Heterolytic cleavage of dihydrogen into a proton and a hydride ion is a fundamentally important step in many reactions, including the oxidation of hydrogen by hydrogenase enzymes and ionic hydrogenation of organic compounds. We report the facile, reversible heterolytic cleavage of H-2 in a manganese complex bearing a pendant amine, leading to the formation of a manganese hydride and a protonated amine that undergo H+/H- exchange at an estimated rate of >10(7) s(-1) at 25 degrees C.