Structural and spectroscopic characterisation of tris(2-benzimidazolylmethyl)amine coordination compounds of Zn(II), Cd(II) and Hg(II)

Zinc(II), cadmium(II) and mercury(II) coordination compounds derived from t ris(2-benzimidazolylmethyl)amine (ntb) were characterised by H-1 and C-13 N MR in solution, IR and X-ray single crystal diffraction for [Zn(ntb)Cl](2)[ ZnCl4]. 4EtOH, [Cd(ntb)(mu(2)-NO3)]NO3. 2DMSO and [Hg(ntb)Cl](2)[HgCl4]. 4E tOH. The complexes derived from zinc(II), cadmium(II) and mercury(II) halid es form [M(ntb)X](+) cations, where the metal ions are pentacoordinated and have a distorted trigonal bipyramidal geometry, with tetrahedral anions [M X4](2). In the [Cd(ntb)(mu(2)-NO3)]NO3. 2DMSO complex, by analogy with the Zn(II) and Hg(II) compounds, the NO3- could be considered as the fifth apic al substituent in a distorted trigonal bipyramid geometry. In all complexes the ligand is coordinated to the metal through the imidazolic nitrogen ato ms and has a weak coordination with the tertiary amine. The counter ion (ha lide or nitrate) remains bonded to the metal ion in solution and in the sol id state as was evidenced by NMR and X-ray diffraction. The structures pres ented interactions between the coordinated counterion and the nearest C-H o f the aromatic rings. All cations show an approximate C3 symmetry. The dist ortions found in the solid state were attributed to intermolecular hydrogen bonding and stacking between the benzimidazolic rings of neighbouring mole cules. (C) 2000 Elsevier Science Ltd. All lights reserved.