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–)n aggregates, established that these clusters display unique topologies and hydrogen-bonding connectivities.