oa South African Journal of Chemistry - Di-µ-hydroxo Bridge Cleavage Reactions between Co(nta)(µ-OH)]22- and various N, N-Bidentate Ligands
The cleavage of the di-µ-hydroxo bridges of [Co(nta)(µ-OH)]22- by en and N, N-Et2en (en = ethylenediamine and N, N-Et2en = N, N-diethylethylene-diamine) has been investigated. [Co(nta)(µ-OH)]22- equilibrates rapidly in aqueous basic solutions, yielding a mono-µ-hydroxo-bridged Co(III) complex [pKOH = 3.3(1)] and both these species react with the incoming ligand to form different ion associated species. These, in turn, react to form presumably a ligand-substituted, mono-bridged species, [(nta)(OH)Co-µ-OH-Co(nta)(L-L)]2-, which upon ring-closure rapidly form the products. Values for k2, the preferred pathway for these reactions, vary between 1.42(4) x 10-2 s-1 (en) and 3.2(1) x 10-3 s-1 (N, N-Et2en) at 25.0°C, µ = 0.2 M (NaClO4).
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