SYNTHESIS, CRYSTAL-STRUCTURE AND SPECTROSCOPIC STUDY OF RANS-DIAZIDOBIS(2,4,6-TRIMETHYLPYRIDINE)COPPER(II) AND AZIDOTETRAKIS(3-ETHYL-4-METHYLPYRIDINE)COPPER(II) NITRATE - [CU(S-COLLIDINE)(2)(N-3)(2)] AND [CU(BETA-COLLIDINE)(4)(N-3)](NO3)

Two monomeric complexes of copper(II) azide with 2,4,6-trimethylpyridi ne and 3-ethyl-4-methylpyridine, namely trans-diazidobis (s-collidine) copper(II) (1) and azidotetrakis-(beta-collidine)copper(II) nitrate ( 2), have been prepared and characterized by spectroscopic and X-ray cr ystalographic methods. The spectral results suggest terminal azido lig ands in both complexes and ionic nitrate in 2. The structure of 1 cons ists of isolated polyhedra of trans-[Cu(2,4,6-trimethylpyridine)(2)(N- 3)(2)], in which the copper atom is located at the inversion centre an d has an almost regular square-planar geometry. The Cu-N(N-3) and Cu-N (L) bond lengths are 1.954(4) and 2.022(3) Angstrom, respectively. The terminal azido ligands are linear and slightly asymmetric [N-alpha-N- beta = 1.184(5) and NbetaNgamma = 1.163(6) Angstrom]. The structure of complex 2 consists of isolated [Cu(3-ethyl-4-methylpyridine)(4)(N-3)] (+) cations and NO3- counter anions. The coordination of the copper at om in the cation is a regular tetragonal pyramid with four collidine l igands occupying the basal sites [Cu-N-av = 2.028(10) Angstrom] and a terminal azido ligand at the apical position with a Cu-N distance of 2 .193(7)Angstrom.