Novel lanthanoid fluoroarsenates

Abstract A family of lanthanoid(III) hexafluoroarsenates(V), La (AsF 6 ) 3 , LnF(AsF 6 ) 2 , Ln = Ce–Er, and Ln 2 F 3 (AsF 6 ) 3 , Ln = Tm, Yb, Lu, has been stabilized with some fluoro bases as additional ligands forming new compounds: La(HF) 2 (AsF 6 ) 3 , La(XeF 2 ) 2.5 (AsF 6 ) 3 and Ln(AsF 3 ) 3 (AsF 6 ) 3 , Ln = Ce, Pr. La(HF) 2 (AsF 6 ) 3 was prepared by solvothermal reaction in AsF 5 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 AsF 5 /aHF superacid medium the oxonium compounds of the type (H 3 O) x Ln y F z (AsF 6 ) x +3 y − z were synthesized. The crystal structures of (H 3 O) 8 La 2 F(AsF 6 ) 13 , (H 3 O) 4 La 2 F(AsF 3 ) 2 (AsF 6 ) 9 , La(HF) 2 (AsF 6 ) 3 and La(XeF 2 ) 2.5 (AsF 6 ) 3 exhibit low-dimensional structural features, while the structure of Ln(AsF 3 ) 3 (AsF 6 ) 3 (Ln = Ce, Pr) shows a three-dimensional network. In the structure of La(HF) 2 (AsF 6 ) 3 bonding interaction between HF and a metal centre is described for the first time.