Design, synthesis, and characterization of bis(.mu.-oxo)dimanganese(III,III) complexes. Steric and electronic control of redox potentials

The syntheses of three bis({mu}-oxo)dimanganese(III,III) complexes and one bis({mu}-oxo)dimanganese(III,IV) complex are described. The Mn(III/III) complexes are all of the general formulation ((L)MnO){sub 2}{sup 2+}, where the ligands L are related to N,N{prime}-bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen, 1a) and tris(2-pyridylmethyl)amine (tmpa, 2a). The complex bis({mu}-oxo)bis(N,N{prime}-bis((6-methylpyrid-2-yl)methyl)ethane-1,2-diamine)dimanganese(III) perchlorate monohydrate, ((1b)MnO){sub 2}(ClO{sub 4}){sub 2}{center dot}H{sub 2}O, Mn{sub 2}C{sub 32}H{sub 46}Cl{sub 2}N{sub 8}O{sub 11} (4), crystallizes in the triclinic space group P{anti 1} with two binuclear complexes in a cell of dimensions a = 8.487 (3) {angstrom}, b = 10.868 (2) {angstrom}, c = 20.816 (5) {angstrom}, {alpha} = 77.34 (2){degree}, {beta} = 88.28 (2){degree}, and {gamma} = 84.02 (2){degree}. The complex bis({mu}-oxo)bis(N,N-bis((6-methylpyrid-2-yl)methyl)-N-2-pyridylmethylamine)dimanganese(III) nitrate hexahydrate, ((2c)MnO){sub 2}(NO{sub 3}){sub 2}{center dot}6H{sub 2}O, Mn{sub 2}C{sub 40}H{sub 56}N{sub 10}O{sub 14} (5), crystallizes in the monoclinic space group C2/c with four binuclear complexes in a cell of dimensions a = 22.122 (7) {angstrom}, b = 16.419 (6) {angstrom}, c = 14.461 (4) {angstrom}, {beta} = 117.15 (2){degree}.