The novel binucleating ligand, 6,6'-methylene-bis(5'-amino-3',4'-benzo-2'-thiapentyl)-1,11-diamino-2,3:9,10-dibenzo-4,8-dithiaundecane (H4L) was prepared and reacted with copper(II) salts in dry MeOH to yield mixtures of copper(I) and copper(II) complexes with Cl- and ClO4- counter ions. The amine functions on the ligand release protons to form copper(I) complexes: (Cu2L)X-2, where X = Cl-, ClO4-. The complexes were oxidized to (Cu2L)X-4 with H2O2 in DMF; Cu(NO3)(2) gave a different complex, [Cu-2(H4L)(NO3)(2)](NO3)(2), as regards proton releasing ability, coordination and oxidation number. Evidence for the structures of this new tetraamino-tetrathioether ligand and its copper complexes is provided by H-1-, C-13-n.m.r., mass, u.v.-vis., i.r. spectra, elemental analyses, molar conductivities and magnetic moments.