Planar or tetrahedral coordination in copper(II) complexes induced by bromo substitution

The diffraction study of bis(5-bromo-N-m-tolylsalicylaldiminate)copper(II) shows the copper atom in a centrosymmetric position and the two ligands displayed trans to each other in a planar environment. Two additional weak interactions due to Br atoms (Jahn-Teller effect) of neighboring units complete the coordination sphere, Cu-Br = 3.662(2) Angstrom, so that the complex is formally a polynuclear two-dimensional species. On the contrary, bis(3,5-dibromo-N-p-tolylsalicylaldinate)copper(II) is mononuclear and shows only the two ligands coordinated and the geometry is distorted 'tetrahedral'. The distortion is due to intramolecular repulsion interactions. Electronic spectra of these two compounds show a single asymmetric band at 700 nm for the former, and two bands located at 650 and 850 nm for the latter. Both compounds are monoclinic, space group P2(1)/c with a=9.919(2) Angstrom, b=10.965(2) Angstrom, c=12.283(2) Angstrom, beta=105.88(1)degrees, Z=2 for the former, and a=13.290(2) Angstrom, b=12.195(2) Angstrom, c=17.891(2) Angstrom, beta=105.38(1)degrees, Z=4 for the latter. (C) 1998 Elsevier Science S.A.