Complexes of cobalt(II) and nickel(II) halides with imidazole

Abstract
The preparation and spectral and magnetic properties are reported for complexes of cobalt(II) and nickel(II) halides with imidazole (lz). The compounds Iz4NiX2(X = Cl, Br, or l), lz2NiX2(X = Cl or Br), Iz NiX2(X = Cl or Br), and lz CoCl2 possess essentially octahedral structures whilst lz2Nil2, Iz Nil2, lz2CoX2(X = Cl, Br, or l), and Iz CoX2(X = Br or l) are pseudotetrahedral. The product of fusing a 4 : 1 mole ratio of imidazole and cobalt(II) chloride has been shown to be an equimolar mixture of Iz6CoCl2 and lz2CoCl2. The M–lz stretching vibration occurs at a higher frequency in these complexes than the M–pyridine vibration in the corresponding pyridine complexes. The ligand field parameter Dq appears to be less for imidazole than for pyridine.
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