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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: The spin-forbidden reaction mechanism of Ir+ with CH3F to yield H2 or HF has been investigated using density functional theory (DFT) calculations. The overall H2 elimination reaction is calculated to be exothermic, by 36.3 kcal/mol. One pathway is found on three potential energy surfaces (PESs), whereas the HF-elimination reaction is exothermic by 32.8 kcal/mol, two reaction pathways are identified on the quintet and triplet surfaces, only one reaction pathway is identified on the singlet surface. The reaction mechanism can be explained by the simple donor–acceptor model. According to the revealed mechanism and the calculated potential energy surfaces, H2-elimination is energetically much more favorable than HF-elimination. These conclusions are consistent with the experimental observations. [Copyright &y& Elsevier]