11 research outputs found

    Metal–Ligand Synergistic Effects in the Complex Ni(η 2

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    In the current investigation, reactions of the bow-tie Ni(η2-TEMPO)2 complex with an assortment of donor ligands have been characterized experimentally and computationally. While the Ni(η2-TEMPO)2 complex has trans-disposed TEMPO ligands, proton transfer from the C-H bond of alkyne substrates (phenylacetylene, acetylene, trimethylsilyl acetylene, and 1,4-diethynylbenzene) produce cis-disposed ligands of the form Ni(η2-TEMPO) (κ1-TEMPOH)(κ1-R). In the case of 1,4-diethynylbenzene, a two-stage reaction occurs. The initial product Ni(η2-TEMPO)(κ1-TEMPOH)[κ1- CC(C6H4)CCH] is formed first but can react further with another equivalent of Ni(η2-TEMPO)2 to form the bridged complex Ni(η2-TEMPO)(κ1-TEMPOH) [κ1-κ1-CC(C6H4)CC] Ni(η2-TEMPO)(κ1-TEMPOH). The corresponding reaction with acetylene, which could conceivably also yield a bridging complex, does not occur. Via density functional theory (DFT), addition mechanisms are proposed in order to rationalize thermodynamic and kinetic selectivity. Computations have also been used to probe the relative thermodynamic stabilities of the cis and trans addition products and are in accord with experimental results. Based upon the computational results and the geometry of the experimentally observed product, a trans-cis isomerization must occur. © 2013 American Chemical Society

    Scavenging of Organic C-Centered Radicals by Nitroxides

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    International audienceWOS:00033607820001

    Scavenging of Organic C-Centered Radicals by Nitroxides

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    Chemical Routes for the Transformation of Biomass into Chemicals

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