15276-47-8Relevant articles and documents
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.
