A theoretical mechanistic study for C-H and C-C bond activations of cyclohexane catalyzed by NiAl+ in the gas phase

摘要

The first thorough theoretical mechanism analysis of heteronuclear bimetallic cation NiAl+ with cyclohexane has been investigated on singlet and triplet potential energy surfaces (PESs) by using density functional theory. Our calculated results show that NiAl+ can assist in the decomposition of cyclohexane to form benzene through two types of reaction channel: C-H bond activation and H-2 formation; C-C bond activation and HD formation. The most important conclusion is that NiAl+ exhibits high efficiency and also high regioselectivity for C-H bond oxidation. However, the high zero-point vibrational energy (ZPVE) value for the cleavage of inert C-C bond is also the origin of its failure to form HD. In the process of the first C-H and C-C bond activations, crossing points (CPs) have been appeared between the two adiabatic surfaces, respectively. The minimum energy crossing points (MECPs) are gotten using the algorithmin Harvey method. Density of states (DOS) is used to obtain a deeper understanding for the roles of the front molecular orbital of the initial complexes. The bonding properties of the special intermediates involved in the process of C-C bond activations are discussed by the IR spectrum methods. (C) 2018 Elsevier B.V. All rights reserved.