Oxidative Addition Reactions of I2 with [HIr4(CO)10-n(PPh3 )n(μ-PPh2)] (n = 1 and 2) and Crystal and Molecular Structure of [HIr4(μ-I)2(CO)7 (PPh3)(μ-PPh2)]

the reactions of the cluster compounds [hir4(co)10-n(pph3 )n(μ-pph2)] [n = 0, (1); 1, (2) and 2, (3)] with i2 have been investigated. compound 1 does not react, however, the presence of pph3 in place of co ligand(s) activates the cluster. both compounds 2 and 3 react with i2 under mild conditions to give [hir4(μ-i)2(co)7(pph3)(μ-pph 2)] (4), as the result of oxidative addition of i2 and dissociation of two co ligands, or one co and one pph3 ligands, respectively. the molecular structure of 4, determined by an x-ray diffraction study, exhibits a butterfly arrangement of iridium atoms with the wings spanned by a μ-pph2 ligand, the hinge bridged by a μ-h ligand, two hinge to wing tip edges bridged by iodine atoms and all metal atoms bearing two co ligands, with the exception of one of the hinge atoms that contains a co and a pph3 ligands. this cluster exhibits the shortest average ir？ir bond length [2.698(2) ？] observed so far for a derivative of 1 and this is in accord with the relatively high average oxidation state of its metal atoms (+1) for a carbonyl cluster compound.