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 Introduction 2 Well-Defined Manganese-Complex-Catalyzed Hydrogenation Reactions 2.1 Hydrogenation of Nitriles 2.2 Hydrogenation of Aldehydes and Ketones 2.3 Hydrogenation of Esters 2.4 Hydrogenation of Amides 2.5 Hydrogenation of Carbon Dioxide 3 Manganese-Catalyzed Dehydrogenation Reactions 3.1 Selective Dehydrogenation of Methanol 3.2 Dehydrogenative N-Formylation of Amines by Methanol 3.3 Dehydrogenative Coupling Reactions of Alcohols 3.4 Imine Synthesis via Dehydrogenative Coupling of Alcohols and Amines 3.5 Synthesis of N-Heterocycles via Dehydrogenative Coupling 4 Manganese-Catalyzed Dehydrogenation–Hydrogenation Cascades 4.1 N-Alkylation of Amines with Primary Alcohols 4.2 α-Alkylation of Ketones with Primary Alcohols 4.3 Transfer Hydrogenation of Ketones 5 Conclusion