Doris Melgarejo -  Halide and Nitrite Recognizing Hexanuclear Metallacycle Copper(II) Pyrazolates.

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  Inorganic Chemistry (Washington, DC, United States)    (2011),  50(3),  1014-1020. Mohamed, Ahmed A.; Ricci,   Simone; Burini, Alfredo; Galassi, Rossana; Santini, Carlo;   Chiarella, Gina M.; Melgarejo, Doris Y.; Fackler, John P., Jr.


  Halide-centered hexanuclear, anionic copper(II) pyrazolate   complexes [trans-Cu6((3,5-CF3)2pz)6(OH)6X]- (X = Cl, Br, I;   (3,5-CF3)2pz = 3,5-bis(trifluoromethyl)pyrazole) were isolated in   a good yield from the redox reaction of the trinuclear copper(I)   pyrazolate complex [.mu.-Cu3((3,5-CF3)2pz)3] with a halide source   such as PPh3AuCl or [Bu4N]X, X = Cl, Br, or I, in air.    X-ray structures of the anion-centered hexanuclear complexes show   that the six copper atoms are bridged by   bis(3,5-trifluoromethyl)pyrazolate and hydroxyl ligands above and   below the six copper atom plane.  The anions are located at   the center of the cavity and weakly bound to the six copper atoms   in a .mu.6-arrangement, Cu-X .simeq.3.1 .ANG..  A   nitrite-centered hexanuclear copper(II) pyrazolate complex   [trans-Cu6((3,5-CF3)2pz)6(OH)6(NO2)]- was obtained when a soln.   of [PPN]NO2 (PPN = bis(triphenylphosphoranylidene)ammonium) in   CH3CN was added dropwise to the trinuclear copper(I) pyrazolate   complex [.mu.-Cu3((3,5-CF3)2pz)3] dissolved in CH3CN, in   air.  Blue crystals were produced by slow evapn. of the   acetonitrile solvent.  The x-ray structure of   [PPN][trans-Cu6((3,5-CF3)2pz)6(OH)6(NO2)] complex shows the   nitrite anion sits in the hexanuclear cavity and is perpendicular   to the copper plane with a O-N-O angle of 118.3(7).  The 19F   and 1H NMR of the pyrazolate ring atoms are sensitive to the   anion present in the ring.  Anion exchange of the NO2- by   Cl- can be obsd. easily by 1H NMR.

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