Structure expansion of the Ir-4 cluster core induced by the short bite of the 2-(biphenylphosphino)pyridine ligand. Reaction of [Ir-4(CO)(10)(Ph(2)PPy)(2)] with [Cu(NCCH3)(4)]BF4 and AgPF6 leading to higher-nuclearity Ir4Cu and Ir4Ag cluster compounds

[Ir-4(CO)(11)Br]NEt(4) reacts with Ph(2)PPy, in the molar ratio 1:2, in dichloromethane solution, to give [Ir-4(CO)(10)(Ph(2)PPy)(2)], 1. In this compound the tetrahedral Ir-4 cluster can be seen also as a trigonal pyramid with the three basal edges bridged by carbonyls lying roughly in the basal plane. The two Ph(2)PPy act as monodentate P-bonded ligands and are coordinated at two basal iridium atoms occupying an axial and an equatorial position, respectively. The occurrence in CDCl3 solution, at room temperature, of a scrambling process of the Ph(2)PPy ligands between equatorial and axial positions was evidenced by P-31{H-1} NMR spectroscopy At lower temperature this process is frozen. Compound 1 was structurally characterized by an X-ray study. The complex 1 reacts with [Cu(NCCH3)(4)]BF4 and AgPF6, in dichloromethane solution, in the molar ratio 1:1, affording, almost quantitatively, the ionic compounds [Ir(4)M(CO)(10)(Ph(2)PPy)2]Y (2, M = Cu, Y = BF4; 3, M = Ag, Y = PF6). The re action of 1 with [Au(tht)]PF6 (tht = tetrahydrothiophene) proceeds similarly, but the reaction product was not fully characterized. A full characterization of the acetone solvate of 2 was obtained by an X-ray crystal structure analysis. The cation of 2 consists of a trigonal bipyramid Ir4Cu core, with the copper atom in an axial position; the copper atom is formally five-coordinated being bonded to three iridium atoms and to two nitrogen atoms of the Ph(2)PPy ligands.