The synthesis of the flexible ligand 2,6-bis-{[bis-(2-aminoethyl)amino]methyl}-benzene (L1) is reported. The basicity behavior of the ligand in aqueous solution was studied by potentiometry (25 o C, I=0.15 mol dm - 3 , Me 4 NCl). L1 behaves as pentaprotic base (logK 1 =10.39(2), logK 2 =9.72(1), logK 3 =9.11(1), logK 4 =8.72(1), logK 5 =2.03(2)). The stability constants for Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) complexes were determined by potentiometry under the same experimental conditions and they were compared with those of ligands L2 having the same two tri-amine subunits linked by a phenol, rather than a benzene, spacer. L1 forms mono nuclear species with logK M L =9.65(1) for Co(II), 13.92(1) for Ni(II), 17.59(1) for Cu(II), 10.45(1) for Zn(II) and 9.24(1) for Cd(II) and binuclear species with logK M 2 L =15.28(1) for Co(II), 19.24(3) for Ni(II), 28.32(2) for Cu(II), 16.94(1) for Zn(II) and 14.88(1) for Cd(II). The role of the benzene and phenol as spacers of two amine functions in metal ion coordination is discussed.