Neutral Mo6Q8-clusters with terminal phosphane ligands – a route to water-soluble molecular units of Chevrel phases

Abstract

Despite the numerous studies on Chevrel phases, their building blocks – molecular compounds containing the {Mo₆Q₈} cluster core – are hardly presented in the literature. Here we present rare examples of phosphane molybdenum chalcogenide clusters – [{Mo₆Q₈}(Ph₂PC₂H₄COOH)₆] (Q = S or Se) – which have been obtained by the direct interaction of (Bu₄N)₂[{Mo₆Cl₈}Cl₆] with in situ generated Na₂Q in the presence of a phosphane pro-ligand. Crystal structure determination has confirmed the formation of a homoleptic six-substituted neutral complex. The redox and optical properties were also studied. Due to the presence of six carboxylate groups in phosphane ligands, both clusters form a stable solution in alkaline water. Besides the known K₇[{Mo₆Se₈}(CN)₆]·8H₂O, the compounds obtained here are the only examples of water-soluble complexes of such types.