The bis-ligand cobalt(II)
complexes of 6-methylpyrid-2-yi-N-(2?-
methylthio-phenyl)methyleneimine (SNNMe) are
spin-free and the corresponding complexes of 2-pyridyl-N-(2?- methylthiophenyl)methyleneimine
(SNN) are spin-paired. This difference in magnetic behaviour arises from a
lower effective ligand field strength of SNNMe,
presumably due to the steric inter-ligand interference introduced by the methyl
group in the 6-position of SNNMe. The moments of the
cobalt(II) complexes are dependent on temperature and the departures from the
Curie-Weiss law are quite anomalous. No quantitative treatment is given for the
anomalous magnetic behaviour; however, the results are best explained as a
thermal equilibrium between the nearly equi-energetic
spin-paired and spin-free states of the cobalt(II) atom.
The syntheses and characterization of 12 new 14- to 17-membered macrocycles incorporating pendant hydroxyethyl cyanoethyl or carbamoylethyl groups are reported. The macrocyclic ring in each of these new ligands contains an O2N2-donor set. The X-ray structure of the di(hydroxyethyl) derivative of the 14-membered macrocycle is described.
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