Synthesis and Structural Characterization of 1,2-Benzenedisulfonate Complexes of the Heavy Group 2 Elements

Reaction of the commercially available potassium 1,2-benzenedisulfonate (K2L) with calcium chloride, strontium nitrate, and barium chloride in aqueous solution yielded [Ca2L2(H2O)4], [Sr4L4(H2O)8]·1.5H2O and [Ba2L2(H2O)5]·H2O in a form suitable for single-crystal X-ray determination. From one preparation of the calcium complex a few crystals of [K2CaL2(H2O)3]·0.5H2O were obtained but were not representative of the bulk product. From reaction of CaCO3 with H2L and recrystallization from aqueous ethanol, crystals of [Ca2L2(H2O)6]·EtOH deposited. All complexes are coordination polymers with metal atoms being bridged and chelated by 1,2-benzenedisulfonate groups, which show an enormous variety of coordination modes, and coordinated by water molecules, some of which are bridging. Calcium has an eight-coordinate ion in all compounds, potassium six-coordinate in the bimetallic complex; the strontium complex has eight- and nine-coordinate strontium atoms and the barium complex nine- and eleven-coordinate barium atoms.