Synthesis and Reactivity of Diphosphine-Bridged Diruthenium Complexes

Treatment of a chloride-bridged tetraruthenium complex with tetramethyldiphoshine and tetraphenyldiphosphine affords a different type of diphosphine-bridged diruthenium complexes, which are further transformed into the corresponding cationic complexes by treatment with silver trifluoromethanesulfonate. Some diphosphine-bridged diruthenium complexes show a catalytic activity toward the quantitative cyclotrimerization of ethyl propiolate to two regioisomeric benzene derivatives.