Benzene 1,2,4,5-tetrasulfonic acid (H4B4S) was prepared in two steps starting from 1,2,4,5-Te¬tra¬chlorobenzene. Slow evaporation of an aqueous reaction mixture of H4B4S and Cu2(OH)2(CO3) led to light green single crystals of [Cu2(B4S)(H2O)8] • 0.5 H2O. X-ray single crystal investi¬ga¬tions revealed the compound to be triclinic [P-1, Z = 1, a = 710.0(1), b = 713.7(1), c = 1077.1(2) pm, α = 98.41(2)°, β = 102.91(2)°, γ = 100.69(2)°]. In the crystal struc-ture the Cu2+ ions are coordinated by four water molecules and two monodentate sulfo¬na¬te anions yielding a tetragonally distorted [CuO6] octahedron. The anions are connected to fur-ther copper ions leading to ladder shaped chains running along the [110] direction. Accor¬ding to DTA/TG investi¬gations the dehydration of the compound is finished at 240°C and the de-com¬position of the anhydrous sulfonate starts at 340°C.