Reactions of the linear triosmium cluster [Os3H(CO)11(η2-C6F 5NNNC6F5)] with [Os3(CO)12-n(NCMe)n] (n = 1 or 2): Crystal structures of [Os4(μ-H)-(CO)14(η2-C6F 5NNNC6F5)] and [Os5(μ-H)...

Abstract

Title full: Reactions of the linear triosmium cluster [Os3H(CO)11(η2-C6F 5NNNC6F5)] with [Os3(CO)12-n(NCMe)n] (n = 1 or 2): Crystal structures of [Os4(μ-H)-(CO)14(η2-C6F 5NNNC6F5)] and [Os5(μ-H)(CO)17(η2-C6F 5NNNC6F5)]. Reaction of the linear triosmium carbonyl cluster [Os3H(CO)11(η2-C6F 5NNNC6F5)] with [Os3(CO)11-(NCMe)] in hexane at 60°C under vacuum afforded the 'spiked' tetraosmium cluster [Os4(μ-H)(CO)14(η2-C6F 5NNNC6F5)] 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-C 6F5NNNC6F5)] 2. Cluster 2 is reactive and converts into the 'spiked' pentaosmium cluster [Os5(μ-H)(CO)17(η2-C6F 5NNNC6F5)] 3 and a known cluster [Os5(CO)16] respectively when heated with and without C6F5N=NNHC6F5. 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-C6F5NNNC 6F5) 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-C6F5NNNC 6F5) group. The hydride ligand bridges, in a cis manner, the Os-Os edge where the Os(CO)3(η2-C6F5NNNC 6F5) 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-C6F5NNNC 6F5) 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-C6F 5NNNC6F5) bound to one atom in the osmium triangle at an equatorial co-ordination site. The transformation of cluster 2 and the formation of cluster 1 are also briefly discussed.