Synthesis of ionic phosphines and corresponding ionic transition metal complexes and their applications in homogeneous catalysis

Compared to the traditional neutral phosphine-ligated transition metal complexes (PTMCs), the ionic phosphine-ligated ones as the ionic salts are composed with the ion-pairs with unusual electronic effect and varied structural configurations. In these ionic PTMCs, not only the coordinating interaction but also the strong electron-withdrawing effect of the positive-charge and the electrostatic interaction between cations and anion are involved which correspond to the unique catalytic performance. In recent decade, the study on the ionic PTMCs has been concerned as a hot topic in coordination chemistry and homogeneous catalysis. In addition, when the ionic PTMCs are used as the catalysts in combination with the room temperature ionic liquids (RTILs, as the solvents) for catalytic reactions, the advantages such as the available recovery and recyclability of the catalysts, and the avoided catalyst leaching are evidently observed, which endows theses ionic transition metal complexes great potential applications in green chemistry. In this review, the syntheses of the ionic phosphines and the corresponding ionic PTMC (M=Rh, Pd, Ru, Pt, Au, Ni, Cu) and their applications for homogeneous catalysis, which have been developed in the past ten years, are summarized.