Small organic molecules provide a promising solution for the requirement to store large amounts of hydrogen in a future hydrogen-based energy system. Herein, we report that diolefin–ruthenium complexes containing the chemically and redox non-innocent ligand trop₂dad catalyse the production of H₂ from formaldehyde and water in the presence of a base. The process involves the catalytic conversion to carbonate salt using aqueous solutions and is the fastest reported for acceptorless formalin dehydrogenation to date. A mechanism supported by density functional theory calculations postulates protonation of a ruthenium hydride to form a low-valent active species, the reversible uptake of dihydrogen by the ligand and active participation of both the ligand and the metal in substrate activation and dihydrogen bond formation.

Tris(quinolin‐8‐yl)phosphite, P(Oquin)₃, promotes the dehydrogenation of H₃N·BH₃ (AB) and the transfer hydrogenation of azoarenes using ammonia borane (AB) as H₂ source. The metal‐free reduction of azoarenes proceeds under mild reaction conditions upon which several diphenylhydrazine derivatives are obtained in high yields. The reactivity of P(Oquin)₃ toward AB was evaluated through NMR in situ tests. The rate of the reaction, activation parameters, deuterium kinetic isotope effect (DKIE) and linear‐free energy relationship were investigated. Such mechanistic and kinetic studies suggest that P(Oquin)₃ is a precatalyst and that AB is likely involved in more than one stage of the reaction pathway. Furthermore, the kinetic data indicate that the reaction proceeds through an ordered transition state, possibly associative.