Na 3 B 3 O 3 F 6 : Synthesis, Crystal Structure, and Ionic Conductivity

Crystalline Na 3 B 3 O 3 F 6 was synthesized from H 3 BO 3 and NaBF 4 at 623 K, alternatively NaBO 2 can be reacted with NaBF 4 at 673 K. The title compound ( C 2/ c , a = 11.866(7), b = 6.901(4), c = 9.367(6) Å, β = 113.724(9)°) contains the cyclo‐fluorooxotriborate anion B 3 O 3 F 6 3– , which displays a planar B 3 O 3 ring. Within the margins of experimental error, its point group symmetry is D 3 h . Layers of fluorinated boroxine rings and sodium atoms are stacked in an alternating manner in parallel to the ab plane. The novel sodium fluorooxoborate is a poor sodium ion conductor with conductivities of 8.7 × 10 –5 and 3.6 × 10 –3 S · cm –1 at 523 and 623 K, respectively.