Reactions of chlorotrifluoromethyldisulphane

摘要

614 J.C.S. Perkin I:Reactions of Chlorotrif luoromet hyld isul phaneBy Neil R. Zack and Jean'ne83843, U.S.A.M. Shreeve.' Department of Chemistry, University of Idaho, Moscow, IdahoChlorotrifluoromethyldisulphane undergoes metathetical reactions with MeSH, EtSH, AcSH, CF,-C(0)SH.CF3*SH, Ag N CO, and (CF,),C:N Li t o form M eS*S*S*CF,. EtSSSCF,. AcS-S-S-CF,, CF,*C( 0) S-S 5.C F,CF,S*S-S*CF,, CF,*S*S-NCO, and CF,*S*S*N:C( CF,),, respectively. Free-radical addition t o olefins gives productswhich are formed by attack of CI* and CF,SS. on the olefin. With tetrafluoroethylene, hexafluoropropene, hexa-fluorocyclobutene, chlorotrifluoroethylene. and 1.2-dichloro-I .2-difluoroethylene, CF,*S*S*CF,*CF,CI, CF,*S*S-CF(CF,)*CF,CI, CF,*S-S*CF,*CFCI*CF,, CF,-S*S*CF*CFB*CF2*CFCI, CF,*S*S*CFCI*CF,CI, CF,*S-S*CF2*CFCI,, andCF,*S*S-CFCI*CFCI, were prepared.Only tetrafluoroethylene gives a higher telomer. CF,*S*S*[CF,*CF,],CI.insertion into the sulphur-sulphur bond does not occur.t fTHE preparation and characterisation of chlorotrifluoro-methyldisulphane has been reported recent1y.l Directfluorination techniques could not be used to preparethis compound from its chlorinated analogue owingto the ease of sulphur-sulphur bond rupture and thesimultaneous oxidation of sulphur. A method estab-lished by Feher was utilized to produce this precursorof some novel mixed polyfhoroalkyl-di- and -tri-sulphanes.RESULTS AND DISCUSSIONTriszcZfiCtanes.-The preparation of bis(po1yfluoro-alky1)trisulphanes has generally been limited to methodswhich involve the reaction of sulphur with polyfluoro-alkyl iodides ,s4 or olefins 4 ~ 5 at high temperatures andwhich produce numerous other sulphides and poly-sulphanes.While these methods usually can be usedto prepare symmetric trisulphanes, e.g. CF31 and sulphurare used to produce bis(trifluoromethy1) trisulphane,there has been no convenient route reported for thesynthesis of non-symmetric polyfluoroalkyltrisulphanes.Reactions of chlorotrifluoromethyldisulphane, whichbehaves as a relatively reactive acid chloride, provide aconvenient route to new trisulphanes.Methanethiol, ethanethiol, thioacetic acid, trifluoro-thioacetic acid, and trifluoromethanethiol react smoothlywith CF,*S*SCl to produce the respective trisulphanes,CF,*S*S*SMe, CF,*S*S*SEt, AcS*S*S-CF,, CF,C (0) S*S*S*-CF,, and CF,*S*S.S*CF, in high yields.In contrast tothe data presented below and those reported5 for di-sulphanes, there is no spin-spin coupling of proton orfluorine substituents across the trisulphane linkage.A low temperature lH and 19F n.m.r. spectral studyof methyltrifluoromethyltrisulphane demonstrates thatno conformation arises where interaction can occuracross the sulphur bonds, even when rotation about thebonds is substantially reduced.The gas-phase reaction of hydrogen sulphide withCF,*S*SCl produces high yields of bis(trifluoromethy1)-pentasulphane even when the ratio of H2S to CF,*S*SClis large. Under various conditions, reactions of CF,--SSC1 with polyfluoro-alcohols, NN-bis(trifluoromethy1)-N. R.Zack and J. M. Shreeve, Inorg. Nuclear Chem. Letters,1974, 10, 619. * F. Feher and D. Grodau, 2. Naturforsch., 1971,26b, 614.G. A. R. Brandt, H. J. Emeldus, and R. N. Haszeldine, J.Chem. Soc., 1962, 2198. * G. G. Krespan and C. M. Longkammer, J. Org. Chem., 1962,27, 3584.hydroxylamine, and trifluoroacetic acid failed to yieldthe analogous substitution products.DiszcZ@hanes.-Dimethylamine reacts with the activechlorine of CF,*S*SCl (2 : 1 molar ratio) to producedimethylaminotrifluoromethyldisulphane. The lH and19F n.m.r. spectra show a quartet centred at 6 2.66for the methyl protons and a septet at 42.8 p.p.m.for the trifluoromethyl group, respectively. As thetemperature is lowered, no change occurs in the 19Fspectrum. The amino-disulphane reacts with HC1to regenerate CF,*S*SCl.CF,*S*SCl will undergo metathetical reactions withseveral salts.Bis (trifluoromet h ylt hio)mercury reactsquantitatively to produce CF,*S*S*S*CF,, and metallicmercury decomposes the disulphane to HgS and un-identified solid products. The reaction of silver saltswith CF,*S*SCl provides a convenient method of pre-paring perfluoropseudohalogenoids.6 Silver cyanideforms the previously reported unstable CF,-S*S*CN,which decomposes at 25". Freshly prepared silverisocyanate is used to synthesise CF,*S*S*NCO. 1.r.and n.m.r. spectral data indicate that only the monomeris formed a t room temperature.The reaction of lithium salts with CF,*S*SCl providesa means of introducing the CF,SS unit into usuallyunreceptive systems.The lithio-imine (I) reactswith CF,*S*SCl to form the disulphane (11) in highyield, Other lithium salts can be employed to formCF,*S.SCl(CF,),C:NLi --w CF,*S*S*N:C(CF,), + LiCl(1) (11)non-symmetric disulphanes, e.g. n-butyl-lithium formsCF3*S*SBun in moderate yield (68%).Alkali metal fluorides either do not react with CF,*S*-SC1 or cause it to decompose to CF,*S*S*CF, or CF,*-S*S*S*CF,. No evidence for the formation of CF,*S*SFwas obtained under the conditions employed. Althoughthe use of chlorine monofluoride as an oxidising agentfor sulphur-containing compounds is well establi~hed,~C1F severs the sulphur-sulphur bond to form CF3*SF,,C. G. Krespan and W. R. Brasen, J .Org. Chem., 1962, 27,3996.13 L. Birckenbach and K. Kellerman, Chem. Ber., 1925. 68,786, 2377.H. J. Emeldus and A. Haas, J. Chem. Soc., 1963, 1273.R. F. Swindell, D. P. Babb, T. J. Ouellette, and J; M.D. T. Sauer and J. M. Shreeve, J . Fluorine Chem., 1971/72,1,Shreeve, Inorg. Chem., 1972,11, 242.1; T. Abe and J. M. Shreeve, ibid., 1973/74, 3, 1871975SF,, and Cl,, at 0, -78, and -120" in either a metal or aglass vessel.The ease with which the sulphur-chlorine bond ofCF,*S*SCl is broken suggests that insertion of inorganicmaterials into this bond should occur. However,irradiation of CF,*S-SCl in the presence of a large excessof SF,, PF,, or SO, failed to give products which wouldbe expected from insertion into either the S-Cl or theS-S bond.Harris l0*l1 has shown that trifluoromethanesulphenylchloride and trifluoromethanethiol add across poly-fluoro-olefins by a free-radical process involving cleavageof the S-C1 and S-H bonds, respectively.For CF,*SCl,the major attacking species is considered to be C1*,and CF,S* assumes that role for CF,*SH. Sharp andhis co-workers l2 studied the reactions of chlorotetra-fluoro(trifluoromethy1)sulphur with olefins and found,that under photolytic conditions, CF,SF,* is the attack-ing radical. Thermal reactions of fluoro-olefins withdisulphur dichloride carried out by Knunyants et d.13resulted in severing of the S-S bond and the S-C1 bondas well as rearrangement of the products.Analogous to CF,*SCl, CF3*S*SC1 reacts with poly-halogeno-olefins in Pyrex vessels when exposed to sun-light or a medium-pressure U.V.source to give newnon-symmetric disulphanes in yields of 10-60y0.No trisulphanes or products derived from cleavageof the sulphur-sulphur bond of CF,*S*SCl are obtained.Highest yields of addition products are obtained whenthe olefins used are totally fluorinated, and the yieldsdecrease rapidly as fluorine is replaced by chlorine orhydrogen.When tetrafluoroethylene reacts with CF,*S-SCl,the adducts CF,*S*S*[CF,-CF,],Cl (n = 1 or 2) areformed. No higher telomers are detected. Withthe other olefins, telomerisation does not occur. TheseNo reaction occurs without photolysis.m/e 330 is observed in the mass spectrum of the ad-duct formed with the latter.The two possible struc-tural isomers (IIIa and b) expected from the reactionwith CFJFC1 were not separable by g.1.c. but wereclearly identifiable by their lSF n.m.r. spectra. Com-pound (IIIa) constitutes 80% of the total addition pro-ducts found. Initial radical attack in radical additionsto perfluoro-olefins usually occurs on the terminalCF, group but various factors (steric effects, stabilityof intermediate radical, electronic character of theradical, etc.) influence orientation of the attackingreagent so that mixtures are often obtained. Additionproducts in this case indicate that both CF,*S*S* andC1- must participate in initiating the reaction sequence(Scheme 1). Reaction (iii) must be of lesser import-ance than (ii) since (IIIb) is formed in low yield and noCF,.S*SCl __t CF,*S*S.+ C1hv(i)CF,*S.SClC1* + CF,:CFCl ---w CF,CI-cFCl -WCF,ClCFCl*S.SCF, (ii)(IIIa)CF,-S.SClCF,*S*S + CF,:CFCl -S CF,*S*S-CF,*eFCl-)CF,S .S*CF,*CFCl, (iii)(IIIb)SCHEME 1CF,*S*SCF,*CFCl*S-S*CF, is isolated. Small amountsof CF,Cl*CFCl, and CF,*S*S*S*S*CF, are formed.The reaction of CF,*S*SCl with hexafluoropropene isanalogous. The major isomer formed is CF,*S*S*CF-(CF,)CF,Cl, which suggests that most often the initialattack is by C1- on the terminal CF, group to form themore stable intermediate radical, C1CF,*CF(CF3).l5However, radical additions to unsymmetrical fluoro-olefins are frequently bidirectional, especially whenheteroatom radicals are involved.16 Since the productsmajorpath /(major) /(minor)C1.+ CF,*CF:CF, + ClCF,*cF.CF, + Cl?,*CFCl-eF,CF,*S*SCl CF,S-SCICICF,CF(CF,).S*SCF, CF,*CFCl*CF,*S.S*CF,CF,.S * SCI CF,. 5SC Iminor t T CF,.S-S + CF,*CF:CF, + CF3.S*S*CF(CF3)dF, + CF,*S*S*CF,dF.CF,path (minor) (major)SCHEME 2results are in contrast to the olefin addition reactionsof CF36*S*CF,,14 which with C,F,, gives as main pro-ducts the adducts CF,*S[CF,*CF&SCF, (n = 2 and alarge number).Photolysis of CF,*S*SCl in the presence of chlorotri-fluoroethylene or 1,2-dichloro-l ,Zdifluoroethylene pro-duces disulphanes in low yields. A molecular ion atlo J. F. Harris, J . Amer. Chem. SOC., 1962, 84. 3148.l1 J . F. Harris and F. W. Stacey, J . Amev. Chem. SOC., 1961,83,l2 J. 1. Darragh, G. Haran, and D.\V. A. Sharp, J.C.S. Daltoii,A 1 : 1 adduct is not reported.840.1073, 2289.from the CF2:CFCl reaction show that both CF*S*S*and C1* attack the olefin, it is likely that the productsfrom the hexafluoropropene reaction are formed viabidirectional addition of both attacking species (Scheme2). Compound (IVa) constitutes 70% of the totall3 I. L. Knunyants and A. V. Fokin, Bull. Acad. Sci. U.S.S.R.,Div. Chem. Sci., 1966, 627; I . L. Knunyants and E. G. Vykhous-kaya, ibid., 1966, 769.l4 G. Haran and D. W. A. Sharp, J.C.S. Perkin I, 1972, 34.R. N. Haszeldine and B. R. Steele, J . Chew SOC., 1957, 2193.l6 R. D. Chambers, ' Fluorine in Organic Chemistry, Wiley,New York, 1973, pp. 173-176 and references therein616 J.C.S. Perkin Iaddition products. The 17 eV mass spectrum of (IVa)contains an intense peak at m/e 85 ([CF,Cl]+} and apeak at m/e 233 ([CF,SSCF(CF,)]+).A peak at m/e183 {[CF,SSCF,]+) is observed in the spectrum of(IVb). The mass and 19F n.m.r. spectra confirm thestructural assignments for (IVa and b).Photolysis of CF,-S*SCl in the presence of ethylenethrough Pyrex yields only the monosulphur additionproduct, CF3*S*CH,*CH2C1,11 and sulphur. Similarly, noaddition occurs in the reaction with (CF,),C:NH; themajor products are bis(trifluoromethy1)disulphane anddisulphur dichloride. Reaction of CF,*S*SCl with hexa-fluorocyclobutene produces a coin pound, CF,*S*S*-CF*CF2*CF,*CFC1, with a complex n.m.r. spectrumsimilar to that of the product of addition of CF,*O*OFto o~tafluorocyclopentene.~7All the foregoing reactions of CF,*S*SCl with olefinswere also studied under thermal conditions.After 3 hat 220°, only tetrafluoroethylene formed an additionproduct (32% yield). At 125", for longer periods, asmall amount of product was formed with C,F,; noreaction occurred with the other olefins tested.Although telomers are observed only with the tetra-fluoroethylene reaction, the olefin addition reactionsdo occur via a free-radical process involving formationof CF,S*S* and C1* by photolysis through Pyrex. Par-ticularly in the reactions involving t he polychloro-olefins, CF3*S*S-S*S.CF3 is observed as a major product,and some C1, addition products are also formed. Sucha free-radical process must be closely related to thoseoutlined in the literature.llJ3The reactions of CF,-S-SCl with olefins are analogousto those recently reported for CF3*O*OC1.18 Theperoxy-compound is far more reactive in that it addsacross olefinic double bonds below -78".t IEXPERIMENTALA standard Pyrex high-vacuum system equipped with aHeise-Bourdon tube gauge was used in all manipulations.Quantities of gaseous materials were measured on theassumption of ideal gas behaviour.1.r. spectra wererecorded on Perkin-Elmer 237 and 457 spectrometers.A Varian HA- 100 spectrometer (internal references tetra-methylsilane and trichlorofluoromethane as needed) wasused to obtain lH and 19F n.m.r. spectral data. Massspectra were recorded with a Perkin-Elmer RMU-6Espectrometer operating a t 17 and 70 eV.Molecularweights were determined generally by mass spectrometry.All reaction materials are available commerciallv and,with the exception of AgOCN, were used as received. Thelatter was prepared before each reacti0n.1~ CF,*S*SCIwas obtained as previously described.' All new com-pounds were purified by g.1.c. (gas injection system;2.3, 2.7, and 4.2 m columns of 20% KeEF on ChromosorbP or 0-8 m column of 15% DMS on Chromosorb P).Equimolar quantities of CF,*S*SCI and thiols or acidswere condensed together into small glass vessels andallowed to remain at 20' for 0.5 h, after which the mixturewas fractionated. As indicated by the disappearanceof the yellow colour due to CF,-S*SCl, reactions were com-plete within 5 min.Salt reactions were carried out by condensing a knownamount of CF,*S*SCl onto an excess of the dried salt in aglass or stainless steel vessel; with the.exception of thereaction of (CF,),C:NLi, in which CF,*S*SCl was used inslight excess. The reactants were then allowed to warmslowly from -196 to 20" and the product mixture wasseparated and examined.Preparation of the disulphanes from olefins was generallyaccomplished by placing equimolar quantities of CF,*S*SCIand the olefin in a 350 ml Pyrex vessel and irradiating themixture with sunlight or a Hanovia utility ultravioletquartz lamp for 16-24 h. Usually mixtures wereirradiated until no further change was observed in theyellow colour. Thermal reactions were attempted by con-densing a slight excess of the olefin with CF,-S-SCl into asmall glass tube, which was sealed and placed in a controlledtemperature oven for 3-12 h.The polychloro-olefinand hexafluorocyclobutene addition products could not beseparated from CF,=S*S-S*S-CF, by either low temperaturedistillation or g.1.c. techniques.With the exception of CF,*S*S*NCO, all the new poly-sulphanes are stable in air and at room temperature. Theyare colourless, evil-smelling compounds and probablyextremely toxic.Elemental analyses were obtained from MikroanalytischesLaboratorium Beller. These data, as well as i.r., mass,and n.m.r. spectra data, are available as SupplementaryPublication No. SUP 21247 (3 pp.).tFluorine research at the University of Idaho is supportedby the Office of Naval Research and the National ScienceFoundation. We thank a referee for suggestions concerningthe mechanisms of the olefin reactions.[4/1791 Received, 29th August, 19741t For details of Supplementary Publications, see Notice to1' F. A. Hohorst, Ph.D. Thesis, Northeastern University, 1973.18 D. D. DesMarteau, F. A. Hohorst, and N. Walker, presentedat the 7th International Symposium on Fluorine Chemistry,Santa Cruz, California, July 1973.19 R. G. Neville and T. 1. McGee. Inow. Svnth.. 1966. 8. 23.Authors No. 7 in J.C.S. Perkin I, 1974, Index issue.0 Copyright 1975 by The Chemical Societ