Heterolytic Bond Cleavage and Formation based on the Metal-Ligand Cooperative Function of Cyclopentadienone Metal Complexes

Metal−ligand cooperation, in which both metal and ligand participate in bond cleavage and formation, is gathering great attention in recent years. While many types of complexes have been employed in metal–ligand cooperative heterolytic cleavage of H–H bond, a cyclopentadienone–hydroxycyclopentadienyl-based metal complex, originally reported by Shvo, has a unique character, that is, red/ox activity of the metal center along with the heterolytic bond cleavage. To date, various transition-metal complexes (M = Ru, Fe, Re, Mo, Ir, Rh, Pt, etc.) having cyclopentadienone/ hydroxycyclopentadienyl ligands are reported to show catalytic reactions utilizing the heterolytic cleavage/formation of H–H bond. On the other hand, there are substantial efforts to expand the scope of the bond to be cleaved other than the H−H bond. This article summarizes our recent progress in the metal−ligand cooperative cleavages of C–H, B–H and Si−H bonds by cyclopentadienone metal complexes with introduction of the historical background.