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The mechanism of C-H bond activation of ethane was catalyzed by palladium halide cations (PdX+ (X = F, Cl, Br, H, and CH3)), which was investigated using density functional theory (DFT) at B3LYP level. The reaction mechanism was taken into account in triplet and singlet spin state potential energy surfaces. For PdF+, PdCl+, and PdBr+, the high spin states were the ground states, whereas the ground states were the low spin states in PdH+ and PdCH3+. The reaction of PdF+, PdCl+, and PdBr+ with ethane occurred via a typical "two-state reactivity" mechanism. In contrast, for PdH+ and PdCH3+, the overall reaction performed on the ground state PESs in a spin-conserving manner. The crossing points between two potential energy surfaces were observed and effectively decreased the activation barrier in PdX+/C2H6 (X = F, Cl, and Br). The minimum energy crossing points (MECP) were obtained used the algorithm in Harvey method. The natural valence electron configuration calculations were analyzed by natural bond orbital. The distribution and contribution of the front molecular orbital of the initial complexes could be further understand by the density of states. The feature of the bonding evolution in the main pathways was studied using topological analysis including localized orbital locator and atoms in molecules. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]