NH3 Synthesis in the N-2/H-2 Reaction System using Cooperative Molecular Tungsten/Rhodium Catalysis in Ionic Hydrogenation: ADFT Study

摘要

The ionic hydrogenation of N-2 with H-2 to give NH3 is investigated by means of density functional theory (DFT) computations using a cooperatively acting catalyst system. In this system, N-2 binds to a neutral tungsten pincer complex of the type (PNP)W(N-2)(3) (PNP=pincer ligand) and is reduced to NH3. The protons and hydride centers necessary for the reduction are delivered by heterolytic cleavage of H-2 between the N-2-tungsten complex and the cationic rhodium complex Cp*Rh{2-(2-pyridyl)phenyl}(CH3CN)(+). Successive transfer of protons and hydrides to the bound N-2, as well as all NxHy units that occur during the reaction, enable the computation of closed catalytic cycles in the gas and in the solvent phase. By optimizing the pincer ligands of the tungsten complex, energy spans as low as 39.3kcalmol(-1) could be obtained, which is unprecedented in molecular catalysis for the N-2/H-2 reaction system.