trifluoro-l-iodo-propene (AS). Acetylene (3.0 g, 115 mmoles) and trifluoromethyl iodide (21.30 g, 109 mmoles) were irradiated for 14 days (100 watt U.V. source) 209h as described by Haszeldine. The product 3,3,3-trifluoro-l-iodopropene (16.5 g, 69% yield) was purified by d i s t i l l a t i o n , b.p. 9 0 Q 70.5° - 73.0° (760 mm) (b.p. l i t . value: 70.2° (760 mm) ), and was further identified by microanalysis. Anal. Found: C, 16.19; H, 0.85; I. 57.01%. Calc. for C 3HF 3I: C, 16.21; H, 0.90; I, 57.70%. Infrared spectrum (vapour): 3098 (vw), 1641 (m(sh)), 1638 (m), 1314 (s), 1309 (s), 1289 (s), 1225 (m), 1205 (w), 1160 (s), 1145 (s), 951 (w), 867 (vw), 730 (w) cm The "'"H n.m.r. spectrum of the propene was unaltered after d i s t i l l a t i o n and showed only the trans isomer. The isomer ratio, 19 trans:cis = 6.7:1 was determined from the F n.m.r. spectrum. The chemical shift values and coupling constants are summarized in Figures (52) and (53) and in Table XXV, p. 205. For the addresses of the suppliers - see Appendix 2. - 201 -2. Preparation of 3,3,4,4,4-Pentafluoro-l-iodobutene.(50). 3,3,4,4,4-Pentafluoro-l-iodobutene was also prepared as 35 previously described. In two separate experiments pentafluoroethyl iodide and a 20% molar excess of acetylene were irradiated with 100 and 450 watt U.V. sources for 14 days each. The former produced an 87% yield of the butene, the latter a 78% yield, b.p. 89° (760 mm) 35 (b.p. l i t . value 84.4° (760 mm)). Infrared spectrum (vapour): 3095 (w), 1638 (m), 1618 (s), 1345 (s), 1296 (m), 1219 (vs), 1125 (s), 1095 (vs), 942 (m), 645 (s) cm X. The XH n.m.r. spectrum showed only the trans 19 19 isomer; however the F n.m.r. spectrum did show both isomers. The F n.m.r. spectrum of the adduct produced by irradiation under the 450 watt U.V. source showed an isomer ratio of trans:cis = 9.1. The n.m.r. data is summarized in Figures (54) and (55) and in Table XXV, p. 205. A higher boiling fraction (0.35 g), b.p. 97° (48 mm), analysed for the known 5,5,6,6,6-pentafluoro-l-iodohexa-l,3-diene (b.p. l i t . value: 104° (46 mm).35 Anal. Found: C, 23.95; H, 1.48%. Calc. for CgH^I: C, 24.16; H, 1.34%. The infrared spectrum (film) showed absorptions at 1642 and 1573 cm X. 3. Preparation of 3,4,4,4-Tetrafluoro-3-trifluoromethyl-l-iodobutene.(51) Heptafluoroisopropyl iodide (122.67 g, 479 mmoles) and acetylene (13.06 g, 500 mmoles), in six Carius tubes, were irradiated for 14 days (450 watt U.V. source). A small amount of unreacted acetylene (0.4 g) was recovered. The major d i s t i l l a t i o n fraction, b.p. 92° - 120° (760 mm), was found by v.p.c. (20% Kel-F grease at 70°) - 202 -to be a mixture of isomers of 3,4,4,4-tetrafluoro-3-trifluoromethyl-1-iodobutene (113.5 g, 85% yield), (micro b.p. trans: 97.8° (760 mm), micro b.p. cis: 109.7° (760 mm)). Anal.(trans) Found: C, 18.69; H, 0.64; I, 39.12%. Anal, (cis) Found: C, 18.79; H, 0.69, I, 39.38%. Calc. for C 5H 2F 7I: C, 18.65; H, 0.62; I, 39.45%. Infrared spectrum trans (vapour): 3101 (w), 1629 (s), 1333 (s), 1329 (vs), 1295 (s), 1251 (s), 1245 (vs), 1209 (s), 1186 (s), 1146 (w), 1100 (w), 1055 (s), 993 (s), 949 (w), 711 (m), 639 (m) cm Infrared spectrum cis (vapour): 3089 (w), 1632 (m), il338 (m), 1329 (s), 1289 (s), 1269 (s), 1244 (s), 1209 (m), 1182 (m), 1160 (m), 1048 (s), 991 (s), 791 (w), 746 (s) cm-1. The isomer ratio was determined by v.p.c. to be trans:cis = 1.78:1. The n.m.r. data is summarized in Figures (56) and (57) and in Table XXV, p.205. Two smaller higher boiling fractions, b.p. 100° - 114° (285 mm) and b.p. 113° - 114.5° (151 mm), were obtained which both had an infrared spectrum with double bond absorptions at 1648 and 1578 cm 4. Ultraviolet Irradiation of Cis and Trans 3,4,4,4-Tetrafluoro-3- trifluoromethyl-l-iodobutene. In two separate experiments pure samples of c i s - and trans-3,4,4,4-tetrafluoro-3-trifluoromethyl-l-iodobutene were irradiated for 15 days under a 450 watt U.V. source. A v.p.c. examination of the material in both tubes after irradiation showed that the same ratio of isomers, trans:cis = 1.49:1, had been established. Table X X I V 1:1 Adducts from R.I + HCECH h v ( 1 4 d a y s ) > F X > 2850 A REACTANTS 1:1 ADDUCT (YIELD %) ISOMER RATIO TRANS:CIS B.p. , °C C F 3 + HCECH C 2 F 5 I + HCECH ( C F 3 ) 2 C F I + HCECH CF3CH=CHI (69) C2F5CH=CHI (82) d (CF3)2CFCH=CHI(trans) + (CF3)2CFCH=CHI(cis) (85) 6.7:1 9:1 1.78:1 70.5 - 73 89 C 97.8C 109.7 O A small amount of the 1:2 adduct R^ CH=CH-CH=CHI is also produced in a l l three reactions Boiling points recorded at atmospheric pressure Boiling point of isomer mixture Average yield of two experiments Micro boiling points - 204 -RESULTS AND DISCUSSION Table XXIV, p. 204, summarizes the results of the ultraviolet induced addition reactions of R fI (Rf = CF 3, CF(CF 3) 2) to acetylene. 3,3,3-Trifluoro-l-iodopropene (49) and 4,4,4,3,3-pentafluoro-2-iodobutene (50) were prepared by the known ultraviolet induced reactions of trifluoroiodomethane and pentafluoroiodoethane with 35,209b acetylene. The stereochemistry of the olefinic products was determined by n.m.r. The data that was obtained by a f i r s t order 1 19 analysis of the H and F n.m.r. spectra of (49) and (50) is summarized in Table XXV, p. 205, and in Figures (52) - (56) on the page following. The "*"H n.m.r. spectrum of (49) shows only the presence of the trans isomer (52) due to overlapping of the cis isomer peaks; however, 19 the F n.m.r. spectrum shows the presence of the cis isomer (53) as well. The coupling assignments are based on the now well established results for substituted trifluoromethyl compounds: J__, „, s ~ 0, CF„-H(trans) 3 7 91 7 ? 1 R I Q J_„ „, . . ~ 2; and J__ „ ( . ~ 8. J /^ '' A X° The integrated X*F CF,,-H(cis) CF3~H(gem) b n.m.r. spectrum of (49) gives the ratio trans:cis =6.7:1. Both the trans (54) and the cis (55) isomers are shown in the 19 F n.m.r. spectrum of 3,3,4,4,4-pentafluoro-l-iodobut-2-ene (50). As with (49) the "Ti n.m.r. spectrum shows only the trans isomer (54) due to peak overlap. Because the H-H coupling could not be established, the coupling assignments are based on the finding that J^, „, x in the G & ° F-H(gem) 217 cis isomer (55) > J„ T T / v in the trans isomer (54). This same ^—' F-H(gem) — - 205 -order is seen in (52) and (53). This basis gives consistent values for the other couplings, especially the J T T T T / N (54) of 15 cps which r • r J H-H(trans) — TABLE XXV ra Summary of Chemical Shifts of Some Olefins RfCH=CHl' H a H b CF 3 CF 2 CF (52) CF„CH -=CH, I(trans) -6.57b -7.29b 65.85 v — ' 3 a b (53) CF 3CH a=CH bI(cis) 61.95 (54) C-Fj-CH =CH, I(trans) -6.59b -7.33b 85.7 116.1 — 2 5 a b (55) C,FCCH =CH, I(cis) 85.85 114.5 — 2 5 a b (56) (CF 3) 2CFCH d=CR bI(trans) -6.53b -7.21b 77.7 196.3 (57) (CF 3) 2CFCH a=CH bI(cis) -6.61b -7.24b 77.6 189.4 a 1 19 In p.p.m. with respect to external (CH^^Si ( H) and internal CFC&3 ( F) b Middle of appropriate doublet of basic AB quartet. is the same as in (52). Confirmation of the predominantly trans structure comes from the infrared spectrum of (54) which shows the band -1 219 at 942 cm , characteristic of trans olefins. The isomer distribu-19 tion, trans:cis = 9:1, was determined from the integrated F n.m.r. spectrum. 4,4,4,3-trifluoro-3-trifluoromethyl-l-iodobutene (53) can be prepared by reacting heptafluoroisopropyl iodide with acetylene under - 206 -1.85 - 207 -ultraviolet light. The reaction gives an 85% yield of a mixture of trans (56) and cis (57) isomers which can be separated by v.p.c. Two smaller higher boiling fractions are also obtained which have almost identical infrared spectra with double bond absorptions at 1648 and 1578 cm X . These are presumably mixtures of.isomers of the diene, (CF3)2CFCH=CH-CH=CHI. Similar diadducts are formed in the 35 209b ultraviolet induced reactions of CF^I and C^FfjI W l t n acetylene. * The n.m.r. data obtained for the two isomers of (51) is summarized in Table XXIII and in (56) (trans) and (57) (cis). The coupling assign-ments are based on the now generally accepted rule that for olefins J T. T T / N > J T, T T / . The assigned coupling constants are of the H-H(trans) H-H(cis) 6 r & same order of magnitude as those found for trans and cis (CF^^CFCR^ 220 CHF. Confirmation of the trans assignment comes from the infrared spectrum of (55) which shows the characteristic trans out-of-plane hydrogen deformation at 949 cm X . The isomer distribution, trans:cis = 1.78:1, was determined by v.p.c. Interconversion of (56) and (57) occurs readily under ultra-violet irradiation to give an equilibrium mixture of trans (56): cis (57) = 1.49:1. The ratio present in the product mixture (51) is greater than this, namely, trans:cis = 1.78:1 indicating that the trans isomer (56) is formed preferentially by trans addition as i t is in the reactions giving (49) and (50). As mentioned in the Introduction cis addition of trifluoromethyl iodide to 3,3,3-trifluoropropyne seems 210 to take place although preferential trans addition of tr i f l u o r o -- 208 -methyl iodide to propaynyl alcohol may take place. 214 Although, with respect to the double bond, J , . . > that as fluorine atoms are substituted by hydrogen J F-H(trans) decreases from + 0.03 to - 0.89 cps and J , . . decreases from - 2.22 to - 4.32 cps in going from 3,3,3-trifluoropropene to 3-fluoropropene. It is possible that our results have a similar explanation, however, a complete explanation lies in a determination of the relative populations of the most preferred rotamers and the relative signs and contributions of the couplings of each rotamer to the observed averaged coupling constant. This, however, was beyond the scope of the proposed investigation. - 209 -APPENDIX 2 ADDRESSES OF CHEMICAL SUPPLIERS Alfa Inorganics Ltd., 8 Congress Street, Beverley, Massachusetts, 01915, U.S.A. Columbia Organic Chemicals, 912 Drake Street, Cedar Terrace, Columbia, South Carolina, U.S.A. Dow-Corning Ltd., 1 Tippet Road, Downsview P.O., Metropolitan Toronto, Ontario. Fisher-Scientific Company, Chemical Manufacturing Division, Fair Lawn, New Jersey, U.S.A. - Vancouver Sales Branch: 196 West 3rd Avenue, Vancouver, British Columbia. Hynes Chemical Research, 308 Bon Air Avenue, Durham, North Carolina, 27704, U.S.A. Peninsular Chemresearch Inc., P.O. 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The compounds are divided into two main sections: organic and organo-metallic. ORGANIC Page A. Saturated 1. (CF 3) 2CN 2: Bis(trifluoromethyl)diazirine 151 2. (CF 3) 2CN 2: Bis(trifluoromethyl)diazomethane 150 3. CH3CHCHCH3CF : T rans-1,1-difluoro-2,3-dimethylcyclopropane ... 93 4. CH3CHCHCH3CF2: Cis-1,1-difluoro-2,3-dimethylcyclopropane 94 B. Containing a C=C Bond 1. ICH=CHCF3: 3,3,3-Trifluoro-l-iodopropene 200 2. ICH=CHCF2CF3: 3,3,4,4,4-Pentafluoro-l-iodobutene 201 3. ICH=CHCF(CF3)2: 3,4,4,4-Tetrafluoro-3-trifluoromethyl-l-iodobutene 201 4. HC=CCF3(CF2 ): Trifluoromethyl-3,3-difluorocyclopropene 81 5. HC=CCF2CF3(CF2): Pentafluoroethyl-3,3-difluorocyclopropene ... 87 6. HC=CCF(CF 3) 2(CF 2): Heptafluoroisopropy1-3,3-difluorocyclopropene 91 7. HC=CCF„(C(CF„)9: 1,3,3-Tris(trifluoromethyl)cyclopropene 151 8. CF„C=CCF„(C(CFJ9: 1,2,3,3-Tetrakis ( t r i f luoromethyl)cyclopropene 153,154 - 225 -B. (continued) Page 9. HC=C(CF3)N=N(C(CF3)2: 3,3,5-Tris(trifluoromethyl)isopyrazole ... 151 10. CF3C=C(CF3)N=N(C(CF3)2): 3,3,4,5-tetrakis(trifluoromethyl)-isopyrazole 153 C. Containing a CEC Bond 1. HCECCF 3: Trifluoropropyne 13 2. HCECCF 2CF 3: 3,3,4,4,4-Pentafluorobutyne 13 3. HCECCF(CF3)2: 3,4,4,4-Tetrafluoro-3-trifluoromethylbutyne 14 ORGANOMETALLIC A. Silicon 1. (CH 3) 3SiCH-CH 2(CF 2): 2,2-difluorocyclopropyltrimethylsilane ... 96 2. (CH 3) 2Si(CECCF 3) 2: Bis(3,3,3-trifluoropropynyl)dimethylsilane . 19 B. Germanium 1. (CH3)3GeH: Trimethylgermane 1 5 1 2. (CH3)3GeBr: TrimethylgermaniUm bromide 15 3. (CH 3) 3GeGe(CH 3) 3: Hexamethyldigermane 151 4. (CH3)3GeC=CCF3(CF2): 2-Trifluoromethyl-3,3-difluorocyclopropeny1-trimethylgermane 82 5. (CH 3) 2Ge(C=CCF 3(CF,)) 2: Bis(2-trifluoromethyl-3,3-difluorocyclo-propenyl)dimethylgermane 83 6. (CH 3) 3GeC=CCF 2CF 3(CF 2): 2-Pentafluoroethyl-3,3-difluorocyclo-propenyltrimethylgermane 88 - 226 -Page B. (continued) 7. (CH 3) 2Ge(C=CCF 2CF 3(CF 2)) 2: Bis(2-pentafluoroethyl)-3,3-difluoro-cyclopropenyldimethylgermane 89 8. (CH 3) 3GeC=CCF(CF 3) 2(CF 2): 2-Heptafluoroisopropy1-3,3-difluoro-cyclopropenyltrimethylgermane 92 9. (CH 3) 3GeC=CCF 3(C(CF 3) 2): 2,3,3-Tris(trifluoromethyl)cyclopropenyl- • trimethylgermane 155,158 10. (CH3)3GeCHCCF3: 3,3,3-Trifluoropropynyltrimethylgermane 21 11. (CH 3) 2Ge(CECCF 3) 2: Bis(3,3,3-trifluoropropynyl)dimethylgermane . 22 12. CH 3Ge(CsCCF 3) 3: Tris(3,3,3-trifluoropropynyl)methylgermane 24 13. Ge(C=CCF3)^: Tetrakis(3,3,3-trifluoropropynyl)germane 25 14. (CH3)3GeC=CCF2CF3: 3,3,4,4,4-Pentafluorobutynyltrimethylgermane. 29 15. (CH 3) 2Ge(C=CCF 2CF 3) 2: Bis(3,3,4,4,4-pentafluorobutynyl)dimethyl-germane 30 16. (CH 3) 3GeCECCF(CF 3) 3: 3,4,4,4-Tetrafluoro-3-trifluoromethylbutynyl-trimethylgermane 32 C. Tin 1. (CH3)3SnH: Trimethyltin hydride 7 7 2. (CH 3) 3SnC£: Trimethyltin chloride I 6 3. (CH 3) 3SnCF 2H: Difluoromethyltrimethyltin 97 4. (CH 3) 3SnC(CF 3) 2H: 1,1,1,3,3,3-hexafluoroisopropyltrimethyltin ... 1 5 9 5. (CH 3) 3SnCF 3: Trifluoromethyltrimethyltin 7 8 6. (CH )„SnCF„CF„: Pentafluoroethyltrimethyltin 7 8 - 227 -Page, C. (continued) 7. (CH 3) 3SnCF(CF 3) 2: Heptafluoroisopropytrimethyltin 79 8. (CH3)3SnCF=CF2: Trifluorovinyltrimethyltin 80 9. (CH 3) 3SnC=CCF 3(CF 2): 2-Trifluoromethyl-3,3-difluorocyclopropenyl-trimethyltin . 84 10. (CH 3) 2Sn(C=CCF 3(CF 2)) 2: Bis(2-trifluoromethyl-3,3-difluorocyclo-propenyldimethyltin 86 11. (CH 3) 3SnC=CCF 2CF 3(CF 2): 2-Pentafluoroethyl-3,3-difluorocyclo-propenyltrimethyltin 90 12. (CH 3) 3SnC=CCF 3(C(CF 3) 2): 2,3,3-Tris(trifluoromethyl)cyclopropenyl-trimethyltin 156 13. (CH3)3SnCECCF3: 3,3,3-Trifluoropropynyltrimethyltin 26 14. (CH 3) 2Sn(CECCF 3) 2: Bis(3,3,3-trifluoropropynyl)dimethyltin 27 15. (CH ) SnCECCF^CF,: 3,3,4,4,4-Pentafluorobutynyltrimethyltin ... 31 D. Arsenic 1. (CH„)9AsC(CF,)„H: 1,1,1,3,3,3-hexafluoroisopropyldimethylarsine .. 160 - 228 -

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