SYNTHESIS AND CHARACTERIZATION OF COBALT(III) AZIDO COMPLEXES OF SOMEDISUBSTITUTED PYRIDINE LIGANDS AND X-RAY CRYSTAL-STRUCTURE OF MER-[CO(3,4-DIMETHYLPYRIDINE)(3)(N-3)(3)] AND MER-[CO(3,5-DIMETHYLPYRIDINE)(3)(N-3)(3)]

Cobalt (III) azido complexes of some disubstituted pyridine ligands of the type CoL3(N-3)(3) have been prepared and characterized. The compl exes gave non-conducting solutions and their solid state and solution electronic spectra are discussed. The IR spectra reveal the asymmetric nature of the azido ligands and the mer-formulation was confirmed by the number of Co-N(N-3) and Co-N(L) stretching bands observed in the f ar-IR region. X-ray crystal structure determinations were done for mer -[Co(3,4-dimethylpyridine)(3)(N-3)(3)] (1) and mer-[Co(3,5-dimethylpyr idine)(3)(N-3)(3)] (2). Both compounds contain discrete molecules with approximately octahedral cobalt (III) ion. The Co-N(N-3) distances ar e variable from 1.931(4) to 1.959(4) Angstrom and from 1.944(3) to 1.9 65(3) Angstrom whereas Co-N(L) bond lengths are from 1.955(3) to 1.994 (3) and from 1.973(3) to 1.990(3) Angstrom for 1 and 2, respectively. The thermal decomposition of complexes (1) and (2) were investigated d rivatographically in nitrogen. Complex (1) explodes completely in one step at 175 degrees, whereas complex (2) loses one 3,5-DMPy molecule a nd an azide ion in the first step around 139 degrees and then explodes at 172 degrees. (C) 1997 Elsevier Science Ltd.