Structural and Spectroscopic Studies of Transition Metal Nitrite Complexes. IV Crystal Structure and Spectra of cis-Aquabis[N, N-dimethyl(ethane-1, 2-diamine)]-nitronickel(II) Perchlorate

The crystal and molecular structure of the complex cis-aquabis[N, N-dimethyl(ethane-l, 2-diamine)]-nitronickel(II) perchlorate is reported and the stereochemistry is compared with those observed for other nickel nitrite complexes formed by substituted amines. The electronic spectrum of the complex in the VIsible region is unusual, showing bands with maxima at 17750 and 21000 cm^-1. The latter peak consists of a poorly resolved VIbrational progression having an interval of c. 600 cm^-1. While the lower energy band is assigned to the second spin-allowed ‘d-d’ transition of an octahedral nickel(11) complex, it is suggested that the band at 21000 cm^-1 is due either to a metal→tligand charge-transfer transition, or to an internal n(O) → π* nitrite transition.