Synthesis, Structure, and Properties of Bismuth(III) Salts with Malonic Acid

The precipitation process of bismuth(III) from perchloric acid solutions upon the addition of malonic acid has been studied as a function of the molar ratio of malonate ions to bismuth in the system. A basic bismuth malonate with the composition BiOH(C₃H₂O₄) (compound I) was synthesized, along with two structurally distinct but compositionally identical bismuth malonates containing a water molecule: Bi(C₃H₂O₄)(C₃H₃O₄)H₂O (II) and [Bi(C₃H₂O₄)(C₃H₃O₄)]⋅H₂O (III). Compound I was obtained in an X‑ray amorphous form, whereas the crystal structures of compounds II and III were determined by X-ray diffraction. In compound II, the water molecule coordinates directly to the bismuth atom as a ligand, whereas in compound III this is not observed. Both compounds form one-dimensional (1D) coordination polymers. Upon calcination of compounds II and III at 120°C, anhydrous bismuth malonate with the composition Bi(C₃H₂O₄)(C₃H₃O₄) (IV) is produced via dehydration. All new compounds (I–IV) were characterized by IR spectroscopy, thermal analysis, and powder X-ray diffraction, and their compositions were confirmed by elemental analysis. The structural features of polymers II and III are discussed, including a topological analysis of the electron density in Bi–O contacts, allowing for the identification of primary and secondary bonds within the coordination polyhedra.