Heterolytic H2 Activation by Dihydrogen Complexes. Effects of the Ligand X in [M(X)H2{Ph2P(CH2)3PPh2}2]n+ (M = Ru, Os; X = CO, Cl, H)

Abstract

Complexes of the general formula [MXH2(dppp)2]n+ (M = Ru, Os; X = H, Cl, CO; dppp = 1,3-bis(diphenylphosphino)propane) have been prepared and characterized, and the effect of the donor/acceptor properties of X on their structure and acidity has been studied. The five-coordinate complexes [MCl(dppp)2]+ (M = Ru (1a), Os (1b)) react with H2 gas in CH2Cl2 to give the complexes [MCl(η2-H2)(dppp)2]+ (M = Ru (2a), Os (2b)) containing elongated dihydrogen ligands. The molecular structure of 2b has been determined by X-ray crystallography (monoclinic, space group P21/n with a = 13.314(7) A, b = 18.63(2) A, c = 23.20(2) A, β = 94.58(6)°, and Z = 4). Chlorohydride [OsH(Cl)(dppp)2] (3b) reacts with H2 gas in the presence of Na[BPh4] forming [OsH3(dppp)2]+ (4b). Protonation of [OsH2(dppp)2] (5b) with HBF4·Et2O also gives 4b. A combination of X-ray crystallography (monoclinic, space group P21/n with a = 13.392(3) A, b = 25.306(7) A, c = 21.247(7) A, β = 91.15(2)°, and Z = 4) and 1H and 31P NMR studies indicate that 4b ...