Reactions of the linear triosmium cluster [Os3H(CO)11(η2-C6F5NNNC6F5)] with [Os3(CO)12–n(NCMe)n](n= 1 or 2): crystal structures of [Os4(µ-H)(CO)14(η2-C6F5NNNC6F5)] and [Os5(µ-H)(CO)17(η2-C6F5NNNC6F5)]

Abstract

Reaction of the linear triosmium carbonyl cluster [Os₃H(CO)₁₁(η²-C₆F₅NNNC₆F₅)] with [Os₃(CO)₁₁(NCMe)] in hexane at 60 °C under vacuum afforded the ‘spiked’ tetraosmium cluster [Os₄(µ-H)(CO)₁₄(η²-C₆F₅NNNC₆F₅)]1. Reaction with [Os₃(CO)₁₀(NCMe)₂] in CH₂Cl₂ at room temperature gave the ‘spiked’ hexaosmium cluster [Os₆(µ-H)(CO)₂₁(NCMe)(η²-C₆F₅NNNC₆F₅)]2. Cluster 2 is reactive and converts into the ‘spiked’ pentaosmium cluster [Os₅(µ-H)(CO)₁₇(η²-C₆F₅NNNC₆F₅)]3 and a known cluster [Os₅(CO)₁₆] respectively when heated with and without C₆F₅NNNHC₆F₅. Clusters 1 and 3 were characterized by single-crystal X-ray crystallography. The structure of 1 consists of a triangular unit with a Os(CO)₃(η²-C₆F₅NNNC₆F₅) portion ‘spiked’ equatorially to it. The two nitrogen atoms in the triazenide ligand occupy an axial and an equatorial position in the Os(CO)₃(η²-C₆F₅NNNC₆F₅) group. The hydride ligand bridges, in a cis manner, the Os–Os edge where the Os(CO)₃(η²-C₆F₅NNNC₆F₅) portion is attached. The structure of 3 adopts a ‘4 + 1 spiked’ geometry hitherto unknown. Its metal core consists of a planar ‘kite-like’ Os₄ unit with the Os(CO)₃(η²-C₆F₅NNNC₆F₅) portion ‘spiked’ to one of the equatorial co-ordination sites of an osmium atom. The two nitrogen atoms in the triazenide ligand and the hydride are bonded as in cluster 1. Based upon ¹³C NMR studies, the structure of cluster 2 in solution was also deduced to have a ‘spiked’ feature with the linear triosmium fragment Os₃(CO)₁₁(η²-C₆F₅NNNC₆F₅) bound to one atom in the osmium triangle at an eqatorial co-ordination site. The transformation of cluster 2 and the formation of cluster 1 are also briefly discussed.