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

Reactions of Os₃(CO)₁₀(NCMe)₂ with HGePh₃ have yielded the compounds Os₃(CO)₁₀(NCMe)­(GePh₃)­(μ-H) (<b>1</b>) and Os₃(CO)₁₀(GePh₃)₂(μ-H)₂ (<b>2</b>) by the sequential replacement of the NCMe ligands and the oxidative addition of the GeH bonds of one and two HGePh₃ molecules, respectively, to the osmium atoms of the cluster. Compound <b>2</b> exists as two isomers in solution at low temperatures which interconvert rapidly on the ¹H NMR time scale at room temperature. When it was heated, <b>1</b> was transformed into the pentaosmium complex Os₅(CO)₁₇(μ-GePh₂) (<b>3</b>), which exhibits a planar raft structure with one bridging GePh₂ ligand. Compound <b>1</b> reacts with the compound PhAu­(PPh₃) to yield the compound Os₃(CO)₈(μ-CO)­(μ-OCPh)­(μ-GePh₂)­(μ-AuPPh₃) (<b>4</b>), 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) (<b>5</b>), was also obtained in this reaction. Compound <b>4</b> was also obtained from the reaction of <b>1</b> with CH₃Au­(PPh₃). Compound <b>4</b> reacted with PhC₂Ph to yield the complex Os₃(CO)₇(μ-GePh₂)­(μ-AuPPh₃)­[μ-(O)­CPhCPhCPh)] (<b>6</b>), which contains a novel bridging oxametallacycle formed by the coupling of PhC₂Ph to the bridging OCPh ligand in <b>4</b> 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 <b>4</b> and <b>6</b> was investigated by DFT computational analyses