Mixed-metal cluster chemistry XII:: isocyanide derivatives of [CpWIr3(CO)11];: X-ray crystal structure of [CpWIr3(CO)9(CNC6H3Me2-2,6)2]

Reactions of [CpWIr3(CO)(11)] (1) with stoichiometric amounts of isocyanides afford the clusters [CpWIr3(CO)(11-n)(CNR)(n)] [R = Xy (C6H3Me2-2,6), n = 1 (2), 2 (3), 3 (4); R = Bu-t, n = 1 (5), 2 (6), 3 (7)] in good to excellent yields (47-63%). The products exhibit ligand fluxionality in solution, with the C-13-NMR spectra of 4-6 revealing that the carbonyls are undergoing fast exchange at 143 K. A single-crystal X-ray study of [CpWIr3(CO)(9)(CNXy)(2)] (3) reveals that the coordination sphere of the cluster has an all-terminal ligand geometry, the first for a ligand substituted derivative of 1. The two iridium-ligated 2,6-dimethylphenylisocyanide ligands are coordinated to the same iridium vertex, the second example of this coordination geometry for a transition metal cluster. (C) 1999 Elsevier Science S.A. All rights reserved.