Synthesis and Characterization of Molybdenum(0) and Tungsten(0) Complexes of Tetramethylthiourea: Single-Source Precursors for MoS2 and WS2

The molybdenum­(0) and tungsten(0) carbonyl complexes, [M­(CO)n­(TMTU)6–n] (M = Mo and W; TMTU = tetramethylthiourea; n = 4 and 5), have been prepared by addition of TMTU to the appropriate carbonyl precursors. In the solid state, the compounds are monomeric and feature octahedral coordination geometries about the metal. In the case of [M­(CO)4­(TMTU)2], the TMTU ligands are bound in a cis fashion. Dissolution of cis-[M­(CO)4­(TMTU)2] produces an equilibrium mixture of cis-[M­(CO)4­(TMTU)2], free TMTU, and the putative dimeric species, cis,cis-[M2(CO)8­(μ-TMTU)2]. Attempts to prepare the tricarbonyl complex, [Mo­(CO)3­(TMTU)3], by addition of TMTU to fac-[Mo­(CO)3­(η6-cyclo­heptatriene)] results in isolation of cis-[Mo­(CO)4­(TMTU)2], demonstrating that exchange of CO and TMTU ligands is facile in these compounds. Each of the compounds decomposes readily in the solid state above 110 °C, ultimately forming the tetravalent metal disulfide. Thermolysis reactions of [M­(CO)n­(TMTU)6–n] complexes at 300 °C under an argon atmosphere produces amorphous MS2, establishing the utility of these compounds as precursors to molybdenum and tungsten disulfide materials under relatively mild conditions.