Synthesis and spectroscopic properties for six 7,16-dibenzoylated tetraaza[14]annulene nickel(II) complexes

The condensation reaction between tetraaza14]annulene nickel(II) complex and a series of para-substituted benzoyl chlorides gave the corresponding 7,16-dibenzoylated products in 53–98% yields. The mass spectra exhibit molecular ion peaks ascribed to the 7,16-dibenzoylated products. The intense ir band due to the C?O stretching mode in these nickel(II) complexes is present in the 1650–1658 cm^?1 range upon the benzoylation. Even though the ligand moiety of these six complexes is changed by benzoylation, the electronic spectra hardly vary. These nickel(II) complexes assume roughly the square-planar coordinations as judged by the ligand-field transition bands. The olefinic proton peaks at the 7- and 16-positions vanish on benzoylation in the proton nmr spectra and the proton signals of the para-substituted benzoyl groups are observed in the 2.4–8.4 ppm region. The results of the carbon-13 nmr spectra are compatible with those for the proton nmr spectra.