CHEMISTRY OF IRIDIUM CARBONYL CLUSTERS - SYNTHESIS AND CHEMICAL CHARACTERIZATION OF THE HEXANUCLEAR ANIONS [IR6(CO)15(CO2ME)]-, [IR6(CO)15(CO2ET)] AND [IR6(CO)14(CO2ME))2]2- - CRYSTAL AND MOLECULAR-STRUCTURE OF [N(PPH3)2][IR6(MU-CO)4(CO)11(CO2ME)]

full title:Chemistry of iridium carbonyl clusters. Synthesis and chemical characterization of the hexanuclear anions [Ir6(CO)15(CO2R)]- (R = Me or Et) and [Ir6(CO)14(CO2Me)2]2-. Crystal and molecular structure of [n(PPh3)2][Ir6(μ-CO)4(CO) 11(CO2Me)] The anions [Ir6(CO)15(CO2R)]- (R = Me or Et) and [Ir6(CO)14(CO2Me)2]2- have been prepared by reacting [Ir6(CO)16] with Na(OR) in dry alcohol under an atmosphere of carbon monoxide. The reaction of [Ir6(CO)15(CO2Me)]- with primary and secondary alcohols such as EtOH and PriOH gives rise to specific alcoholysis. The anions [Ir6(CO)15(CO2R)] - ( R = Me or Et) and [Ir6(CO)14-(CO2Me)2]2- react with acids in tetrahydrofuran solution to give quantitatively [Ir6(CO)16]. The chemical and spectroscopic characterization of the hexanuclear anions is reported. Crystals of [N(PPh3)2] [Ir6(CO)15(CO2Me)] are triclinic, space group P1, with unit-cell dimensions a = 10.813(3), b = 16.613(3), c = 16.061(2) Å, α = 97.96(1), β = 96.20(1), γ = 94.58(2)°, and Z = 2. The X-ray structure has been solved by the heavy-atom method and refined by least squares to a final conventional R of 0.033 for 5 291 independent observed reflections. The anion consists of a slightly distorted octahedron of iridium atoms with eleven terminal and four edge-bridging CO groups and a methoxycarbonyl group σ-bonded to a metal atom. The Ir-Ir bond lengths are in the range 2.703(1)-2.870(1) Å, with an average value of 2.793 Å. Other average bond distances are Ir-Cterminal 1.878 and C-Oterminal 1.135 Å.