Stoicheiometric dehydrogenation of cyclic alkenes without hydrogen acceptors using the ‘(C5Me5)Ru+’ fragment. X-Ray crystal structure of [(η5-C5Me5)Ru-(µ2, η5, η5-C5Me4OH)-Ru(η5-C5Me5)]CF3SO3·CH2Cl2

Abstract

The reaction of [(C₅Me₅)Ru(OMe)]₂(2) with CF₃SO₃H in the presence of cyclic alkenes (cyclohexene or 4-methylcyclohexene) affords the π-arena derivatives [(C₅Me₅)Ru(η⁶-C₆H₆)]CF₃SO₃(4) and [(C₅Me₅)Ru(η⁶-C₅H₅Me)](CF₃SO₃)(5) in 40–60% isolated yield (100% spectroscopic yield) while the same reaction with tetramethylcyclopentenone affords the novel triple-decker title complex (3) in 90% yield; a mechanism involving unstable dihydrogen intermediate complexes is proposed.