Rhodium Cluster Complexes Containing Bridging Phenylgermanium Ligands

The reaction of Rh4(CO)12 with Ph3GeH at 97 °C has yielded the first rhodium cluster complexes containing bridging germylene and germylyne ligands: Rh8(CO)12 ((mu)4-GePh)6, 9, and Rh3(CO)5(GePh3)((mu)-GePh2)3((mu)3-GePh)((mu)-H), 10. When the reaction is performed under hydrogen, the yield of 9 is increased to 42% and no 10 is formed. Compound 9 contains a cluster of eight rhodium atoms arranged in the form of a distorted cube. There are six (mu)4-GePh groups bridging each face of this distorted cube. Four of the rhodium atoms have two terminal carbonyl ligands, while the remaining four rhodium atoms have only one carbonyl ligand. Compound 10 contains a triangular cluster of three rhodium atoms with one terminal GePh3 ligand, three bridging GePh2 ligands, and one triply bridging GePh ligand. There is also one hydrido ligand that is believed to bridge one of the Rh-Ge bonds. Compound 9 reacted with PPhMe2 at 25 °C to give the tetraphosphine derivative Rh8(CO)8(PPhMe2)4((mu)4-GePh)6, 11. The structure of 11 is similar to 9 except that a PPhMe2 ligand has replaced a carbonyl ligand on each the four Rh(CO)2 groups. Compound 10 reacted with CO at 68 °C to give the complex Rh3(CO)6((mu)-GePh2)3((mu)3-GePh), 12. Compound 12 is formed by the loss of the hydrido ligand and the terminal GePh3 ligand from 10 and the addition of one carbonyl ligand. All compounds were fully characterized by IR, NMR, elemental, and single-crystal X-ray diffraction analyses.