Exploring the activities of vanadium, niobium, and tantalum PNP pincer complexes in the hydrogenation of phenyl-substituted C equivalent to N, C=N, C equivalent to C, C=C, and C=O functional groups

摘要

The structures and stability of the designed PNP pincer amido M(NO)(2)(PNP) and amino M-H(NO)(2)((PNP)-P-H) complexes [M = V, Nb, and Ta, PNP = N(CH2CH2P(isopropyl)(2))(2), (PNP)-P-H = N-H(CH2CH2P(isopropyl)(2))(2)] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H-2 environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal-ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-C equivalent to N, Ph-CH=NH, Ph-CH=NH-Ph, Ph-CH=N-CH2Ph, Ph-C equivalent to CH, Ph-CH=CH2, Ph-CHO, and Ph-CO-CH3, the reaction prefers either a two-step or one-step mechanism for the hydridic M-H and protonic N-H transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.