Synthesis, Crystal Structures, and Properties of Novel Lamellar Gallium Methylenediphosphonates

Three new gallium methylenediphosphonates: (C5H 5NH)[Ga2(H2O)2(O3PCH 2PO3)(O3PCH2PO3H)] (1) (monoclinic, P21/c, a = 11.0848(2) Å, b = 8.4441(2) Å, c = 9.4419(1) Å, β = 104.537(1)°, Z = 2), [(CH3) 4N][Ga2(H2O)2(O3PCH 2PO3)(O3PCH2PO3H)] (2) (monoclinic, C2/c, a = 22.1628(8) Å, b = 8.5724(2) Å, c = 9.4455(2) Å, β = 95.486(3)°, Z = 4), and (C5H 5NH)[Ga(H2O)(O3PCH2PO3)] (3) (monoclinic, P21/a, a = 9.5721(7) Å, b = 8.6140(6) Å, c = 12.894(1) Å, β = 99.961(3)°, Z = 4) have been synthesized by solvothermal methods in the presence of organocations, and their structures were determined using powder (1 and 2) and single-crystal X-ray diffraction data (3). All three materials contain a novel corrugated [Ga(H 2O)(O3PCH2PO3)]- layer motif composed of octahedral GaO5(OH2) units that are linked together by the diphosphonate groups. One of the oxygen atoms of each diphosphonate group protrudes into the interlamellar region where it hydrogen bonds to adjacent layers in 1 and 2 to form hydrogen-bonded framework structures, or to the pyridinium cations in the lamellar material 3. The stacking arrangement of the layers in 1 and 2 is shown to be dependent on the organocations present during the synthesis, and to form materials with one- or two-types of hydrogen-bonded channels, respectively. Material 3 is an intermediate phase isolatable during formation of 1 and is convertible to the type of hydrogen-bonded framework of 1 by solvothermal, thermal, or solution ion-exchange methods.