| Abstract
| - The reactions of AlCl3·6H2O and GaCl3 with 2-pyridylphosphonic acid (2PypoH2) and 4-pyridylphosphonic acid (4PypoH2) afford cyclic aluminum and gallium phosphonate structures of [(2PypoH)4Al4(OH2)12]Cl8·6H2O (1), [(4PypoH)4Al4(OH2)12]Cl8·11H2O (2), [(2PypoH)4Al4(OH2)12](NO3)8·7H2O (3), [(2PypoH)2(2Pypo)4Ga8Cl12(OH2)4(thf)2](GaCl4)2··8thf (4), and [(2PypoH)2(2Pypo)4Ga8Cl12(OH2)4(thf)2](NO3)2·9thf (5). Structures 1−3 feature four aluminum atoms bridged by oxygen atoms from the phosphonate moiety and show structural resemblance to the secondary building units found in zeolites and aluminum phosphates. The gallium complexes, 4 and 5, have eight gallium atoms bridged by phosphonate moieties with two GaCl4− counterions present in 4 and nitrate ions in 5. The cage structures 1−3 are interlinked by strong hydrogen bonds, forming polymeric chains that, for aluminum, are thermally robust. Exchange of the phosphonic acid for the more flexible 4PyCH2PO3H2 afforded a coordination polymer with a 1:1 Ga:P ratio, {[(4PyCH2PO3H)Ga(OH2)3](NO3)2·0.5H2O}x (6). Complexes 1−6 were characterized by single-crystal X-ray diffraction, NMR, and mass spectrometry and studied by TGA.
- The reactions of aluminum(III) chloride or nitrate with 2- and 4-pyridylphosphonic acids under mild aqueous conditions afforded a series of alumino phosphonate cages that were characterized by single-crystal X-ray analysis. The cyclic aluminum structures feature four Al atoms bridged by oxygen atoms from the phosphonate moiety and show structural resemblance to the secondary building units found in zeolites and aluminum phosphates. The reaction of gallium(III) chloride with 2-pyridylphosphonic acid yielded cationic gallium phosphonate cages, with eight gallium atoms in the cluster core supported by six pyridylphosphonate ligands, two of which are protonated at the pyridyl nitrogen. Exchange of the phosphonic acid for the more flexible 4PyCH2PO3H2 afforded a coordination polymer with a Ga:P ratio of 1:1.
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