New Zirconium Phosphate Fluorides: Hydrothermal Synthesis and Crystal Structures

✍ Scribed by M. Wloka; S.I. Troyanov; E. Kemnitz

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 522 KB
• Volume: 135
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7639

✦ Synopsis

A series of zirconium phosphate fluorides were synthesized and structurally characterized using different amines as templates. The compounds have the general formulas [amH n ] 1/n [Zr 2 (HPO 4 )(PO 4 ) 2 F] • H 2 O (1, am ‫؍‬ ethylenediamine, n ‫؍‬ 2; 2. am ‫؍‬ N-methylethylenediamine, n ‫؍‬ 2; 3, am ‫؍‬ 1,3-diaminopropane, n ‫؍‬ 2; 4, am ‫؍‬ diethylenetriamine, n ‫؍‬ 3) and [amH 2 ] 0.5 [Zr 2 (HPO 4 ) 2 (PO 4 )F 2 ] • 0.5H 2 O (5, am ‫؍‬ N,N,N,Ntetramethylethylenediamine). In the structures of 2-4 with a Zr:F ratio of 2 : 1, there exists a three-dimensional arrangement of zirconium octahedra (one ZrO 6 and one ZrO 5 F) and phosphate tetrahedra (two PO 4 and one HPO 4 ) connected via common oxygen atoms, whereas fluorine atoms and OH groups are terminal. These compounds crystallize in the ''ZrPO-1'' structure type, which contains channels along the b axis formed by eight-membered rings of alternating PO 4 tetrahedra and ZrO 6 or ZrO 5 F octahedra, respectively. The protonated disordered templates occupy the channels. Half the water molecules are situated in the positions alternatively left free by the disordered templates and the other half are bonded via hydrogen bridges to the terminal OH groups of the HPO 4 tetrahedra. In contrast, the structure of 5 reveals a Zr : F ratio of 1 : 1, consequently forming a layer structure. The layers formed by ZrO 5 F octahedra and PO 4 or HPO 4 tetrahedra, respectively, are linked by hydrogen bridges of type O-H2F and by weak H bonds over the protonated template. The similarities in connectivity pattern between Zr octahedra and P tetrahedra in all known zirconium phosphate fluorides and some zirconium phosphates are discussed.