Synthesis and solid state structures of copper(II) complexes of Schiff bases derived from cyclopropyl and cyclobutylamine

The Schiff base copper(II) complexes (1)-(6) were prepared and characterised by mass, IR, and electronic spectra. Their solid states structures, determined by X-ray crystallography, indicate that the geometry around copper is determined by a combination of steric and electronic effects, as well as crystal packing forces. Thus, complex (1) is the only one in the series to have a square planar geometry. In contrast, complexes (2) and (3) display deformed square planar geometries, despite the small steric effect of the N-cyclopropyl and cyclobutyl groups. Furthermore, a purely electronic argument, based on which complexes (5) and (6) must have deformed tetrahedral structures, fails to account for the observed stepped square planar structures. Finally, complex (4) also has a stepped square planar geometry. (C) 2003 Elsevier B.V. All rights reserved.