Paddlewheel dirhodium(II) complexes with N-heterocyclic carbene or phosphine ligand: New reactivity and selectivity

The dirhodium(II)-catalyzed organic reactions, including asymmetric transformation, are significantly benefitted from the discovery of simple and efficient protocols to introduce various bridging ligands, e.g. carboxylic acids, amide and phosphoric acids. Ligands lying at axial position of dirhodium(II) complexes could strongly affect the activity and selectivity of these metal complexes involved reactions. This review summarizes the newly explored reactivity of dirhodium(II) complexes with N-heterocyclic carbenes or phosphines as the axial ligands. The asymmetric tries are also highlighted, where their stereo-induction were solely from the axial ligand of dirhodium(II) complexes. In the last part, the reactions catalyzed by inherent chiral ortho-metalated dirhodium(II)/ phosphine complexes are also discussed.