Search

The dehydrogenation reaction mechanism of cyclohexane catalyzed by dimer transition metal cluster V2+ has been investigated at the B3LYP/6-31G (d, p) level of density functional theory. Density of states (DOS) graph is used to understand more deeply the roles of the front molecular orbital of the initial complexes. After the first molecular dehydrogenation, the reaction mainly consists of two competition mechanisms. First, the C-H bonds of cyclohexane can be effectively activated by the V2+ cation, yielding the same-face dehydrogenation products. Second, the C-C bonds are activated, forming the different-face dehydrogenation products. Our calculations indicate that the reaction takes place more easily along the low-spin potential energy surface on the same-face and is a low-barrier or even barrier-free transformation. Carbon-carbon single bonds are nonpolar and generally far less reactive. A comparison of the reaction mechanism of V2+ and congener Ti2+ with cyclohexane has been presented. The bond dissociation energies (BDEs) of V2+ are greater than that of Ti2+, leading to difficulties in forming sandwich complexes in the different-face dehydrogenation of cyclohexane, and the same-face dehydrogenation is an important reaction channel. [ABSTRACT FROM AUTHOR]

Abstract: Calculations based on density functional theory (DFT) have been carried out to investigate the multi-centered transition state (MCTS) reaction mechanisms associated with the gas-phase ion/molecule reaction of YNH+ with ethene. The potential energy surfaces (PESs), including both reaction pathways of hydrogen and ammonia elimination, have been explored and characterized. By contrast with ammonia elimination, dehydrogenation reaction channel is energetically favorable, which is in good agreement with the experimental observation. Moreover, the dominating product (YC2H3N+) can further react with ethene and the corresponding reaction mechanism which proceeds in a two-step manner and leads to the six-membered metallacyclic structure YC4H5N+, has also been investigated. [Copyright &y& Elsevier]