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metal-organic compounds
Potassium tartronate (potassium hydroxypropanedioate, 2K+.C3H2O52-), (I), crystallizes in the monoclinic P21/n space group, with Z = 4, and ammonium tartronate (ammonium hydroxypropanedioate, 2NH4+.C3H2O52-), (II), is orthorhombic, Pna21, Z = 4. There are two symmetry-independent cations in both (I) and (II). The coordination number of the K+ ion in (I) is seven, and the number of hydrogen bonds around the NH4+ ion in (II) is four. This difference arises from the fact that the hydrogen bonding governs the number of O atoms around NH4+ in (II), in contrast to the electrostatic interactions in (I).