An optically active nickel(II) Schiff base coordination compound N,N '-(1R,2R)-(-)-1,2-cyclohexylenebis (2-hydroxyacetophenonylideneiminato)nickel(II)

The Schiff base between trans-(1R,2R)-1,2-cyclohexanediamine and 2 mol of 2 -hydroxyacetophenone has been used as a ligand for nickel(II). The coordina tion compound has been studied by NMR, W-Vis absorption and circular dichro ism spectroscopy in solution. The crystal structure of the N,N'-(1R,2R)-(-) -1,2-cyclohexylenebis(2-hydroxyacetophenonylideneiminato)nickel(II) complex ([Ni(R,R)-chxn(hapi)(2)]) was determined by the X-ray diffraction method. The molecule has an umbrella geometry, the dihedral angle between the plane s defined by the two acetophenonylideneimine moieties of the ligand is 43.5 (1)degrees. The Ni(II) atom is situated in a slightly distorted square-plan ar environment. The Ni-O distances vary from 1.811(4) to 1.824(4) Angstrom and Ni-N distances are 1.857(5) and 1.873(5) Angstrom. The cyclohexane ring of the Schiff base is in the chair conformation. Both the cyclohexane ring chiral carbon atoms C11 and C16 are positioned on the same side of the coo rdination NiN2O2 plane, the distances to the best plane being - 0.849 and - 0.303 Angstrom, respectively. The crystal data and nuclear Overhauser effe ct (NOE) experiment revealed interaction of the methyl group with protons f rom cyclohexyl methine and methylene and phenyl hydrogens, both in the crys tal and solution. (C) 1999 Elsevier Science S.A. All rights reserved.