Novel lanthanoid fluoroarsenates

A family of lanthanoid(III) hexafluoroarsenates(V), La (AsF6)(3), LnF(AsF6)(2), Ln = Ce-Er, and Ln(2)F(3)(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 Ln(2)O(3) were used as starting compounds in the AsF5/aHF superacid medium the oxonium compounds of the type (H3O)(x)Ln(y)F(z)(AsF6)(x+3y-z) were synthesized. The crystal structures of (H3O)(8)La2F(AsF6)(13), (H3O)(4)La2F(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. (C) 2000 Elsevier Science S.A. All rights reserved.