An unusual partial occupancy of labile chloride and aqua ligands in cocrystallized isomers of a nickel(II) complex bearing a tripodal N4-donor ligand.

Abstract

A novel Ni2+ complex with the N4-donor tripodal ligand bis[(1-methyl-1H-imidazol-2-yl)methyl][2-(pyridin-2-yl)ethyl]amine (L), namely, aqua{bis[(1-methyl-1H-imidazol-2-yl-κN3)methyl][2-(pyridin-2-yl-κN)ethyl]amine-κN}chloridonickel(II) perchlorate, [NiCl(C17H22N6)(H2O)]ClO4 or [NiCl(H2O)(L)Cl]ClO4 (1), was synthesized and characterized by spectroscopic and spectrometric methods. The crystal structure of 1 reveals an interesting and unusual cocrystallization of isomeric complexes, which are crystallographically disordered with partial occupancy of the labile cis aqua and chloride ligands. The Ni2+ centre exhibits a distorted octahedral environment, with similar bond lengths for the two Ni-N(imidazole) bonds. The bond length increases for Ni-N(pyridine) and Ni-N(amine), which is in agreement with literature examples. The bond lengths of the disordered labile sites are also in the expected range and the Ni-Cl and Ni-O bond lengths are comparable with similar compounds. The electronic, redox and solution stability behaviour of 1 were also evaluated, and the data obtained suggest the maintenance of structural integrity, with no sign of demetalation or decomposition under the studied conditions.