Formation of a Dithiophosphinate Ligand Ph₂PS₂ by Sulfur Insertion into the Metal−Phosphido Bond on Heterobimetallic Phosphido-Bridged Complex Cp(CO)₂W(μ-PPh₂)Mo(CO)₅:  A Rare Example of a Neutral Six-Electron Mixed-Metal Cluster with a Mo₂WS₄ Core

Reflux of a dichloromethane solution of elemental sulfur and phosphido-bridged heterodinuclear complex (1) afforded (2) and a neutral six-electron mixed-metal incomplete cubane-like cluster, CpW(μ₃-S)(μ-S)₂Mo₂(μ-S)(μ-S₂PPh₂)(S₂PPh₂)₂ (3), together with known compounds Cp(CO)₃W(μ-PPh₂)Mo(CO)₅ and (CpW(S)(μ-S))₂. The electron-deficient 28e heterodinuclear complex 2 is stabilized via S(p_π) → Mo(d) ligand-to-metal dative π-bonding interactions. Room-temperature stirring of a THF solution of 2 and DMAD (dimethyl acetylenedicarboxalate) yielded compounds (4) and (5). Compounds 2−5 were characterized by single-crystal X-ray diffraction analysis. Molecular structures of 2 and 3 reveal sulfur insertion into the metal−phosphido bond on 1, resulting in a dithiophosphinate ligand Ph₂PS₂. Formation of the C−S bonds in 4 and 5 has resulted through the reaction of sulfide ligands on 2 and DMAD.