Theoretical Study Of C-X Bond(C=O,C-O And C-H)and N-H Bond By Transition Metal Complexes

This thesis focuses on the theoretical study of catalytic activation of C-X bond(C=O,C-O and C-H)and N-H bond by transition metal complexes.It mainly includes the theoretical study on the deoxyborohydride of carboxylic acid catalyzed by ruthenium complex and the theoretical study on C-O bond activation catalyzed by palladium complex.1.Theoretical study on the deoxyborohydride of carboxylic acid catalyzed by ruthenium complex:Using density functional theory method to study the reaction mechanism of the deoxyborohydride of carboxylic acid catalyzed by ruthenium complex,analyze the end-on coordination and the side-on coordination between carbonyl complex with transition metal center,and the effects of the coordination of different molecules HBpin with the transition metal center on the reactivity were considered.The calculation results show that the catalytic cycle is divided into four stages,which consist of two hydrogen transfers and two Bpin group migration alternations.The key intermediates[(?6-p-cymene)Ru-(HBpin)(Bpin)(OR)],(R=CHPh(OBpin),CH2Ph)involved in the process of the whole reaction,namely the intermediate of the second molecule HBpin coordination with Ru center has a lower energy barrier in the process of elimination of products and by-products,and the reasons for the decrease in energy barrier are analyzed from the perspectives of bond length,bond level and NBO charge.2.Theoretical study on C-O bond activation catalyzed by palladium complex:The reaction mechanism of C-O bond activation catalyzed by palladium complex was studied by using density functional theory(DFT)method.The results show that the reaction involves five steps:activation of N-H and C-H bonds,coupling of C-N bonds,and reduction of C-H and N-H bonds.In the C-N coupling step,the nucleophile is coordinated with the alkyl palladium intermediate to release the by-product PhOH,and then the C-N bond coupling is favorable pathway.In addition,by change the AQ group of the substrate to phenyl,it was found that after losing the AQ group,the catalyst first activated its own N-H bond,and then activated the N-H bond of the second substrate molecular,which was opposite to the activation of its own C-H bond in the presence of the AQ group,so that the target product could not be obtained after the loss of the AQ group,which was consistent with the result that the product could not be observed after modulation in the experiment.The presence of the AQ group can reduce the energy barrier for activating its own C-H bond and avoid N-H bond activation of the second substrate molecular.