STUDIES ON OUTER-SPHERE ASSOCIATION OF SOME COBALT(III) MIXED-LIGAND COMPLEXES IN AQUEOUS-SOLUTIONS

The outer-sphere association of Co(III) mixed ligand complexes of the type [Co(L)(AMUH)2] X3 (L = ethylenediamine, 2,2'-dipyridyl and 1,10-p henanthroline; AMUH = 1-amidino-O-alkylurea; X = Cl, Br and I) has bee n studied. Coductometric studies of the equilibrium [Co(L)(AMUH)2]3+ X-reversible {[Co(L)(AMUH)2]X}2+ have been carried out in aqueous sol ution at 25 +/- 0.1(0). The association constants of the outer-sphere complexes follow the order: (a) Cl- > Br- > I- and (b) ethylenediamine > 2,2'-dipyridine > 1,10-phenanthroline. Sizes of the ion-pairs have also been evaluated from limiting conductance data using Bjerrum equat ion.