Iridium clusters containing η1 organic ligands: the synthesis and the solid state structure of [Ir4(CO)11(CPhCHPh)]− and [Ir6(CO)14(COOMe)2]2−

The cluster [Ir4(CO)11(CPhCHPh)]− was obtained by reaction of [HIr4(CO)11]− and diphenylacetylene by refluxing in tetrahydrofuran (THF), with yields approaching 80%. The solid state structure was determined on the [NEt4]+ salt; the cluster possesses a tetrahedral metallic framework, with three edge bridging carbonyls. The vinyl fragment, having two phenyl rings in cis, is bound in axial position and donates only one electron to the cluster, since the CC double bond (1.34 Å) does not interact with any iridium atom. The 13C-NMR of the cluster, recorded at −90°C, allows full assignment of the signals. The cluster [Ir6(CO)14(COOMe)2]2− was obtained by nucleophilic attack of MeONa on [Ir6(CO)16], in anhydrous methanol at room temperature. The solid state structure was determined on its [N(PPh3)2]+ salt. Two methoxycarbonyl fragments are on adjacent metal vertices of the octahedral framework.