Hafnium−Rhodium and Hafnium−Iridium Heterobimetallic Complexes Featuring the Bridging Germole Dianion Ligand [GeC₄Me₄]²^-

The complex [Cp*(η5-C4Me4Ge)HfMe2Li(THF)]2 (1; Cp* = C5Me5), prepared via treatment of Cp*HfMe2Cl with 2 equiv of Li[C4Me4GeSiMe3], reacted rapidly with 2 equiv of (PMe3)4RhOTf (OTf = OSO2CF3) to give the novel Rh(III) zwitterionic complex ansa-{η4-C4Me4Ge[Rh(PMe3)4H](η5-C5Me4CH2)}HfMe2 (2), via loss of LiOTf. An intermediate in this reaction, presumed to be Cp*{η5-C4Me4Ge[Rh(PMe3)4]}HfMe2 (3), was observed at low temperature by 31P NMR spectroscopy. Reactions of 1 with (dmpe)2MOTf (dmpe = 1,2-bis(dimethylphosphino)ethane; M = Rh, Ir) produced the complexes Cp*{η5-C4Me4Ge[Rh(dmpe)2]}HfMe2 (5) and Cp*{η5-C4Me4Ge[Ir(dmpe)2]}HfMe2 (6), respectively. Complexes 5 and 6 possess the [GeC4Me4]2- ligand, which bridges the two metal atoms in a σ,π fashion.