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. Selected bond distances are: IrIr(average) 2.774, IrC(terminal, average) 1.85, IrC(edge bridging, average) 2.13, IrC(face bridging, average) 2.22, IrCl 2.395(5) Å. 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 IrIr 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 [Cl bridges Ir(4)Ir(3), C(13) bridges Ir(1)Ir(6), C(14) bridges Ir(2)Ir(3)]; i.e. each of the six iridium atoms is involved in only one bridge. Average selected bond distances are: IrIr 2.767, IrC(terminal) 1.85, IrC(edge bridging) 2.05, IrCl 2.484 Å. © 1990.