Catalytic activity of asymmetric monobenzoylmonobenzotetraazacyclo[14]tetradecinatonickel(II) complexes: X-ray crystal structure of monobenzo-2,4,9,11-tetramethyl-1,5,8,12-tetraazacyclo[14]tetradecinatonickel(II)

Author： Kim Dong Il Hee Kim Eun Ghosh Roy Tapashi Gil Na Hun Ung Bae Zun Chul Park Yu

Publisher： Taylor & Francis Ltd

ISSN： 0095-8972

Source： Journal of Coordination Chemistry, Vol.58, Iss.3, 2005-02, pp. : 231-242

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Abstract

The complexes, 3-( p -Ymonobenzoyl)-Xmonobenzo-2,4,9,11-tetramethyl-1,5,8,12-tetraazacyclo [14]tetradecinato(2−)nickel(II), Y = CH 3 , H, Cl, NO 2 or OCH 3 , X = H ( A ) or NO 2 ( B ) have been synthesized and characterized. IR spectra of the complexes show intense bands in the region 1641-1647 cm −1 attributed to the stretching modes of C=O. Electronic absorption spectra for the A series exhibit &pgr; → &pgr; * and ligand to metal charge transfer (LMCT) transitions, while for the B series an additional band appears between 440 and 452 nm, which might be due to another charge transfer. 1 H NMR spectra show an anisotropic magnetic effect due to the benzoyl group. Voltammograms of the complexes show two one-electron irreversible oxidation peaks in the range +100 to +800 mV and two, three or four reduction peaks between −1200 and −2800 mV, depending on substituents. Hammett plots of first and second oxidation potentials for the A series had slopes of 37 and 54 mV (22 and 39 mV for the B series), respectively. In oxidations of p -Zstyrenes (Z = OCH 3 , CH 3 , H, F or Cl) catalyzed by the complexes, conversion yields of substrates are appreciably affected by substituents of substrates and complexes. The structure of the precursor complex 1 with X = H and without any attached benzoyl group (orthorhombic, P 2 1 2 1 2 1 , a = 7.923(6), b = 8.429(7), c = 24.18(2) Å, Z = 4, R 1 = 0.0224 and wR 2 = 0.0577) was characterized using single-crystal X-ray diffraction methods.