Chiral and achiral diphosphine complexes of ruthenium(II) incorporating labile nitrile ligands: Synthesis and solution chemistry of mono- and dinuclear derivatives of Ru2Cl4(PP)(2) (PP equals chelating diphosphine)

A family of nitrile complexes has been prepared by reaction of Ru2Cl4(PP)(2) Or RuCl2(PP)(PPh3) (PP = Ph2P(CH2)(4)PPh2 (dppb), Ph2PCH2CHOCMe2OCHCH2PPh2 (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 PF6 salt) by abstraction of the chloride counterion with NH4PF6. Use of 2 equiv of NH4PF6 generates Ru(PP)(RCN)(4)(2+)(PF6-)(2) (PP = dppb). In the absence of a halide-abstracting agent, addition of hexanes or diethyl ether precipitates neutral RuCl2(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 Ru2Cl3(PP)(2)(RCN)(2)X-+(-) (X = Cl) and, in benzene, Ru2Cl4(PP)(2)(RCN). The dinuclear cation (X = PF6) is also accessible by reaction of RuCl(PP)(RCN)(3)+PF6- with CH2Cl2 or CDCl3, while the mononitrile can be obtained directly by reaction of Ru2Cl4(PP)(2) or RuCl2(PP)(PPh3) with small amounts of nitrile in benzene.