Structural and spectroscopic study of carbonatodiaquobisimidazole-cobalt(II), a bidentate carbonato-complex of cobalt(II)

Abstract

Carbonatodiaquobisimidazolecobalt(II), [Co(CO₃)(OH₂)₂(imH)₂](imidazole = imH), crystallises with Z= 4 in a monoclinic unit-cell of dimensions a= 10·13(1), b= 7·53(1), c= 14·14(2)Å, and β= 94·73(6)°. The spacegroup is A2/a(C_2h⁶). The crystal structure has been solved by use of counter data for 1029 reflections (141 unobserved) recorded with Cu-K_α radiation, and refined to R 0·062. The arrangement of the ligands about the Co^II atom is cis-aquo, trans-imidazole, and the carbonato-group functions as a bidentate chelate. The O–Co–O angle (61·2°) in the resulting four-membered chelate ring represents the main deviation from regular octahedral co-ordination geometry. The metal–donor bond lengths are Co^II–O(carbonato) 2·143(5), Co^II–(water) 2·166(6), and Co^II–N(imidazole) 2·112(7)Å. The complexes are linked in chains by pairs of OH₂⋯O(carbonato) hydrogen bonds, with N(imidazole)–H⋯O(carbonato) and OH₂⋯O(carbonato) hydrogen bonds between adjacent chains. Magnetic moments, u.v. visible and i.r. spectra for this complex, and for [Co(imH)₆]SO₄ and [Co(im)₂]_x, have been recorded and are interpreted.