Dicarbonylcyclopentadienyliridium, (η-C5H5)Ir(CO)2, as a ligand

The following complexes, in which CpIr(CO)(2) acts as a 2e donor ligand, have been prepared: Cp(OC)(2)IrW(CO)(5) (1), Cp(OC)(2)IrRu(CO)(3)(SiCl3)(2), Cp(OC)(2)IrOs(CO)(3)(GeCl3)(Cl) (2), Cp(OC)(2)IrOs(CO)(3)(X)(2) (X = Cl, Br (3), I). The characterization of the complexes included the crystal structures of 1, 2, and 3, which reveal that all contain an unbridged metal-metal bond. The carbonyl ligands of 1 in solution undergo exchange on the NMR time scale above -40 degrees C. With the exception of 2, all the complexes dissociate in solution at room temperature, some rapidly so. Only in the case of 3 is an equilibrium with the dissociation products established. The results indicate that Cplr(CO)(2) is a weak ligand.