The University of British Columbia
FACULTY OF GRADUATE STUDIES
PROGRAMME OF THE
FINAL ORAL EXAMINATION
FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
OF
DAVID STUART DAWSON
B. sc, M.Sc,, University of British Columbia
MONDAY, JUNE 12, at 3:30 P.M.
IN ROOM 261, CHEMISTRY BUILDING
COMMITTEE IN CHARGE
Chairman: B. N. Moyls E. Peters - D.E. McGreer C. A. McDowell N.L. Paddock A. Storr . G.B. Porter External Examiner: H.J. Emeleus
University Chemical Laboratory Lensfield Road Cambridge, England
Research Supervisor: W.R. Cullen REACTIONS OF SOME UNSATURATED FLUOROCARBON DERIVATIVES
WITH ORGANO COMPOUNDS OF PHOSPHOROUS AND NITROGEN
ABSTRACT Perfluorocyclobutene and 1,2-dichlorotetrafluoro- cylobutene react readily with diethylphosphine at 20° to give unstable mono-subs'titution products, 1-diethyl- phosphino-2-halotetrafluorocyclobutenes. With tetra- methyldiphosphine, low yields of 1,2-bis(dimethylphos- phino)tetrafluorocyclobutene and trifluorodimethylphos- phorane are obtained from the chloro- and perfluoro- butenes respectively. Diphenylphosphine also gives the 1,2-disubstituted product at.20°, from perfluorocyclo• butene only. This olefin interacts with tetraphenyl- diphosphine (130°) to give 1-diphenylphosphinotrifluoro- cyclobutenone (from 95% ethanol). Under identical conditions the chloro-butene reacts with the phenyl- phosphines to give trifluorodiphenylphosphorane and fluorodiphenylphosphine oxide. Tetrakis (trifluoro- methyl)diphosphine on heating or ultra-violet irradia• tion reacts only very slightly, while bis(trifluoro- methyl)phosphine is essentially inert towards the cyclobutenes.
Dimethylamine readily adds to hexafluorobutyne-2 at 20°to give the 1:1 adduct, 2-dimethylamino-3-H-hexa- fluorobutene-2, the ratio of trans:cis isomers being 6.2:1. -.The cis isomer is converted by distillation, but not by heating in a sealed tube, to the trans form. This latter isomer quickly achieves an equilibrium with the cis configuration on exposure to the air;; at equi• librium, trans:cis 1.6:1. Hexafluorobutyne-2 reacts vigorously at 20° with a trimethylamine-water mixture. The major products of the complex reaction are a bis(hex- afluorobutenyl) ether and trans-3-H-heptafluorobutene-2. When the reaction mixture is permitted to reach room temperature only slowly, the ether predominates. In the absence of water a high polymer of the butyne is slowly deposited. Chlorodimethylamine requires heating or ultra-violet irradiation to react with the butyne. The reaction is complex. At 85° (also on1 irradiation), the major product is the 1:1 adduct (1007. cis) ; at 139°, trans-2-chloro-3-H-hexaf luoro• butene-2 predominates. Prolonged ultra-violet irradiation of a bis(tri- fluoromethyl)phosphine-hexafluorobutyne-2 mixture affords a mixture of 1:1 and 2:1 adducts. The expected 1,1,1,4, 4,4-hexafluorobut-2-enyl derivatives are obtained from the acetylene and diethylphosphine, "diphenylphosphine and tetraphenyldiphosphine (130°) „ Tetramethy.ldiphosphine gives a low yield of methyldifluorophosphine oxide. Triphenylphosphine vigorously catalyzes the'polymeriz• ation of the butyne at -78°. Chlorodimethylphosphine and hexafluorobutyne-2 afford trans-3-H-2-chlorohexa- fluorobutene-2 and trifluorodimethylphosphorane, while chlorodimethylphosphine sulfide does not react on heating (106°) or ultra-violet irradiation. Tetra- methyldiphosphine disulfide and iodine afford a loosely- bound 1:1 complex at 20° in the absence of excess iodine. Trifluoromethyl iodide does not react with the disulfide at 104° and only slightly on prolonged ultra-violet irradiation.
Dimethylphosphine readily adds to hexafluoroacetone and 1,1,1-trifluoroacetone, giving the 2-dimethylphos- phino-isopropanols. The reaction with hexafluoroacetone also gives a 1:3 phosphineacetone adduct.' The product from T,3-dichlorotetrafluoroacetone decomposes violently on reaching room temperature. The reactions of these fluorinated ketones with diphenylphosphine are more complex. The products include a mixture of 1:1 adducts; namely, 2-diphenylphosphino-isopropanols and isopropyl- diphenylphosphine oxides. The latter probably are a result of an Arbuzov rearrangement of isopropoxydiphenyl- phosphines. Tetramethyldiphosphine and hexafluoro• acetone give a 1:3 adduct along with the 1:3 dimethyl• phosphine -hexaf luoroacetone adduct-. GRADUATE STUDIES
Field of Study: Chemistry
Topics in Physical Chemistry A.V. Bree,J.A.R. Coope
Seminar in Chemistry W.A. Bryce
Topics in Inorganic Chemistry N. Bartlett W.R... Cullen The Chemistry of Organometallic Compounds H.C. Clark
Topics in Organic Chemistry F. McCapra,A.I. Scott, J.P. Kutney
Recent Synthetic Methods in G.G.S. Dutton, Organic Chemistry A. Rosenthal
Spectroscopy and Molecular Structure B.A. Dunell, A.V. Bree,C. Reid Advanced Inorganic Chemistry Organic Reaction Mechanism B.R. James,G.B. Porter Physical Organic Chemistry L.D. Hall,D.E. McGreer, T. Money, F. McCapra Organic Reaction Mechanisms R.E. Pincock Related Studies: Organic Medicinal Products T.H. Brown
PUBLICATIONS
M.M. Baig, W.R. Cullen and D.S. Dawson, Reaction of Iodomethane and Tertiary Arsine Mercuric Iodide Complexes, Can. J. Chem. 40, 46 (1962)
W.R. Cullen, D.S. Dawson, N.K. Hota and G.E. Styan, Some New Derivatives of. Dimethylarsine, Chemistry and Industry 983 (1963)
W.R. Cullen, D.S. Dawson and P.S. Dhaliwal, Cyclobutenyl Derivatives of Phosphorus and Sulphur, Can. J. Chem. 45, 683 (1967) REACTIONS OP SOME•UNSATURATED FLUOROCARBON DERIVATIVES WITH ORGANO COMPOUNDS OF PHOSPHORUS AND NITROGEN by DAVID S. DAWSON B.Sc, University of British Columbia, 1961 M.Sc, University of British Columbia, 1964 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
April 1967 In presenting this, thesis in partial fulfilment of the requirements for an
advanced degree at the University of -British Columbia, I agree that the
Library shall make it freely available for reference and study. I further
agree that permission for extensive copying of this thesis for scholarly
purposes may be granted' by the Head of my Department or by his represen•
tatives. It is understood that copying or publication of this thesis for
financial gain shall not be allowed without my written permission.
for David Dawson
Department nf Chemistry
The University of British Columbia Vancouver 8, Canada
Date January 18, 1968 i ABSTRACT
Perfluorocyclobutene and 1,2-dichlorotetrafluorocylobutene react readily with diethylph.osph.ine at 20° to give unstable mono- substitution products, l-diethylphosphino-2-halotetrafluorocy- clobutenes. With tetramethyldiphosphine, low yields of 1,2- bis(dimethylphosphino)tetrafluorocyclobutene and trifluorodi- methylphosphorane are obtained from the chloro- and perfluoro- butenes respectively. Diphenylphosphine also gives the 1,2- disubstituted product at 20°, from perfluorocyclobutene only.
This- olefin interacts with te traphenyldi'phosphine (130 ) to give Irdiphenylphosphinotrlfluorocyclobutenone (from 95$ ethanol).
Under identical conditions the chloro-butene reacts with the phenyl-phosphines to give trifluorodiphehylphosphorane and fluoro- diphenylphosphine oxide, Tetrakis (trif luor'omethyl) diphosphlne on heating or ultra-violet irradiation reacts only very slightly, while bis(trifluoromethyl)phosphine is essentially inert to• wards the cyclobutenes.
Dimethylamine readily adds to hexafluorobutyne-2 at 20° to give the lsl adduct, 2=dimethylamino-3-H-hexafluorobutene-2, the ratio of trans:cis Isomers being 6.2sl. The cis isomer Is converted by distillation,? but not by heating in a sealed tube, to the trans form. This latter isomer quickly achieves an equil• ibrium with the cis configuration on exposure to the afrj at equilibriums transscis^1.6;1. Hexafluorobutyne-2 reacts vig• orously at 20° with a trimethylamine-water mixture. The major products of the complex reaction are a bis(hexafluorobutenyl) ether and trans-3-H-heptafluorobutene-2. When the reaction mix• ture is permitted to reach room temperature only-slowly, the " ether predominates. In the absence of water a high polymer of the butyne is slowly deposited. Chlorodimethylamine requires heating or ultra-violet irradiation to react with the butyne.
The reaction is complex. At 85° • (also on irradiation), the major product is the 1°1 adduct (100$ cis)j at 139°, trans-2-chloro~3-
H-hexafluorobutene-2 predominates.
Prolonged ultra-violet irradiation of a bis(trifluorometh- yl)phosphine-hexafluorobutyne-2 mixture affords a mixture of 1:1 and 2sl adducts. The expected l,l,l,4,4,4-hexafluorobut-2-enyl
derivatives, are obtained from the acetylene and diethylphosphine,
diphenylphosphine and tetraphenyldiphosphine (130°). Tetra-
methyldiphosphine gives a low yield of methyldifluorophosphine
oxide. Triphenylphosphine vigorously catalyzes the polymeriz•
ation of the butyne at =-78°. Chloro dime thy Iphosphine and hexa-
fluorobutyne-2 afford trans-3-H-2-chlorohexafluorobutene-2 and
trifluorodimethylphosphorane, while chlorodimethy Iphosphine sul•
fide does not react on heating (106°) or ultra-violet irradiation
Tetramethyldiphosphine disulfide and iodine afford a loosely-
bound lsl complex at 20° in the absence of excess iodine. Tri-
fluoromethyl iodide does not react with the disulfide at 104°
and only slightly on prolonged ultra-violet irradiation.
DimethyIphosphine readily adds to hexafluoroacetone and lsl,
trifluoroaeetone, giving the 2~dimethylphosphino~Isopropanols.
The reaction with hexafluoroacetone also gives a 1:3 phosphine-
acetone adduct. The product from 1,3-diehlorotetrafluoroacetone
decomposes violently on reaching room temperature. The reac•
tions of these fluorinated ketones with diphenylphosphine are
more complex. The products inclxide a mixture of Isl adducts $
namely, 2=diphenylphosphino='isopropanols and isopropyldiphenyl-
phosphine oxides. The latter probably ar e a result of an Arb- iii
U2ov rearrangement of isopropoxydiphenyl-phosphines, Tetramethyl- diphosphine and hexafluoroacetone give a 1:3 adduct along with the
1:3 dimefchylphosphine-hexafluoroacetone adduct. iv
TABLE OP CONTENTS
ABSTRACT i
LIST OF FIGURES v
LIST OP TABLES v
ACKNOWLEDGEMENTS vi
GENERAL INTRODUCTION ' 1
CHAPTER I. PERPLUOROCYCLOBUTENE AND 1,2-DICHLOROTETRAFLUORO- • CYCLOBUTENE INTRODUCTION 3 EXPERIMENTAL A. Apparatus and Techniques 6 B. Starting Materials 7 C. Reactions with the Phosphines . 9 DISCUSSION A. Results (1) R = Trifluoromethyl 18 (2) R = Phenyl 19 (3) R = Methyl, Ethyl 21 B. Proposed Mechanisms 25
CHAPTER II. HEXAPLUOROBUTYNE-2 INTRODUCTION 35 EXPERIMENTAL A. Starting Materials 37 B. Reactions with the Amines and Phosphines 38 , DISCUSSION A. . Nitrogen'Compounds (1) Results 57 (2;) Proposed Mechanisms 63 B. Phosphorus Compounds (1) Results 71 (2) Proposed Mechanisms 82 *•> CHAPTER I'll. PLUOROACETONES INTRODUCTION 88 "-EXPERIMENTAL A. Starting'Materials 90 3. Reactions with the Phosphines 90 DISCUSSION A. Results 10S B. Proposed Mechanisms 111 CHAPTER IV GENERAL DISCUSSION , 114
BIBLIOGRAPHY 124 V
LIST OF FIGURES .
Figure Page
1. Trigonal Bipyramidal Structure of TrIfluorodimethyl- 22* phosphorane i 9
2. P n.m.r. Spectrum of the Olefinlc Fluorine Atom in 43 trans-3-H-Heptafluorobutene-2 3. "*"H n.m.r. Spectrum of trans-2-Diethylphosphino-3-H- ^ hexafluorobutene-2
4. Coupling Constants In the Butenyl Ether 60
LIST OP TABLES
Table Page
I. C=C and C-P Stretching Bands of the Phosphino-Butenes 24
II. Isomerization of 2-Dimethylamino-3-H-hexafluorobutene-fi ^9 in Air 19 III. P n.m.r. Spectrum of the Butenyl Ether 41 IV. ~^P n.m.r. Spectrum of trans-2-Chloro-3-H-hexafluoro• 53 butene-2
V. Infra-Red Spectra of Tetramethyldiphosphine Disulfide 55 and the 1:1 Complex with Iodine
VI. Products of the Reaction CF3C=CCF3 + H_0 + (CR"3)3N 59
VII. Some Characteristic Infra-Red Absorptions of the Hexa- 72 fluorobutenyl Derivatives
VIII. Double Bond Frequencies of Some But-2-enyl Derivatives «>79
IX. Isomer Distribution of the Hexafluorobutenyl Deriv- Q2
'atives R2EC (CP3)=CHCP3 "> 19
X. ~H and P n.m.r. Data of the Phosphino-Isopropanois ..r and Isoprcpyl-Phosphine Oxides
XI.' Infra-Red Spectra of the Hexafluoro-Isopropanols, ir)c
•(CF3)2C(0H)E(CH3)2
XII. Index of the Perbalocyclobutene Reactions 121
XIII. Index of the Hexafluorobutyne-2 Reactions 122
XIV. Index of the Pluorinated Acetone Reactions 123 vi
ACKNOWLEDGEMENTS
I wish to express my sincere gratitude to Dr. W. R. Cullen for his continued conscientious supervision throughout the entire period of my training In chemical research at the university.
I am Indebted to Drs.'D. McGreer and A. Storr for criticism of the manuscript, and to Dr. L. Hall for obtaining some of the 19
F n.m.r. spectra.
I thank my wife for many hours spent assisting with the initial and', final typing of the thesis.
Financial support from the Defense Research Board of Canada
Is gratefully acknowledged. 1
GENERAL INTRODUCTION
The scientific study of organic compounds of phosphorus dates back to the early nineteenth century, with the esterifi- cation of dehydrated phosphoric acids with alcohols. Following the preparation of phosphine derivatives some twenty years later, organo-phosphorus chemistry began to develop at a rapid rate on
Into the present century. The past two decades have seen a particularly expanded interest in the field, partly because of the Importance of phosphorus compounds in biological systemsj for example,, phosphorus esters, play a vital role in nucleic acid syntheses and in the formation of carbon-carbon bonds in terpene and steroid syntheses.. In addition to this, phosphorus compounds have found wide industrial application, and trivalent derivatives and phosphonium salts have been put to good use in the develop• ment of novel synthetic methods, a notable example of which is the WIttig reaction, reported1 in 1954, e.g.
(C6H5VGH2R Z=K^ (C6H5)3P=CHR + R2C0 > (C6H5)3P0 + RgC=CHR • The interest in the reactions of organometallic compounds with unsaturated organic compounds was stimulated by the demand for synthetic rubber and other stable polymeric materials created during the last war. The addition of organometallic reagents to olefins was first reported during the 1920's by 23 3 4 Ziegler and his co-workers . In 1950 Ziegler provided a great commercial Interest with" his discovery that lithium alkyls could polymerize ethylenes LiC2H5 + n C2H4—* Li(~CH2CV)nC2H5 A great, deal of attention has been directed towards fluoro- 2 carbon chemistry in recent years, largely because of the grvailibliity of completely fluoroinated materials containing a wide range of functional groups. The more important of these derivatives include the large number of commercially available olefins.- These (and acetylenes) are conveniently prepared by dehydrohalogenatlon or dehalogenation of suitable precursors. The initial Interest in fluorocarbons was a result of their high thermal stability and chemical inertness. However, the electronegative fluorine atoms can result in a highly reactive molecule. The compounds investigated in this thesis are examples of this. These unsaturated fluorocarbons are found to be very susceptible to nucleophilic attack. The first chapter of the thesis entails the investigation of the reactions of two cyclic fluorocarbons, perfluorocyclo• butene and lj,2-dichlorotetrafluorocyclobutene, while the second chapter is concerned with hexafluorobutyne-2. The third chapter deals with three fjluoroace tones , hexaf luoroace tone, 1,5-dichloro- tetrafluoroacetone, and 1,1,1-trifluoroacetone. 3 CHAPTER I PERPLUOROCYCLOBUTENE AND 1,2-DICHL0R0TETRAPLU0R0CYCL0BUTENE INTRODUCTION The reactions of fluorinated olefins with nucleophilic reagents have received extensive study during the past two decades. Published studies of perfluorocyclobutene date back as early as 1949, when Park et al. reacted the olefin with methanolic potassium hydroxide, to obtain disubstitution CP=CFCP2CP2 c™h* CH30C=C(0CH3)CP2CF2 3 When the vinylic carbon atoms are bound to hydrogen, allylic 6,7,8, substitution obtains e.g. KQH HC=CHC rF CF — * CH=CHCP CF(0C H ) ———CH=CHCP C(OC H ) ^ 2 *2 C2H50H ^2wi^2n5; CgHgOH 2 2 5 2 The behaviour of perfluorocyclobutene towards aryl and alkyl lithiums has been investigated by Dixon9. The alkyls gave mono- and disubstitution, while., the aryl reagents gave only the latter CF=CFCFgCFg + RLi -—» CR-CFCFgpFg + CR=CRCFgCFg R = alkyl CF=CFCF0CF0 + C.H^Li —*> C/,H(-C=C(CCH_)CF„CPp 2; 2 65 65 6 5^^ Park and co-workers7 obtained the same product from ethoxide attack on two different cyclobutenes CH=CClCFgCFg . , / 0oH 0"* CF=CC1CH(0C H )CP c H y» C rLOC^CTJJHCOC^ 2 5 CH=CClCFClCF2 2 5 * The behaviour of both perfluorocyclobutene and the 1,2-dichloro analogue towards alkyl and aryl Grignard reagents has been studied. Park and Pontanelli10 obtained monosubstitution using mild conditions with the alkyl reagents CX=CXCF20F2 + RMgX —* RC=OXCF26Fg R = alkyl j X=C1,P More forcing conditions gave the disubstituted compounds, e.g. G H C=:C (G H )CP CP GgH5C=CFCFgCF2 + CgHgMgBr —*• g 5 2 5 2 2 Disubstitution proved more difficult for X=C1. Phenylmagnesium bromide and perfluorocyclobutene gave mono- and diphenyl derivatives under mild conditions. 11 Rapp et al. isolated mono- and disubstituted derivatives, in addition to a diadduct (a cyclobut-&ne), from the base- catalyzed reaction of the perfluoro-butene with mercaptans RSH + CF=CFCF0CF0 ,„ ^ RSC=CFCFgCF2 + RSC=C (SR)CF2CF2 2 2 (C„H )3N + RSCFCH(SR)CF CF The latter decomposed on distillation to give the bis(mercapto)- 12 olefin. Cuprous mercaptides have been found to give disub• stituted derivatives with 1,2-dichloroperfluorocycloalkenes CUSR + CCi=CCl(CF2)n —* RSC=C(SR) (CF^ n= 2,3,4? R = C^CH^ CgHg Pruett and co-workers reacted perfluorocyclobutene with amines, e.g. RgNH fiP=GPCP2fiPg *> R2NC=CPCP26F2 + RgNHgP R = alkyl The reactions with primary amines were more,complex, Perfluorocyclobutene and triethylphosphite have been 1 4 found to afford a monosubstituted product containing a five- coordinated phosphorus atom (C2H50)3P + CP=CFCPgCP2 —* (C2H50)3P(P)C=CPCP^P2 15 Trlalkylphosphites and 1,2-dIchlorotetrafluorocyclobutene gave *" Arbuzov type products (RO)^F 4 CCi-CCKCFj^ —> (R0)2F(0)C=C.(P(0) (0R)g) (CPg)n n=2,3,4 Fluorodimethylarsine and 1-dimethylarsinopentafluorocyclo- butene were the products from cacodyl and the fluoro-butene 5 (CH3)4As2 + CP=CFCP2CP2 —* (CH3)2ASC=CPCP2CP2 + (CH3)2AsF 17 The chloro-butene reacted analogously . The same two cyclo- 18 butenylarsines were obtained by Cullen and co-workers by reacting the cyclobutenes with dimethylarsine (CH ) AsH + CX=CXCF2CF2 —* (CH3)gAsC«CXGFgCFg + HX X =- F,C1 19 Muramatsu and co-workers found that V-irradiation induced addition of ethers ( ©C-hydrogen atoms)' to 1,2-dichlorotetrafluoro• cyclobutene to give the cyclobutane,as well as a cyclobutene, through- some elimination of hydrogen chloride , i "Vray s (,'RGH )g0 •+ CClaCClCF CFg — * RCHgOCH(R)C=CClCFgCFg + RCHo0CH( R) C C1G HC IGF C F 20 The analogous reactions occurred using primary and secondary alcohols;eogo RR'CHOH ^G€1=CC1CF2CF2 RRC (OH) C=CGICFg CFg + RR* C (0H))CC1CHC1CF2CF2 This work ex tends,,-.the investigation of the reactions of perf luorocyclobutene and 1,2-dichlorotetraf luorocyclobutene. with Group V compounds to include secondary phosphines and diphosphinesa The results of these reactions are presented and discussed In the following section. EXPERIMENTAL A. Apparatus and Techniques The following description will apply to the apparatus and general techniques used for the experimental work in all three chapters of the thesis. Unless otherwise indicated, reactions were carried out in thick walled Pyrex Carius tubes and worked' up using standard vacuum techniques^ volatile products were separated by cooling the traps with suitable low temperature baths. Irradiation with ultra-violet light was done with the sample held 10 cm. from a 100 watt source. Unless otherwise stated, molecular weights were determined by Regnaulfs method. Involatile air sensitive compounds were handled In a nitrogen filled dry box. Separations by vapour phase chromatography(v.p.c.) were achieved using an Aerograph A-90-P machine, using an injector temperature approximately 10 higher, and a detector temperature 30-35° greater than that of the column. The carrier gas was purified nitrogen. Infra-red spectra were in the main run on a calibrated Perkin Elmer model 137. When greater detail was desired, the Perkin Elmer 21 was used (indicated in the text with an asterisk) The. ^-H nuclear magnetic resonance (n.m.r.) spectra were recorded on a Varian A-60 instrument relative to tetramethylsilane. The 19 F n.m.r. spectra were run on Varian HR-60 and HA-100 spectro• meters, at 56.4 and 94.07 Mc/s respectively, relative to tri- 31 fluoroacetlc acid(TFA) and Freon 11(CFC13) respectively. P n.m spectra were run relative to phosphorous bromide(PBr^) on the HA-100 machine at 40.48 Mc/s. All reference standards,, unless otherwise stated, were external. Chemical shifts are reported 7 in parts per million(p.p.m.)(negative values to the low field side of the standard). Microanalyses indicated with an asterisk were done by the Schwarzkopf Microanalytical Laboratory, Woodside 77, N. Y.j those marked with a dagger were run in the microanalytical laboratory in the Department of Chemistry, University of British Columbia. The remainder were carried out by Dr. Alfred Bernhardt, iu'u hii.-., Germany. B, Starting Materials The perfluorocyclobutene was obtained from Peninsular ChemResearch Inc.5 the dichlorocyclobutene from Columbia Organic Chemicals Co. Inc. 1. Tetrakis(trifluoromethyl)diphosphine was obtained by reacting lodobis(trifluoromethyl)phosphlne with mercury. The iodo-phosphine was synthesized by heating red phosphorus with trifluoromethyl iodide21 in Carius tubes at 206° (41 hrs.) and separating the volatile products (fluoroform, tris(trifluoro• methyl )phosphine, iodobis(trifluoromethyl)phosphine and dilodo- (trif luoromethyl)phosphine) by trap-to-trap disti Llation, 2. Diphenylphosphine was prepared by reacting triphenyl- phosphine (78.6 g9 0.3 mole) with sodium (15.0 g,, 0.65 g=atom) In liquid ammonia, followed by ammonium chloride (1.07 mole) 22 in liquid ammonia , The residue was extracted with benzene o 23 and the solute distilled at 154-155 (11 mm.) (lit. value o 150=154 ) (11 mm.).v The distillate showed the characteristic P-H absorption at 2325 cm 3.. Tetraphenyldiphosphine was prepared2^ by refluxing diphenylphosphine with an equimolar amount of chlorodiphenyl- phosphine in petroleum ether (100-120° range) for 4 hrs. The 8 diphosphine was filtered off and washed with 30-60° petroleum 24 ether. The purity was checked by the infra-red spectrum 4. Bis(trifluoromethyl)phosphlne was synthesized by reducing iodobis(trifluoromethyl)phosphine with mercury and hydrogen Iodide. The reaction proceeded rapidly at room temperature. It was found that,all excess hydrogen iodide was converted to mercury iodides and hydrogen, hence only a relatively small excess of hydrogen iodide could be used. The purity of the phosphine was checked by its' molecular weight (Pound: 175, CgHPgP requires 170) and -^H n.m.r. spectrum, which consisted of the expected doublet (J = 216 c.p.s.) of septets (J = 10 H-P H-GF3 c.p.s.) 5. Tetramethyldiphosphine was prepared by heating its disulfide (10.31 g, 55.5 mmoles) with tributylphosphine (27.54 g, 136.3 mmoles) at 229° in a sealed tube (40 hrs.) The volatile materials, separated by a —64° bath, consisted of the diphosphine (4.54 g, 37.2 mmoles) and dime thyIphosphine (0.8 g, 12.9 mmoles). The purity of the diphosphine was checked by its "4l. n.m.r. spectrum, which consisted of a triplet (J = 7 c.p.s.)2^ centred at —0.24 p.p.m. The tetramethyldiphosphine disulfide was prepared by reacting 26 thiophosphorus trichloride with methyl magnesium iodide 6. DiethyIphosphine was obtained by a modification of the 27 procudureof Issleib and Tzschach • Tetraethyldiphosphine disulfide (17.0 g, 70.3 mmoles) was reduced with lithium aluminum hydride (8.0 g, 210 mmoles) in diethyl ether. Excess water was then added and the mixture distilled. The distillate was collected as the.temperature steadily climbed from 34-75°. At this point the temperature rose quickly to 100°. The ether and 9 phosphine were separated In the vacuum system using -78° and -64° bathso C. Reactions With The Cyclobutenes 1. Tetrakis(trifluoromethyl)diphosphine (a) 1,2-Dichlorotetrafluorocyclobutene (1.5 g, 7.7 mmoles) and the diphosphine (2.3 g, 6.8 mmoles) did not react appreciably at 175° (4 days) nor under ultra-violet irradiation (2 days). Small quantities of tris(trifluoromethyl)phosphine and silicon tetrafluoride, of known infra-red spectra, were formed at 175°. A little tris(trifluoromethyl)phosphlne was also produced by the irradiation. Finally the mixture was heated at 230° (2 days). Very little reaction transpired; the product could not be separated from the reac^ants and was not identified. The infra-red spectrum however contained a sharp band at 159G cm \ A fraction passing through a -78° bath (1.0 g) was combined with an excess of water In a sealed tube. Tris(trifluoromethyl)- phosphine (0.8 g) was recovered. (b) Perfluorocyclobutene (1,3 g, 8.0 mmoles) and the diphosphine (2.4 g, 7.1 mmoles) behaved In a similar manner a very small amount of new material was produced (230°, 2 days), but could not be separated from the unreached diphosphine. The mass spectrum showed a small peak at 312; the infra-red spectrum contained a sharp new band at 1760 cmT1* in addition to the peaks due to starting materials. A fraction which passed through a -78° bath (1.6 g) had a molecular weight of 171. This material was treated with an excess o of water. The recovered volatiles were separated using a -150 bath. The condensed material (1.4 g) was unreacted butene with 10 a small amount of tris(trifluoromethyl)phosphine. The material passing through (0.0165 g) was identified as fluoroform, of known infra-red spectrum. 2. Bis(trifluoromethyl)phosphine (a) The phosphine (2,3 g, 13.5 mmoles) and 1,2-di- chlorotetrafluorocyclobutene (3.2 g, 16.4 mmoles) did not react significantly after 40 hrs. at 202°, of under ultra-violet Irradiation (41 hrs.). Separation using a -78° bath gave unreacted butene (2.95 g) and phosphine (2.3 g)(M, 169.4; CgHPgP requires 170.0)o (b) Perfluorocyclobutene (1.4 g, 8.65 mmoles) and the phosphine (1.3 gs 7.65 mmoles) did not react appreciably at 142°(46 hrs.)5 176° (16.5 hrs.) or under ultra-violet irradiation (20.5 hrs.). Only the gas phase was present at 1760« The compounds cannot be separated by trap-to-trap distillation. 3. Diphenylphosphine (a) The chloro-butene (16.8 g, 86.1 mmoles) and diphenylphosphine (5.9 g, 31.7 mmoles) reacted on mixing to give a greenish yellowish material suspended in the excess butene. After three days an amber colored material was deposited. A small fraction (0.1 g) which passed through a -78° bath was identified as hydrogen chloride, containing a little silicon tetraf luoride^ by means of its infra-red spectrum and molecular- weight (Pound: 41.5S HC1 requires 36.5). Unreacted butene (13.5 gP 69.3 mmoles)9 which was the only other volatile material recovered from the tube, passed through a -23° bath and condensed in the -78° trap. The involatile matter was extracted with chloroform and distilled at lo"3ra>M three fractions were obtained: 112-115° 11 (very small), 115-119° (small), 139=147° (large, most at 146°). Although the analysis of the large fraction was not simple (Pound: C, 62.72; H, 4.02; Cl, 0.26; P, 24.74; P, 8.07 %; M, 375 (Rast), . ]_Q corresponding to an empirical formula of ^21^16^b 2^'> ^ne F n.m.r. spectrum (TFA) showed that the fraction consisted of a mixture of 28 trifluorodiphenylphosphorane and probably fluorodiphenylphosphine oxide. The latter gave a doublet (J„ ._ = 1020 c.p.s.) (lit. value29 1020) centred at -4.06 p.p.m., while the phosphorane gave a doublet (J p = 836 c.p.s.) of doublets (J = 39.2 c.p.s.), centred at -44.0 p.p.m., and a doublet (J^ = 968 c.p.s.) of triplets e i (J „ = 39.2 c.p.s.), centred at +1.05 p.p.m. H n.m.r. spectrum: e" a complex ortho hydrogen bands centred at -7.4 p.p.m. and the meta-para peak at -6,85 p.p.m., area ratio 2:3. Infra-red spectrum (liquid film)? 3080 m, 1590 m, 1480 vw, 1430 s, 1315 m, 1275 m(sh), 1250 s, 1235 m(sh), 1140 vs, 1120 s(sh), 1000 w, 855 s(broad), 840 a, 746 s 1 (broad), 736 s9 693 s cm' . (b) Perfluorocyclobutene (11.1 g, 68.5 mmoles) reacted vigorously on mixing with diphenylphosphine (6.7 g, 36.0 mmoles) to give, after several color changes, a mass of primrose crystals. The volatile materials (9.1 g) had the infra-red spectrum of the un• reacted butene together with some silicon tetrafluoride. After recrystallization thrice from acetone, the crystals (1,0 g, 11 %) analysed to be 1,2-bia (diphenylphosphine) tetrafluorocyclobutene, m.p. 129.5-130.5°. Founds Cs 67.95; H, 4.08; F, 15.51; P, 12.47 %\ M, 484 (Rast). Calc. for C__Hg0F4P_s C, 68=00: H, 4.05; F, 15.39; P. 1.2.56 %i M, 494. Infra-red spectrum* (KBr disc): 3100 w, 1970 vw, : 1890 vw, 1817 vw, 1587 vw, 1574 vw, 1482 m, 1440 ms 1335 w (sh), 1316 m (sh), 1302 vs, 1220 s (sh), 1216 s, 1186 m, 1160 s (sh), 1154 s, 1132 m, 1115 m, 1090 vs, 1068 s, 1040 w, 1025 m, 998 m, 992 w (sh), 970 vw. 12 916 w, 829 a, 821 m, 761 s, 741 s, 724 s, 704 m (sh), 692 s cmT1 "^H n.m.r. spectrum (CDCl^ solution): one band (-7.3 5 p.p.m. ) / \ 19 showing small secondary splitting (J«2 c.p.sj, F n.m.r. spec• trum (CHC13 solution) (TFA): a doublet (JQF _p = 7.74 c.p.s.) centred at +28.7 p.p.m. 4. Tetraphenyldiphosphine (a) The diphosphine (3.6 g, 9.73 mmoles) and the chloro- butene (16.5 g, 84.6 mmoles) did not react at 20°. Reaction did however occur at 130° (2 hrs.). A very small fraction which passed through a =64° bath consisted of silicon tetrafluoride and carbon dioxide. Unreacted butene (14.5 g, 74.3 mmoles) condensed in the -64° trap. The involatile material was extracted with chloroform. Ad• dition of petroleum ether precipitated a small amount of cream coloured solid, m.p. 247° dec, which although recrystallized from benzene could not be identified. The elemental analysis corresponded with the empirical formula CgyHg^FsPOg, The remain• ing material was distilled at 10~3 mm, to give two cuts, 141-146° o ]_g and 146-148 (larger). P n.m.r. analysis (TFA) of the first fraction, revealed a mixture containing appreciable amounts of both diphenylphbsphorus fluorides described in 3 above. Sev• eral unidentified .peaks were observed, the significant ones being three apparent doublets, centred at =52.85 (J = ,9 c.p.s,), +8.71 (J = 46 c.p.s.) and +14.03 p.p.m. (J = 46 c.p.s.). The latter pair in fact appeared to be a doublet of doublets, showing in addition•further splitting into apparent triplets (JSS2.6 c.p.s.). 19 The F n.m.r. spectrum showed that the second fraction was mainly fluorodiphenylphosphine oxide, the'^H n.m.r. spectrum having con• sisted of a broad (24 c.p.s. at half height) multiplet of eight 13 peakss centred at -7,22 p.p.m., and a narrow (7 c.p.s. at half height) multiplet of five peaks centred at -6.75 p.p.m., of area ratio 2:3. Infra-red spectrum (liquid film): 3120 w, 1600 m, 1480 vw, 1430 a, 1335 w, 1280 m, 1250 vs, 1135 vs, 1110 m, 1075 vw, 1025 w, 996 w, 840 a, 752 a, 735 vs, 692 s cmT1 (b) Tetraphenyldiphosphine (4.0 g, 10,8 mmoles) and the fluorobutene (29.7 g, 183 mmoles) were heated at 130° (2 hrs Unreached butene (28.2 g, 174 mmoles) containing some silicon tetrafluoride was recovered. The involatile products consisted of solid and oily materials; the oil was extracted with benzene -3 0 and distilled at 10 mm. Two cuts were taken; 142-148 and o 148-151 , and both had the infra-red spectrum of fluorodiphenyl- 1 19 phosphine oxide. The H and " P n.m.r. spectra of the second fraction also corresponded with those of this compound. How• ever the elemental analysis indicated trifluorodiphenylphosphor- ane (Pounds C, 61.26; H, 4.42; P, 22.49; P, 12.31 %; M (Rast), 264. Cl2H10P3P requires: C, 59.5; H, 4.1; P, 23.6; P, 12.8 %; M, 242). Attempts to recrystalllze the solid were unsuccessful. How ever an ethanol solution yielded, on addition of petroleum ether o a buff colored precipitate, m.p. 120-124 , which analyzed as 1- diphenylphosphinotrifluorocyclobutenone (Pound: C, 62,55; H, 3.48; P, 18«87; p, 10.07 %. Calc. for C H P OP: C, 62.8; H, lo 10 o 3.27; P, 18.62; P, 10.13 %). Infra-red spectrum (Nujol mull): 1770 m, 1670 a, 1480 w, 1430 s, 1335 vw, 1310 vw, 1240 a, 1190 w (broad), 1120 m, 1105 w (sh), 1070 w, 1000 w, 772: vw, 749 w (broad), 730 m, 695 m cm. 5, Tetramethyldiphosphine (a) 1,2-Dichlorotetrafluorocyclobutene (2.58 g, 13.24 14 mmoles) reacted immediately on mixing with tetramethyldlphos- phine (1.24 g, 10.16 mmoles). A white solid was produced but disappeared within an hour, leaving a paste of orange crystals and a little mobile liquid. After 16: .days the color had darkened considerably; virtually no volatile material remained. The mat• erial was extracted with chloroform but only a small amount dis• solved. This solute (0.2; g) was recrystallized twice from car• bon tetrachloride to yield white crystals of 1,2-bis(dimethyl- phosphino)tetrafluorocyclobutene (0.1 g, 8$), m.p. 137-139°.. Infra-red spectrum (Nujol and Halocarbon mulls): 3030 m, 2940 m, 2440 vw, 21.70 vw, ^000 vw, 1770 vw, 1640 m, 1560 m, 1440 w (sh), 1410 m, 1310 vs, 1240 vs, 1205 vs, 1190 vs, 1160 vs, 1125 vs, 1040 m (sh), 944 vs, 922 vs, 909 vs, 885 s, 874 s, 827 s, 755 s, -1 1 735 ,sp 702 s cm. The H n.m.r. spectrum (CHC1 solution) con- o sisted of a doublet (J p. = 14 c.p.s.) centred at -1.91 p.p.m.? 19 CH3~* the F spectrum (CHC1 solution, internal CFC1 , 56.4 Mc/s) was 3 o a doublet (Jn-r-, _2J2.5 c.p.s.) centred at +109.6 p.p.m. The elemental analysis corresponded with the monoxide. Found: C, 36.34s H, 4.85;' F, 29.28; P, 23.75 %, Calc. for C H F OP : C, 36.7; H, 4.6; F, 29.0; P, 23.6 The remaining material was readily taken up with methanol, but could not be identified owing to decomposition. (b) Perfluorocyclobutene (10.2 g, 63.0 mmoles) and the diphosphine (1.5 g, 12.3 0 mmoles) reacted vigorously on mixing to yiald a brown-black mass. Unreacted butene (7.11 g, 43.9 mmoles) was recovered when passed through a =64° bath. Most of •'li• the -64° fraction (0.2 g) passed through a -23 bath; this mat• erial was identified as trifluorodimethylphosphorane, Infra-red spectrum (vapor): 3080 w, 2990 w, 1420 w, 1300 s, 1025 s (sh), 976 vs, 939 s (sh), 889 vs, 851 m (sh), 837 s, 826 m (sh), 755 vs cm.1 The n.m.r. spectrum consisted of a doublet {J„„ _p = 17.2 30 c.p.s.) (lit. value 17.3) centred at -1.42 p.p.m. No H-F coup• ling was observed*^' The n.m.r. spectrum contained a doublet 28 («3p n~765 c.p.s. ) (lit. value 772) centred approximately at a +4.47 p.p.m. (lit. value +2.55) and doublet (Jp :p^970 c.p.s.) e (lit. value 960) centred approximately at +86.4 p.p.m. (lit. value 86.35), relative intensity 2?1. The bands were very broad (^120 c.p.s. at half height) but could not be resolved further. The black involatile material proved completely insoluble in chloroform and was decomposed by methanol, 6• Diethylphosphine (a) The phosphine (1,45 g, 15,6 mmoles) reacted smoothly on mixing with the chloro-butene (6.16 g, 31.6 mmoles) to give a white paste. After one hour this slowly liquified, finally giving a larger colorless liquid phase below a smaller pale yellow one. The tube was then cooled to -78° until work-up. Trap-to-trap distillation yielded unreacted butene (3.48 g, o 17.85 mmoles), which passed through a -46 bath and stopped in a -64° trap. A fraction which stopped in a -23° bath contained a colorless liquid and a little white solid; the two reacted at room temperature; The.'liquid was thus freed from the solid by allowing completion of the reaction and condensing the remaining liquid into a clean trap. This condensate was identified as 2- chloro-l-diethylphosphinotetrafluorocyclobutene (1.4 g, 56%) (Found^t: C, 38,77; H, 4,40; P, 12.81 %, Calc. for CgH-^ClF^s . C, 38.6; H, 4.03; P, 12.47 %). Infra-red spectrum (liquid film): 3030 m, 2940 w (sh), 1590 w, 15/60 m, 1495 vw, 1460 m, 1420 w, 1380 w, 1315 vs, 1240 vs, 1110 vs, 1040 m, 1030 w, 954. vw, 939 vw, 16 855 s, 833 m, 770 m, 749 w (sh), 717 vw (broad), 685 vw (broad) cmT^" The ^"H n.m.r. spectrum (-5°) consisted of a distorted quartet (J„ «s 7 c.p.s.) of doublets ( JJJ _p**2 c.p.s.) centred at -1.57 p.p.m. | and a multiplet (JTT n «7 c.p.s.) of five peaks centred, at -0.81 p.p.m. with virtually no secondary splitting (I.e. =p ~14 c.p.s.). The compound was unstable at 0°, and ^ o decomposed in vacuo in a few hours at 20 . A water sensitive fraction of very slight volatility was produced whose analysis' Indicated a mixture of chlorodlethylphos- phine and diethylphosphorus fluorides (Pound • C, 34.71; H, 7.05; CI, 28.06; F, 11.38; P, 17.51 '%). A fraction which passed through a -136° bath was identified as hydrogen chloride (M, 38.3; HC1 requires 36,5) containing a little silicon tetrafluoride, of known Infra-red spectrum. (b) DIethylphosphine (1.4 g, 15.6 mmoles) and perfluoro- cyclobutene (7.0 g, 43.2 mmoles) reacted immediately on mixing to give an increasingly darker red-brown liquid. After half an hour red-brown solid appeared^ whereupon the tube was cooled to -78° until work-up. Unreacted butene (5.0 g,,30.9 mmoles) passed through a -78° bath (Mj 159.5; C Fg requires 162.0). The infra-red spectrum of the fraction revealed a trace of silicon tetrafluoride. The involatile product readily dissolved in chloroform. Treatment of the solution with petroleum ether precipltat ed a red-brown paste. The remaining solution was concentrated, then cooled, yielding crystals which were very soluble in halogenated or aromatic hydrocarbons. Recrystallization from cyclohexane was unsatisfactory owing to the lesser solubility of the red- brown material. Purification was effected by dissolving the solid in 3s1 petroleum ethersbenzene, which would not dissolve the col• ored material. The resulting colourless compound was 1-diethy1- phosphinopentafluorocyclobutene (0.4 g, 11%) m.p. 101-103° (Pound: C, 41.17: H, 4.33; F, 40.79; P, 13.30 %. Gale, for CgH10P5P: C, 41.39; H, 4.34; F, 40.93; P, 13.34 %). Infra-red spectrum (Nujol and Halocarbon mulls)? 2980 m, 2900 w (sh), 1960 vw, 1640 vw (broad), 1540 m, 1450 s, 1420 w, 1370 m, 1310 s, 1250 s, 1170 vs, 1155 vs, 1120 vs (broad), 1050 m, 1040 w (sh), 1020 m, 859 w, 824 s, 790 s, 746 m, 687 s cmT1 The n.m.r. spectrum consisted of a multiplet centred at -2.18 p.p.m. (-CH -), and a doublet (J„ _ = 25 c.p.s.) of triplets (J = 7 c.p.s.) centred at -1.29 p.p.m. The compound decomposed under nitrogen within two weeks. DISCUSSION A . Results This section .deals with the reactions of 1,2-dichlorotet- rafluorocyclobutene and perfluorocyclobutene with compounds of the type RgPPRg and R?PH; R = CP C H CH3 or 1. R = Trifluoromethyl The cyclobutenes and tetrakis(trifluoromethyl)diphosphine show little tendency to react. Thus the diphosphine and the chloro-butene give little or no reaction at 175° or under ultra- o violet irradiation, sin d at 230 the only significant product is tris(trifluoromethyl)phosphine. The band at 1590 cm.^ in the infra-red spectrum Indicates the formation of a compound con• taining a new double bond, which may be due to a small amount of 1-bis(trifluorome thyl)phosphino-2-chlorotetrafluorocyclobutene: (CP3)4P2 4- CC1=CC1CF2CF2 —(CF3)2PC=CC1CF2CF2 + (CF3)gPCl Perfluorocyclobutene and the diphosphine behave in a similar manner. A small amount of new material is produced which may be 1-bis(trifluoromethyl)phosphinopentafluorocyclobutene: (CF-KP- + CF=CFCF0CP0 » (CP ) p6=CFCF CP + (CP ) PF A new band at 1760 cmT1 in the infra-red, and a small peak at 312 in the mass spectrum support this conjecture. Evidence for • * the formation of fluorobis(trifluoromethyl)phosphine is the prod• uction of fluoroform- on treating the most volatile reaction products with waters (CF3)2PF 4 2 HgO —*» CF3P0QHg + CHP3 4- HF 31 Only compounds of the type (OF )gPX and CF^PX^ react in this way Bis(trifluoromethyl)phosphine Is almost totally inert toward the cyclobutenes; no significant reaction with either butene oc- curs on heating or ultra-violet irradiation. 19 2. R = Phenyl Tetraphenyldiphosphine and the cyclobutenes do not react at o ° 20 but do so readily at 130 | diphenylphosphine reacts easily at 20°. Diphenylphosphine and perfluorocyclobutene give 1,2- o bis(diphenylphosphino)tetrafluorocyclobutene, m.p. 129.5-130.5 , a in low yield s 2 (C6H5)2PH + CF=CPCF2CF2 —(CgH5 )2PC=CP (C6H"5 )2CF2CF2 The compound was identified by elemental analysis. It has been assigned the 1,2 configuration rather than 1,3 or 1,4 on the 19 basis of the F n.m.r. spectrum, which contained only one band (a narrow doublet), and the weak double bond absorption in the infra-red. An unsymmetrical cyclobutene would be expected to 32 absorb strongly in the double bond region , e.g. 1-dimethyl- 17 arsIno-2-chlorotetrafluorobutene Tetraphenyldiphosphine and the fluoro-butene react to give a solid and an oil. The former could not be recrystalliz^d; however treatment of an alcoholic solution with petroleum ether o yields 1-diphenylphosphinotrifluorocyclobutenone, m.p. 120-124 , identified by elemental and infra-red analysis. Although the position of the oxygen atom is not definitely known, it is prob• ably situated at the 3 "position (see discussion of mechanisms). The liquid, product is likely fluorodiphenylphosphine oxide. iT* CPH,0HXi * (C6H5)2PC-CPC0CF2 {G E ? + '2 5- 6 5h 2 ftF=CFCP2fiFg. — (CgHgJgP^CFCFgTiFg + (CgH^PFv The evidence for the formation of the phosphine oxide is mainly spectroscopic. The P=0 and P-F stretching frequencies, 1250 and -1 840 em. respect!vely, are Ih.good agreement, with published values No attempt was made to optimize the yield. Further work has shown (32a) that by holding the temperature below 0 , the yield is greatly increased. 20 -1 of 1256 f'rid 835 cm. The fluorine-phosphorus splitting of 1020 H9 c.p.s. is in exact agreement with the literature value . How• ever, the elemental analysis, done some time after the spectra were obtained, indicated the sample to be mainly trifluorodi- phenylphosphorane. This material may arisef rom disproportion- 33 ation of the unknown fluorodiphenylphosphine , the expected elimination products 3 (C6H5)2PP —(C6H5)2PF3 + (C6H5)4P2 19 The P n.m.r. spectrum refutes trifluorodiphenylphosphoran e as an initial reaction product. Fluorodiphenylphosphine oxide might 34 arise from hydrolysis of the trifluoro-phosphorane s cr pos• sibly from oxides of tetraphenyldiphosphine in the reactant. The reactions of 1,2-dichlorotetrafluorocyclobutere with tetraphenyldiphosphine and diphenylphosphine may be summarized as follows?; (C6H5)2PR f CC1=CC1CF2CF2.. (CgH^gPPO + Wfo)^ + RC1 + .... R = P(CfiH_)_, H 6 5 2 The reaction with the diphosphine gives mainly fluorodiphenyl- 19 phosphine oxlde^ as identified by P n.m.r.. and infra-red spec• troscopy. The "^F n.m.r. spectrum reveals lesser amounts of the fluoro-phosphorane, plus unidentified material, in the distillate of the oil. An unidentified solid, m.p. 247° dec, of empirical formula C27H21F5P03 (microanalysis) » ^s also produced. The formation of the expected ehlorodiphenyIphosphine is not proven. It is net separable from the oil mixture and is not distinguish- 1 able by H n.m.r. spectroscopy. Diphenylphosphine and the chloro-butene afford both the 19 above diphenylphosphorus fluorides, as identified by F n.m.r. and infra-red spectroscopy. Hydrogen chloride, identified by molecular weight, is produced, 3. R = Methyl, Ethyl The cyclobutenes react vigorously with tetramethyldiphos- o phine and diethylphosphine at 20 , Thus the diphosphine and the chlorb-butene give 1,2-bis(dimethylphosphino)tetrafluorocyclo- o * butene, m.p. 137-139 , in low yields. (CH3)4P2 + CCI=CG1CP2CP2 —-*> (CH3) 2P0=C (P (CH3) 2)CFgCFg The compound Is best Identified by its n.m.r. spectra. The "*"H 19 spectrum consists of one well defined doublet, as does the P spectrum; the dimethylphosphino groups are thus both situated at the vinylic positions. Although the elemental analysis indicated the monoxide, the oxide was not the original product. This is shown.by the "^H and "^9P n.m.r. spectra, both of which show only one type of hydrogen (aid fluorine) atom present. The H-P spin- spin coupling (14 c.p.s.) is worthy of comment. Most dimethyl• phosphino. compounds exhibiting splitting of this magnitude con• tain pentavalent pho sphorus, e.g. (CH3)2PC1S (13.4 c.p.s.), (CH^gPFS (13.7 c.p.s.), while the trivalent derivatives are considerably 30 lower, e.g. (CH^P (2,7 c.p.s.), (CHgJgPCl (8.4 c.p.s.) 0 The large splitting in the bis(dimethylpliosphlno)-butene is likely due to resonance delocalization of the lone pairs, i.e. P P P , P P . « F (CHgJglg P(CH3)2 (CH3)2P P(GH3)2 (CH3)2P-^(CE3)2 The magnitude of the H-P coupling in this compound is large enough in fact to suggest that this resonance makes a large contribution; the resonance hybrid is likely further stabilized by d^-p^, overlap of the carbanion lone pair into the vacant phosphorus 3d orbitals. Perfluorocyclobutene and tetramethyldiphosphine give a brown- black mass plus a small amount of trifluorodimethylphosphorane. 1 19 The fluoro-phosphorane was identified by its H and P n.i.r, spectra. The infra-red spectrum contained very strong absorptions; in the P-F stretching regions and no C-F stretching bands. The 19 28 P spectrum is of particular interest. Muetterties et al. re• port the spectrum of this compound to be a doublet of doublets plus a doublet of-triplets, owing to non-equivalent fluorine atoms (J_ „ ~ 26 c.p.3.) F—F 3 Figure Is Trigonal Blpyramidal Structure of Trif luorodime thy lphosphorene analogous to the case of trifluorodlphenylphosphorane . Di- chloro- and dibromotrifluorophosphorane do not contain non-equiv• alent fluorine atoms at room temperatures owing to exchange through 35 19 vibrational excitation • . In the present investigation, the p n.m.r. spectrum was run on two occasions. In one case (see p,15), the F-F doublets consisted of very broad peaks (VL20 c.p.s. at half height) which could not be resolved, while on the other oc• casion no fluorine resonance was observed. It thus appears that the trigonal blpyramidal structure collapses as the temperature approaches 50°° The analogous situation obtains for dichloro- 36 o trif luorophosphorane ° at -143. the doublet of doublets and doub- o let of triplets are sharp; at -127 only two very broad doublets o are seen, while at -109 only a slight swell in the base line Is discernible. 23 The reactions of the cyclobutenes with diethylphosphine can be represented thus: = (C2H5)2PH + CX = CXCFgCFg —> (CgH^gPC" CXCFgCFg + HX X = 01,F Thus the chloro-butene affords l-diethylphosphino-2-chlorotetra- fluorocyclobutene, identified by elemental and infra-red analysis. In addition to the peaks presented in Table I (p. 24), a strong band appears at 855 cm.™1 (C-Cl stretch). In agreement with -1\17 l-dimethylarsino-2-chlorotetrafluorocyclobutene (855 cm. ) • The hydrogen chloride was identified by molecular weight. The white solid which appears in the work-up, and reacts with the dlethylphosphino-butene at 20°, is believed to be diethylphos- phonium chloride. The less basic dimethylarsine forms the hydro- o ^7 chloride, stable at —46 . Diethylphosphonium chloride could o be expected to be unstable at 20 : (CgH^gPHgCl" ^ * (CgH5)gPH + HC1 Phosphonium chloride itself is completely dissociated at room 38 temperature , dimethylphosphonium chloride exhibits a vapor o 39 pressure of 1.3 mm, at 25 . In view of the formation of the bisphosphino compounds at 20° In the reactions (C6H5)2PH + CF = CFCF2CF2 —=—(C6H5 ) gPC = CP (CgH5 ) gCFgCFg . (CH3)4P2 + CC1—CClGP^CFg * (CH3)2P6^CP(CH3)2CFjCF2 I-diethylphosphInc-2-chloro-tetrafluorocyclobutene would be expected to react with diethylphosphine at this temperature. Cullen et al. found that l-dimethylarsino~2=chlorotetrafluorocyclobutene reacts with dimethylarsine at 140°» The marked instability of the dlethylphosphino-chlorobutene is worthy of comment. It is possible that the decomposition is 24 catalyzed by residual traces of diethylphosphonium chloride; 40 Dhaliwal found that the nitrogen analogue was unstaole except when purified by v.p.c. The instability may be inherent in the compound however. The resonence hybrid F, 2 JLi.i,.fs! (C„H ) P' 2 © lacks the ^L^rJj^ stabilization postulated earlier for the bis- (dimethylphosphino)-butene. Thus the compound may decompose through halide ion loss to give the polymeric material observed. This possibility Is supported by the decomposition of 1-diethyl- phospn:?nopentafluorocyclobutene (described next), even after purification. The diethylphosphino-chlorobutene also shows 14 c.p.s. hydrogen-phosphorus coupling (Ha) (J £J 2 c.p.s.) The large splitting is again ascribed to lone pair-delocalization from the phosphorus atom. Diethylphosphine and perfluorocyclobutene give l-diethyl- phosphinopentafluorocyclobutene m.p. 101-103°* Identified by elemental and Infra-red analysis.. TABLE I C-G and C~F Stretching Ben ds of the Phosphino-butenes (cm, ) Compr-md 0 .C G-P (C H ) FC=CP(C H ) CF CF*a 1590w. 1300vs 1215s 1185m 1155s 1090vs b52 b 5 2 2 2 b (CAHR)opd^CFC0CFo • 1670 s . 1^403 1120m 6 5 (GH3)2PC=CP(CH3)gCF2CFg 1560m 1310vs 1240vs 1190vs 1160vs I125vs :CoHc,)r>PC=CCl0Fp0Fp' 1560m 1315vs 1240vs lllOvs (G0H5 )2PG^CFCF2CFer 1540m 1310s 1250s 1170vs 1120vs 17 (CH3) pAsC-CClCFgCJFg 1576vs 1528vs 1245vs 1150m 1115vs a c KBr disc mull liquid film The diethylphosphino-f luorobutene also decomposes at 20°, although considerably more slowly than the chloro analogue. The increased stability of the fluoro compound may be due to greater purity? but it must be pointed out that fluoride is a poorer leaving group"than chloride, but that o^-chlorine can better 41 stabilize a carbanion than can o<-fluoride . A striking feature = .of 1-d.iethylphosphinopentafluorocyclobutene is that Jfj^-P 25 c.p.s. (JTT p £f 3 c.p.s.). If the large splittings in these dialkylphosphino-cyclobutenes are due to resonance contributions, then the big increase in ^ on going to a fluorinated from a chlorinated vinyllc carbon atom suggests a big increase In the delocalization of the phosphorus lone pair. B. Proposed Mechanisms The numerous investigations during the last two decades of the reactions of nucleophlles with fluorinated olefins have of• fered three basic reaction paths;; namely, addition-elimination, concerted. SNg substitutions, and reaction via'car banion inter• mediates. In the third case, the leaving group departs before 13 addition can be completed. Pruett et al. proposed addition followed by elimination for the reaction of secondary amines with perf luorocyclobutene RgNH + fecFCF'gCFg —> JRgNCFCHFGFgCFg —» RgNi^CFCFgCF^ + HF An analogous mechanism has been proposed for the reaction of this 42 11 10 olefin with alcohols , mercaptans , and Grlgnard reagents . In the case of mercaptans, the isolation of the (unstable) addition compound along with the elimination product adds weight to this reaction path. Reaction of mercaptans11, an d arsines^ with non- cyclic olefins gives the addition compounds, e.g. (CHj^AsH + OF =*CFCF„ *. (CH,)0AsCF0CHFCF, 26 44 Parshall et al. have found that phosphine•. and phenylphosphine add to halogenated ethylenes at 150°« 6 45 46 47 Roberts' group 5 ' 5 have studied the reactions of halide, hydroxide and alkoxide ions with halogenated cyclobutenes, especially l-phenyl-2-H-perhalocyclobutenes. The results have been interpreted as indieindicatin; g an SNg machanism (I.e. substitution with rearrangement), e.g. m KOH C H C=GG1GF CH(0C H C6H5C=CHCF2CC12 —coH50H * 6 5 2 2 5^ 41 A recent paper by Park et al. describes the behavior of halogenated cyclobutenes towards alkoxide ion. The results are interpreted as indicating that the reactions proceed by elimination of halide ion from discrete carbonions rather than via an SN2 mechanism, e.g. CC1=CC1CF2CF2 + R0~ *> J^OCCl^ClCFgCF^J-^Cl" + R0C=CC1CF2CF2 CF=CC1C(0R)2CF2 + RO"—+ JROGFCCIC ( OR) GCFG ,F" + R0C=CC1C(0R) CF In the second example, the alkoxide ion attacks the vinylic carbon attached to fluorine, with subsequent loss of fluoride. The authors relate this to the known fact that chlorine can better stabilize ' the carbanion carbon atom than can fluorine, rather than because of any increased vulnerability to nucleophilic attack of the carbon attached to fluorine. Frank^-5 finds that 1,2-dichloroperfluorocyclobutenes and tri- alkylphosphites give 1,2-substitution (as opposed to 1,3,3- substitution, the normal sequence when more than one mole of nucleophile attacks) i.e. 27 (RO)gP(0)C=CP(0) (OR)g(fiPg)n 2,3.4, He explains this as follows: the placing of the electronegative P=0 group at the 1 position reverses the polarity of the double bond, as compared to the polarity after one mole of a classical nucleophile, e.g. alkoxide, has attacked, thus causing the next mole of phosphite to attack at the 2 position rather than the 1 position. This work has resulted in two disubstituted species; namely, 1,2-bis(diphenylphosphino)tetrafluorocyclobutene, and the methyl analogue. Since the substitution of dimethylphosphino for chlorine, and diphenylphosphino for fluorine, clearly does not reverse the polarity of the double bond, other factors must be considered to explain the departure from the established pattern of poly substitution. In the present investigation the mechanism of the reactions of the cyclobutenes with secondary phosphines is surely a choice between addition-elimination and the carbonion route (or a competition between these two); an SNg path involves the displace• ment, of a formally charged Ion by a neutral molecule. Eliminating the SNg route, the initial step is clearly R " C2H5sC6H5 possibly R2PH + via X X = CI, F X -A H-?R, The 1,3-dipolar intermediate may undergo' inter- or intra• molecular proton transfer to yield the cyclobutane, followed by rapid elimination of HX, The alternative is elimination of halide first, followed by proton loss, i.e. 28 F_ ' *V • F0 Po xF„. F2 2 i -i 2 *2.., ^2 2 x —x + HX + X la \ X H^fRg X PR2; H-PRp, © The complete absence of any phosphino-cyclobutanes in this, work suggests that this is indeed the path; however, the reaction of diethylphosphine with 1,2~dichlorotetrafluorocyclobutene gives initially a white paste v/hich liquifies within an hour; this may be the cyclobutane. Moreover, Rapp et al.^ isolated a cyclobutane in the reaction of n-butyl mercaptan with the fluoro-butene . 2 , n-C4H9SH •+• CF=CFCF2CF2 » HF + .C4HgS.CHCF(SC4H9)CF2CF2 This cyclobutane eliminates hydrogen fluoride on distillation. It may be significant that with diethylphosphine, perfluoro• cyclobutene gives the simple tertiary phosphine whereas with diphenylphosphine the bis(tertiary phosphine) is obtained. Since diphenylphosphine is a much weaker base than diethylphosphine^®, proton transfer should occur much more readily in the phenyl reaction. Thus if the difference in products is due to a difference in mechanism, then proton transfer is favored for the • phenyl case and initial halide loss in the reactions with diethyl• phosphine . If, however, the monophosphino-butenes.are easily attacked by.a further mole of phosphine,•as is likely8, then the difference in products, may of. course be due to a significant difference of rate in the elimination, in whatever sequence, of the elements of HX. The diethyl compounds would be expected to lose HX much more ' a If they were not, the major product would always be mono substituted because of the excess of reactant cyclobutene. 29 43 slowly. The observed results are consistent with this, Styan favors the Initial attack of dimethylarsine on the fluoro-butenes to give the dipolar intermediate as being the rate determining step, followed by rapid proton transfer and elimination of HX. It appears, however, that for secondary phosphines (R / CF^), the rate determining step is the elimination of the elements of HX. For R = CgH5,GgHg, all reactions proceed immediately on mixing 18 o (whereas dlmethylarsine requires several days at 20 ), and then undergo relatively slow change (15-60 min.). As already mentioned, diethylphosphine and the chloro-butene Immediately give a white paste, which slowly liquifies to give 2-chloro-l-diethylphosphlno- tetrafluorocyclobutene. The failure of bis(trifluoromethylphos• phine to react with the cyclobutenes is clearly due to- the greatly decreased availability of the phosphorus lone pair, caused by the electronegative trifluoromethyl groups. The reactions of the cyclobutenes with the diphosphines (R ^ CF ) also proceed via lone pair attack on a vinylic carbon atom; 3 R4P2 + CX=CXCF2CFg The four-centre Intermediate seems unlikely because of the two pairs of adjacent like-charged + atoms. Subsequent intramolecular transfer, of RgP would give the cyclobutane, followed by rapid elimination of R Attack of a further mole of diphosphine thus would give the bis(tertiary phos• phine). It should be noted that if the dipolar intermediate suf- + fers initial, halide ion loss, subsequent departure of RJ provides a considerably simpler mechanism. In the case of R = CgH.5, a free radical mechanism seems possible at 130°, because of the inductive effect (relative to R = CHg) of the phenyl groups, and the weakness of the P-P bond (18.9 kcal/mole).49 The reactions of the diphosphines with the cyclobutenes provide two interesting contrasts with the analogous secondary phosphine reactionst (1) Tetramethyldiphosphine gives a bis(tertiary phosphine) whilst diethylphosphine gives monosubstituted compounds; tetre- phenyldiphosphine gives the monosubstituted species and diphenyl• phosphine yields the bis(tertiary phosphine). (2) Tetraphenyldiphosphine Is considerably less reactive than diphenylphosphine towards the cylcobutenes; tetrakis(tri- fluoromethyl)diphosphine is more reactive than bis(trifluoro- me thy1)phosphine. Since the formation of the bis(tertiary phosphine) must occur through prior formation of the monosubstituted species, the production or lack of same of the disubstituted compound Is dependent of the rate of formation of the mono-compound. As stated earlier, this is believed relatively slow for the diethyl• phosphine reactions because of the basicity of diethylphosphine. In the case, of tetramethyldiphosphine the migrating group is not a proton. Moreover, the P-H bond strength (63.0 kcal/mole) is considerably greater than that of the P-P bond (18.9 kcal/- ,49 mole; . As previously discussed, the formation of the bis- tertiary phosphine) from diphenylphosphine is ascribed to easy loss of the proton in this case. The failure to obtain the' bia(tertiary phosphine) from tetraphenyldiphosphine may be due to steric hindrance towards the transfer of the second diphenyl- 51 phosphlno group, or even towards the attack of a second mole of tetraphenyldiphosphine. The lesser reactivity of tetraphenyldiphosphine relative to diphen• ylphosphine is probably a combination of steric factors and the electronegativity of diphenylphosphino being greater than that of hydrogen.. The small reaction observed with tetrakis(tri- 'f luoromethyl) diphosphine probably does not involve nucleophilic attack (the lone pair Is less 'withheld in the non-reacting bis- (trlfluoromethyl)phosphine). A free radical mechanism initiated by scission of the relatively weak P-P bond is favored. Thus bis(trifluoromethyl)phosphine would not be expected to react. As stated earlier, the oxygen atom in 1-diphenylphosphlno- trifluorocyclobutenone, obtained from perfluorocyclobutene and tetraphenyldiphosphine (work up with 95 % ethanol) is believed situated at the 3 position. The following arguement in support of this conjecture assumes that the original reaction product Is 1-diphenylphosphinopentafluorocyclobutene: 2:. (0eVap _a If the resonance hybrid was to lose fluoride ion, it would be 41 from the 3 position , i.e. RF F F, F 2\ * (CV.Hj^Ps*g52 - F C F e < 6W This last hybrid could then react with water; • OH + + H (C.„HJ0P F (C6H5)2P- F o 5 2; This alcohol could yield the ketone either by direct loss of hydrogen fluoride (perfluoromethanol and -ethanol are unknown 50 compounds), or by a repeat of the above scheme, Parker found that l-dialkylamino-2-chlorohexafluorocyclopentenes were extremely water sensitive, and that exposure to water gave the analogous ene=3-ones.. No cyclobutenyl compounds could be obtained from the reactions of either diphenylphosphine or tetraphenyldiphosphine with 1,2- dichlorotetrafluorocyclobutene. The only products characterized are trifluorodlphenylphosphorane and (probably) fluorodiphenyl- phosphine oxide. This indicates that l-diphenylphosphino-2- chlorotetrafluorocyclobutene is very unstable, if indeed this species has a'discrete existence8 . It would surely exhibit resonance, since the negative charge is better stabilized by chlorine than by fluorine, and moreover, the P=C bond energy 51 (not yet measured) is relatively high . The hybrid could lose a fluoride ion in the same manner postulated for the formation of the cyclobutenoneo This would provide a source of fluoride to allow the formation of P-P bonds; F F _ P _F c\ n p~ 2i CI F This last species may by classified as a Wittig reagent, and as • such could be expected to react readily with an electrophllic 52 reagent such as 1,2-dichlorotetrafluorocyclobutene, to produce high molecular weight material and perhaps flubrodiphenyIphos• phine. As. previously stated, trif luorodlphenylphosphorane is It probably has, since hydroccen chloride is obtained from diphenyl• phosphine and the chloro-butene, oc probably the result of disproportionation of fluorodiphenyl- phosphine. Trifluorodimethylphosphorane, from tetramethyldi• phosphine and perfluorocyclobutene, is probably the result of similar disproportionation of the unknown fluorodimethylphosphine, the expected elimination product. As mentioned earlier (p.86), the normal sequence for attack by more than one mole of nucleophile has been to give 1,3,3- substitution (i.e. an allylic shift of the double bond). The two bis (tertiary phosphines) obtained in this investigation are however 1,2-substituted, i.e. the second mole of nucleophile attacks at the 2 position. It should be noted, however, that substitution by alkoxide involves the introduction of a formally charged ion. The allylic shift of the double bond requires the departure of halide ion, and this might not occur from a 1,3- dipolar species, the intermediate in the phosphine reactions. However, there seems no reason why addition and elimination could not give 1,3,3-substitution, e.g. ri A The above scheme may not occur because of steric considerations, i.e. the second attack of nucleophile must also come at the 1 position. This of course is just as applicable to any mechanism giving rise to 1,3,3-substitution. CHAPTER II HEXA FLUOROBUTYNE-2 INTRODUCTION Now commercially available,hexafluorobutyne-2 was originally prepared in 1949, by a dehalogenation process: CF,CC1=CC1GF, + Zn ^ CF-zCSCCF-, + ZnClP 3 3 C2H50H 3 3 2 Early investigation of the acetylene by Haszeldlne included the 54 addition of hydrogen halldes , to give 2-halo-3-H-hexafluoro- 55 54 but-2-enes, and bromine, chlorine and hydrogen . He also found that methanol and ethanol, in the presence of their respective alkoxldes, added across the triple bond RQ CF3CSCCF3 + ROH * CF3CH=C(OR)CF3 Chaney obtained both the mono- and diadducts using ethanol and glyoxal, 57 Krespan et al. added a disulfide group across the triple bond by reacting hot sulfur vapor with the butyne CF3CSCCF3 + S > CF3C=C(CF3)S-S 58 Harris and Stacey obtained the monoadduct from the X-ray induced addition of hydrogen sulfide. Numerous studies have been carried out on the behavior of the butyne towards Group V compounds, Haszeldine ^ in 1952 reacted diethylamine with the acetylene (C2H5)2NH + CF3CsCCP3 > (CgHg)gNC(CF3)=CHCF3 5 7 Krespan obtained a cyclic olefinic compound from red phosphorus at 200° in the presence of iodine, Gacodyl added rapidly and quantitatively to the butyne at (GH3)4As2 + GP3C5CCF3 > (CHg)gAsC(CF3)=C(CF3)As(CHg)g Perfluorocacodyl did not react at 150°, but did give59 the expected adduct on ultra-violet irradiation. Tetrakis(trifluoromethyl)- diphosphine did not react at 150°; at 180° a polymeric material 37 was obtained i Dimethylarsine (20°, fast), methylphenylarsine (20°, slow) and bis(trifluoromethyl)arsine (200°) added as expected to hexaf luorobu tyne -2 • •• '• Rr AaH + CF3C=CCF3 > RgAsC (CF3)=CHCF3 The adducts were predominantly trans. Chlorodimethylarsine added5^ on heating or ultra-violet irradiation (CH3)2AsCl + CF3CsCCF3 (CH3)gAsC(CF3)=CC1CF3 but little or no reaction occurred with other chloro-arsines, Considerable Interest has been shown in the reactions of transition metal compounds with the acetylene. For example, Stone and co-workers -s obtained addition with manganese and rhenium pentacarbonyl hydrides (C0)5MH + CF3CSCCF3 3* (CO )5 MC (CF3)=CHCF3 Cullen and Styan studied the reactions of Group IV M-H and M-M bonds with the butyne% for example, hexamethylditin on ultra- violet Irradiation added v across the triple bond (CH3)6Sn2 + CF3CSCCF3 » (CR"3)3SnC(CF3)=C(CF3)Sn(CHg)3 In.'the following section, the reactions of hexaf luorobutyne-2 with organo compounds of nitrogen, and phosphorus are presented and discussed. EXPERIMENTAL A, Starting Materials 1. The hexafluorobutyne-2 was obtained from Peninsular Chem-Research Inc 2. Chlprodimethylamine was prepared by oxidizing dimethyl- amine hydrochloride with 5 % sodium hypochlorite according to the procedure of Coleman63. Di-n-butyl ether was used as the solvent rather than diethyl ether. The ether solution was then placed in a three-necked flask fitted with a nitrogen bleed, mercury dip thermometers and stiilhead connected to a condenser and a trap coolers, to -78°. The chloro-amine distilled over at 46-52° (majority at 47°)(lit. value 46°)I the distillation was discontinued when the temperature in the flask reached 130°. The ami ner was dried with calcium chloride and freed from butyl ether in the vacuum. sys tern using"., a -36° bath (M, 80,1; GgHgCIN requires 79,5), 3. The preparations of the diphosphines and secondary phosphines have been described in Chapter I, page 7 . The di- and trimethylamines were obtained from Eastman Organic Chemical, and the triphenylphosphine from Columbia Chemicals Co. Inc. Chlorodimethylphosphine was obtained by reacting tetra• methyldiphosphine disulfide with phenyldichlorophosphine according to the procedure of Parshall64, b.p. 73-76° (lit. values64*65 77°, o _ o 73 )•, The majority of the product hcwevsr distilled at 190-I9P - 1 and was shown by 'H n.m.r. spectroscopy to contain roughly 23 % phenyldichlorophosphine and another compound. After removal of a the phenyl-phosphine by reaction with hexafluorobutyne-2 the The MegPClS- 0PClg mixture was sealed up with excess butyne and allowed to stand at 20°. A slow, steady darkening of the lower (phosphine) layer was observed, culminating in a dark brown color. The volatile material was unreacted butyne while the remainder, after distillation, consisted of MegPCIS containing approximately 16 % 0PClg. The process was repeated at 106° (see p.54)e remaining material distilled at 179-181° (760 mm.) and following purifcation by v.p.c. (silicone, 155°), the material was identified a . • +• \ as chlorodimethylphosphine sulfide (Pound': C, 18.20; H, 5.19 %. GgHgClPS requires: C, 18.68; Hs 4.70 %). Infra-red spectrum (liquid film)' 3030 w, 2940 w, 2040 vw, 1400 ms 1350 vw, 1300 m, 1290 m, 1275 s, 1210 w, 948 vs, 909 s, 859 m, 746 vs cm"1. The >.• 'H n.m.r. spectrum consisted of a doublet (J^TT „ = 13.3 c.p.s.) 30 (lit. value 13.4) centred at - 2,29 p.p.m. B. Reactions with Hexafluorobutyne-2 1. Dimethylamlne Hexafluorobutyne-2 (7,4 g, 50.2 mmoles) reacted smoothly at 20° with dimethylamlne (1.5 g, 28.9 mmoles). Unreacted butyne (1.8 g, 11.1 mmoles) passed through a -78° bath, V.p.c. analysis (dinonyl phthalate, 82°) of the -78° fraction (6.2 g) revealed two components. The first (20.3 mole %) was identified as 1,1,1,- 4,4,4-hexafluorobutanone (Pound: C, 26.7; H, 1.31; P, 63.14 %'s M, 182. C4H2P60 requires: C, 26,7; H, 1,12; F, 63.3 %; M, 180), Infra-red spectrum (vapor): 3700 w, 2980 m, 2380 w (broad), 1980 vw, 1790 vs, 1495 w, 1460 n, 1410 vs, 1380 vs, 1320 vs, 1290 vs, 1230 vs, 1170 vs. 1125-'vs, 1020 vs', 981 w (sh), 939 m, 820 s, 735 s cm"1. 1H n.m.r. spectrum: a quartet (J = 9.5 c.p.s.) 0H2 oF3 centred at - 3.12 p.p.m. The main component (79,7 mole %) analyzed to be 2-dlmethyi- amino-3-H-hexafluorobutene-2 (5.1 g, 85 %), b.p. 96-97° (760 mm.) (Pound^":C, 34.5; Hs 3.47; N, 7.25 %, Calc. for Cgl^FgNj Cs 34.8; H, 3.4; N, 6.8 %). Infra-red spectrum (vapor, 98 % trans): 2920 m, 2850 m (sh), '1710 w (sh) (broad) ,• 1659 vs, 1514 m, 1467 m, 1433 ss 1309 vs, 1274 vs, 1239 vs, 1195 vs, 1156 vs, 1128 vs, a v gg Schmutz-ler also finds that chlorodime thylphosphine sulfide is a product of this preparation. 1069 s, 930 m, 859 s, 771 m, 731 w, 696 w, 654 s cm"1. The 1H n.m.r. spectrum of the trans isomer consisted of a quartet (j (geminal) =9.5 c.p.s.) {JTTnT 1 (vicinal)ft* 0 ) centred at H-CF3 "3 —4.63 p.p.m. and a singlet (slight secondary splitting of about 19 1 c.p.s.) at —2.50 p.p.m., relative intensity 1:6. The P 'n.m.r. spectrum (TFA) of the trans isomer consisted of a doublet { (geminal) = 9.4 c.p.s, of septets (J^p = 1,75 c.p.s.) 3 3' centred at —24.8 p.p.m., and a singlet at —11.4 p.p.m. The experiment was repeated in a sealed n.m.r. tube; this gave a trans:cis ratio of 6.20:1. The conversion to 98 % trans was accomplished by distillation under nitrogen, but isomerization could not be achieved in a sealed tube at temperatures up to 160°. It was observed that the reverse isomerization occurred at 20° in the presence of air, as shown in Table II: TABLE IT Isomerization of 2-Dimethylamino-3-H-hexafluorobutene-2 in Air time of exposure to air ratio, trans:cis 10 minutes 6.5:1 25 minutes 1.9:1 2 days 1.65:1 13 days 1.58:1 The n.m.r, spectra of the cis-rich mixture:- : two quartets (J n (geminal) = 9,5 c.p.s.) centred at —4.70 (trans) and H-CP3 -4.26 (cis) p.p.m. and two singlets at -2,54 (trans) and -2.38 (cis) p.p.m.; 19P (TFA)s a multiplet at -24.9 p.p.m. (overlap), a quartet (Jpp p-p = 12.6 c.p.s.) centred at -15.35 p.p.m. (cis), 3 3 and a singlet at —11.05 p.p.m. (trans). 2. Trime thylamine 40 (a) With water: Hexaf luorobutyne-2 (13.41 g, 82.9 mmoles), water (1.30 g, 72.2 mmoles)and trimethylamine (6.36 g, 107.9 mmoles) reacted vigorously at 2.0°• The mixture passed through several pronounced color changes involving deep greens and blues, finally terminating in a dark red-brown color. All the butyne was consumed. Carbon dioxide (0.5 g, 13.7 % based on butyne), of known infra• red spectrum,passed through a -130° bath. A fraction passing through a -64° bath (8.6 g) contained unreacted trimsthylamine. The amine (4.5 g) was removed with 50 % acetic acidj the remaining material (4.1 g, 2-7 % of butyne) was identified as trans-3-H- heptafluorobutene-2 (M(mass spectrum), 182. Calc. for C^HPr, , 182). Infra-red spectrun (vapor): 3200 w, 3050 vw (broad), 2850 vw, 2650 vw, 2500 vw, 2400 w, 2300w, 2150 vw, 2050 w, 1940 vw, 1730 s, 1600 w, 1520 w, 1430 m (sh), 1390 s, 1300 vs, 1275 vs (sh), 1270 vs, 1215 vs (sh), 1210 vs, 1195 vs, 1185 vs, 1175 vs (sh), 1115 m, 1090 w (sh), 1060 s, 1020 vw, 937 w, 864 s, 825 m, 735 s cm"1. •*"H n.m.r. spectrum: a doublet (J = 29 c.p.s.) of quartets H—F v(j (geminal& ) = 7.0 c.p.s.) (J (vieinal)0) centred at H-CF3 . . H'-CF, - 5.20 p.p.m. P n.m.r. spectrum (TFA): a multiplet (see p.43) centred at + 22:..1 p.p.m., a doublet (JQP =p(geminal) = 9.25 c.p.s.) 3 of approximate quartets (J = 1.35 c.p.s.), (^cp „CF superimposed 3 3 on weak vicinal CP -H coupling) centred at - 0.57 p.p.m., and a 3 doublet (J„ „(vicinal) = 17.0 c.p.s.) of doublets (J „ w(gemlnal) = 6.8 c.p.s.) of quartets (Jcp _cp = 1.6 c.p.s.) centred at 3 3 - 8.38 p.p.m. The fraction stopping in the -64° trap (6.0 g) was shown by v.p.c. analysis (dlnonyl phthalate, 91°) to contain three major components. The first and third were of essentially equal area (total 38.1 mole %); these were 1,1,1,4,4,4-hexafluorobutanone ' 41 (0.72 gj 4.8 fo) and 2-dimethylamino-3-H-hexafluorobutene-2 (0.83 g, 4.8 %) respectively, of known infra-red spectra. The middle component (61.9 mole %) was identified as cis-3-H-hexafluorobut-2- enyl-trans-3-H-hexafluorobut-2-enyl ether ('4.45 g, 31.4 %), b.p. 104-105° (760 mm.) (Found, :C, 27.95; H, 0.68; F, 66.35 %; M(mass spectrum), 342. Calc. for CgHpF^OsC, 27.95; H, 0.59; F, 66.65 %; it, M, 342. Infra-red spectrum (vapor): 3200 w, 2035 vw, 1693 s, 1397 vs, 1383 s (sh):, 1304'vs, 1276 vs, 1269 vs (sh), 1219 vs, 1186 vs, 1166 vs, 1115 vs, 1035 m, 918 s, 857 m, 826 w, 750 m, 731 m, 717 m, 691 m cmT1 "'"H n.m.r. spectrum: a quartet (trans moiety) (JVrn w (geminal) = 7 c.p.s.) centred at -5.88 p.p.m. and a H-C*3 quartet (cis) (JVr «™ (geminal) = 8 c.p.s.) centred at -5;13 p.p.m.. Although JH-GF (vicinal)#°» quartet of the trans moiety is 3 in somewhat less well resolved. The P n.m.r. spectrum (TFA) is shown In Table III: ... TABLE III 19 F n..m«r. Spectrum (TPA) of the Butenyl Ether Cis Moiety £(p.p.m. ) JGp „CF (c.pvs..) JQp ^(vicinal) JGp _H(geminal) 3 33 3 3 -21.5 10.2 — . • • 7.8 - 8.06 10.2 Trans Moiety -15.82 <2 —:,.'' 7.1 - 6.31 <2 <2 ~- The experiment was repeated with the mixture being cooled during the reaction, then slowly allowed to reach room temperature. Again a series of blues and greens was observed, with a blue-green colour persisting at 20°. After one day the colour was green; after one week, red-brown. The main product was the butenyl-ether. A small amount of the dlmethylamino-butene was produced along with an unidentified liquid (M(mass spectrum), 566) whose analysis cor• responded roughly with the empirical formula G-^jJi^F^^' Also formed were traces of the hexafluorobutanone and carbon dioxide, but the heptafluorobutene was absent. Both experiments yielded moderately small amounts of red- brown solid, Elution with ace tone dissolved a red-brown paste which was mostly undlstillable. The remaining white acetone-in• soluble crystals were soluble In alcohol and water, gave a pre- ++ clpltate with Ca , and released trimethylamine on treatment with NaOH. (b) In the absence of water % Hexafluorobutyne-2 (1.64 g, 10.1 mmoles) (dried over P 0 ) and:trlmethylamine (5.72 g, 97.0 mmoles) 2 o formed one colorless liquid phase at -78 . At 20° a small amount of flocculent white precipitate appeared; the liquid phase was pale blue. After two days the color of the liquid was a very pale dirty yellow-green. The volatile material (colorless) passed through a -64° bath and consisted entirely of the reactants, of known infra• red spectra. The solid analyzed as a polymer of the butyne (0.29 g, 17,7$), m.p0>550° (Pounds C, 29.85; H, 0.20; P, 70.25 %. Calc. for (C4P6)ns C, 29.6; H, 0.00; F, 70.4 %). Infra-red spec• trum (Nujol and halocarbon mulls); 2940 vw, 2280 vw, 1630 w (broad) 1190 vs (very broad), 894 vw (sh), 878 m, 772 w, 715 m vm"1 The volatile material when returned to a clean Carius tube gave a repeat of the reaction. The reaction was repeated using a 2% 1 molar ratio of butyne to amine. A slight amount of the polymer was found at -78°, but- otherwise the observations were identical with those using excess 43 44 amine. The reaction was worked up after ten minutes at 20°. The blue color remained in the tube and disappeared when the liquid had all been pumped off, leaving the white solid (some yellow- green coloration). The material was again sealed up and allowed to stand (20°, 2 days). The volatile material was again unreacted butyne and amine c ontaining a trace of 2-dimethylamino-3~H-hexa- fluorobutene-2. The solid again was the high polymer of the butyne. 3. Chloro dl me thylamine Hexafluorobutyne-2 (8.20 g, 50.6 mmoles) and chlorodimethyl• amine (3.98 g, 50.1 mmoles) did not react at 20°. Irradiation with ultra-violet light (23 hrs.) resulted in reaction, but work• up revealed unconsumed reactants. The material was irradiated further (46 hrs. total) in the presence of additional butyne (5,6 g, 34.6 mmoles) in a clean Carius tube. Again the reaction was not complete, but infra-red analysis revealed 2-chloro-3-H-hexa- fluorobutene-2 (p.53) to be present among the unconsumed chloro- amine, condensing in a trap cooled to -78°. The products stopping in a -46° trap (1.58 g) were analyzed by vapor phase chromatography; the remaining material was combined with additional amine (3.97 g, 50.0 mmoles) and butyne (8.2-4 g, 50.9 mmoles) and heated (139°, 19 hrs.). Total reactantsi 7.95 g chlorodimethylamine (100.1 mmoles) and 22.04 g butyne (136.1 mmoles). The above -46° condensate gave a very complex v.p.c. spectrum (silicone, 91°). The large peak (63 mole %) was Identified as cis- 3-chloro-2-dimethylaminohexafluorobutene-2, b.p. 102° (cap. rise) (Found^S C, 29.97; H, 2.71; 01, 14.40; F, 47.39; N, 6.11 %. Calc. for C6H6C1F6N; C, 29.82; H, 2.50; CI, 14.67; F, 47.19; N, 5.80 %). Infra-red spectrum (liquid film): 2940 w, 2820 vw (sh), 1695 w, 1590 s, 1470 vw (sh), 1095 s, 1065 vw, 980 s, 805 m, 844 m, 739 w, 717 vw, 700 w cm. The H n.m.r. spectrum showed a singlet at -2.50 p.p.m., while the 19P n.m.r. spectrum (CFClg) consisted of two quartets (JCF _CF = 13.5 c.p.s.) at +60.3 and +61.7 p.p.m. 3 3 The thermal reaction gave a considerable quantity of dark brown solid. Work-up of the volatile products gave trans-2-chloro-3-H- hexafluorobutene-2 (7.50 g, 37.8 mmoles)(27.75 % based on butyne) of known Infra-red spectrum (p.53), condensing in a -78° trap. A fraction which passed through this trap was separated by means of a -126° bath into trans-3-H-heptafluorobutene-2 (1.60 g, 8.8 mmoles, 604 5$) of known infra-red spectrum (p.40), and a small quantity of more volatile material which was not identified. The products of lesser volatility (2.57 g) were condensed into a trap cooled to -46° and subjected to v.p.c. analysis (silicone, o, 92 ). The spectrum showed eight components. Although the fifth, seventh, and eighth were large enough for collection, none could be identified. Chlorodimethylamine (3.98 g, 50,1 mmoles) and hexafluorobutyne-2 (11.78 g, 72.7 mmoles) did not react appreciably at 65° (19 hrs.). After 17 hrs. at 85° considerable reaction occurred, although un- reacted chloroamine was s till present as determined by monitoring with infra-red spectroscopy. An additional 22 hrs. at 85° resulted in consumption of all chloro-amlne and butyne. The products pas• sing through a -46° bath were separated by means of a -78° bath into trans-3-H-heptafluorobutene-2 (0.64 g, 3.5 mmoles, 4.85$) and trans- 2-chloro-3~H-hexafluorobutene-2 (2.04 g, 10.3 mmoles, 14.15$). The remaining volatile material condensed in a -46° trap, leaving an involatile yellow oil in the tube. The -46° condensate (7.4 5 g) was distilled at 760 mm.; four cuts were taken: 83-95°, 96-102°, 106-112° (most at 109°), 113-122°. The first, second, and fourth 46 were combined and analyzed by v.p.c. (Kel P grease, 106 ). The mixture consisted of nine components; the third (21.7 mole %), fifth (28.5 %) and eighth (30.5 %) were isolated and identified. The third distillation cut was shown by v.p.c. analysis to consist of 74 mole % component eight. Component three analyzed as per- fluoro-t-butyl chloride (Found C, 19.23; H, 0.00; Gl, 14.47; P, 66.96 %. Calc. for C4FQC1: C, 18.90; H, 0.00; Cl, 13.94; F, 67.2 fc). Infra-red spectrum (liquid film): 1700 vw (broad), 1640 vw, 1380 w, 1335 vw, 1320 m (sh), 1240 vs, 1205 vs, 1175 vs, 1100 vw, 1000 vw, 935 m, 885 vw, 877 vw, 844 m, 820 w, 735 vw (sh), -1 19 733 w cm. The F n.m.r. spectrum contained a singlet at +65,4 p.p.m. The fifth component was trans-3-H-2-dimethylaminohexafluoro• butene-2, of previously determined (p.38) Infra-red and n.m.r. spectra." The eighth component was cis-3-chloro-2-dimethylamino- hexafluorobutene-2, of known infra-red and F n.m.r. spectra (p.44). 4. Bis(trifluoromethyl)phosphine Hexafluorobutyne-2 (6.0 g, 37.1 mmoles) and the phosphine (1.2 g, 7.06 mmoles) reacted only slightly at 105° (38 hrs.). Ultra• violet Irradiation (5 days) produced some reaction. A fraction (5.75 g) passing through a -78° bath was unreacted butyne and phos• phine with a trace of fluoroform. The -78° fraction was separated into a -36° fraction (0.37 g), and two fractions, stopping (0.32 g) and passing through (0.27 g) a -46° trap. The first was identified as a bis(bis(trifluoromethyl)phos- phino)-l,l,l,4,4,4-hexafluorobutane (21$) (Found: C, 19.01; H, 0.03; F, 67.89; P, 12.17 Calc. for C8R"2F18P2: C, 19.14; H, 0.40; F, 68.1; P, 12.36 %). Infra-red spectrum (vapor):; 2780 vw (broad), 2410 vw, 1630 vw, 1290 m (sh), 1265 vs (sh), 1250 vs, 1220 vs (sh), 1190 vs, 1150 vs, 1135 vs, 1120 vs, 1095 w (sh), 1020 w, 948 w (broad), 926 vw (sh), 830 w, 800 vw, 746 m, 728 m cm. H n.m.r. spectrum: two broad very complex bands centred at -6.95 19 and -2.9 p.p.m. (area ratio 1:1). The P n.m.r. spectrum (CFC1 ) o consisted of a complex band whose most intense peak was at +51.3 p.p.m. The second (-46° trap) component was identified as bis(tri- fluoromethyl)phosphino-1,1,1,4,4,4-hexafluorobutene-2 (Pound: C, 21.48; H, 0.28; P, 68.68; P, 9.50 %. Calc. for 0^HP1oP: C, 21.71; 6 1*2 H, 0.33; F, 68.65; P, 9.34 %). Infra-red spectrum (vapor)j 2860 vw (broad), 2410 w, 1760 vw, 1630 m, 1380 w, 1335 s (sh), 1310 vs (ah), 1260 vs, 1240 vs, 1210 vs, 1190 vs, 1170 vs (sh), 1150 vs, 1135 vs, 1110 vs (sh), 1020 s, 971 m, 948 w (sh), 939 w (sh), 921 vw (sh), 896 vw, 885. w, 859 vw, 800 w, 746 s, 727 m, 705 m, 671 s cm?1 XH n.m.r. spectrum:: a quartet (J = 7 c.p.s.), with slight secondary splitting (J«l c.p.s.) centred at -7.18 p.p.m,; a broad very complex band centred at -6.55 p.p.m.; and a broad complex band centred at approximately -2.6 p.p.m. Area ratios 1:3.89:2.76. 19 The F n.m.r. spectrum (CFClg) contained two very complex bands centred approximately at +59.9 and +48.2 p.p.m. The third component (through a -46° trap) also analyzed to \ \ be bis(trifluoromethyl)phosphlno-1,1,1,4,4,4-hexafluorobutene-2 (total 25$) (Pound: C, 21.54; H, 0.36; F, 68,45 %)„ Infra-red spectrum (vapor): 2860 vw (broad), 2380 w, 1760 vw, 1670 m, 1610 w, 1480 vw, 1420 m, 1390 m (sh), 1370 s, 1325 s, 1310 vs, 1290 vs, 1260 vs, 1240 vs (sh), 1205 vs, 1190 vs, 1165 vs, 1150 vs, 1130 vs, 1075 w, 1015 s, 990 m, 966 w, 948 w, 885 w (sh), 870 m, 82:4 vw, 747 m, 707 m, 667 s cm/ "^H :n.m.r. spectrum: broad com• plex bands centred at -7.2, -6.5,-5.65 and -2.55 p.p.m. (area 19 ratios roughly l::4sls2). The F n.m.r. spectrum (CFC1 )C on- 48 sis ted of two very complex bands centred at roughly +60.35 and + 50.1 p.p.m. 5. Diphenylphosphine Hexafluorobutyne (8.6 g, 53.0 mmoles) and the phosphine (6.1 g, 32.8 mmoles) reacted vigorously on mixing to give a dark red syrupy liquid. The mixture contained only a trace of volatile material. The product was extracted with chloroform and distilled 3 at 10" mm. The middle cut (127°) analyzed to be 2-diphenyl- phosphino-3-H-hexafluorobutene-2 (Pound: C, 55.05; H, 2.96; H F P: Cj 55 2 F, 32.92; P, 8.74 M (Rast), 353. Gale, for G16 n 6 « J H, 3.16; F, 32.8; P, 8.91 %; M, 348). Infra-red spectrum^ (liquid film): 3100 w, 1641 w, 1596 vw, 1488w, 1445 m, 1367 w,, a a a a 1334 w, 1282 s (sh), 1263 vs, 1238 vs (broad), 1202 Vs (sh) (broad), 1167a s (sh), 1119a m (sh), 1091 w, 1072 w, 1026 w, 1000 w, 881 w, 858 w, 841 vw (sh), 742 s, 733 vw (sh), 694 s cm."1 ^H n.m.r. spectrum: -a large aromatic peak at -6.85 p.p.m.; a quartet (J „ =8 c.p.s.) centred at -5.22 p.p.m., and a multi- H-CF3 plet extending from the base of the aromatic peak (-6.6 p.p.m.) upfield to -5.84 p.p.m. 6.. Tetraphenyl diphosphine The diphosphine (6.0 g, 16.2 mmoles) reacted readily with hexafluorobutyne-2 (12.4 g, 76.6 mmoles) at 130° (2 hrs.). Unreacted butyne (10.5 g, 64.8 mmoles) was recovered; small amounts of carbon dioxide and silicon tetrafluoride, of known infra-red spectra, were produced. The non-volatile product was extracted — 3 with chloroform and twice distilled at 10 mm. A fraction distilling at 138-141° was identified as 2,3-bis(diphenylphosphino)- hexafluorobutene-2 (Found: C, 63.23; H, 3.90; F, 21.34; P, 11.55 $; a CC14 solution 49 c H F P M (Rast), 269. Calc. for 28 20 6 g5 C, 63.1; H, 3*76; Ps .21.4; P, 11.65 %\ M, 532). Infra-red spectrum^ (liquid film): 3080 vw (broad), 1592 m, 1488 vw, 1443 s, 1365 vw, 1258 vs, 1162 s(broad), 1135 vs, 1114 m (sh), 1068 vw, 1025 w, .995 vw, 961 vw (broadly 837 s,751 s, 730 vs, 690 vs cm."1 The 1 H n.m.r. spectrum consisted of a broad (25 c.p.s.) multiplet of eight p|pks (ortho hydrogen), area ratio 2, centred at -7.30 p.p.m., and a much narrower band (meta-para hydrogen) centred at -6.84, p.p.m. The 19 latter peak showed distinct splitting (J£* 3 c.p.s.). The p n.m.r. spectrum (TFA) contained a doublet (J^p _p = 313 c.p.s.) of quartets (Jnr, ^10 c.p.s.) centred at -21.9 p.p.m. A doublet 0*3-0*3 (Jp_p = 1024 c.p.s.) centred at -4.1 p.p.m. indicated the presence of fluorodiphenylphosphine oxide (p.Il). 7. Triphenylphosphine j Triphenylphospine (5.03 g, 19.2 mmoles) in tolu'ene (12 cc.) reacted immediately on mixing with hexafluorobutyne-2 (15.81 g, 97.7 mmoles); the reaction was vigorous in a -78° bath. Copious amounts of solid were produced. Unreacted toluene (11 cc) was recovered in a -78° trap. ' A very small amount of unidentified material passed through this trap. The Involatile material was washed four times with chloroform. The residue (14.60 g, 92.4 %) was the high polymer of the butyne, of known infra-red spectrum (p.42). The dissolved material was recrystallized from cyclohexarie. The first crop (0.8 g) was unreacted triphenylphosphine;.the second (0.4-g) was identified as triphenylphosphine oxide, m.p. 150-1*53° (lit. value67 152-153°), 1 68 1 2)?=Q, 1190 cmr (lit. value H90 cm" ) (Found: C, 78.06; H, 5.51; P, 9.82 %\ M(Rast), 292. C^H^PO requires: C, 77.7; H, 5.54; P, ll.ll.5g; M, 278). 50 In the absence of solvent the phosphine and butyne did not react at room temperature. Very gentle heating however quickly triggered a violent reaction. 8. Diethylphosphine Hexafluorobutyne-2 (9.8 g, 60.5 mmoles) reacted very vigorously on mixing with diethylphosphine (1.5 g, 16.7 mmoles); the reaction was controlled by cooling the sealed tube In a -78° bath. Unreacted butyne (5.64 g, 34.8 mmoles.) passed through a o o -78 bath. The -78 fraotlon was separated into an unidentified yellow oil (0.23 g, stopping in a -15° trap) and trans-2-diethyl- pho3phino-3-H-hexafluorobutene-2 (1.9 g, 45$), b.p. 132° (cap. rise) (Found*; C, 37.84; H, 4.30;-F, 42.66; P, 12.20 $. Calc. for CQH-L^P; C, 38.11; H, 4.40; F, 45.22; P, 12.27 $). Infra• red spectrum* (liquid film); 2980 w, 2920 w (sh), 1636 vw, 1466 w 1432 vw, 1387 vw, 1340 m, 1290 w (sh), 1253 s, 1145 vs, 1051 vw, 1029 vw, 1014 vw, 876 vW, §51 w, 765 vw,. 747 VW, 684 vw, 645 in omT •^•H n.m.r. spectrum (p. 5l): a doublet (Jjj^p = 20 c.p.s.) of quar• tets (JH-Cp (geminal) = 7*4 c.p.s.) of quartets (Jg^Qp (vicinal) 3 - A . • . • • • "33 = 1.7 c.p.s.) centred at *-6.63 p.p.m.; a multiplet (-CHg-) cen• tred at -1.48 p.p.m.; and a multiplet (5 peaks) («GHg) (.^{j* 7 Cip.s«) centred at -0*82 p.p.m. The relative intensity of the 19- ethyi to olefinic protons was 11:1 (calc* 10:1)* The F rnnur* 'spectrum (CFClg) consisted of a doublet (Jgfi j (Vicinal) S3 53 3 Cip»s.) of doublets {w(geminal)ftJ 7*5 c«pii* centreda t • - Gig-H +57.0 p.pim.* and a siriglet •( JQ£ -p(gemin&l)«* 0) at +61*8 p.p.m. 3 The IriVolatile material contained the high polymer of the butyne, iii addition^tQ more unidentified yellow oil (0.1 g). - \,V: 9. Te tr ame thyldipho sphihe HexaflUorobUtyne*2 (9.19 g, 56.7 inmoles) and tetiramethyldi- -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 - 1.0 ppm(8) Figure 3: 1H n.m.r. Spectrum of trans-2-Diethylphosphino-3-H-hexafluorobutene-2. Curve 2 is an expansion of the downfield multiplets. phosphine (2.,43 g, 19.9 mmoles) reacted violently as the latter began to melt. The reaction was quenched with a -23° bath and then allowed to proceed by removing the tube from the bath. The process was repeated several times until all the diphosphine was consumed. The products appeared as a brown-black mass. The vol• atile matter was worked up initially using a -78° bath. The mat• erial which passed through was separated by means of a -130° bath into unreacted butyne (3.39 g,. 20.9 mmoles) and a small quantity of more-volatile material which contained silicon tetrafluoride. The -78° fraction was worked up using a -23° bath. The material which passed through the bath (0.88 g) was purified by v.p.c. (Kel F grease, 105°) and identified as methyldifluorophosphine 1 30 oxide, of known • H n.m.r. spectrum s a doublet {JNTR - = 20.0 CH3-P c.p.s.) of triplets (J„TT „ = 6.3 c.p.s.).. (Founds J _ = 2.0 5 19 un3"r c.p.s., J = 6,0 c.p.s.).' The F n.m.r. spectrum (CFC'l,) 3"* j contained a doublet (Jp_p = 1102 c.p.s.) of quartets ( F_GJJ = Q 3 5.5 c.p.s.) centred at +62.2 p.p;.m. The -23 condensate (0.25 g) decomposed in vacuo within a week and could not be Identified by elemental analysis. The following.spectra were obtained before decomposition. Infra-red spectrum^ (liquid film)t 3120 m (sh) (broad), 2970 m, 2895 m, 1742 w, 1711 vw, 1699 vw, 1680 vw, 1420 w 1365 w, 1311 s, 1306 s, 1250 vs, 1239 vs, 1215 vs (broad), 1.165 vs (broad), 1042 vw, 945 s, 883 s, 813 m (sh) (broad), 759 w, 718 im cm." H n.m.r. spectrums a doublet (J = 14.75 c.p.s.) of doublet ' v 19 (J = 8.45 c.p.s.) centred at -1.41 p.p.m. F n.m.r. spectrum (CFC1 )s. two broad (^30 c.p.s. at half height) unresolvable bands 3 of equal intensity, at +63.5 and +74.0 p.p.m. 10. Chlorodimethylphosphine Hexafluorobutyne-2•(15.86 g, 97.8 mmoles) reacted vigorously with the phosphine (5.06 g, 52.5 mmoles) on mixing; the reaction could not successfully be controlled by cooling because of the high melting point of the phosphine (-1° 65). A considerable am• ount of dark brown solid was formed. Unreacted butyne (8.24 g) passed through a -78° bath. The o oo -78 fraction was separated with -46 and -64 baths into three components. The fraction which passed through the -64° trap (4.19 g, 21$) was identified as trans-2-chloro-3-H-hexafluoro• butene-2 (Found: C, 24.07; H, 0.44; CI, 17.73; F, 57.18 $; M, 193. C.HC1F' requires: G, 24.20; H, 0.51; CI, 17.88; F, 57.42 $; 4 6 M, 198.5). Tnfra-red spectrum (vapor) s 3180 w, 2350 vw, 2170 vw, 2040 vw, 1670 vs, 1505 vw, 1410 vw, 1320 vs, 1290 vs, 1260 vs, 1185 vs, 1165 vs, 1100 m, 1020 m, 957 vs, 859 s, 739 m, 712 m cmT1 The '''H n.m.r, spectrum consisted of a quartet (J^ _„ (geminal) = . ... a.—or g 6.7 c.p.s.) of quartets (J (vicinal) = 1.0 c.p.s.) centred at H cp • 19 " - 3 -6.21 p.p.m. The F n.m.r. spectrum is shown below in Table IV: TABLE IV 19 F n.m.r, Spectrum (CFClg) of trans-2-Chloro-3-H-hexafluorobutene &(p.p.m.) JQF _CF (c.p.s.) JQP__h(geminal) JCP _H(vicinal) 3 3 5 3J F°""d vaV value69 value Found ^ +63.4 +61.2 1.3 1.0 6.6 (6.7 ) 5.4 +73.2, +70.8 -- -- 1.0 1.2 s. Internal standard Obtained from the H n.m.r. spectrum The -64° component (0.62 g, 10$) was trifluorodimethylphosphorsne, 1 19 of known infra-red, and H and p n.m.r., spectra (p.14). n 19 The -46 fraction was not fully characterized.' The F n.m.r 1 ' spectrum was complex. The H n.m.r. spectrum strongly suggested 2-dimethylphosphino-3-H-hexafluorobutene-2 containing some fluorodimethylphosphine oxide: a doublet (J = 27 c.p.s.) of quartets (J = 8.2 c.p.s.) centred at -6.36 p.p.m, and a doublet (J = 14 c.p.s.) centred at -1.64 p.p.m,, relative intensity approximately 1:6 (calc. 1:6); in addition a doublet (J = 15 c.p.s.) of doublets (J = 8,2 c.p.s.) was centred at -1.23 p.p.m. (li t. values" for „)pPPO: j = 16S.J„W _ = 8.9 c.p.s.). Purification by (CHo *s CHg-r on^-r v.p.c, was attempted but this resulted in the loss of the small amount of material. 11. Chlorodimethylphosphine Sulfide The impure (see page 37) sulfide (2.92 g) was heated with hexa- fluorobutyne-2 (10,17 g) at 106° (24 hrs,),. The mixture still consisted of two liquid•phases although the lower was very dark brown. All liquid material entered the vacuum system. Subsequent work-up yielded unreacted chlorodimethylphosphine sulfide (1.65 g), free from phenyldichlorophosphine, Unreacted butyne (8.64 g) passed through a -78° trap (M, 162; C4Fg requires 162), The -78° fraction was separated by a -64° bath into trans-2-chloro-3-H- hexafluorobutene-2 (0,32 g) of known infra-red spectrum, and an unidentified material (0.44 g) of complex XH n.m.r. and infra-red spectra, The sulfide (1,49 g, 11.6 mmoles) and butyne (8.64 g, 53.3 mmoles) did not react on irradiation with ultra-violet light ( 52 hrs.)» 12, Tetramethyldiphosphine Di sulfide (a) Trifluoromethyl iodide Tetramethyldiphosphine disulfide (6.27 g, 33.7 mmoles) and trifluoromethyl iodide (20.65 g, 105 mmoles) did not react appreciably at 104° (24 hrs.). The mixture was then subjected 0 5 to ultra-violet Irradiation (6 days). Unchanged trifluoromethyl iodide (19.82 g, 101 mmoles) passed through a -96° bath, while traces of fluoroform, of known infra-red spectrum, passed through a trap cooled to -130°, A small fraction (0,2 g) which condensed in a -78° trap was identified as fluorodimethylphosphine sulfide (Pound: C, 21,72; H, 5.52; P, 16.93 %. CgHgFPS requires: C, 21.44; •l H, 5.36; F, 16.96 %). H n.m.r. spectrum: a doublet (J = 13.8 On,,— r c.p.s.) of doublets (JQJJ _p = 8.0 c.p.s.) (lit. values 13.7, 8.0 3" c.p.s.) centred at -1.93 p.p.m. The non-volatile material consisted almost entirely of unchanged diphosphine disulfide, of 1 known infra-red and ""H n.m.r, spectra. The non-volatile material was washed with aqueous sodium bicarbonate and the filtrate acidified and shaken with diethyl ether. The ether layer was evaporated to dryness. Only a slight amount of material remained; this was largely tetramethyldiphosphine disulfide, (b) Iodine A solution^of iodine (1.27 g, 5.00 mmoles). in chloroform was added dropwise with stirring to a solution of tetramethyl• diphosphine disulfide (0,93 g, 5.00 mmoles) in chloroform. The purple color Immediately changed to the characteristic red-brown color of iodineinoxygenated solvents. Evaporation of the solvent afforded red-brown crystals, m.p, 92° dec, whose % n.m0r. spectrum (CHClg solution) was structurally identical with that of tetramethyldi• phosphine disulfide. The infra-red spectra of tetramethyldiphos• phine disulfide and the complex with iodine are presented in Table V, Table V, Infra-Red Spectra8 of Tetramethyldiphosphine Disulfide and the 1:1 Complex with Iodine (cmT^") TABLE V Infra-red Spectraa of Tetramethyldiphosphine Disulfide and the lsl Complex with Iodine' (cmT1)' (CH3)'4P2Sp • 1390 m 1275 s 935 s 881 vs 859 w (sh) 8854'vw 746 m 733 s 569 vs (broad) (CH„) .P'S- *I0 1400 m 1280*1275 w 950 s 878 s 863 w (sh) 829 vw 752 w 727 s 554 s (broad) Nujol mulls A 251 molar ratio of iodine to disulfide resulted in moderate decomposition of the latter (1 day), as determined by "''H n.m.r. spectroscopy. A 10:1 ratio gave complete decomposition of the diphosphine disulfide. The 111 complex slowly lost Iodine when allowed to stand open to the air, but was stable indefinitely in a closed container. Treatment of the complex with aqueous potas• sium iodide readily afforded the uncomplexed disulfide. A solu• tion of tetraethyldiphosphine disulfide in chloroform also gave the red-brown color on treatment with iodine. DISCUSSION A o Ni trogen Compounds I. Results (a) Dime thylamine The reaction between hexafluorobutyne-2 and dimethylamine was Investigated in order to study the geometry of the expected adduct, to shed further light on the mechanism of this type of reaction. Dimethylamine and hexafluorobutyne-2 give 1,1,1,4,4, 4-hexaf luoro- butanone and 2~dimethylamino-3-H-hexafluorobutene-2, b.p* 96-97°, the latter in 85 % yield: (CHg)gNH + CF3C«CGF3 » (CH3)2NC(CF3)=CHCF3 + CFgCOCHgCFg The ketone was identified by elemental analysis and molecular weight. The infra-red spectrum shows a strong carbonyl absorption 1 T at 1790 cm. and the ~H n.m.r. spectrum gives the expected quartet (JH-CF = 9.5 c.p.s.}. 3 The main reaction product, the 1:1 adduct, was identified by microanalysis, and the isomer distribution was established by n.m.r, spectroscopy. . The 1H n.m.r. spectrum of the trans isomer consisted of a downfield quartet UH_CP (geminal) = 9.5 c.p.s.), 5 (j (vicinal)fiJ 0) and an upfield singlet (slight secondary H—CF3 splitting), relative intensity 1:6. Such geminal and vicinal H-CF coupling is now well known to fall in the ranges 6-10 and 0=2.5 c.p.s, respectively, e.g. in the case of trans-2-dimethyl- 60 arsino-3-H-hexafluorobutene-2, the couplings are 8.3 and 2.0 c.p.3, The H n.m.r,, spectrum of the cis-aminobutene is identical with that of the trans isomer, with the two bands to slightly higher field. The assignments of the sets of signals to trans and cis 19 configurations is corroborated by F n.m.r. analysis of the pure 58 trans isomer, and of an isomer mixture. The cis CF^-CF^ coupling is an order of magnitude greater than that of the trans, consistent with earlier observations61'62 and other findings of this investigation. The 1^F.n.m.r. spectrum of the amino-butene is noteworthy for the apparent cis vicinal CF^-CH^ coupling (1.75 c.p.s.) occurring in the trans isomer. This long range (6-bond) coupling is of similar magnitude to that observed In o-fluoro-N-cyclohexyl- 70 N-methylbenzamide . This vicinal coupling of the fluorine atoms with the methylprotons suggests an appreciable contribution from resonance, i.e. CF3 H CF3 H c 4- > / C—C\ X CF3 CF3 This would provide the conjugation presumably necessary for the observed CF,-CH coupling. A further manifestation of such ^3 delocalizing of the lone pair would be a lowering of proton affinity. The compound is in fact only very slightly soluble in 12N hydro• chloric acid. The reaction conducted in an n.m.r. tube gives a transscis ratio of the product of 6.2rl. The amino-butene on distillation under nitrogen is isomerized essentially quantitatively into the trans form; however, heating in a sealed tube at temperatures up to 160° fails to effect Isomerization. A reverse transformation takes place on exposure to the atmosphere at 20°. Thus a trans- rich mixture is quickly converted to roughly 40 % cis on exposure (b) Tr ime thylamIne As already described, 1,1,1,4,4,4-hexafluorobutanone is a by-product of the synthesis of 2~dimethylamino-3-H=hexafluorobut• ene-2 from (wet) dimethylamine and hexafluorobutyne-2; i.e. the amine apparently catalyzed the hydration of the butyne (see dis• cussion of mechanisms)? GF3^C0F3 + HgO (c%)8m> CP6COO V8 It was thought that trimethylamine would give a much higher yield of the butanone than does dimethylamine, since the latter Itself reacts readily with the butyne and is thus removed,while the ter• tiary amine would not be consumed. Hexafluorobutyne-2, water and trimethylamine react vigorously at 20° to give six compounds, as listed in Table VI TABLE VI Products of the Reaction CF3C£CCF3 + HgO + (CH ) N Product Yielda, % C0g 13.7 trans-CF3CH=CFCF3 27.0 CF3G0CH2CF3 4.8 (CH3)2NC(CF3)=CHCF3 4,8 OF, JCF, G=G N H^ ° 0V JCF, 31,4 ^G=G; 3 N CF(f H • 3 (CH3)3NHF a ": Based on hexafluorobutyne-2 h 1 The trimethylamine was shown by H n.m.r. spectroscopy to be free from dimethylamine The carbon dioxide, hexafluorobutanone and amino-butene were id• entified by their known infra-r'ed spectra. The heptafluorobutene was Identified by Its mass spectrum which showed a parent peak at m/e = 182.. Other strong peaks were present at 163 (182-P)S 1 19 113 (182-CF3) and 69 (CFg). The H and F n.m.r. spectra are mutually consistent and in accord with the assigned structure. The complex resonance of the olefinic fluorine atom is shown in ! Figure 2 (p.43'' . The same coupling,.JH_F(trans) = 29 c.p.s., is 1 also obtained from the H n.m.r0 spectrum. The butenyl-ether, b.p. 104-105°, was identified by micro• analysis and the mass spectrum. The latter showed a parent ion at m/e ='®42, with other strong peaks at 323 (342-F), 273 (342-CF3), 1 19 16S (GF3CCCF3) and 69 (CFg). The H and F n.m.r. spectra, mut• ually consistent, allow complete elucidation of the geometry of the molecule. The "*"H n.m.r. spectrum consisted of two quartets, of equal area, showing expected magnitude of splitting for geminal 19 H-CF3 interaction, as shown in Figure 4. The F n.m..r. spectrum •consisted of four signals of equal intensity. The splittings are shown in the figure. Figure 4: Coupling Constants in the Butenyl-ether Although an equimolar mixture of the trans-trans and cis-cis ethers might be expected to have the observed n.m.r. spectra, the trans- els ether is favored, V.p.c. analysis (Kel F grease, 100°) showed only one peak. 61 The trimethyiammonium fluoride was identified by the pos• itive test for fluoride ion and the generation of trimethylamine on treatment with strong base. When the reaction between hexafluorobutyne-2, water and tri• methylamine is carried out below room temperature and the mixture is allowed to reach 20° only very slowly,, the butyne is largely converted into the butenyl-ether: 2 CP3CSCCF5 + HgO -j—^£F3CH=C CCP3IJ ^ Small amounts of 2-dimethylamino-3-H-hexafluorobutene-2 aid an unidentified liquid are obtained together with traces of carbon dioxide and-..the hexaf luorobutanone. The heptaf luorobutene is not formed. Trimethylammonium fluoride is again observed. In the absence of water, a 10:1 molar ratio of trimethylamine: hexafluorobutyne-2 gives a pale blue solution at 20° which slowly deposits a high polymer of the butyne in 18$ yield over two days. The white solid, Identified,by elemental analysis, has m.p.> 350° and is insoluble in organic solvents or strong acids. The re• maining butyne is not consumed. A 2:1 ratio of butyne to amine also produces a pale blue color, which disappears if the volatile material is pumped from the tube. The blue color forms again If the material is returned to a clean Carius tube. Two days reaction also produces the polymer along with unconsumed reactants and a trace of 2-dimethylamino-3-H-hexa- fluoro butene-2. (c) Chlorodimethylamine 71 Young et:al. find that bromobis(trifluoromethyl)amine adds o readily at 20 to perfluoropropene (CF3)2NBr + CF2=CFCF3 (CF3)2NCF2CFBrCF3 More recently Haszeldine and Tipping in a more'extensive investigation have found that the bromo-amine adds to a variety of fluorinated olefins, and to ethylene, under mild conditions to give lsl adducts in high yield, e.g. (CP3)2NBr + CH2=CPg > (CF3)gNCHgCFgBr Chlorodimethylarsine requires ultra-violet irradiation or heating to react with hexafluorobutyne-2; the product is the expected 1:1 adduct, 2-dimeth.ylarsino-3-chloroh.exaf luorobutene-2 95 % trans4. \5) 9 . Chlorodimethylamine does not react with hexafluorobutyne-2 at 20°s n°r appreciably at 65°. Heating at 85° slowly (39 hrs.) affords a moderately good yield of the expected 1:1 adduct, 2=dimethylamino-3~chlorohexafluorobutene-2, unexpectedly 100 % o , .< cis, "D.p. 102 (cap. rise), along with significant amounts of 2-dimethylamino-3-H-hexafluorobutene-2, perflucro-t-butyl chloride, trans-2-chloro-3-H-hexafluorobutene-2 and a small quantity of trans-3-H-heptafluorobutene-2, o (C^3)gNCl + CPgCSCCP :—Cis-(CH3)2NC(CP3)=CC1CP3 + (CH3^NC(CF3)=CHCF3 + t-C4F9Cl + trans-CF3CH=CClCF3 + trans~CF3CH=CFCF3 At 139° the main product is the 2-chloro-3-H-hexafluorobutene-2. The only other product identified was the heptaflucrobutene. Ultra• violet irradiation does not give rise to complete consumption of the amine even after 46 hrs. The main product is the (cis) adduct; trans-2-chloro-3-H-hexafluorobutene-2 was also Identified. The lsl adduct was Identified by microanalysis; the geometry was determined by "^F n.m.r. spectroscopy. The two quartets in the spectrum exhibited splitting of 13.5-c.p.s., which magnitude is well established as being due to the cis-CF3C=CCF3 residue, as discussed in the section concerning the dimethylamine adduct. The 2-dimethylamino-3-H-hexafluorobutene-2 was identified by means of its previously determined "^H n,m.r. spectrum. The 2=halo-3-H-hexafluorobutenes were identified by their known infra• red spectra (pp.53,40, respectively). The perfluoro-butyl chloride was identified by elemental analysis, with the geometry having been revealed by the 19F n.m.r. spectrum, a singlet. 2. Proposec Mechanisms There seems little doubt that the addition of dimethylamine to hexaflurorbutyne-2 occurs via nucleophilic. attack by the amine, presumably by the lone pair, on the acetylene. Alkoxide ion 54 easily attacks the butyne, as does diethylamine : CF3C=CCF3 + ROH *R0C(CF3)=CHCF3 CF3CSCCF3 + (CgH5)gNH • > (CgH5)gNC(CF^=CHCP' Extensive studies have since been made of nucleophilic attack on acetylenes; from these the generalization has emerged that such "3 attack culminates in trans addition,' at least when a mobile proton Is attached to the nucleophile, although a few exceptions 74 have been noted , e.g. COONa CH3 SH + C6H5CSCC00Na CH3 60 Cullen st al» propose lone pair attack leading to trans addition In the reaction with dimethylarsine: (CH3)gAsH + CP3CSCCP3- C=C° (CH„) _AsC (CF„)-CHCF„ 3 2 o 3 H trans :cis&15 sl This same mechanism is proposed for the addition of dimethylamine, although the intermediate may be a charge transfer complex, i.e., CF 3\, \0/ CH CH, H The reaction however gives <—'14 % of the cis isomer. Cis addition probably occurs either by four centre addition, i.e. CF CF, (CH3)g,N H or by hyperconjugative stabilization of the 1,3-dipolar inter- mediate co give CP X C=C=CF0F / * (CH,)r 3 £ O^H This latter species could give either the trans or cis config• uration, Clearly the proton transfer may be an intra- or inter• rnolecular process. Preliminary results using deuterc-arsines 75 indicate that interrnolecular proton transfer is at least significant. The conversion of trans-2-dimethylamino-3-H-hexa- fluorobutene-2 to the cis isomer on exposure to air Is probably caused by oxygen, perhaps as follows: 0 I >=C\ + °2 ^ /C~\ N CP3 H CP3 (CH3)2N H \ / 2 CFJ^ \ CP 3 3 The isomerization of stilbene by hydrogen bromide is greatly accelerated by air, light or peroxide; dichlorostilbene is said to be Isomerized by hydrogen bromide only in the presence of 75a oxygen The formation of 1,1,1,4,4,4-hexafluorobutanone from hexa- fluorobutyne-2 and dimethylamine represents a catalyzed reaction between the butyne and waters CP„C=CCP. + Ho0 * CF„C0CHOCP„ 6 6 6 6 * (CH3)2NH .- * The following reaction path is proposed? = + (CH3)2NH + HO 0H + (CH- ) NH 0® (S> k G OH + CF3C=CCP3—• CP3C(OH)=CCP3?== CP3C0CHCP34—> CP3C=CHCP3 The anion would readily abstract a proton from dimethylammonium ion or water,, The tautomerization probably occurs before proton abstraction, since' for simple ketones the enol form is almost non-existent, Moreover, the concentration of water (and hence of dime thy1ammonium ion) is low. The formation of the heptafluorobutene and especially carbon dioxide (from trimethylamine, water and hexafluorobutyne-2) indicates complete destruction of some of the hexafluorobutenyl units. The mechanism of carbon dioxide formation is not clear, but probably the reaction commences with the 1,3-dipolar inter• mediate C-C This could be expected to abstract a proton from trimethyl- arnmonium ion or water. This sequence is reported for acetylene, 76 77 trimethylamine and water . Reppe reports that tertiary amines or their salts react with acetylene or its monosubstituted derivatives in the presence of water to yield quarternary vinyl- ammonium bases. The dipolar intermediate should be formed much more readily with the electron withdrawing trifluoromethyl groups being present. The resulting cation would be expected to undergo attack by hydroxide ion, viz. CF, H . OH" „ CF,COCH?CF_ N C=C' » CF,C=CHCF_- »-0FQCF=CHCF, * H0CFoCF=CHCF, 3 3 2 3 L 2 \ \ -(CH3)3N 21 (CH3)3N^ CF3 The 1,2-shift of fluoride ion might be expected since the vinyl 78 carbonium ion is likely a rather high energy species , The addition of" trif luoroace tic acid to 5-chloropentyne-l results in a ,78 1,4-chloride shift to the extent of 50 % 01 H CF^COO. —*> il_—». ^Cl-^* 00CCF„ (The authors point out that the above mode of ring opening is n>>7 presumably directed by the lesser stability of the vinyl cation). The resulting alcohol would surely be unstable (perfluoromethanol and -ethanol are not known). Decomposition of this alcohol in the presence of hydroxide ion may produce carbon dioxide and would surely yield fluoride ion. Another source of the latter may be loss of fluoride from the dipolar intermediate, i.e. (CH3) 3^C(CP3)=C=CP29 Fluoride ion attack on hexafluorobutyne-2 is probably the initial step in the formation of the heptafluorobutene. This would be followed by proton abstraction: CF CF H \ 0 Hp0 or \ / CF^CSCCF, + F » ^C=Cr ~ .C=Cv 3 3 + ' / \ (CH3)3NH / \ CP CF • P 3 F 3 Since the butene is all trans, the fluoride must attack before the proton is attached. The reverse CP3 H H C=(T » CF_C=C' > CF,CF=CHCF, {CE3h% ^F3 CF3 would yield a random distribution of cis and trans configurations, © / because of the linearity of the CF3C=C^ moiety. The formation of 1,1,1,4,4,4-hexafluorobutanone has already been discussed (p.65 )« The mechanism for production of 2-dimethyl- amino-3-H-hexafluorobutene-2 is not fully understood. This reaction also probably is initiated by the 1,3-dipolar intermediate, 79 Alalmo and Farnum report an analogous product for the reaction between triethylamine and acetylene dicarboxylates (only in the presence of a proton source) but propose no mechanism, CH300CC=CC00CH3 + (CgH5)3NHBr + (CgH5 )3 N(CgHg) gNC (C00CH3)=CHC00CH3 68 The route to the bis(hexafluorobutenyl) ether seems clear. The reaction is initiated in the same way as Is the formation of the hexafluorobutanone, viz. initial attack by hydroxide ion: CP f~i 3 CF3CSJCCF3 + OH~—* ^:c=c® ^ CP -O-?HCF «-*CF3C=CHCP ' The formation of the ether shows that the anion is best represented by the enolate structure. Attack by the enolate ion on a second mole of butyne, followed by proton abstraction, would give the ether: CP H \3 CF, H CF, H W C C HO or c C CF,C=CHCP, + CF.CSCCP, » || || Tr^Tlw+"> II II 3 3 3 3 (CH3)3NH g , o® / Nox \ / N^V CP, CP, CF_ CP, 3 3 3 3 A repeat of the reaction at lower temperatures would be expected to result in a considerably reduced destruction of hexa- fluorobutenyl units to give carbon dioxide and fluoride ion. This is in fact observed: only traces of carbon dioxide and fluoride ion (as trimethylammonium fluoride) are formed. The complete absence of heptafluorobutene may indicate that the butyne Is not attacked by fluoride at the temperatures involved. Trimethylamine is found to slowly catalyze the polymerization of hexafluoro- butyne-2. This reaction presumably transpires by nucleophilic attack of the 1,3-dipole on the butyne; CF3 CF3 \ © ^ \ © CP, \ N (CH,),N -i- CF,C2CCF, ^== G=Cv ^ \ || / \ CP CSCCP/ >^C< etc cp 5 3 {CE 3 ^hh% 3 zh% bp 3 69 The great insolubility, thermal stability and chemical inertness of this polymer indicate a good deal of cross-linking. Such a polymer has been prepared80 by Y~ieradiation of hexafluorobutyne-2; it is more thermally stable than polytetrafluoroethylene. The most significant aspect of the reaction between chlorodi- methylamine and hexafluorobutyne-2 is that the 1:1 adduct is entirely cisa. This result would appear to indicate that the adduct is formed exclusively via a four-centre reaction intermediate viz. • OF-* CF„ \ / 3 (CH3)gN ,; Cl 72 Haszeldine and Tipping consider a free radical and/or ionic mechanism for the addition of bromobis(trifluoromethyl)amine to olefins, and favor the former. Clearly neither of these paths could give an exclusively cis product, and would very likely give a trans bent intermediate , CF3 CF3 ^0=0° or ^C=C® Y = Cl or (CH_)0N / \ / \ 32 Y CF3 Cl CF3 as would nucleophilic attack by the nitrogen lone pair to give the 1,3-dipolar intermediate. Moreover, the slowness of the reaction may be considered a manifestation of the orientation necessary for a" The compound, from both Irradigtion and thermal reactions, was purified by v.p.c. (91 and 106 ) prior to n.m.r. analysis. Although thermal conversion of trans to cis would be very unusual, the possibility is acknowledged. Cis-Me NC(CF )=CHCF is conver• ted to trans on distillation. b The 2-halo-3~H-hexafluorobutenes produced were wholly trans. 70 a four-centre.mechanism. The presence of the other products indicates that the overall picture (at 85°) is rather more corilplex. The presence of fairly large yields of the three 3-H-bu'tejtfyl .^derivatives (2-chloro + 2- fluoro = 19 %) must result from/.kydrogen loss (abstraction) from dimethylamino groups. Similarly, the perfluoro-t-butyl chloride attests to the disintegration of hexafluorobutenyl units. It is proposed that at 85°, chlorodimethylamine does dissociate to some extent, but that the Intermediates resulting from attack by the radicals (or possibly chloride ion) on hexafluorobutyne-2, I depicted above, abstract.hydrogen (ion) Immediately on collision with chlorodime thylamine.| Attack by (CH3)gNs< is not considered because the butyne Is not vgry sensitive*-to eleetrophiles, because 81 of the electrons!thdrawing trif iuorom'e thyl groups. Haszeldine has found that catalysts are required to induce reaction with eieotrophilic reagents. The above arguementa are corroborated by the results of the experiment conducted at 139°. The main reaction product was trans-2-chloro-3-H-hexafluorobutene-2 (28 %); the only other product identified was the heptafluoro analogue |6.5 %). The •-main inference from this result is that at this temperature the chloro-amine is very definitely dissociated, to the extent, in fact, that the (slow) reaction involving the four-centre inter• mediate (to give the 1:1 adduct) does not occur. The large yield of CP„CH=CC1CP^ coupled with the lack of (CH_)_NC(CF_)=>CHCF_ o o o 2 3 3 suggests that the dissociation is ionic (as previously mentioned, + (CH ) N would not likely attack the butyne). The formation of 3 2 the heptafluorobutene also suggests as ionic mechanism, via the following anion which may be stabilized by hyperconjugation Cl + CF3c£CCF3 > CF3CC1=CCF3< • CF3CCl=C=CFgF® Loss of fluoride ion could provide the heptafluorobutene in a manner analogous to the formation of trans-2-chloro-5-H-hexa- fluorobutene-2, B. Phosphorus Compounds 1. Results (a) Phosphorus-Hydrogen and Phosphorus-Phosphorus Bonds Hexafluorobutyne-2 and bis(trifluoromethyl)phosphine react only slightly at 105°, However prolonged irradiation with ultra• violet light gives both mono- and diadducts, bis(trifluoromethyl) phosphino-l,l,l,4,4,4-hexafluorobutene-2 and bis (bis (trif luoro• methyl )phosphino)-1,1,1,4,4,4-hexafluorobutane, In moderate yields, (CF^)pP c H + CF,CICCF„^-»(CF„)0PC(CF„)=CHCF, + (CF ) PCH(CF )CH(CF )P(Cpr. ° ° o 6 2 3 3 32 3 3 c These compounds were identified by elemental analysis. The n.m.r. spectra were too complex to permit elucidation of the geometries of the molecules. However the infra-red spectra of the two fractions obtained which analyzed as the monoadduct suggest that a partial separation of cis and trans isomers had been achieved by trap to trap distillation. Several prominent peaks in each spectrum show complete coincidence, but some variations in the C-F stretching region are apparent. The fractions show different double bond absorptions, at 1630 and 1670 cm ~< The fingerprint regions show several differences. The spectrum of the diadduct shows no prominent band In the double bond region. The more characteristic infra-red absorptions of the hexafluorobut-2-enyl-phosphines prepared In this Investigation appear in Table VII, Although 68 — 1 Bellamy gives 790-840 cm," as the range for the C—H out of plane deformation mode, the butenyl-derivatives prepared in this work absorb to slightly -higher energy. The hexafluorobut-2-enyl TABLE VII Some Characteristic Infra-Red Absorptions of the Hexafluorobutenyl Derivatives Compound C=.C str. C-F stretch C=C-H b (CF3)2PC(CF3)=CHCFg 1630m 1260vs 1240vs 1210,1190vs 1135vs 859vw, 1670m 12£0vs 1205,1190vs 1165vs 870m d C 1596vw (C6H5)2PC(CF3)=CHCF3 1263vs 1238vs 1202 vs 1167vs 1137s 858w 1641w C d cis -(C6H5)2PC(CF3)=C(CF3)P(C6H5)2 1592m I258vs 1162vs 1135vs — trans -(C2H5)2PC(CF3)=CHCF3 1636vw 1253s 1145vs 851w a trans ~(CH3)2NC (CF3)=CHCF3 1659vs 1274vs 1239vs 1195vs 1156vs ll28vs 859s C 1265vs cis - (CH3)2 NC (CF3)=CC1CF3 1590s . 1250vs 1190vs 1175vs 1150vs trans -CF,CH=CClCF,a 1670vs 1260vs 1185vs 1165vs 859s o 3 Vapor Assignment uncertain c Liquid film May be aromatic C=C stretch derivatives of trialkylsllanes, -germanes and -stanhanes prepared Arc =1 by Styan absorb in the range 849-850 cm, Diphenylphosphine and the butyne give the expected adduct, 2.-diphenylphosphino-3-H-hexaf luorobutene-2, b.p, 127° (10~3 mm.), readily at 20°. (C6H5)2PH + CP3CSCCF3 (C6H5)2PC(CF3)=CHCF3 The compound was identified by microanalysis. The "^H n.m.r. spec trum showed an isolated quartet ( JJJ gp = 9 c.p.s.) which was cen 3 tred 40 c.p.s. upfield from the upper extremity of an olefinic multiplet which in turn blended into the large aromatic band. This upfield quartet is assigned to the cis isomer on the basis of the now well established pattern whereby the proton in the cis-CF3C=CHCF3 residue is chemically shifted upfield from that in the trans isomer, e.g. 2-dimethylsmino-3-H-hexafluorobutene-2 60 (p. 39) and Its arsenic analogue , If Jjj_p(vicinal) 5?0 in the cis Isomer, then the quartet may be assigned to one proton. If, however, Jg_p > 40 c.p.s., the quartet represents only half a proton, with the other half overlapping with the resonance of the olefinic proton In the trans Isomer, or the aromatic hydrogen atoms. The latter case is more likely, since in trans-2-diethyl- phosphino-3-H-hexafluorobutene-2, Jjj=p = 20 c.p.s. (p. 50). More- 82 over, Jjj=p in trivinylphosphine is given as 30 and 14 c.p.s. for the trans and cis hydrogen atoms respectively. On the basis ' of JHi_p > 40 c.p.s, for the cis-phosphino butene, the Isomer ratio trans;cis is approximately 3:2. As seen in Table VII, two bands in the C=C stretching region both very weak, are observed in the infra-red spectrum. The band at 1596 cm~^~ Is probably due to the aromatic C=C stretching mode. Bellamy68 gives 1600 t 5 cmT"^ as the range when monosubstituted 74 benzene rings are involved. Tetraphenyldiphosphine and hexafluorobutyne-2 heated at 130° readily afford the 1:1 adduct, 2,3-bis(diphenylphosphino)- 0 -3 hexafluorobutene-2, b.p. 138-141 (10 mm.), identified by elemental analysis. o i: (C6H5)4P2 + CP3teCCP3- ^(C6H5)2PC(CP3)=C(CP3)P(C6H5)2 19 The compound was subjected to P n.m.r. analysis, which indicated the presence of only the cis isomer. The spectrum consisted of a doublet of quartets (Jgp _CF ~10 c.p.s.). As discussed earlier 3 3 in the section describing 2-dimethylamino-3-H-hexafluorobutene-2, this magnitude of coupling arises from cis, but not trans, tri- fluoromethyl groups in the hexafluorobutenyl unit. The spectrum of the bis(phosphino)butene is noteworthy on two accounts: (1) The fluorine atoms couple with only one phosphorus atom. This phenomenon also occurs in the case of trans-2-diethylphosphino-3-H-hexafluoro• butene-2, described later in this section. In this case JVjp _p 3 (geminal)2*0. (2) The chemically equivalent fluorine atoms are apparently magnetically inequivalent. The chemical equivalence Is in itself, of course, no barrier to spin-spin coupling; for = 13,4 C S The example, for cis-CF3CCl=CCl CF^CF -CF 'P' « » 3 3 ,«; presence of a double bond5 absorption of medium intensity at 1592 cm. 1 in the infra-red spectrum further supports the assignment of the cis configuration. Symmetrical trans olefins are known to 83 give little or no double bond absorption ; the cis-isomers of (CH3)2AsSC(CF3)=C(CF3)SAs(CH3)2 and (CH3)gAsC(CF )=C(CF )As(CH ) 59 show pronounced absorption in the double bond region. Although the band at 1592 cm.''" may (also) be the aromatic C=C stretching modeof 2-diphenylphosphino-3-H-hexafluorobutene-, it should be noted that this peak is 2muc han dweake triphenylphosphiner in the case . Diethylphosphine and hexafluorobutyne-2 react vigorously on mixing; control of the reaction by means of a cold bath affords trans-2-diethylphosphino-3-H-hexafluorobutene-2, b.p. 132° (cap. rise) in 45 % yield. (C2H5)2PH + CP3C=CCP3 * trans-(C2H5)2PC(CF3)=CHCP3 The trans configuration is readily determined by "^H n.m.r. and n.m.r. apectrostiopy. The doublet of downfield quartets in the "^H spectrum showed secondary splitting into further quartets (J = 1.7 c.p.s.). This coupling is assignable to vicinal cis, but not trans, H-CP3 interaction, as established by previous work, e.g. fiO 84 (CHj0AsC(CF„)=CHCF„ , (CO) c-ReC (CF~)=CHCF, and hexafluorobut-2- 3 2 3 3 ° a o enyl derivatives of tin, germanium and silicon . The F n.m.r. spectrum connate d of a doublet (J£253 c.p.s.) of doublets (J«7.5 c.p.s.), and a singlet. The splitting of 7.5 c.p.s. is due to geminal CFs/^H coupling; this is confirmed by the1 H n.m.r. spectrum. Clearly, then, the splitting of 53 c.p.s. is due to the vicinal CF -P interaction. The remaining band, the singlet, at once reveals •- -3 that J p(geminal)'55? 0 in this molecule, and that the trifluoro- methyl groups are trans to each other. As discussed in the section on dimethylamine, cis-CP 6=CCF coupling is an order of magnitude 3 o 61 larger than is the trans; e.g. Trelchel et al. report values of .11.5 and"2.3 c.p.s. respectively for CP3GF=CC1CF3; for 2-dimethyl- amino-3-H-hexafluorobutene-2, the values are found to be 12.6 and ***»Q c.p.s. As seen from Table VII, 2-diethylphosphlno-3-H-hexa- fluorobutene-2 has only a very weak band in the C=C stretching region of the infra-red spectrum. This situation also exists in the case of analogous trialky1tin compounds43. This phenomenon Is apparently due to small dipole moments In these molecules, i.e. the electronegativities of dialkylphosphorus and trlalkyltin are very 76 nearly equal to that of hydrogen, Hexafluorobutyne-2 and tetramethyldiphosphine react violently upon melting of the diphosphine. Because of the; relatively high melting point of the diphosphine (^0°), the reaction can not effectively be controlled by cold baths. The only product identified, •.other than a trace of ^ilicon tetrafluorjlde, was methyldifluoro- phosphine oxide (in low yield), of known "'"H n.m.r. spectrum. (CH3)4P2 + CP3C=CCF3 • CH3P0P2 + .... A small quantity of unstable material of low volatility Is produced. A The infra-red spectrum of this material is suggestive of the expected adduct, 2,3-bis(dimethylphosphino)hexafluorobutene-2, particularly the strong absorption in the C-F stretching region. 19 The F n.m.r. spectrum showed two bands of equal intensity, an apparent doublet, with J = 977 c.p.s. The bisphosphino-butene would be expected to give one (if J ^(geminal)«0) or two V e p CF3- doublets per isomer; however, splitting of this magnitude is likely associated with direct P-F linkages. (b) Miscellaneous Phosphorus Compounds (I) Triphenylphosphines- It has been found that triphenyl- phosphine will interact vigorously with activated triple bonds to give ls2 adducts in the form ofAcyclic phosphoranes; for example^ esters of acetylene dicarb oxylic acid at -50° give a cyclic 85 ' • phosphorane which rearranges at room temperature 0 0 AcO OAc „ AcO OAc r. . (C H ) P + 2CH 0CC=CC0CH' „ O» AcO & ^OAc • AcO // \V OAc 6 5 3 3 3 / \ The acetylenedicarbonitrile cyclic phosjpho'rane adduct is stable 77 to 245° 86. .Triphenylphosphine, dissolved in toluene, reacts extremely vigorously at -78° with hexafluorobutyne-2, affording an almost quantitative polymerization of the butyne. The polymer has the same infra-red spectrum and physical characteristics as the polymer obtained by the interaction of the butyne with trimethylamine. The reaction also gives a small quantity of triphenylphosphine oxide along with unreacted triphenylphosphine. The oxide was Identified by elemental analysis, melting point and the P=0 stretching frequency in the Infra-red. (ii) Chlorodimethylphosphine:- Hexafluorobutyne-2 and chloro- dimethylarsIne have been found to give the 1:1 adduct, 2-dimethyl- arsino-3-chlorohexafJ?upr,obutene-2, on ultra-violet irradiation or heating (140°). (CH3)2AsCl + CP3C3CCF3 ¥ (CH3)gAsC(CF3)=CClCF3 The adduct consists largely of the trans isomer, 95 % in the case of irradiation. The reaction of the butyne with chlorodimethyl• amine is described earlier in this thesis. Again, irradiation or heating is required for reaction to occur; however, the resulting lsl adduct is in both cases cis. It was therefore of interest to investigate the analogous reaction with chlorodime th ylphosphine, to compare (l) the isomer distribution of the 1:1 adduct, if formed, and (2) the conditions required to produce reaction. Hexafluorobutyne-2 and chlorodimethylphosphine react vigorously immediately upon melting of the phosphine. As in the case of tetramethyldiphosphine, the reaction can not be moderated successfully using cold baths because of the relatively high melting point of the chlorophosphine (-1°). The reaction may be summarized as follows: (CH3)2PC1 + CP3C=CCP3 •> trans-CP3CCl=CHCP3 + (CH3)gPF3 a + (CH3)gPC(CP3)=CHCP3 + (CH3)2PF0 + (CH3)gPC(CF3)=CC1CF* The major volatile product is trans-2-chloro-3-H-hexafluorobutene-2, identified by elemental analysis, molecular weight and n.m.r. spectra. The n.m.r. spectrum consisted of a quartet of quartets (J = 6.7 and 1.0 c.p.s.); the magnitudes of splittings are within the established ranges for geminal and vicinal H-CF3 coupling respectively. The geometry is confirmed by the 19F n.m.r. spectrum, which shows the CF3-CF3 coupling to be 1.3 c.p.s., clearly a trans CPg-CFg interaction. As can be seen from Table IV (p. 53), a 69 reasonably large discrepancy exists between the found and published (5.4 c.p.s.) values.for the geminal CP3-H coupling. The value obtained In this work is supported by the n.m.r. spectrum. The value of 5.4 c.p.s. would represent an unusually low value for this type of coupling. The trifluorodimethylphosphorane was identified by its infra- 1 19 19 red, and H and . F n.m.r.j spectra... The F n.m.r. spectrum was discussed earlier (p. 22). The evidence for 2-dimethylphosphino- 3-H-hexafluorobutene-2, fluorodimethyIphosphine oxide and 2-di- methylphosphIno-3-chlorohexafluorobutene-2 is spectroscopic. The n.m.r. spectrum of the mixture showed a downfield doublet (J = 27 c.p.s.) of quartets (J = 8.2 c.p.s.); for 2-diethylphosphino- 3-H-hexafluorobutene-2 the splittings are 20 and 7.4 c.p.s. (p.50). The spectrum also showed an upfjg^ld doublet,.presumably due to the methyl. protons, approximate^^ix times more intense than the downfield peaks. The upfield region also contained a sharp . doublet (J = 15 c.p.s.) of doublets (J = 8.2 c.p.s.). The Evidence not conclusive 30 published values for fluorodimethylphosphine oxide are 16 and 8.9 c.p.s. The infra-red spectrum contained weak C=C double bond absorptions at 1665 and 1590 cm"1. Table VIII shows the C=C stretching frequencies of related butenyl derivatives. TABLE VIII Double Bond Frequencies of Some But-2-enyl Derivatives Compound (CH„)0AsC(CF,)=CHCF, 1643 w o d o o a (CH3)2NC(CF3)=CHCF3 1659 vs (CgH5)2PC(CF3)=CHCF3 1636 vw 59 (CH3)2AsC (CF3)=C'C1CF3 1584 m C (CH3)gNC(CF3)=CClCF3 1590 s a This thesis, p. 38 b Ibid, p. 50 c Ibid. p. 44 The observed absorptions in the double bond region thus might be interpreted as being due•to 2-dimethylphosphino-3-H-hexafluoro• butene-2 (1665 cm \) and a trace of 2-dimethylphosphino-3-chloro- -1 hexafluorobutene-2 (1590 cm .). (iii) Chlorodimethylphosphine Sulfide:- Hexafluorobutyne-2 and chlorodimethylphosphine sulfide do not react on ultra-violet irradiation. Unreacted phosphine sulfide was recovered when the o butyne was heated at 106 with the sulfide, contaminated with phenyldichlorophosphine. A small amount of trans-2-chloro-3-H-hexa' :fluorobutene-2 and•unidentifIed material was produced, but little can be said regarding these products since they may well have arisen because of the reaction between the phenyl-phosphine and the 87 butyne. The latter is known to react with phenyldichlorophosphine 88 (iv) Tetramethyldiphosphine Disulfide:- Chlorine and 89 bromine cleave the phosphorus-phorphorus hond in tetramethyldi• phosphine disulfide at 20° giving the halodimethylphosphine sulfide. (CH3)gP(S)P(S)(CH3)2 + X2 >2(CH3)2PXS X = Cl,Br It was therefore of interest to investigate the reactivity of this phosphorus-phosphorus bond towards iodine at 20°, and also towards trifluoromethyl iodide (under more forcing conditions). Trifluoromethyl iodide and the disulfide do not react o appreciably at 104 j prolonged irradiation with ultra-violet light causes only very slight/reaction, the products being fluorodimethyl• phosphine sulfide and 'traces of fluoroform. The f luorodime thyl• phosphine sulfide was identified by elemental analysis and n.m.r. spectroscopy. The coupling constants, J v = 13.8 c.p.s. and ° 30 ^n-a TP = 8.0 c.p.s., are in excellent agreement with the published CH3 values of 13.7 and 8.0 c.p.s. Areas of red-brown coloration in the unreacted disulfide indicated traces of iodine. Tt was expected that if reaction took place, it would occur as follows: (CH3)4P2S2 + CF3I 9- (CH3)2P(S)CF3 + (CH^PIS The work-up of the volatile products revealed no dimethyltrifluoro- methylphosphine sulfide. Treatment of the iodo compound with aqueous bicarbonate would give the corresponding thio acid, thus enabling separation from the unreacted disulfide HC0" (CH3)2PrS + H20 »(CH3)2P(S)0H ^(CHg) gP(S)0~ Work-up of the bicarbonate extract, however, gave only a small amount of tetramethyldiphosphine disulfide. Iodine does not cleave the phosphorus-phosphorus bond of tetramethyldiphosphine disulfide at 20° (CH3)4P2S2 + I2:^U 2 (CH3)2PIS provided there is no molar excess of the halogen. Instead a loosely bound complex is formed. The 1H n.m.r. spectrum is structurally Identical with that of the diphosphine disulfide? iododimethylphosphine sulfide would give a doublet. The color of the product (reddish-brown), both solid and in solution, clearly Indicates that any elemental Iodine is complexed, in the sense that iodine is complexed by oxygenated solvents0 In such solvents, Iodine is in equilibrium with iodine bound by coordinate linkages to the oxygen9^. By analogy, the iodine-tetramethyldlphosphine disulfide complex exists because of coordinate bonds from the sulfur atoms to the iodine molecules. This is corroborated by the infra• red spectra of the complexed and uncomplexed disulfides (p. 56). 91 The P=S stretching frequency is shifted markedly by the Iodine, from 569 to 554 cml1 (I.e. a shift of 0.45yn to the red). This absorption is weaker and slightly broader in the complex. Meek 91 ^ and NIpcon report thatV for trimethyIphosphine sulfide -1 (565 cmr1) is shifted to 535 and 538 cm. for ZnLglg and CdLglg respectively (L = (CH3)3PS)„ The spectra differ significantly in one 92 other area. The P-CH^ mode j although not shifted, becomes in the complex a doublet, with the intensity much reduced. Meek and NIpcon find that the spectra of the diphosphine disulfide complexes are much more complex than that of the free ligand. They interpret this as being due to the loss of a centre of symmetry, caused by the diphosphine disulfide units assuming the cis configuration, with both sulfur atoms being bound to the central metal ions The spectrum of the Iodine complex, however, with the exception of the two bands mentioned above, is almost identical with that of the free ligand, indicating that the disulfide still maintains the trans configuration, the known geometry of diphosphine disulfides 93 In the solid state . This is consistent with the observed instability of the complex, since formation of a chelate with a diphosphine disulfide molecule would require that the complex be sufficiently stable to permit the ligand to overcome the barrier 91 to rotation about the phosphorus-phosphorus, bond in solution In view of the failure of the iodine to cleave the phosphorus- o phosphorus bond at 20 , a comment on bond strengths seems in order0 The net increases in bond energy, using the bond strengths given 49 by fauling s for the reaction P-P + X-X -r-^ 2 P-X are 48.9, 33.4 and 15.2 kcal/mole respectively for X = 01, Br, I. 2, Proposed Mechanisms The mechanism proposed for the addition of dimethylamine to hexafluorobutyne-2 (p. 64) may equally well be applied to the reactions of the acetylene with diethyl- and diphenylphosphine; namely CF \ © R2PH + CF3CSCCF3—* C=C R = C^, 0^ followed by Inter- and/or intra-molecular proton transfer, to give the trans-hexafluorobut-2-enyl-phosphines. The cis isomer (from diphenylphosphine only) is probably the result of four-centre addition or hyperconjugative stabilization of the 1,3-dipolar intermediate, as previously discussed. The isomer distribution varies markedly among various hexafluorobutenyl derivatives of Group V, as exemplified by Table IX Table IX Isomer Distribution of the Hexafluorobutenyl Derivatives RgEC(CF3)=CHCF3 83 Table IX Isomer Distribution of the Hexafluorobutenyl Derivatives R EC(CF._)=CHCF_ <~> o 3 a R E % cis (approximate) P 0 C2H5 C 40 6H5 P H 14 ° 3 N 60 CH As 6 3 a Determined by n.m.r. spectroscopy Thus the formation of the cis form does not seem dependent on the nature of the metalloid atom. The limited data at hand suggests that cis formation is favored by phenyl groups on the metalloid atom. It is difficult to visulize the phenyl groups stimulating hyperconjugation of the intermediate; however, they might favor a four-centred intermediate (relative to R = alkyl) because of their greater electronegativity. This factor at once reduces the avail• ability of the metalloid lone pair, and increases the lability of the hydrogen atom. The'likelihood of the reaction between bis(trifluoromethyl)- phosphine and hexafluorobutyne-2 (CP3)2PH + CP3C=COP3^^(CP3)gPC(CPg_)_=CHCP3 + (CPg) pPCHCP CHOP P (CP ) occurring by means of nucleophilic attack--toy the phosphine is slight, because of the powerful electron-withdrawing effect of the trifluoromethyl groups. The compounds 'do not react appreciably at 105°; prolonged ultra-violet irradiation Is required to give moderate reaction. The reaction is surely induced by excitation of the butyne to an excited state, which then interacts with a bis- (trifluoromethyl)phosphine molecule. Addition of chlorodimethyl- arsine°^ and trimethylsilane43 across the butyne is Induced by ultra- 84 violet irradiation. Thus the proposed reaction path may be repre' sented as follows: - CF,C=CCP„-^—» CF^CsCCF? (excited state) CF • / 3 CFgCsCCFg. + (CFJ)2PH- c=c . y / ^>P(CF,3)2 CF PT 3 The radical intermediate could t.hen give the 1:1 adduct via inter- or intramolecular hydrogen transfer. The probability of the reaction being induced by ultra-violet excitation of the phosphine. I.e. it v (CFg)gPH V v (CFg)gPH , *(CF3)gP« + H* seems slight, In light of the failure of the phosphine to react, under identical conditions, with perfluorocyclobutene or 1,2- dlchlorotetrafluorocyclobutene. The difference In mechanism for the reaction of the relative inert bis(trifluoromethyl)phosphlne with hexafluorobutyne-2 is further evidenced by the formation of the diadduct, a bis(bis(tri- f luorome thyl) phosphl.no) =1,1,1,4,4,4-hexafluorobutane. No diadduct formation Is observed in the case of diphenyl- or diethylphosphine If the radical intermediate proposed above for the formation of the monoadduct has a finite lifetime, then it could Interact with a second molecule of phosphine CF~ •. CF3 N>(CFg)2 " \=C° + (CF,)0PH (CF3)2PN CF, H ~ H Interrnolecular hydrogen transfer would then give the diadduct. It should.-be noted that although the actual geometry of this diadduct could not be determined, the above mechanism would give rise to a 85 2,3-configuration. The reaction of hexafluorobutyne=2 with tetramethyldiphos• phine may also.be considered to be the result of lone pair attack on an acetylenic carbon atom, analogous to the initial step proposed for the reaction with the cyclobutenes: CF. (CH,)4PP + CF„CSCCF,—• C=C 6 4 d 3 3 ©/ SCF, (CH3)2P-P(CH3)2 Little can be said, however, about the course of the reaction beyond this stage, In view of Its violence, giving an"involatile charred mass along with a small yield of methyldifluorophosphine oxide„ 19 I"f the ' F n.m.r. spectrum of the tetraphenyldiphosphine- hexafluorobutyne-2 adduct has been interpreted correctly, the compound is entirely cis. This result casts some uncertainty on the proposed mechanism of the reaction. A 1,3-dipolar intermediate would be expected to give rise to a predominantly trans product. At any rate, it seems unlikely that steric hindrance from the phenyl groups could quantitatively force a cis-bent intermediate. A more likely reaction path Is one involving a four-centred intermediate ^G=C r—j (C6H5>2pL"i(C6H5)2 Tt will be recalled that diphenylphosphine gave*^40 fo cis adduct. A free radical mechanism, although plausible at 130°, is not considered likely because of the all-cis geometry of the adduct. The proposed mechanism of the catalytic polymerization of hexafluorobutyne-2 by triphenylphosphine is the same as that postulated for the polymerization by trimethylamine, viz. 86 CF II OF, CP c , \ /V 6 5 3 3 *0CP3- \=? CF,CsCCF, (C H ) P + CP C ; 2 3 C=G / \ — - -* P C H CF C H P / VCF < 6 5>S © 3 ( 6 5>3 © • 3 The contrast between the trimethylamine and triphenylphosphine catalyzed polymerizations is an interesting one, in that the latter one occurs so very much more readily. The contrast is of such interest because triphenylphosphine is so feeble a base compared with trimethylamine. This suggests that in the latter Instance the 1,3-dipolar intermediate is in rapid equilibrium with the reactants, while the phosphine intermediate is somehow stabilized. Evidently the Tf-electron system of the double bond overlaps to 86 some extent with the vacant phosphorus d-orbitals. Reddy and Weis suggest that the marked stability of the phospholes NC N NC CN NC CN NC CN NC CN NC CN V is due to such overlap involving the e<-cyano groups. The reaction of chlorodimethylphosphine with hexafluoro- 59 butyngo.2 provides an analogous comparison: chlorodimethyl-arsine and -amine react much less easily. Again, the greatly increased reactivity of' $the phosphorus compound is ascribed to 6jf ~VTf stabilization of the 1,3-dipolar Intermediate. As in the case of tetramethyldiphosphine, speculation on any reaction paths beyond the Initial nucleophilic attack would be unwise, in view of the nature of the products".-' The formation of dimethyltrifluorophos• phorane (10 %) represents disintegration of hexafluorobutenyl 87 units, while the 3 -H-2-chlorohexaf luorobutene-2 (21 %) is a result of destruction of dimethylphosphino moieties, the only hydrogen source. 88 CHAPTER III FLUOROACETONES • INTRODUCTION Following the preparation of hexafluoroacetone in 1941 by ". " 94 - Fukuhara and Bigelow , an extensive list of fluorinated ketones 95 94 has been prepared. These include both partially and completely * 963,97,98 fluorinated ketones. The significant dividing line is whether the o£-carbon atoms are bound to hydrogen or fluorine atoms. The earlier work was primarily concerned with the former case. o^-Fluoroketones, however, show a greatly enhanced reactivity as Lewis acids. Isolable hydrates, hemiketals and ammonia adducts can be formed99^ for example, water adds quantitatively^6'^1'10° at 20° Rf CO + H 0 > Rf C(0H) 2 2 2 2 101 Harris reported analogous adducts from hydrogen sulfide. At low temperatures^ the addition of hydrogen halides to 102 perfluorocyclobutanone"gives high yields of CFgCFgCFgCO + HX t»CF CF CFgCX0H X = F,Cl,Br,I 103 2 This ketone was found to give a diadduct with di-n-butylsilane (n-e4H9)gSIHg + CFgCFgCFgCO »(n-C4H9)gSi(OCHCFgCFgCFg) g This result was followed by more extensive investigations of the 104 reactions of silanes, with hexafluoroacetone, by Janzen and Willis , and the hydrides of silicon, germanium and tin by Cullen and 105 Styan .. In all cases the direction of addition gave the M-O-C-H system. Previous investigations of the reactions of fluorinated ketones with Group V compounds have dealt primarily with N-H bonds, e.g. ammonia106, amines10,7, amides108 and urea108. The work has been extended1 to^compounds of phosphorus and arsenic. Cullen and 89 . Styan109 found that dimethylarsine added to hexafluoroacetone to give the alcohol * (CH3)2AsH + (CP3)2G0 > (CH3)2AsC(0H)(CP3)2 Cacodyl and trimethylarsine were found to form complexes with hexa- fluoroacetone; the latter was essentially completely dissociated at room temperature under high acetone-pressures while the former was only slightly dissociated in vacuo. The reactions of trialkyl phosphites with fluoro-ketones have received100' 110,111 considerable attention in the last two years.. The products vary widely with the ketone used, e.g. (C2P5)2C0 + (CH30)3P > CgPgC_(0CH3) = CPCP3 + (CH30)gPP0 (CP2C1)2C0 + (CgH50)3P—•CgHgCl + (C2H50)2P(0)0C(CPgCl)=CP2 (CF3)2C0 + (CH30)3P • (CH30)3POC(CP3)2C(CP3)gO This type of reaction occurs under very mild conditions; for example, the reactions between trimethyl phosphite and perfluoro- cyclobutanone,. and triphenylphosphine and hexafluoroacetone, occur at =70°. The former ketone has been reacted with phosphine by 103 Parshall , who obtained both mono- and diadducts, depending on the ratio of reactants PH3 + CFgCF2CF2c'0 APgCPgOPgC(OH)PHg + (CFgCPgCFgCOH) gPH The following section presents and discusses the reactions of organo-phosphorus compounds, in particular diphenyl- and dimethyl- phosphine, with hexafluoroacetone, 1,3-dichlorotetrafluoroacetone and 1,1,1-trifluoroacetone. 90 EXPERIMENTAL A . Starting Materials 1. Hexafluoroacetone (6PK) was obtained from E. I. du Pont de Nemours and Co. Inc.; 1,3-dichlorotetrafluoroacetone (4FK), from Allied Chemical Corp. (General Chemical Division); and 1,1,1-tri- fluoroacetone (3FK), from Peninsular ChemResearch, Inc. 2. The synthesis of diphenylphosphine has already been described in Chapter I (p. 7 ). Tetramethyldiphosphine was made by desulfurizing Its disulfide with tributylphosphine according to 112 the procedure of Parshall . The triethylphosphine was a.gift from H. C. Clark. 3. Dimethylphosphine was obtained by reducing chlorodi• methylphosphine sulfide (29.7 g, containing 23 % phenyldichloro• phosphine, see p. 37) with lithium aluminum hydride (11 g). The sulfide, diluted with an equal volume of dioxane, was added drop- wise; onto the crushed hydride, covered with dioxane (150 cc.) in a 3-hecfeed flask, (1/2/litre). The flask was equipped with a magnetic stirrer, nitrogen bleed and stillhead. The latter was connected to a -78° bath followed by a -196° trap. After a sluggish start the reaction proceeded vigorously. Following addition of the sulfide^the flask was heated to 65° and cooled. The excess hydride was destroyed with dropwise addition of water (50 cc). Dioxane (50 cc.) was added and the mixture heated (15 min.) without distilling the dioxane. The phosphine was freed from dioxane and water (-64° bath) and hydrogen sulfide (-130° bath)> and the purity checked by the molecular weight (Found: 61.55, CgH^P requires 62.1). Yield: 5.44 g (^49 %) . B. Reactions with the Fluoroacetones 1. Hexafluoroacetone (6FK) 91 (a) Diphenylphosphine The phosphine (4.17 g, 22.4 mmoles) and 6PK (8.60 g, 51.8 mmoles) reacted Immediately on mixing to give a white solid. This material slowly changed to a yellow oil (3 days). Excess 6FK (4.20 g, 25.3 mmoles) passed through a -78° trap. Hexafluoro-2-H-isopropanol 43 (<0.1 g)s of known Infra-red spectrum , condensed in the -78° trap. The involatile material was extracted with chloroform and the solvent removed by distilling under nitrogen (760 mm.). The residue o o was distilled at 10 " mm., giving two cuts, 132-134 and 136-139 . The former was identified as hexafluoro-2-H-isopropyldiphenylphosphine oxide (Pounds C, 51.32; H, 3.25; F, 32.26; P, 9.02 %• M(Rast), 325. Gale, for C-^H-^FgOP s G, 51.2; H, 3.15; P, 32.4; Ps 8.79 %s M, 352) . Infra-red spectrum (liquid film)s 3130 w, 2990 vw, 1900 vw, 1790 w, 1590 m, 1480 w, 1430 ss 1370 m, 1325 w, 1280 s, 1260 vw, 1235 vs (sh), 1230 vs, 1200 vs, 1155 s, 1130 vs, 1105 vs, 1070 w (sh), 1025 w, -1 1 1000 w, 901 m, 870 s, 840 ss 752 s, 736 vs, 690 vs cm . H n.m.r. spectrum? a broad (25 c.p.s. at half height) multiplet of eight peaks (ortho-H) centred at -7.32 p.p.m., a multiplet (8 c.p.s. wide at half height)(meta and para-H) at -6.85 p.p.m. (area ratio 2s3), 19 and a septet (JH=QJP = 5.9 c.p.s. ) at -5.65 p,p0m. The P n.m.r. 3 = spectrum (CFCIg) contained a doublet (JQF „p i^O c.p.s.) of doublets (Jo„ c.p.s.) centred at +74.75 p.p.m. A doublet 3 centred at +75.1 p.p.m. was also present, believed due to fluoro- 2 9 diphenylphosphine oxide (J_ _. = 1026 c.p.s.) (lit. value 1020 c.p.s.). r — r This doublet was the largest resonance in the second fraction of the distillate (Pounds C, 58.93; H, 4,22; F, 20.26 %), whose infra-red spectrum contained all the peaks present In the spectrum proposed as that of this phosphine oxide (p. 13). The ^lp n.m.r. spectrum contained a doublet (Jp ™ = 1017 c.p.s.) centred at +188,2 92 p.p.m.| the bands were resolvable into narrow quintets. The n.m.r. spectrum contained an ill-defined septet (Jft! 7 c.p.s.), centred at -3.44 p.p.m., believed due to hexafluoro-2-diphenyl- phosphinoisopropanol. (b) Dime thylphosphine The phosphine (2.33 g, 37.5' mmoles) reacted immediately on mixing with 6FK (16.31 g, 98.3 mmoles); at -78°. the tube contained a white solid in the excess acetone.' As the mixture approached room temperature further reaction occurred violently and was quenched with the -78° bath. The solution was very dark brown in color. Most of the material (colorless) went into the vacuum system. Unreacted acetone (4,01 g, 24.1 mmoles) passed twice through a trap cooled to -78°. 1 The remaining volatile material included white crystals; these were separated out using a -23° bath, and removed from the vacuum system by dissolution into carbon tetra• chloride under nitrogen. The material exhibited a wide melting range i*-* 20-40°), and supercooling, but its composition (followed by H n.m.r, spectroscopy) could not be changed by sublimation. Tt analyzed as a 1:3 dime thyIphosphine-hexafluoroacetone adduct. (Found*: C, 23.80; H, 1.41; F, 60.96; P, 5.56 %. Calc. for H P P; Gs 23 60 E C IJ 7 18°3 ° >' > 1*26; F, 61.03; P, 5.55 %)t Infra-red spectrum (liquid film): 3280 vw, 3035 m, 2425 vw, 2000 vw, 1610 vw, 1440 w (sh), 1400 m, 1370 vs, 1340 vs, 1325 vs, 1310 vs, 1290 vs, 1285 vs, 1250 vs (sh), 1210 vvs, 1150 s, 1120 vs (sh), 1100 vs, 1080 vs (sh), 952 vs, 935 s, 909 vs, 870 vs, 844 m (sh), 806 s, 775 s, 755 s, 733 s, 717 s, 685 vs, 671 m cm"1. 1H n.m.r. spectrum (Cel., solution) : a broad (28 c.p.s. at half height) band centred *.x at -4.94 p.p.m,, a doublet (J = 21 c.p.s.) centred at -3.84 p.p.m., 93 and a doublet (J = 16 c.p.s.) at -1.81 p.p.m., relative intensities 2:2:3. The downfield signal at 100 Mc/s (67°) appeared as a septet 19 (J = 5.5 c.p.s.) of doubletsteJ.J.=.2.5 c.p.3.), F n.m.r. spectrum (CCl4solution) (CFClj) :. a singlet (14 c.p.s. at half height) at +74.5 p.p.m. and a broad (39 c.p.s. at half height) band at +77.8 p.p.m., area ratio approximately 2:1. The high field peak is 31 partially split Into a septet (J = 10 c.p.s.). The P n.m.r. spectrum (CCl^ solution) contained an approximate septet (J 2J 16 c.p.s.) with small secondary splitting, centred at +239 p.p.m. Separation of the liquid product using a -36° bath gave hexafluoro-2-H-isopr.opanol (0.1 g) and a material (3.04 g) of complex 19F n.m.r. spec trum^ which on v.p.c..analysis (dinonyl phthalate, 130°) gave three major peal|s. The latter two were very close together (totSl 64 mole %) and both were shown by infra- red, \ n.m.r. and 19F n.^. analysis to consist largely of the hexafluoro-isopropanol. ,J?he proton spectra contained a singlet at 6 c.p.s. )....$f$s-4.1 p.p.m., relative Intensity 1:1; the fluorine spectra conl/^jied a large doublet (J „ = 6.12 c.p.s.) at >•••*?•>, CF3-H ' +77. 5 p.p .m. The first peak (35 mole %) consisted mainly of 2-dimethyl- phosphinohexafluoroisopropanol (Found i C, 22,52; H, 3.04; F, 50.94; P, 10.33 %. Calc. for Cg^F OP: C, 26.32; H, 3.10; F, 49.98; P, 13,60 %). Infra-red spectrum (liquid film): 3230 w, 3030 vw, 2940 vw, 1370 m, 1350 w (sh), 1310 m (sh), 1280 s, 1260 m, 1220 vs', 1190 vs, 1175 m (sh), 1135 s, 1100s, 981 w, 948 m, 900 m (sh), 885 m, 837 w, 781 w, 736 m, 709 m (broad), 688 m cmr1 The H n.m.r. spectrum contained a poorly defined septet (Jjj-p*^6 c.p.s.) centred at -4.9 p.p.m. (OH) and a large band (20 c.p.s. wide at half height) centred at -1*35 p.p.in. (CH ) „ No meaningful integral was obtained because of overlapping impurity--a doublet (J = 15 cp.s,) of triplets (Ji= 4 c.p.s.) centred at -1.26 p.p.m. Additional signals were observed at -6.27 p.p.m. (doublet, J = 7 c.p.s.) and -4.06 p.p.m. (multiplet, J ~ 6.5 c.p.s,)(hexafluoro- 19 isopropanol)o The F n.m.r. spectrum (CFC1 ) consisted of a o doublet (JQP =p = 6.5 c.p.s,,) centred at 4-76.7 p.p.m. A doublet ^CFg-H = c.p.s.), due to hexafluoroisopropanol, was centred at +75.6 p.p.m., and a multiplet (J = 9 c.p.s.), at +75.1 p.p.m. .(c) Tetramethyldi phosphine e^':'"1 ' The diphosphine (2.19 g, 17.95 mmoles), immediately on melting, reacted vigorously with 6FK (9.03 g, 54.4 mmoles). The reaction was controlled with a -78° bath and then allowed to reach room temperature. All the-6FK was consumed. The products were stable to air and indifferent towards water. The material was distilled at 38 mm.; fractions were taken at 83-102° (most at 97°). 102-120°(most at 114°) and 120-150°(very small, most at o \ 1 142 ). The H n.m.r. spectra of these fractions did not correspond with that of the undistilled material. The first cut was redistill o at 69 mm.; the distillate was collected at 102-103 . The remaining fractions were then-added to the still pot and the distillation o continued. The temperature rose steadily until 120 ; a second o fraction v/as collected at 120-122 . The 102° cut (69 mm.) consisted largely of the 3:1 6FK- dime.thylphosphine adduct, of known infra-red and "^H n.m.r. spectra (p. &£). The second fraction analyzed as a 3:1 6FK-tetramethyl- diphosphine adduct, b.p. 120° (69 mm.)(Found^: C, 24,67; H, 1.78; F ? F, 55.68 %o Calc. for ^13^12 18°3 2'° Cs 25.2; H, 1,95; F, 55.1 %) Infra-red spectrum (liquid film): 3330 w (sh), 3280 m, 2980 vw, 95 2780 vw, 1755 vw, 1460 vw, 1420 w, 1370 s, 1310 s, 1290 vs (sh), 1265 vs, 1235 vs (sh), 1220 vs, 1205 vs (sh), 1190 vs (sh), 1175 vs, 1170 vs (sh), 1100 vs, 1035 w, 1000 vw, 966 s, 944 m, 918 m (sh), 900 s, 881 m, 870 w (sh), 844 w, 758 w, 741 w, 717 w, 710 w, 688 s cm"1. The n.m.r*. spectrum showed a doublet (J« 7 c.p.s.) (secondary splitting of ~1 c.p.s.) centred at -6.89 p.p.m., a very broad (-^35 c.p.s. at half height) band centred at -5.16 p.p.m., and a large, complex, irregular band centred at -1.53 p.p.m. The relative intensities were 1:1:12. The upfield signal showed prominences at -1.46 and -1.25 p.p.m.; these were doublets, with J = 3 and 2 c.p.s. 19 respectively. The F n.m.r. spectrum (CFC1 ) contained a doublet o (J = 6 c.p.s.) at +75.9 p.p.m., and a complex, irregular multiplet centred at +78.9 p.p.m. (d) Triethylphosphine TriethyIphosphine (1.05 g, 8.90 mmoles) and 6FK (6.70 g, 40.35 mmoles) reacted vigorously on mixing. The reaction was controlled with a -78° bath." The volatile material consisted entirely ©f unreacted 6FK (3.98 g, 24.05 mmoles). The remaining products were involatile and were .distilled at 180 mm. Two fractions were obtained: 147-156° and 157-159°. These cuts had almost identical infra-red spectra and elemental analyses; the spectra, however, differed from that of the undistilled product. The 19 analyses and F n.m.r. spectra indicated the presence of several compounds„• These substances could not be separated and were not further characterized. 2. 1,3-Dichlorotetrafluoroacetone (4FK) (a) Diphenylphosphine The phosphine (5.71 g, 30.7 mmoles) reacted immediately on mixing with 4FK (8j99 g, 45.1 mmoles) to give white crystals* Within half an hour the crystals quickly changed to an amber colored oil. Work-up of the volatile products gave only unreacted 4PK (0.35 g, 1.8 mmoles). The remaining material was distilled at 10"3 mm. Three fractions were taken: 133-146°; 146-156° (some levelling off at 156°) and 156-178°. The distillate was identified as a mixture of l,3-dichloro-2-H-tetrafluoroisopropyl diphenyl• phosphine oxide, and 1,3-dichloro-2-diphenylphosphinotetrafluoro- isopropanol, contaminated with trifluorodlphenylphosphorane and fluorodiphenyIphosphine oxide. The following analytical, infra• red and "'"H n.m.r. data were obtained from the middle fraction of the distillate. Found^: C, 47.40; H, 3.13; CI, 15.37; F, 18.74; P, 8.71 %. Calc. for C^H^ClgF^OP: C, 46.80; H, 2.88; CI, 18.41, F, 19.73; P, 8.04 %. Infra-red spectrum (liquid film): 3130 w, 2300 vw (broad), 1960 vw,.1890 vs , 1820 vw, 1755 vw, 1590 w, 1470 w, 1420 s, 1370 w, 1335 w, 1315 w, 1265 w (sh), 1250 vw, 1230 m (sh), 1210 s, 1145 vs, 1120 vs, 1065 m, 1020 w (sh), 995 m, 961 m, 862; m (broad), 837 m (sh), 781 w (sh), 749 s (sh), 733 s, 687 s cm"1. The 1H n.m.r. spectrum contained complex bands associated with the aromatic protons. Two-thirds of the area lay under one large peak at -6.84 p.p.m., which showed splitting of ^2 c.p.s. The remainder of the aromatic bands lay further downfield, centred approximately at -7.76, -7.54 and -7,18 p.p.m. A multiplet • (J S3 6 c.p.s,) was centred at -5.35 p.p.m. This multiplet was much more clearly defined in the spectra of the first and third fractions of the distillate; in the case of the latter a quintet (J = 6 c.p.s.), which showed slight secondary splitting, occurred 19 at -5,58 p.p.m. The F n.m.r. spectra (CFC1 ) of the second and third cuts showed the characteristic bands of trifluorodlphenyl• phosphorane and fluorodiphenyIphosphine oxide (see-p. 11 ), and an un- assigned doublet (J = 805 c.p.s.) centred at +39.85 p.p.m. In addition these spectra contained a pair of doublets, centred at +58..35 p.p.m. ( (b) Dimethylphosphine Dimethylphosphine (1.93 g, 31,1 mmoles) and 4FK (6.70 g, 33.7 mmoles) reacted, immediately on mixing to give a white solid which melted just below room temperature. After two or three minutes the liquid violently decomposed, leaving a mass of black solid. Work-up of the volatile products gave trifluorodimethyl- 1 19 phosphorane (0.39 g). of known infra-red, and H and F n.m.r., spectra (p. 14), condensing in a trap cooled to -64°. Unreacted 4PK (0.74 g), contaminated with the phosphorane, passed twice through the -64° bath. Traces of silicon tetrafluoride passed through a -130° bath. A fraction (0,57 g) stopping in a -23° trap had a complex "*"H n.m.r. spectrum whose major feature was a doublets of doublets centred at -1.5 p.p.m., due to fluorodimethyl phosphine oxide (JOTT p = 15 c.p.s., J„u „ = 9 c.p.s.) (lit. value 16 and 9 c . p. s .). 3. 1,1,1-Trlfluoroacetone (5FK) (a) Diphenylphosphine Diphenylphosphine. (4.02 g, 21.6 mmoles) and 3FK (7.46 g, 66.6 mmoles) at 20° afforded one colorle-ss liquid phase which slowly deposited white crystals over a. period of hours. After .98 standing overnight a mass of white crystals was produced. The appearance of the mixture did not change further over 1 week. The volatile matter passed through a -64° bath and was entirely unreacted 3FK (6.64 g, 59.2 mmoles).. The non-volatile products consisted of white crystals and unreacted diphenylphosphine. The solid was purified by washing with benzene. The resulting crystals (0.78 g, 12 %) were identified as l,l,l-trifluoro-2-diphenyl- phosphinoisopropanol, m.p. 142-147° (Found: C, 57.87; H, 4.72; P, 9.21 % M(Rast), 315. Calc. for C15R"l4F30P: C, 61.61; H, 4.60; P, 10.10; M, 307). Infra-red spectrurAKBr disc): 3060 m, 2780 vw, 1584 vw, 1482 w, 1440 m, 1404 w (broad), 1375 vw, 1265 m, 1199 s, 1185 vs, 1144 vs, 1109 s, 1084 s, 1028 vw, 995 w, 935 w, 928 w, 846 vw, 759 w, 746 vw, 733 w, 725 m, 699 m, 690 m cmr1 XH n.m.r. spectrum (CH^OH solution): a complex multiplet centred at -7.7 p.p.m. (ortho-H), a multiplet at approximately -7.15 p.p.m. (meta, para-H), a doublet (J = 13.5 c.p.s.) at -1.2 p.p.m. (CH ); CH^-p <-> 19 the area ratios were 4:7:3 (calc. 4:6:3). F n.m.r. spectrum (CFC13)(CH30H solution): a singlet (4.4 c.p.s. wide at half height) at +73.8 p.p.m. The experiment was repeated at elevated temperatures, using 7.15 g 3FK (63.8 mmoles) and 5.19 g diphenylphosphine (27.9 mmoles). At 96° (47 hrs.), the products appeared no different. Heating to 153° (19 hrs.) afforded a slightly opaque colorless oil, but the products still contained unreacted 3FK (5.38 g, 48.0 mmoles) and diphenylphosphine. The materials we're recombined and heated at 178° (20' hrs.), which gave a- yellowish oil and white crystals. Work-up of the volatile products gave unchanged 3FK (1.67 g, 14.9 mmoles), which passed through a -64° bath and condensed in a trap cooled to -96°« Through this trap passed a small amount of fluoro- form and carbon dioxide, of known infra-red spectra, A -64 condensate (0.4 g) consisted largely of 1,1,1-trifluorolsopropanol of known "^H n.m.r. spectrum (p.100). The involatile material contained only a trace of diphenyl- phosphine, as determined by infra-red spectroscopy (P-H stretching frequency at 2325 cm. ). The mixture was diluted with benzene and the solid filtered off. Removal of benzene under reduced pressure precipitated further solid. The process was repeated twice. The solid (2,0 g, 33 %) was identified as diphenylphosphinic acid, m,p. 190.5-i92.5° (lit. value113 190,5-192°) (Found: C, 65.96; s H, .§,06; P, 14,42$; M(Rast), 413. CHOP requires: C, 66.08; i J. Ci _L J_ 2 H, 5.08$ .P, 14.22 %i M, 218). The remaining material (3.15 g) was distilled at 10° mm. Two fractions were taken: 164-170° and 171-176°. The distillate was identified as 1,1,1-trifluoro- isopropyldiphenylphcsphine oxide, containing some 1,1,1-trif luoro- 2-diphenylphosphinoicopropanol and unidentified material (Found, fraction #1: C, 58.67; H, 4.70;' P, 10.31 M(Rast), 291. Found, fraction #2: C, 62.57; H, 4,98; P, 12.32$; M(Rast), 227. Calc. for C15H14F30P! C, 61.61; Hs 4,60; P. 10.10 %; M, 307). The infra-red spectra were almost identical. Fraction #1; 3280 w, 3125 m, 2325 w, 1960 vw, 1905 vw, 1820 vw, 1755 vw, 1670 vw, 1590 1470 m, 1430 ni, 1370 w, 1320 m, 1275 s, 1235 m (sh),1220 s, 1180 v 1155 s, 1120 vs, 1100 s(sh), 1090 m, 1065 m (sh), 1030 m, 1020 m, 996 w, 976 w (sh), 966 w (ah), 957 m, 944 m, 918 m, 900 w, 878 m, 833 m, 816 w (sh), 800 w, 788 vw, 744 s (broad), 730 s, 717 m, -1 1 695 s cm, H n.m.r. spectra: fraction #1: a broad (~-30 c.p.s. at half height) band at -7.3 p.p.m. (ortho-H); a large signal at -6.85 p.p.m. (meta,.para-H); small, broad unresolved peaks at -5,7, -4,55 and -3,55 p.p.m.; a doublet (J =23 c.p.s.) of 100 doublets (J = 6.5 c.p.s.) centred at -1.11 p.p.m. (overlapping CH^-H impurity at -1.20 p.p.m.). The spectrum of the second cut differed in the non-aromatic region: the only significant downfield resonance was a singlet at -3.65 p.p.m. (OH); the upfield resonance consisted of a doublet (J"CH _p = 13.5 c .p. s. ) (p. 98 ) • centred at -1.4 p.p.m., a singlet at -1.15 p.p.m. and the doublet centred a't -1.1 p.p.m. 19 (lower half hidden). The F n.m.r. spectrum (CPC1 Qf the first cut showed a singlet at -70.9 p.p.m., and a doublVtM _p = 210 3 c.p.s.) of doublets (J „= 5.8 c.p.s.) centred at -78.0 p.p.m., CF3 due to the phosphine oxide., (b) Dime thylphosphine Dimethylphosphine (1.98 g, 31.9 mmoles) and 3PK (5.47 g, 48.8 mmoles) gave one colorless liquid phase at 20°. Unreacted 3PK (0.8 g, '7.15 mmoles) passed through a -64° bath (M, 107.3; . C,H,P,0 requires 112). The -64° condensate was separated by means o o o of a -23° bath. The material which passed'through (0.37 g, 3.25 mmoles) was identified as 1,1,1-trifluoroisopropanol (Pound: C, 32.59; H, 4.85; P, 51.26 $. CgHgFgO requires: C, 31.59; H, 4.42; F, 49.94.$). Infra-red spectrum (liquid filmi) : 3390 m (broad), 3030 w, 2940 vw, 1450 w, 1410 vw, 1370 w, 1325 w, 1300 m, 1265 m, 1250 m, 1165 vs (broad), 1080 s (sh), 1010 s, 971 w, 939 w, 914 w, 878 w (sh), 866 w, 788 vw, 746 vw (broad) cm?1 1H n.m.r. spectrum: a singlet at -4.66 p.p.m. (OH), a septet (jJJ„QH = ^H-GF = 3 " 3 c.p.s.) at -3.81 p.p.m., and a doublet (JQJJ _H = 6.7 c.p.s.) cen- tred at -1.00 p.p.m. o The main reaction product condensed in the -23 trap and was identified as^'M.., 1-trifluoro-2-dlmethylphosphlnoisopropanol (4.15 g, 75$) (Founder; C, ' 33. 31;, H, 5.70; F, 30.99; . P, 16.0'6 $. Calc. : for C5H10F^0P: C, 34.48;: iH,;,5.79; P, 32.71; P, 17.80 $). The 101 compound was air-sensitive. Infra-red spectrum (liquid film): 3230 m (broad), 3010 w, 2940 vw, 1768 vw, 1718 vw, 1467 m, 1432 1385 m, 1338 m, 1300 s, 1279 s, 1260 s (sh), 1162 vs (broad), 1078 s, 1028 w, 974 w, 939 s, 893 m, 865 m, 821 w, 751 w, 713 m 691 w, 676 v/ cm.1 n.m.r. spectrum: a singlet at -3.75 p.p.m (OH), a doublet (J_„ = 8.5 c.p.s.) centred at -1.32 p.p.m. = and a doublet (Jnu p 3.3 c.p.s.) centred at -0.98 p.p.m., 19 area ratios 1:4:6.5 (calc. 1:3:6).- ,P n.m.r. spectrum (CFCl^) doublet (J„„ T> =- 13.8 c.p.s.) centred at +76.85 p.p.m. DISCUSSION A. Results Diphenyl- and dimethylphosphine react with hexafluoro• acetone, 1,3-dichlorotetrafluoroacetone and 1,1,1-trif luoroacetone to give lsl adducts, phosphino-iospropanols and/or isopropyl- phosphine oxides M R2PH + R'COR" > RgPC(OH)R'R " + RgP (0) CHR »R R = C6H5,CH3; R« = R" = CP^ ,CFgCl;R' = CP^R " = CH3 In one instance (R = CR"3>R' = R" = CFgCl), no stable adduct was obtained. The phosphines are readily consumed quantitatively at or below room temperature (except when R = CgHg, R» = CF3,R" = CHg): the products are, however, contaminated with (CFgJgCHOH (CF3(CH3)CH0H) or RgPFO and RgPFg. The pertinent n.m.r. data of the adducts are presented in Table X. 1. Hexafluoroacetone (6FK) (a) Diphenylpholphine Diphenylphosphine and 6FK' readily react at 20° to give a trance of hexafluoro-2-H-isopropanol, and an involatile oil which on distillation affords a 1:1 adduct, hexafluoro-2-H-isopropyl- o -3 diphenylphosphine oxide, b.p. 132-134 (10 mm.), along with some fluorodiphenyIphosphine oxide and possibly hexafluoro-2-diphenyl- phosphinoidopropanol (C6H5)gPH + (CP3)gC0 »(C6H5)gP(0)CH(CF3)g + (CgHgJgPFO + (C6H5)2PC(0H)(CF3)2 The fluorodiphenylphosphine oxide was identified by n.m.r. spectroscopy. The isopropyl-phosphine oxide, identified by elemental analysis, was distinguished from the expected adduct, hexafluoro-2- diphenylphosphinoisbpropanol, primarily-fey n.m.r. spectroscopy. In particular, the ^B. n.m..-r.'_- spectrum contained a sharp septet 103 . TABLE X and 19F n.m.r. Data8 of the Phosphino-lsopropanols and Isopropyl-Phosphine Oxides RgPCCORlR'R" RoP(0)CHR R C H R 3 C H CH, C ff C H R ' CH 6 5 6 5 6% • °6 53 6 5 ! ! R CF CFgCl GP CFr CP CF^Cl CF3 R 3 3 3 8} M R CF3 CFaCl CH3 CH, CF3 CFgCl CH3 R b b b ' c -4.9 ... -3.65 -3.75. -5.65 -5.58 &0H -5.28 £H d ~6' 6-7 ~0 ~0) 5 & 9 J J0H-F H-F e ~1 ~0 ~0 ~»0 ~1 J J0H-P' «1 H-P -1.35 -- — -0.98 CH3(R) f U 3.3 6.5 CH3-P ^CH-j-H -1,2,-1.4 -1.32 -1..11 n &H5(R") ScH3(R ') 13.5 8..5 23 J 4PH3-P ."" CH„-P £.h -*+76.7 +58.91 +73.8S +76.85 +74.75 +58.35 +78.0 Rf 6.5 97" 13.8 170 109 210 T ^Rf-P Rf-P r ~0 o 5,8 Rf-0H.^ ,, ~0 ~0 6.3 2 Rf-H Chemical shifts in...p.p.m. 5 coupling constants in c.p.s, b Solution in other adduct c Indistinguishable from impurity d Not resolvable because of superimposed H=CH3 coupling e Not resolvable f Not determined because of overlapping impurity ^ Solution in methanol h Fluorotrichioromethane reference May indicate p2P(0)C(OH)(CFgCl)2 (see p.109) 1 04 (j = 6 c.p.s.) at -5.65 p.p.m., essentially Identical with the -i r\-i septet (J = 6.2 c.p.s.) (lit. value 6 c.p.s.) due to the methinyl proton in hexafluoro-2-H-isopropanol. Hydroxyl protons in general usually give singlets, including 2-substituted hexafluoroisopropanols, 109 (CF3)gCR0Hs e.g. R = H (p. 93 ), (CH3)gAs . Although some splitting was observed for R = (CH3)gP (p. 9.3 ), the band was poorly witresolvedh littl. e Compoundvariatios n ofi n ththe e typhydrogen-fluorine (CF ) CHR give e spin-spiclear cun t couplingseptets, e.g. R = OH, J = 6.2 c.p.s. (p.93 ), 6 c.p.s.101; R = (CH ) SIO, 105 105 J = 6.0 c.p.s, ; R = (CH3)3SnO,.J =6.1 c.p.s. The compound is formulated as the Isopropyl-phosphine oxide rather than the isopropoxy-phosphine on the basis of the 19F n.m.r. spectrum, which shows J-^ _. = 170 cp.s. The phosphorus and • " • °F3"P fluorine atoms in the isopropoxy compound are separated by four single bonds; if coupling were to occur over such a route, it 111 would be expected to be weak. Ramirez et al, find only singlets .f for the system F„C-C-0-P, The isopropyl-phosphine oxide arises from rearrangement of the isopropoxy-phosphine in the course of distillation. This is an example of the well-known Arbuzov reaction. Phosphinite esters, RgPOR.', can behave in this way in the absence of other reagent (i.e. alkyl halide), cn heating .114 strongly"' 1 The H n.m.r, spectrum of the second fraction of the distilled product contained also an ill-defined septet at -3.44 p.p.m, (JSJ7 c.p.s,). This band may be due to the hydroxyl proton of hexafluoro=2-diphenylphosphinoisopropanol, The hydroxyl hydrogen of the methyl analogue, described below, gave a poorly defined multiplet (JS6 c.p.s,). (b) Dimethylphosphine 105 Dimethylphosphine and 6PK react vigorously below room temperature to give the expected 1:1 adduct, hexafluoro-2-dimethyl- phosphinoisopropanol, along with hexafluoro-2-H-isopropanol and a substance which analyzed as a 1:3 dimethylphosphine-6FK adduct C H P P (CH3)2PH 4 (CP3)2C0 MCF3)gC(0H)P(CH3)2 + (CF^gCHOH + ll 7 18°3 The 1:1 adduct was identified by elemental and spectroscopic analysis. The best evidence was provided by the infra-red spectrum, which was closely similar to that of the arsenic'analogue prepared by Cullen and Styan"1" TABLE XI Infra-Red Spectra (cmT1) of the Hexafluoro- Isopropanols, (CF3)gC(OH)E(CH3)g E = Pa 3230 w 3030 vw 2940 vw 1.370..m' 1280 s 1220 vs 1190 vs . 1135 s 1100 s 948 m 885 m 736 m 709 m E = Asb 3635°m 3020 w ' 2950 w 1379 m 1269 vs 1228 m 1205 vs 1138 m 1107 s 943 m 873 m 750 m 708 m a Liquid film b Vapor The higher value for the 0-H stretching frequency reflects the lack of hydrogen bonding in the vapor phase Work-up of the products in the vacuum system gave only a small amount of hexafluoro-2-H-isopropanolj however, v.p.c, purification (130°) of the main liquid product gave 64 mole % of this compound and only 35 % adduct. The material was shown to be free from (CP3)gCH0H (by ^ n.m.r, spectroscopy) prior to purification. Thus the adduct decomposed to a large extent in the column, The n.m.r, spectra of the purified adduct revealed imparities, the major one having been hexafluoro-2-H-isopropanol. The presence of this compound explains the low phosphorus content- in the analytical sample. The elemental analysis of the sublimed solid product clearly indicates a 1:3 dime thylphosphine-6FK ratio. However, the structure of the adduct could not be determined. It is noteworthy that the substance is a tri-, rather than a di-adduct. This result did not appear surprising in light of the results obtained, by Ramirez}11 who found that 6FK readily reacts with phosphinite, phosphonite and phosphite esters, and triphenylphosphine, to give dioxaphospholanes in good yields F3Cv ,CF3 Y2PZ + 2 (CF3)2G0—• F C F = H 0C H r° 3 Y>Z °6 5* 6 5' alkoxy 0 0 /|\ Y Z Y No monoadducts were observed. Being a tertiary phosphine, the 1:1 adduct, hexafluoro-2-dimethylphosphlnoisopropanol, might be expected to condense with a further two moles of 6FK to give an 1 analogous phospholane, with Y = CHg, Z = (CF3)gC0H. The H n.m.r. spectrum of the product, however, is not consistent with this s true ture0 Although alcohols have been reported, to add across the ^9 carbonyl group of 6FK" , a triadduct formed by the addition of the OH bond of the lsl adduct across a further mole of 6FK seems unlikely, since there appears no reason for the resulting diadduct to be unstable with respect to condensing with a third mole of 6FK. (c} Tetramethyldlphosphine Tetramethyldiphosphine readily reacts with 3 moles of 6FK below room temperature to give an involatile oil which on. distillation affords the 1:3 dimethylphosphlne-6FK adduct described above, along with a material which analyzed as a 1:3 tetramethyldiphosphine-6FK 107 adduct, b,ps 120-122° (69 mm.-),. Double distillation was required to effect a reasonable separation and purification of these substances. Again, however, the structure of the triadduct could not be ascertained. Although the facile consumption of 3 moles of 6PK strongly suggests dioxaphospholane formation, the infra-red and 19F n.m.r. spectra appear to refute this structure. The former contained a medium intensity band in the 0-H stretching region and had only a.weaFband In the asymmetric P-O-C stretching region of 1050-990 cm!1, a strongly" 68 absorbing mode . Even in cyclic systems, the band appears in this region^15. The "^F n.m.r. spectrum showed doublets (J = 6 c.p.s.) rather than singlets; as previously mentioned, Ramirez reports singlets for the F^C-C-O-P system of the dioxaphospholanes.. (d) Tri e thylphosphine Triethylphosphine reacts immediately on melting with 6FK. Even with Immediate cooling by a -78° bath, the phosphine consumed 1.83 moles of 6FK to give a material the 19F n.m.r, spectrum of which, after distillation, indicated the presence of several compounds. These substances could not be separated and thus were not further characterized. The reaction is. significant, however, in that the expected dioxaphospholane, (CgR"5)3P0C (CF3)gC (CF3) g6, is not formed to 19 a great extent, if at all. A doublet (J = 5.5 c.p.s,) in the ' F n.m.r. spectrum may be due to this compound. The results of this reaction reflect the considerably increased nucleophilic strength of triethyl- phosphine compared with the trivalent derivatives used by Ramirez and, co-workers111, who examined phosphites, phosphonites, phosphinites and triphenylphosphine; the phosphbnites and phosphinites were in all cases esters of aromatic.acids. Since triphenylphosphine reacts at o -78 , it is not surprising that the reaction involving triethyl- phosphine should "get out of hand" at the same temperature. 108 2. 1.3-Dichlorotetrafluoroacetone (4FK) (a) Diphenylphosphine Diphenylphosphine and 4FK give an amber oil which on distillation affords a mixture of 111 adducts, l,3-dichloro-2-H- tetrafluoroisopropyldiphenylphosphine oxide and 1,3-dichloro-2- dlphenylphosphinotetrafluoroisopropanol, in roughly equal amounts, contaminated with trif luorodlphenylphosphorane and fluorodiphenyl- phosphine oxide (C6H5)2PH + (CP2Cl)2C0-*(C6H5)2P(0)CH(CPgCl)2 + (CFgCl)g C (0H)P (CgHg)g 1 9 The two phosphorus fluorides were identified by F n.m.r.. spectro- copy. The presence of both adducts, identified by elemental analysis, was shown by n.m.r. spectroscopy. The non-aromatic multiplet in the n.m.r. specfera varied from fraction to fraction of the distillate, indicating changing concentrations of overlapping multiplets (CH and OH). Splitting of the OH band is also observed for hexafluoro-2-dimethylphosphinoisopropanol (p. 93 ). 1 Q The F spectra contained two doublets; the intensities of these varied from fraction to fraction. The doublet corresponding wiith the higher boiling compound was further split into doublets (J ~5.2 c.p.s,, superimposed on slight secondary splitting) while the secondary splitting on the other doublet could not be more precisely resolved. On this basis the higher boiling adduct is assigned the phosphine oxide structure, i.e. the sharper splitting exhibited by Rf-CH over Rf-COH. Thi3 is corroborated by the ^H n.m.r, spectra; that of the final distillation cut showed the non-aromatic signal well resolved Into a quintet (J^_Qp ^6 c.p.s.). The assignment of the isopropyl-phosphine oxide structure rather 109 than the isopropoxy-phosphine has already been discussed (p.104). The magnitude of J p in the phosphino-isopropanol (see Table X) is of the same order as found for the isopropyl-phosphine oxide adducts of this series, which is an order of magnitude greater than what is found for the isopropanols. Therefore the possibility that the alcohol is in fact also a phosphine oxide, i.e. 1,3-dichlorotetrafluoroisopropylol-2-diphenylphosphine oxide, must be acknowledged, (b) Dimethylphosphine Dimethylphosphine and 4PK do not give a stable adduct; rather, the liquid product violently decomposes on reaching room temperature, leaving a mass of black solid and small amounts of trifluorodimethylphosph©rane and fluorodimethylphosphine oxide (and a trace of silicon tetrafluoride) (CH3)2PH + (CP2C1)2C0 •(CH3)2PF3 + -(CHgJgPFO' + .... The oxide was identified by its characteristic "^H n.m.r. spectrum; 1 19 the trifluorlde, by its infra-red, and H and F n.m.r., spectra. 3. I„l,l"Trifluoroacetone (3FK) (a) Diphenylphosphine Diphenylphosphine and 3FK slowly deposit crystals of 1,1,1- o trifiuoro-2-diphenylphosphinoisopropanol, m.p. 142-147 , over a period of several hours. (C6H5)2PH + CF3C0CH3 • (C6H5)2PC(0HXCF3J3H3 No visible change occurs after the materials have been allowed to stand overnight. The reaction is, however, only 12 % complete after 1 week. Reaction-is only partly complete at 153°. At 178°, however, the consumption of diphenylphosphine is almost quantitative, giving mainly 1,1,1-trifluoroisopropyldiphenylphosphine oxide, b.p. no *=• 3 ^170 (10 mm.), along with 1,1,1-trifluoro-2-diphenylphosphino- isopropanol, diphenylphosphinlc acid and 1,1,1-trIfluoroisopropanol (traces of fluopoform and carbon dioxide) 178° (CRHc-)pPH + CF,C0CH, »(C H ) P(0)CH(CF )GH + (C H ) PC (OH) (CP,) CH o o d 6 5 652 33 652 32 + (C6H5)2P(0)0H + CP3(CH3)CH0H The phosphine oxide was identified by elemental analysis and n.m.r. spectroscopy.. Although the methlnyl resonance (broad, unresolved) did not occur as a visible septet (as it does in CF^CHgCHOH) because of superimposed splittings, the methyl hydrogens gave a doublet (JQJJ _p = 23 c.p.s.) of doublets (JQJJ _g = 6.5 c.p.s.). The iq "3 3 P n.m.r'. spectrum showed a doublet of doublets, both splittings feeing of the same orders of magnitude as observed in the analogous adducts obtained from 6FK and 4PK (see Table X). The phosphiRO- isopropanol v/as Identified from its previously determined methyl proton resonance, and the appearance of a singlet at -3.65 p.p.m, (OH) in the spectrum of the material dissolved in the phosphine oxide. The diphenylphosphinic acid was identified by microanalysis and melting point determination, while the trifluoroisopropanol was characterized by its known '''H n.m.r, spectrum, described below, (b) Dimethylphosphine Dime thylphosphine and 3FK react smoothly on mixing to give the expected 1;-1 adduct, 1,1,1-triflucrc-2=>dimethylphosphino- isopropanol, in good yield, along with a little 1,1,1-trifluoro• isopropanol (CH3)2PH + CF3C0CH3 » (CH3)gPC(0H)(CF3)CH3 + CF3(CH3)CH0H The adduct was identified by elemental analysis and n.m.r. spectroscopy. The spectrum consisted of a singlet at -3.75 p.p.m. (OH), a doublet at -1.32 p.p.m. (J n v - 8.5 c.p.s.) and a - • • CH3-0-r- • J = 3o5 doublet at -0.98 p.p.m. ( CH _p c.p.s.), area ratios ls4?6.5 3 1 '1 •] (calc. 1 :3s 6 )„ The appreciably greater magnitude of the three bond coupling Is analogous to that observed for the diethylphosphino- derivatives of the fluorinated cyclobutenes described in Chapter I, 30 This behavior is also noted by Nixon and Schmutzler for tertiary butyl phosphorus derivatives. The 1,1,1-tylfluoroisopropanol was identified by elemental analysis and spectrocopic data. The infra-red spectrum (liquid film) contained the characteristic broad band of medium intensity (0-H stretch) exhibited by alcohols in the liquid phase. The 1H n.m.r. spectrum consisted of a singlet at -4.66 p.p.m.- (OH)., a septet ( JTT = JTJ = 6,7 c.p.s.) at -3,81 p.p.m., and a doublet (JQJJ „JJ = 6.7 c.p.s-.) centred at -1.00 p.p.m. o B. Proposed Mechanisms The route followed by the reactions of the fluorinated acetones with dim.ethylphosphine seems clear--the electron deficient carbonyl carbon atom undergoes nucleophilic attack by the freely available phosphorus lone pair of electrons R R = R' = CP„,CF cia| U (CH3)2PH + RCOR' > (CH3)oP-C-0 R = CF^R' = CH, H R' Intra- or intermolecular proton transfer then gives the 1:1 adduct, a. 2-dimethylphosphino-isopropanol. The reactions are analogous to 109 , i . 103 , , the addition of dimethylarsine s phosphine and secondary 107 amines to polyfluoroketones. In the case of diphenylphosphine, however, the situation is not so simple, in that the direction of addition is mixed, i.e. ID the products are mixtures of the phosphino-isopropanols with iso- a No stable adduct obtained with 4FK. b The formation of (CF3) gC (0H)P (j)g was not proven. 112 propoxyphosphines (the latter having been isomerized via the Arbuzov reaction to isopropyl-phosphlne oxides). The reverse addition was unexpected, since nucleophilic attack would be expected to occur at the carbonyl carbon atom.. The natural polarity of the £+1~ 105 carbonyl group, C=0, is enhanced by ©t-fluorine atoms . However, Ramirez and co-workers1"'"1 find that phosphites, phosphonites, phosphinites and triphenylphosphine Invariably attack the oxygen atom of 6PK (to give dioxaphospholanes), but do not discuss why the (nucleophilic) attack should occur at the. oxygen atom. Certainly diphenylphosphine would be expected to be a weaker nucleophile than dimethyIphosphine, because of inductive considerations, and possible derealization of the lone pair into the aromatic rings H . P H C H e etc butyne-2; the large amount of cis-adduct formed (**40 %). suggests a considerable contribution from a mechanism involving a four- centre intermediate. However, merely reducing the strength of a nucl<;eophile cannot in itself explain a reversal In the direction of addition. Lone pair attack should still occur at the.carbon atom, to give the phosphine-Isopropanol--these compounds are in fact observed. It is therefore likely that the reverse addition is the result of a competing mechanism. Three possibilities are seen. One is reaction via a four-centred intermediate, viz. R J,c_— 0 .rf—P (C6H5)g A possible objection to this path is that the polarity of the P-H bond in diphenylphosphine, although likely slight, would be expected to be P-H because of the somewhat electronegative phenyl- groups. (Phosphorus and hydrogen are equal on the Pauling scale of electronegativities-). In this event the P-H bond should align itself in the opposite direction to that shown. The second possible mechanism seen for initial 0-P bond formation is r.ucleophilic attack by the carbonyl oxygen on the phosphorus atom, to give a five-coordinated intermediate (including the lone pair) H R followed by intra- or intermolecular hydride transfer to give the 105 isopropoxy derivatives. The analogous mechanism has been proffered for the additions of Group IV hydrides to hexafluoroacetone 116 Griffin et al. have reported an example of hydroxide attack on phosphorus, with concomitant hydride shift 0 0 1/ C^CHg-P > Cl + CH3P0(0H)g H X0H The third alternative involves attack by phosphorus on the carbonyl carbon atom, followed by epoxide formation: 0Q~ 0 e i A 0 (C6H5)2PH + RCOR (C6H5).2P-C-R» 0 I I C H P C R ( 6 5)2 - ~ (CFIH5) -i-VO-C-R H R I I H R Simple proton transfer would then give the isopropoxy-phosphine. H A R 117 similar epoxy intermediate is postulated to explain the ready reaction between phenyldichlorophosphine and benzophenone. It should be noted that the greater energy of the P-0 bond over P-C (86 and 65 118 kcal./mole respectively) would provide a driving force for,epoxide formation. 114 CHAPTER IV GENERAL DISCUSSION The most significant point brought to light by the results of this investigation is the special place occupied, by phosphorus--the chemistry of this element is often Irregular beside that of nitrogen and arsenic. In particular, it was found that several compounds of phosphorus showed substantially; grea ter.--react! vi tyy thanp,that t:expected;f romra comparison with the reactions of nitrogen and/or arsenic analogues. The pronounced reactivity of phosphorus is especially noticeable in reactions involving the f luorocarbons, ' particularly hexafluorobutyne-2. The reactions of some of the phosphines with this compound, in fact, provide rather dramatic comparisons with nitrogen and arsenic analogues. Whereas chlorodimethyl-arsine and -amine require ultra• violet irradiation or heat to bring about reaction'with the butyne, the phosphine reacts vigorously, immediately on melting of the phosphine (-M'°), giving' a considerable amount of dark brown solid. No adduct is formed from chlorodime thyl-* phosphinea. The same violent reaction occurs with tetra- methyldiphosphine (m.p.'-'O0), whereas cacodyl (m.p.~0°) reacts smoothly to give the 1:1 adduct. , To explain the paradoxical behavior of these phosphines towards hexaf luorobutyne-2 ,• it is necessary to consider the mechanisms of the general reaction of F,CCSCCF, with R EY, 3 3 2 ' a No solvent was used, since none was used with MepAsCl or Me?NCl. The use of .a solvent, e.g. toluene,'woul3 allow thawing at a much lower--tempera ture . 115 Y = Cl, H, ER2; R / CP,.. For Y = H, ER it is generally conr sidered • that reaction entails. nucleophilic attaclk by the metalloid lone pair on the triple bond, yielding a 1,3- dipolar intermediate: .CF3_ ^ R = alkyl,phenyl R^Y CP ' E = N, P, As % . 3 Prom the vigor of the reactions,' it is inferred that for. E = P, the intermediate is stabilized to an extent not encountered for N or As. Apparently the phosphorus 3d orbitals are eminently suitable for' d^-p^ overlap with the unsaturated carbon-carbon bond. As already mentioned (p-. 86), Redely and Weis have -postulated' such a stabilizing effect to account for thuj considerable stability of two^-cyano phospholes. The analogous situation prevails for triphenylphosphine; however since the intermediate is not subject to transfer of Y* the lifetime of ths dipole is prolonged. The dramatic difference in the reactions of triphenylphosphine (violent at -78°) and trimethylamine (very slow at 20°) with the butyne would appear to provide striking evidence of d^ -p^ bonding. Any concrete conclusions, however, should await complementary investigations, particularly the behavior of . triphenyi-amine and -arsine, and trialkyl-phosphine and -arsine tov/ards hexaf luorobutyne-2. Changes in the electronegativity of the substituents on phosphorus will have a considerable effect on the d_ -p.. 119 bond energy . This point is perhaps important when considering chlorodimethylphosphine — the chlorine atom does not significantly reduce the reactivity of the phosphine (relative to diethyl- \ • 116 phosphine), whereas, the chloro-amine and -arsine are much less reactive towards unsaturated fluorocarbons than the respective hydrides. This is likely the result of d^-p^, interaction between the phosphorus and chlorine atoms influencing the energy of the d^-p ^ bond in-the (CE3) QPC1-F3CC~-CCP3 intermediate. The analogous situation has been stated to occur in phosphine oxides, i.e. the P=0 bond energy is> affected by d.^'-p^ interactions between the 120 phosphorus and substituent atoms. As already mentioned,, the presumed first step in the reaction of the phosphines with the unsaturated fluorocarbons is nucleophilic attack by the lone pair on the unsaturated carbon-carbon bond. This premise is substantiated by the results using bis(trifluoromethyl)phosphine and tetrakis (trifluoromethyl)diphosphine. The lack of reaction of these compounds is consistent with greatly decreased availability 'of the' Ion©, pair owing to the inductive effect of the electro• negative trifluoromethyl groups. Consistent also is the formation of th© diadduct along with monoadduct in the slug-l gish reaction-, .'of: (trif luoromethyl) phosphine;- with hexafluoro- butyne--here a different mechanism appears to take place (see p. 83). . When the lone pair of' the'highly reactive chlorodimethylphosphine is made unavailable (as in chloro• dimethylphosphine sulfide, p. 79), the compound becomes essentially inert'to the butyne. The complete lack of any cis 'isomer in the adduct obtained -from diethylphosphine and hexaf luorobutyne-2 indicates that the cis form o:f R EC (CF )==CHCF, , (R = alkyl, phenyl; & O £ E = N,P,As) originates via a four-centre mechanism rather than 117 through hypercconjugation of the l?3-dipolar intermediate, since there seems no reason why hyperconjugation should occur for R = alkyl, E = N/(l4% cis), As., (&% cis), but not P (p% ci It is manifestly possible, however, that in the case of dialkylphosphinec, the 1,3-dipolar intermediate, because of d^y— p^ stabilization, is favored ,ito,-> the extent of complete exclusion of a four-centred mechanism. -'• It will be recalled that the reactions of the fluorinated acetones with diphenylphosphine give phosphino-lsopropanols and/or isopropyl-phosphine oxides (rearranged isoprppoxy- phosphines). The mechanism of the formation of the P-O-C-K system is 'In doubt, the most likely paths being a four- centre intermediate oP H !. ! 11/ 0-.--C^ or nucleophilic attack of the carbonyl oxygen on the phos• phorus, atom. At room temperature.1,1,1-trifluoroacetone(3PK)- gives exclusively the H-O-C-P compound while hoxafluoroacetone (6FK) gives predominately the P-O-C-H system. However at 178°, 3PK gives rise to both systems? which suggests.. that a *> four-centred intermediate is not involved (cf. the reaction between chlorodimethylamine and hexafluorobutyne-2: at 85° the adduct formed is entirely cis; at 139° no adduct is obtained). Rather, It appears that at'178° nucleophilic attack by 3PK becomes competitive with that by diphenyl• phosphine (with this situation holding for 4PK at room temperature). Hexafluoroacetone is known to be a stronger 121 nucleophile than 3PK. It,would be of great-interest to shed further light on •: 118 the mechanism, of P-O-C-H bond formation "in these ' reactions. One possibility Is the use of deuterated phosphines (with 6FK, to avoid appreciable phosphino-isopropanol•formation)0 In particular, If a mixture of (CgHgJgPD.and ArgPH, Ar ^ C6H5 , was reacted with 6FK, the formation of (CgEgJgP-O-C-H and ArgP-O-C-D systems would strongly argue,against the four- centre path. The'absence of these exchange adducts would not confirm the four-centre mechanism, however, since the Intermediates stemming from nucleophilic attack by the oxygen atom, e.g. CP3 Ar2P— 0—C(© ••' , • '•GP 3 - • ' might yield the -adducts through exclusively intramolecular 75 • hydride transfer. Cullen and Leeder have used this technique in their Investigations of the mechanisms of secondary arsine- hexafluorobutyne-2 reactions. A few compounds synthesized during the course of this investigation merit further comment' here." A further piece of evidence to support the assignment of,the oxygen atom in ^ the diphenylphosphinotrifluorocyclobu'tenone (p. 19) to the 3 position is the infra-red spectrum, , in particular the • • - -A C=C stretching frequency. As seen from Table 1,^0=0 is abnormally high for-the eneone. It is believed that this is a manifestation of conjugation with the ' oxygen atom, involving the phosphorus atom: e 119 The second step would be impossible in the ene-4-one. Certainly one of the most Interesting compounds encountered in this investigation is 2-dimethylamino-3-H-hexafluorobutene-2. In addition to the very."unusual isomerization phenomena exhibited bv the compound " air, 20° trans • — . N. c^s distillation,Kg this amino-butene is less .'soluble in hydrochloric acid than such aromatic amines as aniline and pyridine. The extreme delocalization of the nitrogen lone pair is further demonstrated by the n.m.r. spectra; the. six bond coupling (j = 1.75 c.p.s.) Is presumably made possible by 3 «-> . resonance: CF, • H ' CF H NS> (C'H"3)gN^ ^CFg (CH5)?N^ CF3 These observations suggest further experiments which would be of considerable interest. For instance, the effect of temperature on the cis-trans equilibrium could be established by means "of % n.m.r. spectroscopy. A plot of the logarithm of the equilbrium constant against'the reciprocal of the absolute temperature would allow calculation of the change in enthalpy of the reaction. It would also be of interest 'to see if other members of the series R0NC(CP )=CTICF„, R=CgE3, C^Hg, C^Hgj... behave similarly regarding isomerization ((CH,)0NC(CF,)=CC1CF, and (C0H^ )„PC^CF, )=CHCF, do not). A further, and most interesting, experiment with 2-di• me thylamino-3-H-hexaf luorobutene-2 would be.reaction with brominev-^for two reasons. Firstly, to see if the double bond 120 is brominated. Tho double bonds in 2-dimethyiarsino-3-H- hftxaf luorobutene-2 and the 3-chloro-: analogue., are I inert to bromine at room temperature (although the arsenic atoms are 59 not)o Secondly, if the double bond is not brominated, or only slowly so, it might transpire that the compound is . . . : isomer!zed "by bromine. This possibility is brought to light not only by the isomerization caused by oxygen, but also by the fact that the bromination of 2-dimethylarsino-3-chloro- 59 hexafluorobutene-2 results in an isomerization process : ; trans - (CH3 )2 A s C (C F„) = 0 C1C ?3 + Br2 —: >•..;••. - •:' ',": cis - Br(CH3)AsC(CF3)-CClCF3 + CHgBr Such a study could well be extended to cis-2-dimethylamino-3- chlorohexafluorobutene-2, ' The unstable cyclobutenyl derivatives, (CgH5)gPC=CXCFgCFg, X = F,C1, warrant futher investigation, in particular thoir behavior towards diethylphosphine. It will be recalled (p. 23) that for X = -:C1, the phosphino-butene reacted with a white solid, believed to be diethylphosphonium chloride, during work-up. This suggests that these phosphino-cyclobutenes will react with diethyIphosphine at room temperature, the likely products in both cases being 1,2-bis(die thylphosphino)- tetrafluorocyclobutene and hydrogen halide. ^Dimethylarsine reacts wi th 2-chloro-l-dime thylarsinote trafluorocyclobutene at 140° in this v/ay).18 This compound should be considerably more stable than the l-phosphino-2-halo-c'yclobutenes, by analogy t'o the methyl and phenyl bis tertiary phosphines prepared in this investigation. The following tables- are an index of the reactions ' . - J • described in tfcis thesis, TABLE XII Index of the Perhal ocyclobutene Reactions Reaction Primary Products Identified Page No„ . . ' Experimental Discussion Results Mechanism a DGB + (CF3)4P2 (CF3)pPC=CClCFgCFg (?) Very little reaction 9 18 31 b (CP ) P 0 0 0 9 18 31 PCB +• 3 4 2 (Cl0 PC=CFCF CF (?) Very little reaction 1 DCBi + (CF3)2PH Virtually>no reaction 10 18 29,31 PCB + (CF3)2PH Virtually no reaction 10. 18 29,31 1 + 27,32 (C H 10 20 DGB + (C6K5)2PH. PF ^eVg ™ 6 5>2 3 19 27,33 PCB + (C6H5)2PH (C6H5)2PC=C(P(C6H5)2)CF26F2 11 6 5 2 12 20 29,32 DCB + (C6H5)4P2 (C H ) PF0 • (C6H5)2PC=CFCO F2 + (C6H5)2PFO 13 - 19 29,31 PCB + P 6 (C6H5)4 2 DCB + (CH3)4P2;: (CH3)2PC=C(P(CH3)2)CF2CF2 13 21 29,33 PCB + (CH3)4P2 • " (CH3)2PF3 14 21 29,33 15 ' 23 27 DCB + (C2H5)2PH (C2H5)2PC=CC1CF 2,CF2. i 16 24 2,7 PCB + (C2H5)2PH (C2H5)2PC^GFCF7;P2 1,2-Dichlorotetrafluorocyclobutene Perfluorocyclobutene TABLE XIII Index of the Hexafluorobutyne-2 Reactions Reaction Primary Products Identified Page No-. Experimental Discussion Results Mechanism a - CH3)pNH + HFB - (CH3)gNC(CF3)=CHCF3 + CF3C0CH2CF3 38 57 63 CH3)3N + HgO + HFB (20°) C0p, trans-CF3CH=CFCF3, (C^HFgJgO 40 59 65 CH3)3N+ Hg0 + HFB (cool) (C4HF6)20 41 61 68 CH„) N + HFB (C^Fg)^ (not much reaction) 42 61 68 o o CH„)oN01 + HFB 44. 62 69 (t>£> cis-(CH3)2NC(CF3)=CClCF3 CH3)pNCl + HFB'(139° ) trans-CF3CH=CC1CF3 44 62 70 45 62 .69 CH3)2NC1 + HF'B (85°) cis-(CH )gWC(CF )=CC1CF CF„)0P-H + HFB (CFj„PC(CF„)=C-HCF, + diadduct 46 71 83 o c 3 2 o • . o C6H5)2PH + HFB (CcHj PC(CF )=CHCF„ 48 73 82 o o 2 3 o C6H5)4P2 + HFB (C6H5)gPC(CF3)=C(CF3)P/C6H5)g . 48 74 85 C6H5)3P +HFB - (C4F6)n - 49 .77 85 C2H5)2PH + HFB (C2H5)2PC(CF3)=CHCF •50 75 82 P0Fg 0H3)4P2 + HFB GH3 50 76 85 CH,)QPC1 + HFB trans-CF„CH=CC1CF_ 52 77 86 O 6 CH,)r,PClS + HFB no reaction 54 •.79 - T 0H3)2P2S2 + CF3 (C"H3)2PFS (very little reaction) 54 80 - CH3)4P2Sg + lg (CH P S I 55 80 81 3)4 2 2' 2 TABLE XIV Index of the Fluorinated Acetone Reactions Reaction ' Primary Products Identified . Page No. Experimental Discussion • • Results Mechanism a 6 5 2 ;3 2 91 102 111 6FK + (C H PH (C H ) P(0)CH(CF ) _ 6 5'2 92 6FK + (CH3)2PH. (CH3)2PC(0-H) (CF3)2J 1: 3 adduct 104 111 4 94 106 - 6FK + (CH3)4P2 1:3 adduct MegPH-6FKj 1:3 adduct Me Pg-6FK 6FK + (C2H5)5P None Identified 95 107 b (.C6H5)2PH (C6H5)gP(0)CH(C§?D.g + i5)2PC(0H)(CF2Cl)2 95 108 111 4FK + (v stable adduct) 97 109 111 4FK + (CH3)gPH (CH ) PF + (CH ) PFO (no ' 3 2 3 , 3 2 3FK°+' (20°) (C6H5)2PC(0HJ (CH3)CF3 97 109 111 98 ' 109 111 3FK + (C6H5)2PH (178°) (C H. ) P(0)CK(CH' )CF 6 5 2 o 6 3FK + (CH3)2PH (CH3) PC(OH)(CH3)CF3 100 110 111 a Hexafluoroacetone b 1,3-Dichlorotetrafluoroacetone c . 1,1,1-Trifluoroacetone BIBLIOGRAPHY. G. WITTING and U. SCHOLLKOPF. Bar-. 87, 1318 (1954). K. ZIEGLER and K. BAHR. Ber. 56, 1740, 2453 (1923). K. ZIEGLER, H. GROSSMAN, H. KLEINER and 0. SCHAEPER. Ann. ' 473, 1 (1929). . K. ZIEGLER and H. G. GELLERT. Ann. 567, 195 (1950). J. D. PARK, M. L. SHARRAH and J. R. LACHER. J. Am. Chem. 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