Syntheses and structures of Tetranuclear Cluster complexes of molybdenum [Mo4(?3-S)2(?2-S)4 X 2-(PMe3)6] (X = SH, Cl, Br, I, SCN) and [Mo4(?3-S)2-(?2-S)4 (dtc)2(PMe3)4] (dtc = diethyldithiocarbamate)

Abstract

A molybdenum cluster complex [Mo4(μ3-S)2(μ2-S)4)(SH)2(PMe3 6] has been synthesized by the reaction of (NH4)2Mo3S13 with trimethylphosphine. The cluster core is composed of four molybdenum atoms arranged in the rhombus bridged by two capping and four bridging sulfur atoms. Two SH and six tri-methylphosphine ligands are coordinated to the terminal positions. The mean oxidation stares of molybdenum is +3.5 and there are five Mo-Mo bonds consistent with ten metal cluster electrons. The complex has been converted into [Mo4(μ3-S)2(μ2-S)4 X 2(PMe3)6] (X=Cl, Br, I, SCN) and [Mo4μ3-S2(μ2-S)4 (die)2(PMe3)4] (dtc - diethyldithiocarbamate). In the case of the dtc complex, two terminal trimetlaylphosphine ligands are displaced and dtc ligands are coordinated in chelate fashion. The structures of the SH, Cl, Br, and dtc complexes have been determined by X-ray crystallography. Molecular orbital calculations with DV-Xα method has shown large HOMO-LUMO gaps (1.52-1.74eV) for [Mo4S6 X 2(PH3)4] (X= SH, Cl, and Br).