Partial and gradual hydrolysis of 2,2 '-biimidazoline upon coordination to metal ions, yielding new chelating ligands - Synthesis, characterization and X-ray structure of two examples with cobalt(III) and copper(II)

摘要

The synthesis, a full structural characterization of two transition-metal compounds obtained by in-situ hydrolysis and partly hydrolysis of the ligand 2,2'-biimidazoline (abbreviated as biz) is reported. When the biz ligand is completely hydrolysed the compound, N,N'-bis(2-aminoethyl)oxamide (abbreviated as H(2)oxen) is obtained, while the partial hydrolysis results in the ligand N-(2-aminoethyl)imidazoline-2-carboxamide (abbreviated as Hoxim).The Co-III ion in the mononuclear Co-III compound, [Co(biz)(oxim)(NCS)](ClO4)(C2H5OH)(1/6)(H2O)(1/6) (1), has an octahedral coordination consisting of 6 nitrogen atoms with a distance varying from 1.889(6) to 1.950(5) Angstrom. Two nitrogen atoms originating from a biz molecule, 3 nitrogen atoms are from the oxim ligand and one nitrogen is from the thiocyanate anion.Each Cu-II ion in the dinuclear Cu-II compound, [Cu-2(H(2)oxen)(oxim)(2)(C2H5OH)(2)] (ClO4)(2) (2), has a slightly distorted square-pyramidal structure of which the basal plain consists of3 nitrogen atoms of the oxim ligand and one nitrogen atom of the H(2)oxen ligand, which is used as a "spacer" connecting the second Cu-II atom, with Cu-N distances which vary from 1.944(2) to 2.037(2) Angstrom The apical position is formed by the oxygen atom of a semi-coordinating ethanol molecule with a Cu-O distance of 2.446(2) Angstrom. The compounds are characterized by elemental analysis, ligand field, infrared and, for the Cu-II ion, also by EPR spectroscopy.