Recent Developments of Manganese Complexes for Catalytic Hydrogenation and Dehydrogenation Reactions

Being the third most abundant transition metal in the Earth’s crust (after iron and titanium) and less toxic, reactions catalyzed by manganese are becoming very important. A large number of manganese complexes have been synthesized using bidentate and tridentate ligands. Such manganese complexes display excellent catalytic activities for various important organic transformations, such as hydrogenation, dehydrogenation, dehydrogenative coupling, transfer hydrogenation reactions, etc. In this short review, recent developments of such manganese-catalyzed reactions are presented.1 Introduction2 Well-Defined Manganese-Complex-Catalyzed Hydrogenation Reactions2.1 Hydrogenation of Nitriles2.2 Hydrogenation of Aldehydes and Ketones2.3 Hydrogenation of Esters2.4 Hydrogenation of Amides2.5 Hydrogenation of Carbon Dioxide3 Manganese-Catalyzed Dehydrogenation Reactions3.1 Selective Dehydrogenation of Methanol3.2 Dehydrogenative N-Formylation of Amines by Methanol3.3 Dehydrogenative Coupling Reactions of Alcohols3.4 Imine Synthesis via Dehydrogenative Coupling of Alcohols and Amines3.5 Synthesis of N-Heterocycles via Dehydrogenative Coupling4 Manganese-Catalyzed Dehydrogenation–Hydrogenation Cascades4.1 N-Alkylation of Amines with Primary Alcohols4.2 α-Alkylation of Ketones with Primary Alcohols4.3 Transfer Hydrogenation of Ketones5 Conclusion