ChemInform Abstract: Bronsted-Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Bronsted–Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant KaLAC of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKaLAC and pKaTHF, pKaDCM, pKaMeCN for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKaLAC −18) to least acidic (pKaLAC 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid–base features are analyzed for c...