SYNTHESIS AND CHARACTERIZATION OF COBALT(III) AZIDO COMPLEXES OF SOME DISUBSTITUTED 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)]

摘要

Cobalt (III) azido complexes of some disubstituted pyridine ligands of the type CoL3(N-3)(3) have been prepared and characterized. The complexes 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 far-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-dimethylpyridine)(3)(N-3)(3)] (2). Both compounds contain discrete molecules with approximately octahedral cobalt (III) ion. The Co-N(N-3) distances are variable from 1.931(4) to 1.959(4) Angstrom and from 1.944(3) to 1.965(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 drivatographically in nitrogen. Complex (1) explodes completely in one step at 175 degrees, whereas complex (2) loses one 3,5-DMPy molecule and an azide ion in the first step around 139 degrees and then explodes at 172 degrees. (C) 1997 Elsevier Science Ltd. [References: 32]