Synthesis and characterization of cobalt(III) azido complexes of some disubstituted pyridine ligands and X-ray crystal structure of mer-[Co(3,4-dimethylpridine) 3(N 3) 3] and mer-Co(3,5-dimethylpyridine) 3(N 3) 3

Abstract

Cobalt(III) azido complexes of some disubstituted pyridine ligands of the type CoL 3(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) Å and from 1.944(3) to 1.965(3) Å whereas Co—N(L) bond lenghts are from 1.955(3) to 1.994(3) and from 1.973(3) to 1.990(3) Å 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°, whereas complex ( 2) loses one 3,5-DMPy molecule and an azide ion in the first step around 139° and then explodes at 172°.