摘要:
1972 645Five-co-ordinate Rhodium( I) and Iridium(1) Organomercury ComplexesBy G. M. Intille,’ Central Research Department, Monsanto Company, St. Louis, Missouri 631 66, U.S.AM. J. Braithwaite, Chemistry Department, University College, London W.C.lA series of five-co-ordinate rhodium and iridium organomercury complexes has been prepared. N.m.r. spectraand other analytical data have been used to confirm the structure, which includes a metal-metal bond from theorganomercury group to the transition metal.COMPLEXES containing metal-metal bonds are of in-terest 1r2 because of their versatility in ~ynthesis.~ Wehave now prepared a series of organomercury complexesof rhodium(1) and iridium(1). Although complexescontaining mercury-rhodium or mercury-iridium bondsare known,4$ analogous organomercury-containing com-plexes have not been reported before; * they may,however, be intermediates in several types of rea~tion.~,* It has been brought to the authors’ attention by a refereethat J .P. Collman, J . Amer. Chem. SOC., 1967, 89, 844, hasprevi-ously reported the preparation of a mercury acetylide complex,IrCl(HgECR) (ECR) (CO) (PPh,),.J. Lewis and R. S. Nyholm, Sci. Progr., 1964, 52, 557.B. King, Organornetallic Chem. Rev., 1968, 4, 158.H. Pate1 and W. Graham, J . Amer. Chem. SOC., 1965, 87,673.The complexes were obtained by the oxidative ad-dition of organomercury salts to rhodium or iridiumcomplexes in which the formal oxidation state of thetransition metal was -1. The preparation of thestarting material has been described by Collman et aL8Tetrahydrofuran (THF) solutions of [Ir(CO),PPh,]- or[Rh(CO),(PPh,),]- were obtained by sodium amalgamreduction, under an atmosphere of carbon monoxide,R.S. Nyholm and K. Vrieze, J . Chem. SOC., 1965, 5331;J. P. Collman and C. T. Sears, Inorg. Chem., 1968, 7, 27.R. F. Heck, J . Amer. Chem. SOC., 1968, 90, 5518.D. Seyforth and R. J. Spahn, J . Amer. Chem. Soc., 1969,* J. P. Collman, F. D. Vastine, and W. R. Roper, J . Amer.1965, 5337.91, 3037.Chem. SOC., 1968, 90, 2282of chlorocarbonylbis(tripheny1phosphine)iridium (I) 9 orits rhodium analogue. Upon addition of the desiredorganomercury complex to these solutions, initiallyonly a bridged species was observed [reaction (l)].THFNI2Na+[lr(CO),PPh3]- + 2RHgCI ___).2NaCI + [lr(CO),PPh,],Hg + HgO + R-R (I)Bridged species of this type had already been described.Since phenylmercury chloride should be stable underthese conditions, we felt that the presence of metallicmercury and the coupled organic product (in this casebiphenyl) indicated formation of an organomercuryadduct as an intermediate.Upon careful investigationit was found that the desired product is formed but isair, moisture, and light sensitive. When properprecautions were subsequently taken the followingreaction could be carried out.THFN, darkNa+[lr(CO),PPh,]- + RHgCl -+ Ir(CO),PPh,HgROn exposure to light, air, or moisture, this complexdispro por tionates [react ion (2)]. *light21r(CO),PPh3HgR __t [lr(CO),PPh,],Hg + HgO + R-R (2)The biphenyl which is formed was identified by com-parison of gas chromatographic retention time with thatof an authentic sample.CompoundRh(CO),(PPh,),Hg(p-tolyl) CreamRh(CO),(PPh,),Hg(phenyl) Green-yellow[Rh(CO),(PPh,),I,Hg YellowI r (CO) ,PPh,Hg(p-to1 yl) CreamIr(C0) ,PPh,Hg(phenyl) Pale yellowIr(C0) ,PPh,Hg(benzyl) CreamCIr(C0) ,PPh,l,Hg YellowC55-2555.2558.3540.639-8540.3539.55J.C.S. Daltonhave a strong group of bandst at 1975 cm-l and amedium band a t 1920 cm-l.Both of the tolyl complexesalso have an absorption at 790 cm-l and a group ofabsorptions at ca. 2900 cm-l. These correspond to,respectively, the characteristic aromatic hydrogen wagfor @ara-substituted toluene and the CH stretch of themethyl group.The presence of the bands in the i.r.spectra, in addition to confirming the presence of thetolyl group in the complex, also confirms that no re-arrangement of the para-substitution of the tolyl grouphas occurred.The n.m.r. spectra offered further confirmation of thestructure. In addition to the triphenylphosphine re-sonance at T 2.3 and 2.6, the rhodium compounds haveabsorptions at T 2.7 and 7-6 for the tolyl compoundand T 2-8 for the phenyl analogue. Relative areasare consistent with assignment of the low-field re-sonances to the aromatic protons and the high-fieldresonance to the CH, protons. The triphenylphosphineprotons of the iridium complexes cover the regionsbetween T 2.5-3.0 thus obscuring the aromatic protonsof the organomercury group.However, the -CH,resonance at T 7.4 and the -CH,- resonance at z 7.6can clearly be seen for the tolyl and benzyl derivatives,respectively. The benzyl complex offers additionalinformation about the structure. Since lg9Hg (17%natural abundance) has a nuclear spin of 112 it cancouple with the benzyl protons. In dibenzylmercuryFound CalculatedH3-83.73-852.762.652.62.4P6.156.67.953.83-83.854.9Ir C55.4555-058.2540.5529.0 29.7540.5530.6 39.5H3.83-653.852.652-452.652.35All analytical results were obtained by Galbraith Laboratories, Knoxville, Tennessee.In this manner either the intermediate organo-mercury complex or the bridged species could beisolated.By varying the organomercury chloride aseries of analogous complexes was obtained. A list ofthe compounds prepared in this manner along with theanalytical data are given in the Table.Melting point determination in sealed capillariesindicated that all compounds decomposed withoutmelting above 200 "C.The i.r. spectra of these complexes are consistent withthose of Collman's. The iridium complexes all have avery intense broad band centred at 1950 cm-l and amedium band a t 2000 cm-l. The rhodium complexes* The disproportionation directly to Hgo and R-R may besomewhat surprising since related cobalt systems have been shownto disproportionate as follows: Z(CO),CoHgR+ [(CO),Co],Hg +HgR, (W. Hieber and R. Breu, Chem. Bey., 1957, 90, 1270).However, under our conditions HgR, is stable, discounting thepossibility that the diorganomercury is first formed followedby subsequent elimination of mercury to yield the observedproducts. The possibility of an ' iridium-catalysed ' decom-position of HgR, cannot, of course, be strictly ruled out butsince this would imply some sort of iridium-organomercury in-termediate anyway, i t becomes a circular argument.P Ir6.356-457.93.753.8 28.853.754.85 30.4the coupling constant, J(Hg-H) is 134 Hz.Iridiumon the other hand has a nuclear spin of 3/2 and istherefore expected only to broaden the methyleneresonance. The n.m.r. of the iridium-mercury-benzylcomplex shows mercury coupling with coupling constant,J(Hg-H) 176 Hz.This then allows one to assign thefollowing as the most probable structure.COWhile no positive evidence for this trigonal bipyra-midal structure exists, there is ample precedence forsuggesting it. Hieber lo has suggested that the trigonalbipyramidal structure is favoured over a tetragonalt Unfortunately, solution spectra of these complexes could notbe obtained due to the sensitivity of the solutions to light. Themull and KBr spectra of the solids are undoubtedly complicatedby solid-state effects, especially in the CO stretching region.L. Vaska and J. W. Diluzo, J . Amer. Chem. SOC., 1961, 83,2784.lo W. Hieber and E. Lindener, Chem. Bey., 1965, 98, 39211972 647pyramid while Manning l1 has shown that the analogouscomplex [Co(CO),],Hg reacts with PPh, to form[Co(CO),PPh,],Hg in which the mercury is trans to thephosphine.Similarly the most likely structure for the rhodiumcomplexes is :oc,Ph3P--'Rh - Hg R R = pheny1,tolyl IPPh3The oxidative addition of organomercury salts torhodium( - 1) or iridium( - 1) complexes thereforeappears to yield an organomercury adduct in whichthe mercury-carbon bond remains intact.This resultbecomes even more intriguing in view of recent work inthis laboratory l2 indicating that oxidative-addition oforganomercury salts to rhodium( + 1) and iridium( + 1)complexes results in the cleavage of the mercury-carbon bond, not the mercury-halogen bond.EXPERIMENTAL1.r. spectra were obtained from Nujol or Kel-F mulls orfrom CsI or KBr pellets using a Beckman Model IR 12grating spectrometer with a range of 200-4000 cm-1.M.p.s were determined using a Mel-temp capillary melting-point apparatus.N.m.r. spectra were obtained on aVarian Associates Model T 60 spectrometer using deuterio-chloroform or CaH,]methylene chloride as solvent andtetramethylsilane as internal standard.Rhodium trichloride trihydrate and iridium trichloridetrihydrate were obtained from Matthey-Bishop, Inc.Triphenylphosphine, dibenzylmercury, and diphenyl-mercury were obtained from Strem Chemicals, Inc., andused without further purification. Di-9-tolylmercury wasobtained from Eastman Chemicals. Metallic sodium,mercury, and reagent grade solvents were all obtainedfrom Fisher Chemical. All solvents were dried, distilled,and deaerated prior to use.Preparation of Triscarbonyl(triphenylphosphine)il.idiunt-(- 1) Solution and BiscarbonyZbis(tripheny1phosphine)rho-diurn( - 1) Solution.-Stock solutions of these anions wereprepared by Collman's method.* It was found that filtra-tion of this solution through diatomaceous earth to removecolloidal particles greatly aided the isolation of purecompounds in later steps.Preparation of Organonzercuric Chlorides.-Equimolaramounts of the diorganomercury compound and mercuricchloride were heated under reflux overnight in ethanol.On cooling the desired compound was obtained and wasrecrystallized from ethanol.Preparation of Complexes.-Aliquots from the stock solu-tions of the rhodium or iridium anions were added toequimolar amounts of the organomercuric chloride in a darkbottle.After 30 min these solutions were filtered in thedark to remove the NaCl which formed. The clear solutionwhich remained was evaporated in vacuo at roomtemperature to a small volume. A small amount of meth-anol or ethanol was then added to induce crystallization.In some cases it was found necessary to cool the solutionin a solid CO, -acetone bath before precipitating the productto prevent the deposition of mercury which occurred atroom temperature. All steps in the preparation were doneunder nitrogen. Attempts to recrystallize these compoundsproved unsuccessful due to further reaction to form thebridge complex [Ir(CO) ,PPh,],Hg.[1/1856 Received, 11th October, 19711A. R. Manning, J . Chem. SOC. ( A ) , 1968, 1018.la G. M. Intille, to be published
ISSN:1477-9226
DOI:10.1039/DT9720000645
出版商:RSC
年代:1972
数据来源: RSC