Synthesis and Crystal Structure of a New Potassium−Gadolinium Cyclotetraphosphate, KGdP₄O₁₂

The chemical preparation, crystal structure, and infrared absorption spectrum are given for a new cyclotetraphosphate, KGdP 4 O 12 . X-ray investigations showed that the newly synthesized compound crystallizes in a monoclinic structure, space group C 2/ c with the following unit-cell dimensions: a = 7.875(1), b = 12.431(2), c = 10.537(2) Å, β = 110.94(1)°, V = 963.4(3) Å 3, Z = 4, and ρ = 3.532 g cm -3 . The structure was solved from 1390 independent reflections with R 1 = 2.99 and WR 2 = 7.37%, refined with 84 parameters. As in all atomic arrangements, we observe the formation of an infinite network of P 4 O 12 4- cyclotetraphosphate anions connected with GdO 8 polyhedra to form a three-dimensional framework which delimits interesting tunnels where the K + cations are located. In this structure, the P 4 O 12 ring develops around an inversion center. The reported IR study, recorded at room temperature in the frequency range 400−4000 cm -1, shows some characteristics bands of cyclotetraphosphates.