The syntheses of two new, potentially hexadentate ligands with an N3O3 donor set is reported: 1,4,7-triazacyclononane-N,N′,N″-tris-2-ethanesulfonate (TES) and 1,4,7-triazacyclononane- N,N′,N″-tris-ethylacetate (TEA). Complexes of the divalent transition metals Co(II), Ni(II), Cu(II) containing these ligands have been prepared. The kinetics of the reactions of [Con(TEA)H2O]2+ and [CoII(TCTA)]-(TCTA= 1,4,7-triazacyclononane- N,N′N″-tris-acetate) with [FeIII(CN)6]3-, respectively, have been measured. A stable binuclear [Co(TEA)(CN)6Fe]- species has been characterized in solution whereas the reaction of [Co(TCTA)]- with [Fe(CN)6]3- yields [CoIIITCTA] and [Fe(CN)6]4- via an outer-sphere electron transfer reaction (k = 5,9 × 103 1 mol-1 sec-1; 25 °C, I = 0,26 M). Na[Ni(TES)H2O]·5H2O crystallizes in the triclinic space group P1̄ (Ci1-No 2) with cell constants a = 806,7(4), b = 1468,4(8), c = 2317,9(8) pm, α = 72,36(4)°, β = 83,48 (3)°, γ = 81,99(4)°, and Z = 4. The nickel(II) center is in a distorted octahedral environment of a pentadentate TES ligand (N3O2) and a coordinated H2O. Na[Cu(TES)] 3H2O crystallizes in the triclinic space group P1̄ (Ci1-No 2) with cell constants a = 747,3(3), b - 1082,6(5), c = 1459,3(9) pm, α = 81,13(5)°, β = 84,75(4)°, γ = 79,39(3)°, and Z = 2. The copper(II) center is in a distorted quadratic pyramidal environment of a pentadentate TES ligand. Each of the complex anions contains one uncomplexed CH2-CH2-SO3-group.