Palladium Chemistry in Anhydrous HF/AsF 5 Superacid Medium

Pd metal dissolves in anhydrous HF (aHF) acidified with AsF 5 in the presence of F 2 at ≈298 K to give a blue‐green solution from which green Pd(AsF 6 ) 2 can be isolated. The latter was also prepared by the interaction of PdF 2 and AsF 5 in aHF or by the reaction between PdO and F 2 in aHF acidified with AsF 5 . Powdered Pd(AsF 6 ) 2 slowly loses AsF 5 in a dynamic vacuum. It can therefore be isolated from solution at T < 253 K. Single‐crystals of Pd(AsF 6 ) 2 were prepared by solvothermal synthesis from a Pd/AsF 5 /F 2 /aHF mixture at 393 K. Pd(AsF 6 ) 2 is triclinic with a = 500.9(5), b = 538.3(5), c = 864.9(9) pm, α = 74.46(3), β = 89.97(4), γ = 62.47(2)°, V = 0.1972(3) nm 3 , and Z = 1, space group P $\bar 1$ (No. 2). The six‐coordinate Pd atoms (coordinated with fluorine) are well separated by isolated AsF 6 units. In the 2−175 K temperature range Pd(AsF 6 ) 2 follows the Curie−Weiss law with μ eff = 3.53 B.M., T n = 8 K and θ p = −13 K. Because of cation‐anion interactions, the AsF 6 − anions deviate from ideal O h symmetry. The reduced symmetry can be seen in vibrational spectra, where splitting of the anion vibrational modes can be observed. The oxidation of Pd metal or PdO with F 2 in neutral aHF yielded Pd 2 F 6 . No reaction was observed between Pd, PdO or Pd 2 F 6 and AsF 5 in aHF. All attempts to prepare PdFAsF 6 were unsuccessful. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)