Diphosphine ligand chelation and bridging and regiospecific ortho metalation in the reaction of 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) with Ir4(CO)12: X-ray diffraction structures of Ir4(CO)7(μ-CO)3(bpcd), Ir4(CO)5(μ-CO)3(bpcd)(μ-bpc

The reactivity of the tetrairidium clusters Ir4(CO)12 and [Ir4(CO)11Br][Et4N] with the unsaturated diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) has been investigated. The simple substitution products Ir4(CO)7(μ-CO)3(bpcd) (3) and Ir4(CO)5(μ-CO)3(bpcd)(μ-bpcd) (4) have been isolated and the coordination mode adopted by the bpcd ligand(s) established by X-ray crystallography. Facile loss of a CO group in cluster 4 is accompanied by ortho metalation of one of the aryl rings in the bridging bpcd ligand and formation of the hydride-bridged cluster HIr4(CO)4(μ-CO)3(bpcd)[μ-PhP(C6H4)CC(PPh2)C(O)CH2C(O)] (5).