Reactions of MH(OTf)(NBD) (PPh3)(2) (M = Ru, Os) with H-2

Treatment of RuHCl(NBD)(PPh3)(2) (NBD = norbornadiene) with AgOTf produced RuH(OTf)(NBD)(PPh3)(2). Reaction of RuH(OTf)(NBD)(PPh3)(2) with H-2 in benz ene gave norbornene and [(eta (6)-C6H6)RuH(PPh3)(2)]OTf. The same reaction in CD2Cl2 in the presence of added PPh3 produced norbornane and [RuH(PPh3)( 4)]OTf. Reaction of OsH3Cl(PPh3)(3) with norbornadiene produced OsHCl(NBD)( PPh3)(2), which was converted to OsH(OTf)(NBD)(PPh3)(2) on treatment with A gOTf. Reaction of OsH(OTf)(NBD)(PPh3)(2) with H-2 in benzene gave norbornan e and [(eta (6)-C6H6)OsH(PPh3)(2)]OTf. In dichloromethane, OsH(OTf)(NBD)(PP h3)(2) reacted with H-2 in the presence of added PPh3 to produce norbornane and [OsH3(PPh3)(4)]OTf. Supported by computational studies, it is assumed that; the dihydrogen complexes [MH(H-2)(NBD)(PPh3)(2)](+) (M = Ru, Os) were involved in the hydrogenation reactions. Two reaction pathways for the con version of [RuH(H-2)(NBD)(PH3)(2)](+) to [RuH(NBE)(PH3)(2)](+) (NBE = norbo rnene) have been studied by density functional theory calculations. The res ults show that the first hydrogen transferred to the olefin ligand is more likely from the hydride ligand rather than from the dihydrogen ligand.