The influence of cations on the properties of the hexanitrometallate anions in the K2MIIMII(NO2)6 type of complex of the nickel(II) and copper(II) ions

Abstract

The unit-cell dimensions, infrared spectra, magnetic susceptibilities, and electronic and e.s.r. spectra of four complexes of the type K₂M^IINi(NO₂)₆, where M^II= Ca, Sr, Pb, and Ba, are reported. The unit-cell dimensions and infrared spectra reflect the size effect of the cations present, but the electronic properties of the anions are significantly different in the lead complex from those of the calcium, strontium, and barium complexes. It is suggested that the greater polarising and reducing power of the lead(II) ion is responsible for its greater interaction with the oxygen atoms of the hexanitronickelate(II) anions. It is further suggested that it is this type of interaction which is responsible for the presence of a dynamic Jahn–Teller effect in the complex K₂PbCu(NO₂)₆.