PREPARATION, SPECTRAL AND CRYSTAL-STRUCTURE STUDY OF POLYMERIC 1 1 AND DIMERIC 1/2 COMPLEXES OF COPPER(II) AZIDE WITH PYRIDINE-N-OXIDE AND 3-ACETYLPYRIDINE, [CU(PYRIDINE-N-OXIDE)(N-3)(2)](N) AND [CU(3-ACETYLPYRIDINE)(2)(N-3)(2)](2)/

The synthesis and characterization of two new complexes of copper(II) azide, 1:1 with pyridine-N-oxide (1) and 1:2 with 3-acetylpyridine (2) are described. The structure of complex 1 features five-coordinated c opper in a distorted tetragonal pyramidal environment with N(11), N(11 a), N(21) and N(21b) of the two mu(1,1) bridging azido ligands in basa l sites [Cu-N from 2.003(3) to 2.026(3) Angstrom] and O(1) of the pyri dine-N-oxide molecule occupying the apical position [Cu-O = 2.185(3) A ngstrom]. The chains of polyhedra are directed along the a axis of the unit cell. The dimeric molecule of 2, which possesses a crystallograp hic inversion centre, contains both terminal and mu(1,1) bridging azid o groups. Each copper(II) atom is further coordinated by two nitrogen atoms from 3-acetylpyridine molecules to give a distorted square pyram id. The IR and electronic spectra of the solid complexes are given and discussed.