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2 Polish Journal of Chemistry

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Synthesis of New Co(III) Hetero-Ligand Complexes with Imidazole and 1-Methylimidazole and Their H, C, and Co NMR Spectra

Danilczuk E., Grzelakowska A., Michalska M.

Polish Journal of Chemistry

2000

Vol. 74, nr 2

181-189

Cis-[Co(en)2(1-Melm)2]Cl3, fac-[Co(dien)(ImH)3]X3 (X=Cl-, NO3-,ClO4-) and fac-[Co(dien)(1-Melm)3]Cl3 complexes were prepared and characterized by absorption, 1H NR, 13C NR and 59Co NMR spectra, where en, dien, imH and 1-elm denote ethylenediamine, diethylenetriamine, imidazole and 1-methylimidazole, respectively. Calculated coordination-induced shifts ranged from +0.62 to -0.03 pp for 1H and +7.11 to -1,19 ppm for 13C nuclei of imidazole ligands. The influence of imidazole methylation on 59Co NMR spectra was considered.

Kinetics and mechanism of the acid-catalyzed hydrolysis of [carbonatotetra(1-methylimidazole)cobalt(III)](+) ion

Chatłas J., Danilczuk E., Nasiadko M.

Polish Journal of Chemistry

1998

Vol. 72, nr 4

777-785

The kinetics of acod-catalyzed hydrolysis of the [Co(1-Meim)4(CO3)](+) ion follows the rate law -d ln[complex]/d t=k(1)K[H(+)]/(1 + K[H(+)]) (25:45 degree C, [H(+)]=0.05:1.0 M and I=1.0 M(NaClO4)). The reaction course consists of rapid pre-equilibrium protonation followed by a rate determining ring opening process and the subsequent fast relase of monodentate carbonato ligand. Kinetic parameters, k(1) and K, at 25 degree C are 5.1x 10(-3)s(-1) ans 0.48 M(-1) respectively, and activation parameters for k(1) are Delta H(1)=84.4+:-0.8kJ mol(-1) and DeltaS(1)=-5.8+:-3.7J mol(-1) K(-1). The hydrolysis rate increases with the ionic strengh. The results are compared with those for similar cobalt(III) complexes.