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) (1) and Os3(CO)10(GePh3)2(μ-H)2 (2) 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 2 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, 1 was transformed into the pentaosmium
complex Os5(CO)17(μ-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 Os3(CO)8(μ-CO)­(μ-OCPh)­(μ-GePh2)­(μ-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 Os3(CO)7(μ-GePh2)­(μ-AuPPh3)­[μ-(O)­CPhCPhCPh)] (6), which contains
a novel bridging oxametallacycle 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.