Pressure-Induced Comproportionation in Palladium Trifluoride.

Despite its seeming simple stoichiometry, palladium trifluoride (PdF) is a mixed-valent system better formulated as PdPdF. In an attempt to verify whether the application of high pressure ( > 1 GPa) might force this compound to form a genuine palladium(III) fluoride (PdF), a joint theoretical and experimental study on its properties at large compression was performed. Indeed, hybrid density functional calculations predict the thermodynamic preference for single-valent (comproportionated) polymorphs at pressures exceeding 30 GPa. The ambient-pressure LiSbF-type polymorph of 3̅ symmetry was experimentally observed to transform into a triclinic 1̅ phase above 42 GPa. While this polymorph is still a mixed-valent compound PdPdF, another phase transition, commencing at ∼50 GPa, introduces a monoclinic 2/ phase containing genuine Pd centers. Both high-pressure polymorphs of palladium trifluoride exhibit novel structure types. Moreover, preliminary data suggest that the 2/ comproportionated structure might host strong one-dimensional antiferromagnetic exchange interactions.