J . Am. Chem. SOC.1987, 109, 3157-3158
Comparison of Reactivity Based on Intercalation and Host Lattice Reconstruction. Two Routes for the Conversion of the Lamellar Solid Hydrogen Uranyl Phosphate to a Lamellar Hydrate of Uranyl Phosphate Guy L. Rosenthal and Arthur B. Ellis* Department of Chemistry University of Wisconsin-Madison Madison, Wisconsin 53706 Received November 28, 1986 The solid-state structural changes accompanying intercalation can be profound and have been used to analyze interactions of guest species with host lattices.' We and others have studied hydrogen uranyl phosphate (HUP), HU02P04,and demonstrated that the lamellar solid readily undergoes intercalative ion-exchange reactions, eq 1.2-6 Typically, the protons residing between the
(l/n)M"+
-
+ HU02P04
+
MIInUO2PO4 Hf
(1)
(U02P04),"- sheets can be exchanged simply by slurrying the H U P powder in an aqueous solution containing the ion to be intercalated. It occurred to us that use of U02'+ as the intercalant in eq 1 would lead to formation of uranyl phosphate (UP), (UO,),(PO&. Furthermore, the report' that UP can be prepared from an aqueous H U P slurry by thermal decomposition, eq 2, provided us with a 3 H U 0 2 P 0 4 H 3 P 0 4 + (U02)3(P04)2 (2) novel opportunity to compare two pathways to the same product. We report herein that H U P can be quantitatively converted by intercalation (eq 1) or host lattice reconstruction (eq 2) to a common lamellar hydrate of UP; both reactions are reversible at room temperature. Moreover, an Arrhenius treatment of calculated rates for the forward reactions supports the notion that they proceed by quite different mechanisms. Intercalation was typically effected by slurrying 300 mg of HUP powder' in 20 mL of a 0.5 M aqueous solution of UO2(NO3),6 H 2 0 for several hours. Elemental analysis is consistent with a formula of (U02)3(P04)243H,0.8a A Debye-Scherrer X-ray powder diffraction pattern4i9of the poorly crystalline solid is dominated by a phase that closely matches that previously reported for (U02)3(P04)2.8H20.10 Although we have been unable to obtain single crystals of the intercalated solid, its structure can be inferred from its synthesis by ion exchange and its X-ray data, which can be indexed on the basis of a tetragonal cell with a = 6.93 A, comparable to its value in HUP, and c = 1 1.I A, expanded from an interlamellar spacing of 8.69 A in HUP.' These results imply that (U02)3(P04)2.8H20,
-
*Author to whom correspondence should be addressed. (1) Intercalation Chemistry; Whittingham, M. S., Jacobson, A. J., Eds.; Academic Press: New York, 1982. (2) Olken, M. M.; Biagioni, R. N.; Ellis, A. B. Inorg. Chem. 1983, 22, 4128. (3) Olken, M. M.; Ellis, A. B. J. A m . Chem. SOC.1984, 106, 7468. (4) Olken, M. M.; Verschoor, C. M.; Ellis, A. B. Inorg. Chem. 1986, 25, 80. (5) Pozas-Tormo, R.; Moreno-Real, L.; Martinez-Lara, M.; Bruque-Gamez, S . Can. J. Chem. 1986, 64, 30. (6) Pozas-Tormo, R.; Moreno-Real, L.; Martinez-Lara, M.; RodriguezCastellon, E. Can. J. Chem. 1986, 64, 35. (7) Weigel, F.; Hoffman, G. J. Less-Common Mer. 1976, 44, 99. Our powders were hand-ground with an agate mortar and pestle immediately before use. The mean particle size of the resulting powder was typically 2.5 pm, as determined by quasi-elastic light scattering, as described in: Yu, H . J . Res. NBS 1981, 86, 571. (8) (a) Anal. (Galbraith) Calcd for Hi6022P2U3:H, 1.40; P, 5.42; U, 62.41. Found: H, 1.40 P, 5.37; U, 61.80. IR (Nujol) 1625 (m) (H20), 1165 (s) (Po43-), 1060 (vs) (PO:-), 980 (m) (P043-),930 (vs) (U022'), 850 (m) (U022'). (b) Anal. Calcd (see above). Found: H, 1.45; P, 5.33; U, 61.99. (9) X-ray powder diffraction reflections: d (A) = 11.09 (s), 6.86 (m), 5.56 (m), 4.59 (s), 3.71 (m), 3.28 (s), 2.96 (s), 2.17 (w), 2.07 (w), 1.40 (m), 1.18 (ms), 1.13 (ms). A weak, broad line also appears at d = 4.21 A, indicating the presence of a small amount (
