Metal dithiolene complexes in olefin addition and purification, small molecule adsorption, H2 evolution and CO2 reduction

The transition metal dithiolene complexes bearing unusual electronic and redox non-innocent ligands hold a wide range of applications in the fields of optical materials chemistry, bioinorganic chemistry, electro- or photocatalytic chemistry and reduction chemistry. In this review, we mainly focus on experimental and theoretical works of metal dithiolene complexes and their applications in olefin addition/purification, toxic gas adsorption, H-2 evolution, and CO2 reduction. The coordination of non-innocent dithiolene ligands on transition metal centers give different oxidative state of metals, thus making the reductive character of sulfurs more obvious. And the p orbitals of sulfurs contribute more to the frontier molecular orbitals of metal dithiolene complexes, making the complexes react with olefins on sulfurs rather than metals. The reversable addition of olefins to these ligands could also be achieved, thus releasing olefins to finish the olefin purification process. In this case, metal dithiolenes are facilitating ligand-centered (S) reactivity towards olefin which makes olefin separation easier. Also, metal dithiolene based MOFs are very sophisticated and promising in the term of reduction ability and particular affinity to small molecules. Moreover, to realize a sustainable energy future, electro and photocatalytic manufacturing of H-2 is essential. Here we will also discuss the electro and photocatalyzed proton reductions into H-2 by using metal dithiolene as catalysts in aqueous and weak acetic media. Due to the non-innocent character of dithiolene ligands, the reductive potential of metal dithiolene complexes is usually low, which allows the reduction of CO2 to generate formic acid or CO. In these aspects, many homogeneous and heterogeneous metal dithiolene complexes and related reactions are addressed in this review. (C) 2020 Published by Elsevier B.V.