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 isocyanide s 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 excelle nt yields (47-63%). The products exhibit ligand fluxionality in solution, w ith 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)(CNX y)(2)] (3) reveals that the coordination sphere of the cluster has an all-t erminal ligand geometry, the first for a ligand substituted derivative of 1 . The two iridium-ligated 2,6-dimethylphenylisocyanide ligands are coordina ted to the same iridium vertex, the second example of this coordination geo metry for a transition metal cluster. (C) 1999 Elsevier Science S.A. All ri ghts reserved.