One-electron oxidation capability with Lewis acidity of oxovanadium(v) compounds allows oxidative carbon–carbon bond formation. A combination of boron enolate and silyl enol ether is effective for the selective cross-oxidative coupling. Ligand-coupling reactions, which are coupling reactions of organic substituents on main-group organometallic compounds, are also induced by oxidation with oxovanadium(v) compounds. As main-group metals, Al, Zn, B, etc., can be used in these reactions. Low-valent vanadiums or titaniums contribute to reductive coupling reactions as a catalyst, as exemplified by pinacol coupling reaction, which requires the presence of chlorosilane and co-reductant, zinc. Use of an heterobimetallic catalyst consisted of vanadium and titanium permits the selective cross-coupling between aryl and aliphatic aldehydes.