Cobalt(II) and nickel(II) complexes of some bidentate imidazoline ligands. Stereochemically dependent derealization in the imidazoline rings

Abstract

Tetrahedral and octahedral cobalt(II), and square and octahedral nickel(II) complexes of 1,2-bis(2′-imidazolin-2′-yl)benzene, 1,2-bis(2′-imidazolin-2′-yl)ethane, and some imidazoline ring methyl substituted ligands are reported. The structures are confirmed by three X-ray structural analyses, magnetism, and electronic and vibrational (conventional and far i.r.) spectroscopy. Both cis and trans octahedral complexes of the type M(ligand)₂(NCS)₂ [M = Co(II), Ni(II)] have been characterized, and none of these exhibit splitting of the v(CN)(NCS) absorption in the i.r. spectrum at room temperature. Low temperature studies reveal splitting of the v(CN) band in the cis isomers. Both ¹³C and ¹⁵N satellite absorption is identified. The delocalization of the double bond in the imidazoline rings in these complexes is discussed in terms of the i.r. and X-ray data.