Gopal Mishra - CuII complexes bearing the 2,2,2-tris(1-pyrazolyl)ethanol or 2,2,2-tris(1-pyrazolyl)ethyl methanesulfonate scorpionates. X-Ray structural characterization and application in the mild catalytic peroxidative oxidation of cyclohexane

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      ORTEP diagram of CH3SO2OCH2C(pz)32 (a), [CuCl2{HOCH2C(pz)3}] 3 (b) and [CuCl2{CH3SO2OCH2C(pz)3}]24 (c). Displacement ellipsoids are drawn at the 50% probability level. Symmetry operations to generate equivalent atoms: (i) 1 −x, −y, 2 −z.

      Abstract:

        Reactions between CuCl2    and the functionalized scorpionate 2,2,2-tris(1-pyrazolyl)ethanol   HOCH2C(pz)31     (pz   = pyrazolyl)   or 2,2,2-tris(1-pyrazolyl)ethyl methanesulfonate   CH3SO2OCH2C(pz)32     yield the corresponding water   soluble CuII   complexes [CuCl2{HOCH2C(pz)3}]  3   or [CuCl2{CH3SO2OCH2C(pz)3}]24.   In 3   the scorpionate ligand shows the typical   N,N,N-coordination   mode, whereas in the dinuclear complex 4   it binds the metal as a bidentate species. Compounds 1-4     have been characterized by IR,  far-IR,  elemental analysisand   (for 2-4)  single crystal X-ray diffraction.   The new scorpionate complexes 3   and 4   are shown to act as catalyst   precursors for the peroxidative oxidation   of cyclohexane   to cyclohexanol   (main product) and cyclohexanone,   under mild conditions (at room temperature and using an aqueous   solution of H2O2)   reaching TON values up to 186 in NCMe/H2O.   Their hydrosolubility allows them to operate also in pure aqueous   media (without any organic solvent,   although less effectively), a rare feature of significance   towards a green alkane oxidation   process.

      Address (URL): http://pubs.rsc.org/en/content/articlepdf/2009/dt/b911990f