A tetradentate Schiff-base ligand, N,N′-bis-(4-chlorobenzylidene)-1,2-bis(2-aminophenylthio)ethane, L, and its copper(I) coordination polymers, [Cu 2 (μ-I) 2 -μ-L] n ·2n(CH 3 CN), LCuIS, and [Cu 2 (μ-Cl) 2 -μ-L] n , were prepared. The products were characterized via their analytical and spectral properties. The crystal structures of the ligand molecule, L, and the complex, LCuIS, were determined by single-crystal X-ray diffraction methods. In both the free molecule and the complex, L adopts an anti, staggered, extended conformation. In LCuIS, prepared from L and CuI in acetonitrile, each Cu atom has a distorted tetrahedral coordination sphere composed of a nitrogen atom and a sulfur atom from L and two iodine ligands. LCuIS is a sheet polymer, formed from coordination polymer chains containing the dimetal clusters Cu 2 (μ-I) 2 ; the chains are crosslinked through π⋯π interactions of phenyl rings.