Synthesis, structural characterization, electrochemistry, and reactivities of heptaosmium carbonyl clusters bearing thioxane ligands

Reaction of the activated heptaosmium cluster [Os7(CO)19(MeCN)2] with 1,4-thioxane in CH2Cl2at ambient temperature led to the isolation of three air-stable clusters [Os7(CO)16(μ-S(CH2)2OCH2CaH2(S-Ca)}2] (1), [Os7(CO)17{μ-S(CH2)2OCH2CaH2(S-Ca)}{S(CH2)2OCH2CaH2(S- Ca)}] (2) and [Os7(CO)18{μ-S(CH2)2OCH2CaH2(S-Ca)}] (3). The metal skeletons of these clusters are in the form of a winding helix made up of four tetrahedra sharing three common faces. From electrochemical studies, the extent of the cathodic shifts of the reduction waves of these clusters were found to differ from that of the parent cluster [Os7(CO)21]. Treatment of 2 with carbon monoxide produced an isomer of 3, namely compound 4, which has the same molecular formula as 3, but a different ligand arrangement.