Polarographic and voltammetric studies of tetrabutylammonium hexacyanoferrate(III) and tetrabutylammonium hexacyanomanganate(III) in non-aqueous solvents

Abstract

Tetrabutylammonium hexacyanomanganate(III) [(bu 4N) 3Mn(CN) 6] has been studied by polarography and cyclic voltammetry in formamide, methanol, ethanol, N-methylformamide, dichloromethane, dimethylsulfoxide, acetonitrile, N,N-dimethylformamide, propylenecarbonate, butyrolactone, N-methylthiopyrrolidone(2), N,N-dimethylthioformamide, 1.2-dichloroethane, N-methylpyrrolidone(2) and tetramethylenesulfone. Similar studies have been carried out for tetrabutylammonium hexacyanoferrate(III) [(bu 4N) 3 Fe(CN) 6] in the solvents formamide, N-methylformamide, dichloromethane, butyrolactone, N-methylthiopyrrolidone(2) and tetramethylenesulfone. The half-wave potentials of the reductions (bu 4N) 3Mn(CN) 6 to (bu 4N) 4Mn(CN) 6 and (bu 4N) 3Fe(CN) 6 to (bu 4N) 4Fe(CN) 6 versus bisbiphenylchromium(I)/bisbiphenylchromium(0) as a reference redox system were found to vary with the nature of the solvent. Comparison with data previously obtained for the respective tetraethylammonium salts of hexacyanoferrate(III) and hexacyanomanganate(III) have shown that the redox behaviour of these compounds is influenced by both the solvent and the tetraalkylammonium ions. Correlations exist between the half-wave potentials of (bu 4N) 3Mn(CN) 6 and (bu 4N) 3Fe(CN) 6 and both the acceptor number of the solvents and the free enthalpies of transfer of the chloride ion. The results are discussed in the concept of donor-acceptor interactions.