| Quantum chemistry is a branch of theoretical chemistry. Computational chemistry is more and more applied to experimental research field. Currently, quantum chemistry is deeply developed to be a much useful means to predict and explain molecular bonding, structures and reacton mechanisms. Especially, quantum chemistry has been proved to be a powerful tool in exploring organometallic systems. In treating with the organometallic compounds, density functional theory has been tested much effective.The products of the reactions of [RRh(CO)2Me]BF4 (R = Cp*, Ind*) with nbd are potential catalysts for the catalytic alternating copolymerization of CO and alkenes. The model reactions of [IndRh(CO)2Me]BF4 and [CpRh(CO)2Me]BF4 with nbd have been theoretically studied using density functional theory in this thesis. Our results of calculations reveal that both reactions are favored both kinetically and thermodynamically as a result of relief of ring strain and the chelation effect arisen from the cyclometallation. The methyl migration is the rate-determining step for both reactions. Consistent with the experimental observations, it was found that the reaction of [IndRh(CO)2Me]BF4 with nbd is more favored kinetically than that of [CpRh(CO)2Me]BF4 with nbd. Based on our calculations, it was found that the rotation of indenyl group around the Rh-indenyl axis plays an important role in lowering the reaction barrier.The regioselectivity on the reactions of Cp2Zr(CH2=CH-CH3) with CH2=CH-R (R = -CH3, -Ph ) have been investigated theoretically. The products are five-membered metallacycles containing two Cp rings. Calculated results show that as the methyl group is on p position of the five-membered ring, the resulting precursor, transition state and the product are always more stable than those with the methyl on a position. The electron-donating behavior of themethyl may be responsible for the phenomenon. In contrast, as the phenyl group is on p position of the five-membered ring, the resulting precursor, transition state and the product are always less stabe than those with the phenyl on a position. The electron-accepting behavior of the phenyl may be responsible for the phenomenon. Our results of calculation are well consistent with the experimental observations.In theoretically investigating the regioselectivity on reaction of Cp2Zr(^2(C, N)-{6-methylpyridyl})+ with HCC-R (R = -CH3, -SiMe3), we find whether -CH3, or -SiMe3 is always on the side of Cp ring the products, which is consistent with the experimental results. Our calculated results reveal that both the reactions are much more favored thermodynamical and kinetically. |
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