Novel lanthanoid fluoroarsenates

A family of lanthanoid(III) hexafluoroarsenates(V), La (AsF6)3, LnF(AsF6)2, Ln = Ce–Er, and Ln2F3(AsF6)3, Ln = Tm, Yb, Lu, has been stabilized with some fluoro bases as additional ligands forming new compounds: La(HF)2(AsF6)3, La(XeF2)2.5(AsF6)3 and Ln(AsF3)3(AsF6)3, Ln = Ce, Pr. La(HF)2 (AsF6)3 was prepared by solvothermal reaction in AsF5 above its critical temperature, while syntheses of other compounds were carried out in anhydrous hydrogen fluoride (aHF) as a solvent at ambient temperature. When Ln2O3 were used as starting compounds in the AsF5/aHF superacid medium the oxonium compounds of the type (H3O)xLnyFz(AsF6)x+3y−z were synthesized. The crystal structures of (H3O)8La2F(AsF6)13, (H3O)4La2F(AsF3)2(AsF6)9, La(HF)2(AsF6)3 and La(XeF2)2.5(AsF6)3 exhibit low-dimensional structural features, while the structure of Ln(AsF3)3(AsF6)3 (Ln = Ce, Pr) shows a three-dimensional network. In the structure of La(HF)2(AsF6)3 bonding interaction between HF and a metal centre is described for the first time.