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

Abstract

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)₃SCH₂}] 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)₂SCH₂CH₂}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)(SCH₂SCH₂SCH₂)] 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)₂OCH₂CH₂}{µ-S(CH₂)₂OCH₂CH₂}] 6 and [Os₆(CO)₁₅{O(CH₂)₂SCH₂CH₂}{µ-S(CH₂)₂OCH₂CH₂}] 7. Carboxylation of 6 gave [Os₆(CO)₁₆{µ-S(CH₂)₂OCH₂CH₂}] 8 and [Os₆(CO)₁₈]. Hydrogenation of 6 led to the formation of dihydrido cluster [Os₆(CO)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.