The mechanisms of aqueous methanol dehydrogenation reaction [CH₃OH + H₂O = 3H₂ + CO₂] catalyzed by conjugated PNP pincer amido M(CO)₂(PNP) and amino ^HM(CO)₂(PN^HP) complexes [M = Mn, Re; and PNP = N(CH₂CH₂P(isopropyl)₂)₂] under base-free and strong base conditions as well as the K⁺ promotion effect were studied at the B3PW91 level of density functional theory. Benchmark calculations including dispersion and/or solvation corrections validated the computed gas phase data to be closest to the available kinetic and thermodynamic data from experiments. Under base-free conditions, the innocent mechanism is kinetically more favorable than the non-innocent mechanism. Under strong base conditions, KOH plays a dual role: deprotonating the substrate by OH⁻ and stabilizing the rate-determining transition state by K⁺ by lowering the free energy barrier for H₂ formation by N⋯K⁺⋯O interaction. Considering the special role of formic acid in H₂ storage and CO₂ hydrogenation, formic acid dehydrogenation should be accessible under base-free and strong base conditions.

Hexahydropyrazinoindoles are prepared in a single step from N -sulfonyl triazoles and imidazolidines. Of mechanistic importance, a regiodivergent reactivity can be engineered towards the exclusive formation of 8-membered ring 1,3,6-triazocines.

The presence of single-electron transfer (SET) steps in water oxidation processes catalyzed by first-row transition metal complexes has been recently recognized, but the computational characterization of this type of process is not trivial. We report a systematic theoretical study based on density functional theory (DFT) calculations on the reactivity of a specific copper complex active in water oxidation that reacts through two consecutive single-electron transfers. Both inner-sphere (through transition state location) and outer-sphere (through Marcus theory) mechanisms are analyzed. The first electron transfer is found to operate through outer-sphere, and the second one through inner-sphere. The current work proposes a scheme for the systematic study of single-electron transfer in water oxidation catalysis and beyond.