Abstract

MnII forms a yellow mononuclear species with the title ligand having a 1∶2 stoichiometry and whose conditional stability constant is 8.9 × 1010 m −2. The c.v. of this complex shows an oxidation at +0.78V versus s.c.e. Controlled-potential electrolysis at +0.80V versus s.c.e. yields a binuclear species of MnIII with a 1∶2 metal:ligand stoichiometry. The addition of MnIII(urea)6(ClO4)3 to a solution of the ligand produces a mononuclear complex of MnIII if the concentration of the metal ion is less than 1 mM. At higher concentrations a binuclear species is obtained. The latter is reduced in two steps, at +0.24 and −0.58 V versus s.c.e. Controlled-potential electrolysis at 0.0 V produces a dark green complex after the transfer of 0.5 equivalents of charge per mole of Mn. This binuclear L2MnII-MnIIIL2 mixed-valence complex can be obtained only by electrolysis of the binuclear L2MnIIIMnIIIL2 species. Attempts to prepare the complex chemically were unsuccessful - the binuclear MnIII species was obtained in every case