Dihydrogen Phosphate Clusters: Trapping H₂PO₄^– Tetramers and Hexamers in Urea-Functionalized Molecular Crystals

Co-crystallization of two urea-functionalized ligands with tetrabutylammonium (TBA) dihydrogen phosphate resulted in the isolation of discrete (H₂PO₄^–)₄ and (H₂PO₄^–)₆ clusters stabilized in the crystalline state by multiple urea hydrogen bonds. Structural analysis by single-crystal X-ray diffraction, combined with a Cambridge Structural Database survey of (H₂PO₄^–)_<i>n</i> aggregates, established that these clusters display unique topologies and hydrogen-bonding connectivities