15276-47-8Relevant academic research and scientific papers
Stereoselectivity in the reduction of [Co(ox)3]3- by [Co(en)3]2+ and its derivatives
Marusak, Rosemary A.,Osvath, Peter,Kemper, Margaret,Lappin, A. Graham
, p. 1542 - 1548 (2008/10/08)
The oxidation of cobalt(II) by [Co(ox)3]3- in 1,2-diaminoethane solutions proceeds by both inner-sphere and outer-sphere pathways leading to formation of [Co(en)2(ox)]+ and [Co(en)3]3+ with rate constants 3300 and 390 M-1 s-1, respectively, at 25.0°C and 0.10 M ionic strength. When optically active [Co(ox)3]3- is used, both pathways show stereoselectivity. In the inner-sphere pathway, stereoselectivity is small, 1.5% ΔΔ, a consequence of the separation of the reacting centers by the oxalate bridge. In the outer-sphere pathway, stereoselectivity is 9% ΔΔ. The effect on the stereoselectivity of varying the structure of the reductant for the series [Co(sep)]2+, [Co(sen)]2+, [Co(en)3]2+, [Co((±)-bn)3]2+, and [Co((±)-chxn)3]2+ has been investigated for this pathway. Outersphere stereoseiectivity has also been examined in the reactions of [Co(mal)3]3- with [Co(en)3]2+ and [Co((±)-chxn)3]2+. The stereoselectivity data are consistent with a mechanism in which the carboxylate faces of [Co(ox)3]3- or [Co(mal)3]3- are presented to various orientations of the reductants in strong precursor ion pairs and are dependent on the relative importance of hydrogen-bonding and electrostatic interactions between the complexes.
ECE mechanisms as a tool for the investigation of unstable metal complexes. 3. Polarographic studies of ligand dissociation of dibromocobalt(II) and dibromocobalt(III) complexes
Yamada, Akifumi,Yoshikuni, Tadatsugu,Tanaka, Nobuyuki
, p. 2090 - 2093 (2008/10/08)
The electrode reaction of trans-[CoBr2(N)4]+ ((N)4 = (en)2, (pn)2, (tn)2, and (NH3)4; en = ethylenediamine, pn = propylenediamine, tn = trimethylenediamine) has been examined in 0.1 M sodium acetate buffer solutions at mercury electrodes. All complexes exhibit the complicated electrode processes in which both the parallel ECE reaction and the Br- dissociation of cobalt(III) complexes take place. The dissociation rates of Br- from the Co(III) and Co(II) complexes are determined. The Br--dissociation rate constant (s-1) at 25°C, ΔH≠ (kcal mol-1), and ΔS≠ (cal K-1 mol-1) for trans-[CoIIIBr2(N)4]+ complexes are as follows: en, 1.51 × 10-4, 27.2, +15; pn, 3.30 × 10-4, 19.1, -10; NH3, 4.20 × 10-3, 26.8, +20; tn, 2.12 × 10-2, 15.2, -15. Also, the Br--dissociation rate constant (s-1) at 25°C, ΔH≠ (kcal mol-1), and ΔS≠ (cal K-1 mol-1) for trans-[CoIIBr2(N)4] complexes are as follows: en, 0.508, 1.3, -55; pn, 0.538, 2.9, -50; NH3, 0.610, 1.3, -55; tn, 0.571, 6.5, -38.
