An optically active nickel(II) schiff base coordination compound N,N′-(1R,2R)-(-)-1,2-cyclohexylenebis(salicylideneiminato)nickel(II)

Authors:

• A. Wojtczak,
• E. Szlyk,
• Mariusz Jaskólski,
• E. Larsen

Abstract

The Schiff base between trans-(1R,2R)-1,2-cyclohexanediamine, [(-)_D-chxn] and 2 mol of salicylaldehyde has been used as a ligand for nickel (II). The coordination compound has been studied by UV/VIS absorption and circular dichroism spectroscopy in solution, and the crystal structure has been resolved by X-ray diffraction methods. The spectroscopic properties are related to the molecular structure found in the crystal. The crystal system is monoclinic, the unit cell dimensions are a=10.964(2), b=12.735(3), c=12.329(2) Å, β=95.26(3)°, the volume is 1714.2(6) ų and space group is P2₁ with Z=4. The final residual is 3.6% for 2785 observed reflections. Two symmetry-independent molecules in the crystal lattice are related by a non-crystallographic two-fold axis. They are involved in an extensive network of stacking interactions. The Ni-Ni distance is 3.403 Å. The two N and O atoms of the tetradentate ligand chelating each central Ni^II ion form slightly distorted square-planar environments, the Ni-N distances ranging from 1.848(4) to 1.866(4) Å, and Ni-O distances from 1.835(3) to 1.852(3) Å. The out of plane distortion gives rise to an overall chiral surrounding of the metal ion. The d-d and charge transfer transitions show circular dichroism, and the latter is shown to be consistent with the observed tetrahedral distortion which originates in the (R,R) absolute configuration of the ligand. © Acta Chemica Scandinavica 1997.