SYNTHESIS, SPECTRAL AND STRUCTURAL CHARACTERIZATION OF 2 POLYMERIC 1 1-COMPLEXES OF 2,3-DIMETHYLPYRIDINE AND 5-ETHYL-2-METHYLPYRIDINE WITH COPPER(II) AZIDE - CU(2,3-DIMETHYLPYRIDINE) (N-3)(2) AND CU(2-METHYL-5-ETHYLPYRIDINE) (N-3)(2)/

Two new 1:1 ligand complexes of copper(II) azide with disubstituted py ridine ligands, namely i-mu(1,3)-azido-[di-mu(1,1)-azidobis(2,3-lutidi ne) dicopper(II)] (1) and 1)-azidobis(2-methyl-5-ethylpyridine)dicoppe r(II)] (2), have been synthesized and characterized by spectroscopic a nd X-ray crystallographic methods. The polymeric complex 1 features mo nodentate 2,3-lut ligands, centrosymmetric di-mu(1,1)-azido-bridged Cu 2N2 rings, distorted square-pyramidal copper(II) coordination geometry and di-mu(1,3)-azido bridges which link the centrosymmetric binuclear Cu-2(2,3-lut)(2)(N-3)(2) moieties to form sheets within the ab plane. In the monoclinic crystals of complex 2, the copper(II) centres are p entacoordinated via N(11), N(21), N(11b) and N(21a) from the azido lig ands [Cu-N distances 1.971(5)-2.286(5) Angstrom] and N(1) from the org anic molecule at a Cu-N bond length of 2.001(5) Angstrom. Both azido l igands function as mu(1,1) bridges to form chains of polyhedra along t he short a-axis of the unit cell. The IR absorption spectra reveal tha t each of these complexes contains two independent azide ligands. The solid and solution electronic spectra of complexes 1 and 2 show at lea st three and two strong absorption bands, respectively, associated wit h N-3(-) --> Cu-II charge transfer transitions. The EPR spectra of pow der samples and DMSO solutions at room temperature were recorded and a re discussed. Copyright (C) 1996 Elsevier Science Ltd