Properties And Mechanisms Of Palladium-activated C-H Bond Of Methane

Activation of C-H bond has significant value to organic synthesis. It is meaningful realistically and theoretically to study the C-H bond activation mechanisms, the electron structure changes, the dissociation mechanisms, and the subsequent bonding character. This thesis mainly focused on the study of Pd/CH₄ activation reaction and the electron structure change characters of Pd-activated C-H bond of CH₄ were studied thoroughly with potential energy surface study method combining with wave function analyses. The potential energy surface of Pd/CH₄ activation reaction was calculated on the CCSD?T?/CBS//M06L/AVTZ?-pp?level with Gaussian-09?software?. The wave function analyses was based on M06L/VDZ?-pp?or B3LYP/VDZ?-pp? level using Multiwfn3.2.1 as the main software.The main results are summarized as follows:The activation of Pd atom during the reaction was step by step. The results indicated that the product contains 73% of 4d⁹5s¹ and 27% of 4d¹⁰5s⁰. Since d10 state Pd has no bonding ability, its existence will lead the repulsion between Pd and the ligands?H or CH₃?, which brings the instability of the products. Although d9 state Pd has strong bonding ability and its existence will strengthen the attraction between Pd and ligands, which will add the stability of the products, the Pd/CH₄ activation reaction does not happen, in fact. This mainly because the products contain too much d10 state component, as we proposed. The results also show that the C-atom cannot be activated.The more electron-deficiency of the ligands, the more extent of the Pd atom will be activated, the more 4d⁹5s¹ state will be given by the atom, and the bigger the reaction energy will be. Thus, these bonds, such as F-F bond and Cl-Cl bond, are easily to be inserted into.while those bonds, such as C-H bond, are hard to be inserted into.The Pd-C bond and Pd-H bond are polar covalent bonds with delocalization effects playing an important role.The innovation points of this thesis is: The study of the effect of the electron-deficiency extent to the activation extent of Pd.