Chiral and Achiral Diphosphine Complexes of Ruthenium(II) Incorporating Labile Nitrile Ligands: Synthesis and Solution Chemistry of Mono- and Dinuclear Derivatives of Ru(2)Cl(4)(PP)(2) (PP = Chelating Diphosphine).

Abstract

A family of nitrile complexes has been prepared by reaction of Ru(2)Cl(4)(PP)(2) or RuCl(2)(PP)(PPh(3)) (PP = Ph(2)P(CH(2))(4)PPh(2) (dppb), Ph(2)PCH(2)CHOCMe(2)OCHCH(2)PPh(2) (diop), 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap)) with MeCN or PhCN, the product formed depending strongly on the reaction conditions. At high nitrile concentrations, the principal species present is RuCl(PP)(RCN)(3)(+)X(-) (X = Cl); the cation can generally be isolated (as the PF(6) salt) by abstraction of the chloride counterion with NH(4)PF(6). Use of 2 equiv of NH(4)PF(6) generates Ru(PP)(RCN)(4)(2+)(PF(6)(-))(2) (PP = dppb). In the absence of a halide-abstracting agent, addition of hexanes or diethyl ether precipitates neutral RuCl(2)(PP)(RCN)(2) species, which undergo further loss of nitrile in the solid state (R = Me) or in solution (R = Me, Ph). Redissolution of the neutral species in chlorocarbon solvents gives Ru(2)Cl(3)(PP)(2)(RCN)(2)(+)X(-) (X = Cl) and, in benzene, Ru(2)Cl(4)(PP)(2)(RCN). The dinuclear cation (X = PF(6)) is also accessible by reaction of RuCl(PP)(RCN)(3)(+)PF(6)(-) with CH(2)Cl(2) or CDCl(3), while the mononitrile can be obtained directly by reaction of Ru(2)Cl(4)(PP)(2) or RuCl(2)(PP)(PPh(3)) with small amounts of nitrile in benzene.