Synthesis, structural characterization and reactivities of hexaosmium carbonyl clusters with six-membered cyclic thioether and thioxane ligands

Cluster complexes [Os6(CO)15{S(CH2)4CH2} {μ-S(CH2)4CH2}] 1 and [Os5(CO)15{S(CH2)4CH2}] 2 were isolated from the reaction of [Os6(CO)16(MeCN)2] with S(CH2)4CH2 (L1) in 24 and 22% yields respectively. Cluster degradation from 1 to 2 can be achieved by addition of a stoichiometric quantity of L1 in CHCl3 under reflux. Monosubstituted cluster complex [Os6(CO)16{μ-S(CH2)3SCH 2}] 3 containing a S(CH2)3SCH2 (L2) ligand bridging across an Os-Os edge via one of the sulfur atoms was isolated in good yield from a similar reaction. However, similar reaction between [Os6(CO)16(MeCN)2] and S(CH2)2SCH2CH2 (L3) gave [Os6(CO)16{S(CH2)2SCH 2CH2}2] 4 as the major product instead. The two thio ligands are found to co-ordinate in terminal fashion to two different vertices of the Os6 core. Interaction of tridentate sulfur donor ligand SCH2SCH2SCH2 (L4) with [Os6(CO)16(MeCN)2] afforded [Os6(CO)14-(μ-CO)(SCH2SCH 2SCH2)] 5 in which the ligand L4 was found to cap over a triangular face of the Os6 skeleton. Treatment of mixed-donor ligand S(CH2)2OCH2CH2 (L5) yielded a pair of isomeric complexes [Os6(CO)15-{(S(CH2)2OCH 2CH2} {μ-S(CH2)2OCH2CH2}] 6 and [Os6(CO)15{O(CH2)2SCH 2CH2) {μ-S(CH2)2OCH2CH2}] 7. Carboxylation of 6 gave [Os6(CO)16{μ-S(CH2)2OCH 2CH2}] 8 and [Os6(CO)18]. Hydrogenation of 6 led to the formation of dihydrido cluster [Os6(CQ)15(μ-H)2{S(CH2) 2OCH2CH2} {μ-S(CH2)2OCH2CH2}] 9. The metal skeleton of 9 can be described as two fused tetrahedra sharing a common edge. All new compounds were fully characterized by spectroscopic and analytical techniques. In addition the structures of 1, 2, 3, 4, 5, 6, 8 and 9 were established by X-ray crystallography.