Bond activation by low valent ruthenium complexes

Ru(4-1,5-cyclo-octadiene)(6-1,3,5-cyclo-octatriene)(1) is one of the most versatile zero-valent ruthenium complexes bearing two labile cyclopolyenes and acts as a potential precursor for catalytic processes involving bond cleavage reactions in the presence of suitable Lewis bases. However, detailed studies of the bond cleavage step had, until now, been relatively less explored at a molecular level. The present Perspective is an account of our recent studies concerning: (1) the reactions of 1 with Lewis bases, (2) carbon-oxygen, carbon-sulfur, oxygen-hydrogen, nitrogen-hydrogen and carbon-hydrogen bond cleavage reactions by 1 in the presence of tertiary phosphine, (3) selective sp3 carbon-hydrogen bond cleavage by 1 by use of co-ordination of an anchoring chalcogen atom, and (4) preparation of an enolatoruthenium (II) complex derived from 1 as an active intermediate in chemoselective catalytic Kn?evenagel and Michael reactions.