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

Abstract

A series of green cobalt(III) azido complexes of the type CoL 3(N 3) 3, where L is pyridine, 4-amino-, 4-ethyl- or 3-methyl-pyridine, in addition to another series of brown complexes of the same type for L  4-methyl-, 4-bromo-, 4-aldehyde-, 4-acetyl, 4-cyanopyridines and methyl-, ethyl-nicotinate and isonicotinates, have been prepared by aerial or persulphate oxidation of cobalt(II). The complexes gave non-conducting solutions and their electronic spectra are discussed. The IR spectral results suggest asymmetric azido ligands, whereas the number of CoN(N 3) and CoN(L) stretching bands observed in the far-IR region are consistent with mer-formulation of complexes of both series. X-ray crystal structure determinations were done for mer- [Co(py) 3(N 3) 3] ( 1) and mer- [Co(4-pic) 3(N 3) 3] ( 2). The coordination around the cobalt(III) ion in the discrete molecules of both compounds is approximately octahedral with mean CoN(L) distances of 1.977(7) and 1.973(12) Å and CoN(N 3) lengths of 1.951(9) and 1.949(10) Å for 1 and 2, respectively.