Density-functional-theory (DFT) calculations are carried out for the proposal of a theoretically-plausible reaction pathway for nitrogen fixation catalyzed by dinitrogen-bridged dimolybdenum complexes bearing pincer-type PCP and PNP ligands. The free energy profiles of the entire reaction pathway calculated with a dispersion-corrected functional provide a catalytic mechanism energetically more efficient than the previously proposed one [Nat. Commun. 2014, 5, 3737]. In the newly-proposed mechanism the dinuclear Mo–N≡N–Mo structure should be maintained during the catalytic cycle. Despite the coordination of the triflate group with a strong electron-withdrawing ability, dinitrogen coordinated to a MoI center has higher reactivity with a proton donor than that coordinated to an electron-rich Mo0 center. The calculated results enable us to propose a shortcut pathway in which the regeneration of the dimolybdenum Mo0Mo0 complex is not required. Intermetallic electron transfer between the two Mo centers induced by protonation effectively enhances the reactivity of coordinate N2 with a proton donor. Our calculations reveal that the synergy of the Mo centers at the protonation step is essential for the catalytic performance of the dimolybdenum system.
All Science Journal Classification (ASJC) codes
- Inorganic Chemistry