Chemistry of iridium carbonyl cluster complexes - synthesis, chemical characterization and x-ray crystal-structures of [pph4][ir6(co)15cl].c4h8o and [pph4][ir6(co)14cl]

The anion [Ir6(CO)15Cl]− has been formed by treating [Ir6(CO)15]2− with FeCl3; [Ir6(CO)15Cl]− (1) is the first species formed, but if kept standing 1 slowly loses a CO ligand to give [Ir6(CO)14Cl]− (2). Compound 1 can also be obtained by treating Ir6(CO)16 with LiCl in anhydrous tetrahydrofuran, but, because of the long reaction time needed, a substantial amount of compound 2 is also formed. The crystal structures of [PPh4][Ir6(CO)15Cl] · C4H8O (1) and [PPh4][Ir6(CO)14Cl] (2) have been determined. Anion 1 contains an octahedron of iridium atoms surrounded by eleven terminal, one edge, and three face-bridging carbonyl groups, and by one terminal chlorine atom. The disposition of the bridging carbonyl groups can be related to that of Ir6(CO)16 (red isomer) in which one face-bridging carbonyl group has become edge bridging. Anion 2 contains a slightly distorted octahedron of iridium atoms bearing twelve terminal and two edge-bridging carbon monoxide groups; the chlorine atom bridges an Ir-Ir edge. The stereochemistry of anion 2 is related to that of [Ir6(CO)15]2− by replacing an edge-bridging carbonyl group by the μ-halogen atom i.e. each of the six iridium atoms is involved in only one bridge.