Conceptual Approach to the Reactivity of Dihydrogen

Dihydrogen reactions are mainly reaction-center-mediated. In a systematic approach, these reactions are divided into the steps of splitting of H-2 and H-atom transfers with homolytic and heterolytic splitting at mono- and dinuclear reaction centers, and further homopolar H transfers in Wilkinson-type hydrogenations (insertion and reductive elimination) and heteropolar transfers in ionic hydrogenations (hydride before proton, proton before hydride, simultaneous hydride/proton transfers). Based on these categories, transfer hydrogenations are also surveyed. A separate class of reactions is one-electron reactions of dihydrogen.