Several Ruthenium, Rhodium, Zirconium Metal Organic Reaction Mechanism Theory

Density functional theory (DFT) calculations at the B3LYP level are carried out to study and analyze the following three projects. Our major intention is to investigate the molecular structures, bonding, and mechanisms on the reactions of the organometallic complexes mentioned below.1. The model reaction mechanism on CpRu(PH₃)₂ SSiⁱPr₃ with SNCH, derived from CpRu(PPh₃)₂SSiⁱPr₃ with SCNR (R = Ph, 1-naphthyl), was investigated by using density functional theory (DFT). The structures and bonding involved in the reaction mechanism were analyzed. The phosphine ligand is first dissociated from the reactant to afford an intermediate in the reaction. The sulphur atom in the intermediate formed in the reaction has sp hybridization, and the remaining p orbital is symmetrical to the d orbital of the metal center. Thus, the lone pair on the p orbital can overlap the d orbital to form aπbond, which leads to the coplanarity of the center of Cp ring, Ru, P, S1 and Si atoms. Our results of calculations predict that formation of a four-membered ring containing metal center is the rate-determining step. Decrease of steric hindrance, formation ofπconjugation and occurrence of chelation are responsible for the favorable thermodynamics of the reaction.2. Rh complexes having weakly coordinated ligands, RhCl(L)_n(PR₃)₂ (L=weak ligand, such as CH₂=CH₂), have aroused great interest since they can be well used for the olefin hydrogenation and C-H bond activations. These complexes have been investigated experimentally in recent years. Jun-Chul Choi and his co-workers obtained an unusual bis(ethylene) rhodium(I) complex RhCl(CH₂=CH₂)₂(PMe₃)₂ from the reaction of RhClCH₂=CH₂(PMe₃)₂ with ethylene. Our major concern aims to investigate the reaction mechanisms theoretically. Our calculated results show that the different orientations of the ethylene as coordinating to the metal can lead to two pathways (I and II). The reaction activation free energy is calculated to be 18.93 and 30.96 kcal/mol, respectively. Under the consideration of dynamics, path I should be more favorable than path II. The energy change of the reaction is 1.36 kcal/mol, which reveals that the reactant and the product are in equilibrium with each other. That's in agreement with the experimental results.3. Under the reaction of Cp₂Zr(CH₃)₂ with ON—Ph, Sarah A. Cummings and his collaborators obtained the O-outside product, but nor the O-inside product. The O-outside product has an enantiomer O-inside which is chemically equivalent to the O-outside. According to the experimental observations, we investigated the mechanism of the reaction theoretically. Our calculated results show that ON-Ph has two orientations to coordinate with the reactant and the two kinds of coordination have the same probability, so the two enantiomers are equivalent. The energy of the O-outside product is lower than that of the O-inside by 1.82 kcal/mol, so the O-outside product is more preferred. In addition, the reversible cleavage process of the [M]-N linkage was found.