Crystal and molecular structures of dinitritobis(pyridine)zinc(II), bis(2-methylpyridine)dinitritozinc(II), and dinitritobis(quinoline)nickel(II)

Abstract

The crystal and molecular structures of the title complexes are reported. The overall geometry of the three complexes is similar, with the amine ligands in each case occupying cis co-ordination sites. However, the ways in which the nitrite groups are bound to the metal ions differ considerably, these chelating approximately symmetrically in the nickel compound, but with a marked asymmetry in the compound [Zn(pyridine)₂(NO₂)₂]. In [Zn(2-methylpyridine)₂(NO₂)₂] the nitrite groups are best thought of as unidentate nitrito-ligands with the second oxygen atom semico-ordinated to the metal :[graphic omitted]. The variation in the manner of nitrite co-ordination is probably influenced both by the electronic structure of the metal ions and the steric requirements of the amine ligands. The relationship between the i.r. frequencies and the co-ordination geometry of oxygen-bound nitrite groups is discussed, and it is shown that it is impossible to distinguish h between syn M–[graphic omitted] and anti M–[graphic omitted] nitrito-groups unambiguously using this technique.