Synthesis and characterization of 2-phosphonoethanesulfonic acid and a barium-hydrogenphosphonatoethanesulfonate — BaH(O3P–C2H4–SO3)

Following the strategy of using polyfunctional phosphonic acids for the synthesis of new metal phosphonates, the organic linker molecule 2-phosphonoethanesulfonic acid, H2O3P–C2H4–SO3H (1) (H3L), was synthesized and characterized in detail. The acid was used in a high-throughput (HT) investigation of the system BaCl2/H3L/NaOH/H2O. The HT experiments comprising 48 individual hydrothermal reactions were performed to systematically investigate the influence of pH of the starting mixture as well as the molar ratio Ba2+: H3L. Only two reaction products were observed: small amounts of BaCO3 under basic conditions and BaH(O3P–C2H4–SO3) (2). For compounds 1 and 2 the crystal structures were determined from single-crystal X-ray diffraction data (H2O3P–C2H4–SO3H: trigonal, P32, a=814.58(1), c=861.20(2) pm, Z=3, R1=0.0254, wR2=0.0758 for I>2σ(I); BaH(O3P–C2H4–SO3): orthorhombic, Ibam, a=953.39(19), b=855.55(17), c=867.82(17) pm, Z=4, R1=0.0162, wR2=0.0417 for I>2σ(I)). The structure of H3L (1) is stabilized exclusively by strong hydrogen bonds. Compound 2 is built up by chains of edge sharing BaO8 polyhedra. These chains are connected to a three-dimensional network by the –CH2CH2– linker of the ligand. Thermogravimetric investigation of compound 2, as well as IR spectra of 1 and 2 are presented.