Issue 0, 1968

Transition metal–Schiff's base complexes. Part III. The magnetic properties of some oxygen-carrying cobalt(II) complexes

Abstract

Magnetic studies have been carried out down to liquid-nitrogen temperatures on NN′-ethylenebis(salicylideneiminato)cobalt(II) and many of its ring-substituted derivatives. No relationship between the detailed magnetic properties and oxygen-carrying ability of this type of compound has emerged. A variety of magnetic behavior is exhibited by this type of compound. The majority (the unsubstituted, 5-Me-, 5-Br-, 5-MeO-, 4-Cl-, 3-MeO-, and 3-EtO-substituted compounds) are low-spin, with magnetic moments which are in the range 2·1–2·9 B.M. and almost invariant with temperature, as expected for planar cobalt(II) compounds. In addition to anhydrous, magnetically normal forms, the 3-MeO- and 3-EtO-substituted compounds form monohydrates in which, as judged from the accompanying changes in magnetic, spectral, and oxygen-carrying properties, the water molecule is co-ordinated to give a tetragonal pyramidal structure. The 3-MeO hydrate is an example of the rare high-spin pentaco-ordinate type of cobalt(II) compound. The magnetic behaviour of the 3-EtO hydrate can be explained in terms of a high-spin–low-spin equilibrium. The sharp changes in slope found by earlier workers at about 200°K in the curves of reciprocal susceptibility against temperature of the monopyridine complex and the inactive form of the parent complex have not been confirmed. These, and the 5-nitro- and 3,5-dinitro-substituted complexes, have low-spin magnetic moments which decrease with temperature to values expected for octahedral, low-spin cobalt(II) complexes. This is considered to be due to the effect of axial ligands, i.e., pyridine, or oxygen atoms of adjacent molecules.

Article information

Article type
Paper

J. Chem. Soc. A, 1968, 241-246

Transition metal–Schiff's base complexes. Part III. The magnetic properties of some oxygen-carrying cobalt(II) complexes

A. Earnshaw, P. C. Hewlett, E. A. King and L. F. Larkworthy, J. Chem. Soc. A, 1968, 241 DOI: 10.1039/J19680000241

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