monophosphinic, chromium carbene also have the methylene transfer channel. The most favored reaction channel is chromium carbene with a barrier height only kcal mol-1. The dimerization process occurs between nickel carbenoids and chromium carbene and between chromium. The most favored reaction channel barrier height is kcal mol-1. So, the cyclopropanation reactions and the dimerization reactions petitive. The solvent effect, which mimic dichloromethane, THF, and benzene, both have negligible consequence on the activation barriers. In Chapter 4, a theoretical investigation the cyclopropanation reactions catalyzed by nickel(0) and nickel(II) have been extensively investigated. putation results show that the active catalytic species formed by a CH2 fragment and the Cl2Ni(PH3)2 is carbenoids (PH3)2Ni(CH2Cl)Cl (IMA) and (PH3)Ni(CH2PH3)Cl2 (IMB), but both the carbenes (Cl2NiCH2 (IMC), (PH3)3NiCH2 (IME) and (PH3)2NiCH2 (IMG)) and carbenoids (ClNiCH2Cl (IMD), Ni(CH2PH3)(PH3)2 (IMF) and Ni(CH2PH3)PH3 (IMH)) are active catalytic species obtained from NiCl2, Ni(PH3)3, Ni(PH3)2 and a CH2 fragment. The cyclopropanation reaction proceeds through either concerted or multistep reaction pathway. puted results show that the two-coordinated nickel(II) catalyst is more active than the four-coordinated nickel(II) catalyst, but the two-coordinated nickel(0) catalyzed cyclopropanation reaction is similar with the four-coordinated nickel catalyst, because the four-coordinated nickel catalyst is formed two-coordinated nickel(0) catalyst in the cyclopropanation reaction by loss of a PH3 ligand. The nickel(0) catalyzed cyclopropanation reactions proceed easer than nickel(II). From the ic and thermodynamic viewpoints, the most favored reaction pathway is that nickel(0) catalyzed cyclopropanation reaction. Keywords: Density Functional Theorey (DFT), chromium carbene, nickel carbenoids; cyclopropanation, dimization reaction 目 录 中文摘要................................................
