Organometallics 1983,2, 1061-1062
1061
when the solution is warmed to 0 OC. Boron trifluoride was identified by its gas-phase IR spectrum, and Mn(C0)5Cc13 was isolated in 92% yield by evaporation of solvent followed by sublimation of the solid. The colorless crystalline complex was characterized by its IR spectrum, mass spectrum, and elemental analysisa8 These physical Thomas 0. Rlchmond and Duward F. Shrlver' measurements are all consistent with the formulation of Department of Chemistry, Northwestern University the compound as Mn(C0)&C13. Similarly, the thermally Evanston, Illinois 6020 1 unstable complexes Mn(C0)&Br3 and Mn(CO),CI, were Received May 23, 1983 prepared from the reaction of Mn(C0),$F3 with BBr, and BI,, respectively, and characterized by IR spectroscopy and Summary: Reaction of 6x3 (X = CI, Br, I) with Mnby the evolution of BF, gas from the reaction mixture. In (CO)&H, F-, (n = 0-2) affords the a-halomethyl comthe preparation of Mn(CO)J!13, an approximately equiplexes Mn(CO)&H,X%, (n = 0-2) in high yield under mild molar amount of Mn(CO).Jg is also formed, apparently as with excess conditions. Treatment of Re(CO)&F,CF, a result of competitive cleavage of the Mn-C bond by BI,. BCI, yields exclusively Re(C0)5CCI,CF,. This result shows The frequencies of carbonyl stretching bands for these complexes are nearly identical, although the intensity of that the metal activates the a-C-F bond for electrophilic the high-frequency Al vibration increases in the series F attack. The highly reactive compound CpFe(CO),CCI, < C1 < Br < I. Similar trends in frequencies and intenwas prepared and converted to the known CpFe(CO),CN sities have previously been observed10for the (trihalosily1)-, complex by solvolysis with NH,. (trihalogermy1)-, and (trihalostanny1)manganese pentacarbonyl complexes, X3MMn(CO)5. The carbon-chlorine Our interest' in the interactions of organometallic comstretching frequencies (701,675 cm-') are lower in Mn(Cpounds with Lewis acids prompted us to examine the reO)&c& compared to those observed" in aliphatic comactions of perfluoroalkyl carbonyl complexes with molecpounds. Thus, it is also possible to prepare Mn(CO)5CBr3 ular Lewis acids. Perfluoroalkyl complexes are readily by reaction of Mn(CO)&C13 with BBr,. prepared for nearly all of the late transition metals and Interestingly, the halogen-exchange reaction was found have played an important role in the development of the to be specific to the (Y position of the fluorocarbon ligand. chemistry of the metal-carbon bonds2 In these compounds For example, reaction of Re(CO)5CF2CF312 and excess BC13 the carbon-fluorine bonds a to the metal are weaker than affords exclusively Re(C0)&Cl2CF3l3(eq 2). Comparison in aliphatic compounds as evidenced by their increased bond lengths3and reduced infrared stretching frequencies.* Re(CO)&C12CF3 + BCIFz Re(C0)5CF2CF3+ BCl, Thus, the C-F bond is susceptible to electrophilic a t t a ~ k . ~ 1 2 This communication reports how we have exploited this (2) property of metal fluorocarbon complexes to synthesize of the IR spectra of these complexes shows that the lowa series of a-halocarbon transition-metal cqrbonyl comfrequency bands assigned4ato the CF, group of 1 are abplexes.6 This was achieved for the first time by halosent in 2 although the peaks assigned to the CF, group are gen-exchange reactions with boron trihalides. readily apparent. This complex exhibits a single broad 19F Treatment of (trifluoromethy1)manganese pentaNMR peak at room temperature which sharpens at higher carbonyl' with 1 equiv of BCl, in dichloromethane or temperatures. The spectrum coalesces near 0 "C and at pentane at -78 OC results in rapid halogen exchange to -80 "C exhibits an ABX pattern indicating three inquantitatively produce (trichloromethy1)manganese penequivalent fluorine atoms. Similar NMR properties tacarbonyl (eq 1). The reaction is complete in minutes (presumably a consequence of slow carbon-carbon bond rotation) are observed for Re(CO)5CBr2CF3and for MnMII(CO)~CF,+ BCl, Mn(CO)&C13 + BF, (1) (CO)5CC12CF3,and this behavior will be discussed more fully in a complete paper. (1) (a) Shriver, D. F. J. Organomet. Chem. 1975, 94, 259-271. (b) These results show that the metal is important in acShriver, D. F. Adu. Chem. Ser. 1981, No. 152, 1-18. (c) Butts, S. B.; tivating the carbon-fluorine bond for halogen exchange. Strauss, S. H.; Holt, E.M.; Stimson, R. E.; Alcock, N. W.; Shriver, D. F. J.Am. Chem. SOC.1980,102, 5093-5100. (d) Richmond, T. G.; Basolo, Halogen exchange occurs readily only in noncoordinating F.; Shriver, D. F. Organometallics 1982, 12, 1624-1628. solvents. Also, no reaction is observed when the relatively (2) (a) Treichel, P. L.; Stone, F. G. A. Adu. Organomet. Chem. 1964, mild electrophiles BMe, or B2Hs are employed. This 1,143-220. (b) Bruce, M. I.; Stone, F. G . A. Prep. Inorg. React. 1968,4, 177-235. (c) King, R. B. Acc. Chem. Res. 1970,3, 417-427. suggests that a strong Lewis acid is required for electro(3) (a) Mason, R.; Russell, D. R. Chem. Commun. 1965, 182-183. (b) philic attack at a fluorine substituent. The mechanism of Churchill, M. R. Inorg. Chem. 1965, 4 , 1734-1739. (c) Ibid. 1967, 6, exchange may involve an ionic intermediate 3 or be of a 185-190. (d) Churchill, M. R.; Fennessey, J. R. Ibid. 1967,6, 1213-1220. (4) (a) Pitcher, E.;Stone, F. G . A. Spectrochim. Acta 1962, 18, concerted nature 4. The formation of the strong B-F 585-594. (b) King, R. B.; Bisnette, M. B. J. Organomet. Chem. 1964,2, bond14 is the thermodynamic driving force for the overall 15-37. (c) Cotton, F. A.; McCleverty, J. A. Ibid. 1965,4,490. (d) Cotton, process. An analogous reaction in organic chemistry is the F. A.; Wing, R. M. Ibid. 1967, 9, 511-517. (e) Graham, W. A. G . Inorg. Chem. 1968, 7, 315-321. (0 Hall, M. B.; Fenske, R. F. Ibid. 1972, 21, halogen exchange observed upon treatment of tetraFaclle Electrophlllc Halogen Exchange between Boron Trlhalldes and Transltlon-Metal Perfluoroalkyl Complexes. A Novel Method for the Synthesls of Reactlve Transition-Metal Haloalkyl Complexes
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768-775. (5) (a) Reger, D. L.; Dukes, M. D. J. Organomet. Chem. 1978, 153, 67-72. (b) Clark, B. R.; Hoskins, S. V.; Roper, W. R. Ibid. 1982, 234, (294212. (6) (a) An iridium trichloromethyl complex has been prepared: Demming, A. J.; Shaw, B. L. J. Chem. SOC. A 1969, 1128-1134. (b) Transition-metal monochloromethyl complexes: Moss, J. R.; Pelling, S. J. Organomet. Chem. 1982,236,221-227 and references therein. (c) Transition-metal chloromethyl complexes are not accessible by thermal or photochemical decarbonylation of chloroacetyl precursors: Dilgassa, M.; Curtis, M. D. J . Organomet. Chem. 1979,172,177-184. (d) Main-group trihalogenomethyl complexes are well-known and synthetically useful: Seyferth, D. Acc. Chem. Res. 1972,5, 65-74. (7) King, R. B. 'Organometallic Syntheses"; Academic Press: New York, 1965; Vol. 1.
0276-7333/83/2302-1061$01.50/0
FA-
C, 23.00; C1,33.95. Found: C, 23.12; .., 2046 (s), 2013 (m) cm-' '(9) Quick, M. H.; Angelici, R. J. Inorg. :
