Synthesis and structural characterization of five- and six-coordinate cobalt(II) complexes of tripodal ligand, tris-(2-benzimidazolylmethyl)amine

Abstract

The various cobalt(II) complexes were synthesized and characterized using tris-(2-benzimidazolylmethyl)amine (ntb) as a ligand where the ntb plays as a tripodal tetradentate ligand to form complexes with a trigonal pyramidal geometry. The complexes have 5 and 6 coordinate cobalt(II) ions depending on the additional ligand used. In each complex the additional ligand, chloride anion, or acetate anion occupies the "open" site trans to the apical tertiary nitrogen atom of ntb ligand. Complex 1, [Co(II)(ntb)Cl]Cl has a trigonal bipyramidal geometry. This geometry was easily constructed using ntb as a tetradentate ligand and chloride as a monodentate ligand. The complex is isostructural to the corresponding manganese(II) complex. Crystal data are as follows: [Co(II)(ntb)Cl]Cl·MeOH, 1. triclinic space group P1̄; a=13.524(2) A, b=14.037(2) A, c=17.275(1) A; α= 78.798(9), β=84.159(8)°, γ=65.504(9)°; V=2929.6(6) A3; Z=4; R1=0.0715, wR2 =0.1461 for reflections of I> 2σ(I). Six coordinate complex 2 [Co(ntb)(OAc)](OAc) was synthesized using ntb as a tetradentate ligand and acetate as a bidentate chelating ligand.