POLYMERIC COMPLEXES OF COPPER(II) AZIDE AND 2,5-DIMETHYLPYRIDINE WITHOUT AND WITH SOLVENT MOLECULES - SYNTHESIS, SPECTRAL AND STRUCTURAL CHARACTERIZATION OF [CU(2,5-DIMETHYLPYRIDINE)(N-3)(2)](N) AND [CU(2,5-DIMETHYLPYRIDINE)(N-3)(2)(H2N-CHO)](2)

Catina u(1,1)-azidobis(2,5-dimethylpyridine(dicopper(II)] (1) and di-m u(1,1)-azidobis[azido(2,5-dimethylpyridine) (formamide)]dicopper(II) ( 2) were synthesized and characterized by spectroscopic and crystallogr aphic methods. In the triclinic complex 1 the copper(II) centres are p enta-coordinated by four nitrogen atoms from the azido ligands [Cu-N d istances = 1.980(3)-2.249(4) Angstrom] and a fifth nitrogen from the o rganic molecule at a Cu-N bond length of 2.038(4) Angstrom. Both azido ligands function as mu(1,1) bridges to form chains of polyhedra along the crystallographic a axis. The dimeric molecule 2, which possesses a crystallographic inversion centre, contains both terminal and mu(1,1 ) bridging azido ligands. Each copper(II) atom is further coordinated by a 2,5-dimethylpyridine molecule [Cu-N = 1.998(4) Angstrom] and a fo rmamide molecule via its carbonyl oxygen atom [Cu-O = 2.356(4) Angstro m] to give a distorted square pyramid. The IR absorption spectra revea l asymmetric azido ligands in both complexes, O-bonded formamide and h ydrogen bonds as well, in 2. The solid and solution electronic spectra of both complexes exhibit more than one strong N-3(-) --> Cu-II charg e-transfer transition band. The room-temperature EPR spectra of powder ed samples and DMF solutions were recorded and discussed. (C) 1997 Els evier Science Ltd.