Search

The reaction of Co(AcO)2 with 6-methyl-2-pyridinecarboxylic acid, and that of CoCl2 with the isopropyl ester of 2-pyridinecarboxylic acid, both with a 1:2 metal to ligand molar ratio, afford optimum yields for the synthesis of cis-[Co(MeC5H3NCOO)2(H2O)2] and cis-[CoCl2(C5H4NCOOPri)2], respectively. According to X-ray crystallography they both consist of mononuclear discrete molecules with octahedral coordination around Co(II). The ESR powder spectra of the related Zn phases doped with 0.25% Co(II) show the strong anisotropy of the g and A tensors. The magnetic behaviour of the solid complexes is characteristic of Co(II) systems with important spin–orbit coupling and weak antiferromagnetic interactions. Electronic UV–Vis and magnetic data indicate that these complexes, as well as the already known trans-[Co(C5H4NCOO)2(H2O)2], have a high-spin octahedral geometry in solution. [Copyright &y& Elsevier]

Cobalt(II) complexes obtained by the reaction of cis-[CoCl2(2-C5H4N&z.sbnd;CO2Pri)2] (1) with aqueous solutions of simple alkali metal salts have been prepared and characterized. While the reaction of 1 with KPF6 affords both trans-[Co(2-C5H4N&z.sbnd;CO2Pri)2(H2O)2](PF6)2·2(2-C5H4N&z.sbnd;CO2Pri) (2) and trans-[Co(2-C5H4N&z.sbnd;CO2Pri)2(H2O)2](PF6)2 (3), that with NaBPh4 leads to trans-[Co(2-C5H4N&z.sbnd;CO2Pri)2(H2O)2](BPh4)2·2H2O (5) exclusively. X-ray diffraction data show that the mononuclear cationic units in 2, 3 and 5 share common structural features. The reaction of 1 with KSCN leads to cis-[Co(NCS)2(2-C5H4N&z.sbnd;CO2Pri)2] (4), whose crystal structure shows that it consists of mononuclear discrete molecules. The analogous reaction with NaN3 yields the very slightly soluble complexes [Co(N3)2(2-C5H4N&z.sbnd;CO2Pri)] (7) and [Co2(N3)(2-C5H4N&z.sbnd;CO2Pri)4(H2O)]·3H2O (8) and that with NaOAc results in the formation of the already known complex trans-[Co(2-C5H4N&z.sbnd;CO2)2(H2O)2] (6) as the only product. Electronic UV–Vis and NIR spectral data for 2–5, 7 and 8 and the calculated magnetic moments from NMR measurements on 2–4 and 7 are indicative of high-spin octahedral Co(II) complexes, as already reported for 1 of known structure. [Copyright &y& Elsevier]