title: Activation of Carbon-Hydrogen and Hydrogen-Hydrogen Bonds by Copper-Nitrenes: A Comparison of Density Functional Theory with Single- and Multireference Correlation Consistent Composite Approaches.
abstract: The kinetics and thermodynamics of copper-mediated nitrene insertion into C-H and H-H bonds (the former of methane) have been studied using several levels of theory: B3LYP/6-311++G(d,p), B97-1/cc-pVTZ, PBE1KCIS/cc-pVTZ, and ccCA (correlation consistent Composite Approach). The results show no significant difference among the DFT methods. All three DFT methods predict the ground state of the copper-nitrene model complex, L'Cu(NH), to be a triplet, while single reference ccCA predicts the singlet to be the ground state. The contributions to the total ccCA energy indicate that the singlet state is favored at the MP2/CBS level of theory, while electron correlation beyond this level (CCSD(T)) favors a triplet state, resulting in a close energetic balance between the two states. A multireference ccCA method is applied to the nitrene active species and supports the assignment of a singlet ground state. In general, the largest difference in the model reaction cycles between DFT and ccCA methods is for processes involving radicals and bond dissociation.
authors.affiliation: Department of Chemistry, Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Box 305070, Denton, Texas 76203-5070.
authors.forename: Sammer M
authors.initials: SM
authors.lastname: Tekarli
authors.affiliation: Department of Chemistry, Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Box 305070, Denton, Texas 76203-5070.
authors.forename: T Gavin
authors.initials: TG
authors.lastname: Williams
authors.affiliation: Department of Chemistry, Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Box 305070, Denton, Texas 76203-5070.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Cundari