Synthesis of 1,2,4,5‐Benzenetetrasulfonic Acid (H 4 B4S) and its Implementation as a Linker for Building Metal‐Organic Frameworks on the Example of [Cu 2 (B4S)(H 2 O) 8 ]·0.5H 2 O

Benzene 1,2,4,5‐tetrasulfonic acid (H 4 B4S) was prepared in two steps starting from 1,2,4,5‐Tetrachlorobenzene. Slow evaporation of an aqueous reaction mixture of H 4 B4S and Cu 2 (OH) 2 (CO 3 ) led to light green single crystals of [Cu 2 (B4S)(H 2 O) 8 ] · 0.5H 2 O. X‐ray single crystal investigations revealed the compound to be triclinic [ P $\bar{1}$ , 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 structure the Cu 2+ ions are coordinated by four water molecules and two monodentate sulfonate anions yielding a tetragonally distorted [CuO 6 ] octahedron. The anions are connected to further copper ions leading to ladder shaped chains running along the [100] direction. According to DTA/TG investigations the dehydration of the compound is finished at 240 °C and the decomposition of the anhydrous sulfonate starts at 340 °C.