A new high-pressure polymorph of K 2 MoO 2 F 4 .

In this paper, a new high-pressure (HP) polymorph of the otherwise known oxyfluoride K 2 MoO 2 F 4 is presented. The crystal structure was determined by use of single-crystal X-ray diffractometry and its features are described in detail herein. HP-K 2 MoO 2 F 4 crystallizes in the monoclinic space group C 2/ m (no. 12) with the cell parameters a = 13.8579(5), b = 5.8109(2), c = 6.9442(3) Å, β = 90.36(1)°, V = 559.18(4) Å 3 , and Z = 4 at T = 301(2) K. Bond valence (BV) and charge distribution (CHARDI) calculations were carried out to support the assignment of oxygen and fluorine to the various anion positions and Madelung part of lattice energy (MAPLE) calculations were used to validate the structure model. Infrared spectroscopy provided further information on the structure and water content of the inseparable side phase.