New Pillared Layered Gallium Phosphonates in the Gallium/1,2-Ethylenediphosphonic Acid System

1,2-Ethylenediphosphonic acid reacts with gallium nitrate in water to give new pillared layered gallium
phosphonates, the structure of which depends on the experimental conditions used for their preparation. Thus,
Ga4(O3PC2H4PO3)3 (1) and Ga2(OH)2(O3PC2H4PO3) (2) were isolated and the structure of 1 was solved by single-crystal X-ray diffraction, while 2 was shown to have the same metal/PO3 arrangement as the previously described
Ga(OH)(O3PCH3). Ga4(O3PC2H4PO3)3 (1) is triclinic, with space group P1̄ with Z = 2, a = 5.1480(4), b =
8.0354(7), and c = 12.383(1) Å; α = 91.34(1), β = 101.40(1), and γ = 90.86(1)°; V = 501.9(1) Å3. The structure
of 1 is unusual with (i) mixed GaO4 and GaO5 sites while a 6-fold coordination is observed for gallium in (2) and
(ii) the presence of the organic moiety within both the layers and the interlayer space. The two compounds were
fully characterized using 31P and 71Ga solid-state NMR.