DFT Study For Chelated Ru-catalyzed Ring-opening Cross Metathesis

Extensive efforts have been exerted to achieve olefin metathesis（OM） as it is a powerful tool for constructing carbon–carbon double bonds in organic synthesis and materials chemistry. After people accept the explanation of Chavin, the research of this type is mainly concentrated on the selection, synthesis and development of the catalyst in the reaction. Several Mo-, W-complexes have been used as OM catalysts for the demand of the industrial, and found that the effect of Ru-catalyst is significantly better than the other catalyst. However, significant challenges remain, particularly in terms of catalyst design. In previous studies, most catalysts used in the OM processes prefer the thermodynamically favored（E）-olefin rather than the（Z）-olefin. So extensive efforts have been exerted to design a catalyst with transition metal complexes and achieve highly Z-selective. In recent years, cross-metathesis reactions that favor the（Z）-olefin have been achieved by chealted Ru catalysts which contain a nitrate ligand, and these new catalysts have dramatically extended the scope of（Z）-olefin production through OM, however, the physical origin of this reaction was unclear. In this study, we performed thorough DFT calculations to elucidate the mechanism and efficient Z-selectivity of a chelated Ru catalyst, and analyzed the causes of various phenomena in the process.All reactants, transition states（TSs）, intermediates（Ints）, and reaction products for the reaction were optimized and calculated using B3 LYP with a mixed basis set of LANL2 DZ for Ru and 6-31G（d） for other atoms. All calculations were performed using by Gaussian 09 and based on density functional theory. In order to combine with the actuality, norbornadiene and propylene were taken as the reactants to discuss the mechanism about the reaction which catalyzed by NO₃^-,NO₂^- complexe. The main research contents are as follows:Chapter one described the existing olefin metathesis reaction and its mechanism.The basic theory of calculation（mainly including some basic concepts, density functional theory, the transition state theory, the intrinsic reaction coordinate theory, activation strain model, energetic span model） and some software for calculation（Gaussian, Gaussview and AUTOF） were involved in the second chapter.In chapter three, the reaction catalysed by the nitrato complex has been investigated at the density functional level of the theory using the hybrid exchange correlation functional B3 LYP. All the structures of the reaction were optimized and frequency analysis for the path were described, which was condusive to observe the reaction from microscopics. The reaction began with the reactant combining with the catalyst from the side-bound and forming the Z-olefin.The charge effect was responsible for the side-bound attack and the decisive factor of Z-selectivity could be analysed by activation strain model.The calculation in the chapter four was about the reaction catalysed by the nitrite complex, which was similar with the chapter three. The details about the side-bound and all the process for the final product were introduced in this part. In the fifth chapter, according to the thermodynamic and kinetic datas obtained from the previous research, AUTOF software was used to calculate the TOF of the optimal mechanism for the different catalyst reaction to verify the side-bound mechanism and Z-selectivity. Then, the TOF value for a serious of catalysts were compared as well as the performance of the catalyst were evaluated through steric hindrance effect and electric charge effect analysis.