| Abstract
| - The aluminophsophates A3Al2P3O12 (A = Na, K, Rb, Tl), synthesized by solid-state reactions, contain aluminum in exclusively trigonal bipyramidal or tetrahedral coordination. The three A3Al2P3O12 (A = K, Rb, Tl) compounds have been found, by single-crystal X-ray diffraction, to possess three-dimensional (Al2P3O12)3- frameworks with channels occupied by A+ ions, as illustrated below in the unit cell diagram of the rubidium compound.
- Four aluminophosphates, A3Al2P3O12 (A = Na, K (1), Rb (2), Tl (3)), have been synthesized by solid-state reactionsand characterized by X-ray diffraction and NMR and IR spectroscopic techniques. Aluminum has trigonalbipyramidal coordination in the thallium compound and tetrahedral coordination in the others. Potassium, rubidiumand thallium analogues have been structurally characterized by single-crystal X-ray diffraction and found to possessthree-dimensional (Al2P3O12)3- anionic frameworks with channels occupied by A+ countercations. Theseframeworks are built from corner connections of PO4 tetrahedra with AlO4 tetrahedra in 1 and 2 and with AlO5trigonal bipyramids in 3. Pertinent crystal data are as follows: for 1, orthorhombic space group Pna21, a =8.685(2) Å, b = 16.947(2) Å, c = 8.458(3) Å, Z = 4; for 2, orthorhombic space group Cmc21, a = 17.164(2) Å,b = 8.6270(6) Å, c = 8.8140(14) Å, Z = 4; for 3, orthorhombic space group Pna21, a = 6.1478(15) Å, b =10.396(3) Å, c = 17.787(5) Å, Z = 4. Compound 3 is a rare example of an oxide possessing aluminum exclusivelyin trigonal bipyramidal coordination.
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