ChemInform Abstract: Synthesis and Crystal Structure of the Fluorophosphate Na3Cr2(PO4)2F3.

Abstract

ChemInform Abstract The new title compound is obtained from a melt in the system Na2O-P2O5-Cr2O3-NaF at 950 rc C. It crystallizes in the tetragonal space group I4/mmm with Z=2. The structure consists of slightly distorted CrO4F2 octahedra. The oxygen atoms, which belong to neighboring PO4 tetrahedra, are in the equatorial plane of the octahedra, whose apices are occupied by fluorine atoms. Two of these octahedra are connected via common corners to form centrosymmetrical "dimers". The sodium atoms are statistically distributed in the cavities of the lattice.

NaCo7.38(PO4)4Cl4 in a series of homeotype compounds with stable cationic substructures derived from the sulphohalite archetype

“…Similar transformations can be noticed in isostructural fluoride phosphates Na 3 Cr 2 (PO 4 ) 2 F 3 , 26 Na 3 Al 2 (PO 4 ) 2 F 3 , 27 and Na 3 V 4+ 2 (PO 4 ) 2 O 2 F. 17 However, the last one differs due to the formation of vanadyl( iv ) bonds and consequent strong distortion of VO 5 F octahedra (Table 4). Let us emphasize that symmetrical relations between sulphohalite on one hand, and first row transition metal phosphates Na 3 M 2 (PO 4 ) 2 (F,O) 3 (M = Fe, Cr, Al, V) on the other, are connected by the subordination of the group–subgroup type.…”