| Mixed-valence complexes of ruthenium of general formula Ru(,2)Cl(,5)(P-P)(,2), P-P = chiraphos, norphos, dppp, dppb or diop, have been prepared by reaction of RuCl(,3)P(,2)(DMA).DMA, P = PPh(,3) or P(p-tolyl)(,3), with one equivalent of the appropriate ditertiary phosphine. The solid state structure of the chiraphos derivative is shown to be a symmetrical triply chloro-bridged dimer by X-ray analysis. The extent of electron delocalisation in these mixed-valence complexes has been studied by means of their intervalence transfer bands in the near-infrared region. A low energy absorption is assigned to the dinuclear complex; however, additional absorptions at higher energy indicate more than one species is present in solution.;The complexes RuCl(,2)(P-P) (,2), P-P = chiraphos or diop, catalyse the asymmetric hydrogenation of prochiral alkenes. The nature of the phosphine and substrate are found to be significant in terms of the hydrogenation rate, % e.e., and product configuration. Hydrogenation of (Z)-(alpha)-acetamidocinnamic acid with 97% e.e. has been achieved using the chiraphos derivative.;The reaction of Ru(,2)Cl(,4)(dppb)(,2)(acetone).acetone, 1, with H(,2) has been investigated. In DMA, in the presence of added base, a hydrido-complex is generated, but has not been isolated pure. The reaction of 1 with H(,2) in CH(,2)Cl(,2)/CH(,3)OH produces the dinuclear complex, Ru(,2)H(,2)(CO)Cl(,2)(dppb)(,2). This product is also formed in the absence of H(,2).;Addition of norbornadiene (nbd) to 1 produces RuCl(,2)(nbd)(dppb). The reaction of this complex with H(,2) is complicated by initial dissociation of the norbornadiene ligand. However, one of the minor products is thought to be RuHCl(nbd)(dppb), a stable hydrido-alkene complex, even in the presence of H(,2).;Investigations of the reaction of Ru(,2)Cl(,5)(chiraphos)(,2) with H(,2) in DMA show this to be an autocatalytic reaction. The product generated in situ by reaction with H(,2) is the ionic species, Ru(,2)Cl(,5)(chiraphos)(,2) ('-)DMAH('+). The neutral complexes RuCl(,2)(P-P) (,2), P-P = chiraphos, dppp, dppb, or diop, are isolated via such an ionic complex, or alternatively by reaction in toluene in the presence of added base.;Cationic complexes of ruthenium(II) have been prepared from 1 and Ru(,2)Cl(,5)(dppb)(,2) by halide abstraction using AgPF(,6). These are the dinuclear complexes Ru(,2)Cl(,3)(Dppb)(,2)(S)(,n) ('+)PF(,6)('-), n = 2, S = acetonitrile and n = 1, S = acetone; and the mononuclear complexes RuCl(dppb)(CH(,3)CN)(,3) ('+)PF(,6)('-) and RuCl(dppb)((eta)('6)-toluene) ('+)PF(,6)('-). (Abstract shortened with permission of author.)... |
