Synthesis and Characterization of Molybdenum(0) and Tungsten(0) Complexes of Tetramethylthiourea: Single-Source Precursors for MoS<sub>2</sub> and WS<sub>2</sub>
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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.
本研究通过向相应的羰基前驱体中加入四甲基硫脲(tetramethylthiourea)，合成了钼(0)与钨(0)的羰基配合物[M(CO)ₙ(TMTU)₆–ₙ]（其中M为Mo或W；n=4或5）。固态下，该类配合物均为单核结构，金属中心呈现八面体配位几何构型。对于[M(CO)₄(TMTU)₂]而言，其TMTU配体以顺式方式配位。将cis-[M(CO)₄(TMTU)₂]溶解后，会得到包含cis-[M(CO)₄(TMTU)₂]、游离TMTU以及推定的二聚体物种cis,cis-[M₂(CO)₈(μ-TMTU)₂]的平衡混合物。尝试通过向面式-[Mo(CO)₃(η⁶-环庚三烯)]中加入TMTU来制备三羰基配合物[Mo(CO)₃(TMTU)₃]，最终却分离得到了cis-[Mo(CO)₄(TMTU)₂]，这表明该类配合物中CO与TMTU配体的交换反应极易进行。所有配合物在固态下于110℃以上均易发生分解，最终生成四价金属二硫化物。在氩气氛围下于300℃对[M(CO)ₙ(TMTU)₆–ₙ]配合物进行热解反应，可得到无定形MS₂，这证明了该类配合物作为温和条件下制备二硫化钼与二硫化钨材料前驱体的实用性。
