Osmium-Germanium and Osmium-Germanium-Gold Carbonyl Cluster Complexes: Syntheses, Structures, Bonding, and Reactivity

Reactions of Os-3(CO)(10)(NCMe)(2) with HGePh3 have yielded the compounds Os-3(CO)(10)(NCMe)(GePh3)(mu-H) (1) and Os-3(CO)(10)(GePh3)(2)(mu-H)(2) (2) by the sequential replacement of the and two HGePh3 molecules, respectively, to the osmium atoms of NCMe ligands and the oxidative addition of the GeH bonds of one the cluster. Compound 2 exists as two isomers in solution at low temperatures which interconvert rapidly on the H-1 NMR time scale at room temperature. When it was heated, 1 was transformed into the pentaosmium complex Os-5(CO)(17)(mu-GePh2) (3), which exhibits a planar raft structure with one bridging GePh2 ligand. Compound 1 reacts with the compound PhAu(PPh3) to yield the compound Os-3(CO)(8)(mu-CO)(mu-O=CPh)(mu-GePh2)(mu-AuPPh3) (4), which contains a bridging O=CPh ligand and a Au(PPh3) group that bridges an Os-Ge bond. A minor product, Os(CO)(4)(GePh3)(AuPPh3) (5), was also obtained in this reaction. Compound 4 was also obtained from the reaction of 1 with CH3Au(PPh3). Compound 4 reacted with PhC2Ph to yield the complex Os-3(CO)(7)(mu-GePh2)(mu-AuPPh3)[mu-(O)CPhCPhCPh)] (6), which contains a novel bridging oxametallacyde formed by the coupling of PhC2Ph to the bridging O=CPh ligand in 4 and is another example of a Au(PPh3) group that bridges an Os-Ge bond. The bonding of the bridging Au(PPh3) group to the Os-Ge bonds in 4 and 6 was investigated by DFT computational analyses.