α-Cleavage of Phenyl Groups from GePh3 Ligands in Iridium Carbonyl Cluster Complexes. A Mechanism and Its Role in the Synthesis of Bridging Germylene Ligands

At 110 °C, the compound HIr(CO)3(GePh3)2 (1) was decarbonylated and transformed into five polynuclear iridium compounds, Ir2(CO)6(μ-GePh2)(GePh3)2 (2), Ir3(CO)6(η1-Ph)2(μ-GePh2)3(GePh3) (3), Ir3(CO)6(η1-Ph)(μ-GePh2)3(GePh3)2 (4), Ir3(CO)6(μ-CO)(μ-GePh2)2(GePh3)3 (5), and Ir3(CO)6(η1-Ph)(μ-GePh2)2(GePh3)2[μ-Ge(Ph)(OH)] (6), by a combination of condensation and phenyl-cleavage processes. The triiridium compounds 3–6 are all new and have been characterized by single-crystal X-ray diffraction analyses. Each new compound consists of a closed triangular cluster of three iridium atoms with two or three diphenylgermylene ligands bridging the Ir–Ir bonds. Separately, compound 5 was converted to 4 in 68% yield by decarbonylation and cleavage of a phenyl group from one of its GePh3 ligands by heating a toluene solution to reflux (110 °C) for 1 h. A computational study has revealed that the mechanism of transformation of 5 to 4 occurs by elimination of the bridging carbonyl ligand followed by a “deinsertion” α-cleavage of a phenyl group from one of the GePh3 ligands.