Density functional theory study on the reaction mechanism of Ni+-catalysed cyclohexane dehydrogenation

A detailed theoretical analysis of the mechanism of chemical bond activation in cyclohexane catalysed by the atomic transition-metal cation Ni + was performed by density functional theory/Hartree–Fock method (B3LYP). A potential energy surface (PES) analysis demonstrated the existence of no PES crossover and that the entire reaction proceeded in doublet PESs. The singlet dehydrogenation of cyclohexane can be induced by monometallic cation Ni + , the second molecule H 2 on the same and the first molecule D 2 on the different sides only with low yield. In order to reveal the nature of the reaction, the mechanisms of activation of the cyclohexane C–H and C–C bonds were systematically investigated. Regardless of whether C–H or C–C bonds are activated, the process was predicted to proceed via an insertion–elimination mechanism. The average local ionisation energy indicated the H atom in cyclohexane to be the most vulnerable to electrophilic attack. The molecular orbital interaction analysis of the initial Ni + –C 6 H 12 complex was obtained by a charge decomposition analysis. The Curtin–Hammett principle accurately demonstrated the product ratio of H 2 to be dominant in the two competitive reaction channels. Most importantly, the meaningful molecular structures involved in this subject have been explored in detail.