Isomerism and unusual magnetic behaviour of some benzimidazole complexes of nickel(II)
- 1 January 1967
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 1125-1132
- https://doi.org/10.1039/j19670001125
Abstract
The preparation is described of the compounds NiL4X2, where L = benzimidazole, X = Cl, Br, I, or ClO4. The iodide and perchlorate are diamagnetic; the bromide exists in three isomeric forms, two paramagnetic and one diamagnetic, and the chloride as two paramagnetic isomers. The acetone (= S) solvates NiL4Cl2,S, NiL4Cl2,S2(three isomers), and NiL4Br2,S2 have also been isolated. The electronic spectra of these compounds have been obtained at room temperature and at ca. 80°K, and their magnetic properties have been studied over a temperature range. The diamagnetic complexes contain planar NiL4 units, whereas the paramagnetic compounds are hexacoordinate, but with pronounced distortions from an octahedral configuration. Several of the compounds display unusual magnetic behaviour. The blue form of NiL4Cl2,S2 is magnetically normal, but the green form is antiferromagnetic, with a temperature-dependent exchange integral. The nickel ion in the third complex of this stoicheiometry appears to have a spin-singlet ground state with a thermally accessible spin-triplet level. One form of the compound NiL4Br2 has a temperature-independent susceptibility of ca. 2770 × 10–6 c.g.s.u./mole over the range 300–80°K.Keywords
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