Palladium Compounds with +III Oxidation State

Trivalent oxidation state of palladium has been unambiguously characterized in elpasolites of A 2 BPdF 6 formulation (A, B = alkali metal). At room temperature K 2 LiPdF 6 is cubic (Fm3m space group, a = 8.154 Å) while all other A 2 BPdF 6 compounds possess a tetragonal F4/mmm symmetry with c/a > 1. Phase transitions in Pd elpasolites have been followed using low‐and hightemperature X‐ray diffraction. Between 200 and 500 K every A 2 BPdF 6 compound undergoes a tetragonal ⇄ cubic phase transition. The ESR signals are characteristic of a doublet ground state; they bring up the unequivocal evidence of a t   2g 6 e   g 1configuration of Pd(+III). This configuration is stabilized versus the t   2g 5 e   g 2high ‐spin alternative by an important Jahn‐Teller splitting of the 2 E g ‐state. ESR results confirm that the PdF 6 octahedra are tetragonally elongated in most cases; an additional orthorhombic component is found for Cs 2 KPdF 6 and Cs 2 RbPdF 6 . The occurence of Pd(+III) in a low‐spin state is corroborated by magnetic measurements.