ELECTROSYNTHESIS OF A MANGANESE(III) AMINOPOLYCARBOXYLATE COMPLEX IN ALKALINE MEDIA

Mn(III)CyDTA ns-cyclohexane-1,2-diamine-N,N,N',N'-tetraacetato) mangan ate(III)] was generated electrochemically from Mn(II)CyDTA (6-54 mM) i n 0.1 M NaHCO3 at pH 9.0 and 10.5, respectively, 25 degrees C, for two CyDTA/Mn molar ratios (1/1 and 2/1). A divided batch electrochemical reactor was employed with anode current densities from 2.6 to 102 A m( -2). Separate cyclic voltammetry experiments of Mn(m)CyDTA in alkaline media showed a prepeak behaviour, indicating the adsorption of Mn(II) species. The visible anodic deposit, formed during the electrosynthes is of Mn(III)CyDTA at pH 10.5 and 1/1 CyDTA/Mn molar ratio on stainles s steel and PbO2/Pb, reduces the current efficiency for Mn(III). For a Mn(II) concentration of 18 mM and at 13 A m(-2), the graphite and pla tinized titanium anodes gave a current efficiency for Mn(III) of 78% a nd 66%, respectively, without a visible deposit. A 2/1 CyDTA/Mn molar ratio, avoided a visible anodic deposit formation, but gave lower curr ent efficiencies for Mn(III) than in the case of a 1/1 ligand to metal ratio. The electrosynthesis of Mn(III)CyDTA is recommended for routin e preparation of the complex and is also suitable for in situ electroc hemically mediated oxidations in alkaline media (up to pH 11).