The development and application of homogeneous nickel catalysts for transfer hydrogenation and related reactions

[Display omitted] •Comprehensive review of nickel as versatile catalyst in homogeneous (de)hydrogenation.•Focus on advances in (de)hydrogenation catalysis based on ligand and catalyst design principles.•Mechanistic aspects of nickel-catalysed (de)hydrogenation is emphasised. Nickel has emerged as a versatile catalyst, individually and as part of bimetallic complexes, to hydrogenate and dehydrogenate various unsaturated and saturated compounds, respectively. In this review, the development of various homogeneous Ni catalysts for application in the hydrogenation of compound containing C-C-, C-N-, C-O- and N-O multiple bonds and dehydrogenation of alcohols, amines, ammonia borane and formic acid is discussed. Active Ni intermediates that were identified in mechanistic studies governing the activity of the complex or outcome of the reaction will be illustrated, aiding in the development of novel complexes with excellent activity and selectivity.