Facile Os-Os bond cleavage in the reactions of [Os3(CO)10(NCMe)2] and [Os3(CO)10(μ-H)2] with tetramethylthiuram disulfide (tmtd): Syntheses and crystal structures of new polynuclear osmium carbonyl complexes containing a dimethyldithiocarbamate ligand(s)

Abstract

The reaction of the labile triosmium cluster [Os3(CO)10(NCMe)2] with tetramethylthiuram disulfide [(Me2NCS2)2, tmtd] has been investigated at room temperature. Conducting the reaction under mild conditions has permitted the isolation of the three new polynuclear osmium complexes [Os3(CO)10{κ2(S,S)-S2CNMe2}2] (1), [Os4(CO)12{κ2(S,S)-S2CNMe2}2{μ3-η1(C),κ2(O,O)-CO2)}(μ3-S)] (2) and [Os3(CO)9{μ3-η1(C),κ1(S)-SCNMe2}{μ-κ1(S)-SC(O)NMe2}] (3) in 20, 16 and 10% yield, respectively, in addition to the known mononuclear complex [Os(CO)2{κ2(S,S)-S2CNMe2}2] (4) in 10% yield. The triosmium complex 1 has a linear arrangement of osmium atoms with each terminal osmium center containing a chelating Me2NCS2 ligand. The tetraosmium complex 2 also possesses a μ3-CO2 ligand in addition to capping sulfido and chelating Me2NCS2 ligands. Complex 3 contains an open triosmium core with the open Os···Os edge bridged by a Me2NC(O)S ligand and a capping Me2NCS ligand. A similar reaction between the unsaturated cluster [Os3(CO)10(μ-H)2] and [(Me2NCS2)2] yielded the triosmium complexes [Os3(CO)10{μ-κ1(S)-S2CNMe2}(μ-H)] (5) and [Os3(CO)9{μ3-κ2(S,S)-S2CNMe2}(μ-H)] (6) in addition to compounds 1 and 4 and the known hydroxyl cluster [Os3(CO)10(μ-OH)(μ-H)] (7) in 7, 14, 14, 10, and 6% yield, respectively. Both 5 and 6 possess a triosmium core, and the Me2NCS2 ligand acts in edge-bridging capacity in the former while it serves as a face-capping ligand in the latter. All new complexes have been characterized by combustion analyses and IR and NMR spectroscopies, and the solid-state structures of 1–3, and 6 have been established by X-ray crystallography. The bonding in clusters 1-3 and 6 has been examined by electronic structure calculations, and the thermodynamics for the formation of 1 and MeCN (two equiv) from [Os3(CO)10(MeCN)2] and tmtd, relative to other chelated and bridged isomers of [Os3(CO)10(tmtd)] are discussed.