Syntheses and solution equilibria of nickel(II) chelates. II. Dinuclear mixed ligand species

Abstract

A new class of mixed ligand complexes of nickel(II) are reported. They have the stoichiometry LKNi where L is a potentially tridentate Schiff base anion and K is the corresponding bidentate carbonyl species. The complexes show clearly defined C-O and C-N stretches in the infrared. Where solubility permitted the determination of molecular weights, the compounds were found to be dimeric in freezing benzene and/or bromoform. The complexes are uniformly high-spin and have magnetic moments in the range 3.0–3.2 BM. On the basis of electronic spectral data it is concluded that the compounds have, in general, pseudooctahedral environment around each nickel(II) in the solid state. In one case the environment is believed to be square pyramidal. Structures which accommodate these geometrical requirements are suggested within the dimeric framework. Solution spectra are solvent and temperature dependent. The results are interpreted in terms of equilibria involving the two geometries. The possible occurrence of monomeric species at low concentration is examined.