Co-ordination of oxygen by cobalt(II)–L-ornithinate and –DL-2,3-diaminopropanoate complexes in aqueous solution

Abstract

The oxygenation of cobalt(II) bis(DL-2,3-diaminopropanoate) and bis(L-ornithinate) complexes has been studied in aqueous solution at 25 °C. Equilibrium constants are reported for protonation of the two ligands, and for formation of the complexes [CoL]⁺, [Co(HL)]²⁺, and [CoL₂](HL =DL-2,3-diaminopropanoic acid) and [Co-(HL)]²⁺, [Co(HL)₂]²⁺, and [Co(HL)L]⁺(HL =L-ornithine). Equilibrium data for oxygenation of the DL-2,3-diaminopropanoate complex [CoL₂](log K_O2 8.90 ± 0.08, log K_O2,OH 12.13 ± 0.14) and the L-ornithine complex [Co(HL)L]⁺(log K_O2 7.17 ± 0.12) have been obtained by use of a polarographic oxygen analyser.