Olefin Metathesis. A Mechanistic Study of High-Valent Group 6 Catalysts

The results of an ab initio theoretical mechanistic study are used to suggest that oxo-alkylidene complexes are the active, chain-carrying metathesis catalysts for high-valent Mo, W, and Re complexes and that the oxygen ligand is intimately involved in the catalytic process. Furthermore, we suggest that oxo-alkylidene complexes are formed on supported molybdate and tungstenate catalysts and that dioxo precursors can provide a convenient route to formation of well-defined surface catalysts for olefin metathesis and oxidation reactions. The spectator oxo group is suggested to play a central role in stabilizing the critical intermediate in these reactions and may be important in other reactions of metal oxides (e.g., MnO₄⁻, OsO₄, RuO₄, supported transition-metal oxides).