Synthesis and structure of mononuclear molecular complexes of molybdenum(VI) and tungsten(VI) oxy- and dioxyhalides

Specific features of the synthesis and structure of mononuclear molecular halide oxide complexes of Group VI d ⁰ metals molybdenum(VI) and tungsten(VI) are surveyed. Various methods of synthesis of adducts based on MOX₄ and MO₂X₂ (M = Mo, W; X = F, Cl, Br) are described, such as direct interaction, ligand exchange, and the method of nascent reagents. The principles of formation of a particular geometric isomer are discussed: according to the self-consistency rule, the coordination of a neutral donor ligand L trans to a multiply bonded oxo ligand is preferable to that of acido ligands X⁻ (anions). Rare exceptions are mentioned.