Synthesis and Crystal Structures of Lanthanoid(III) Hexafluoroarsenates with AsF3 Ligands

Abstract

Lanthanoid(III) hexafluoroarsenates with AsF3 as a ligand were prepared with the reactions of solutions of Ln(AsF6)3 in anhydrous hydrogen fluoride and AsF3. Solid products with composition Ln(AsF3)3(AsF6)3 (Ln = La, Nd, Sm, Eu, Gd, Tb, Er, Tm) were isolated at 233 K. The attempt to prepare corresponding Yb and Lu compounds failed. Single crystals of Ln(AsF3)3(AsF6)3 (Ln = Ce, Pr) were prepared by the reaction of LnF3 (Ln = Ce, Pr) with AsF5 and aHF under solvothermal conditions above critical temperature of AsF5. During the crystallization the reduction of some AsF5 occurred and AsF3 was formed. Compounds crystallize in a hexagonal crystal system, space group P 6– 2c (a = 10.6656(7) Ĺ (Ce); 10.6383(7) Ĺ (Pr); c = 10.9113(9) Ĺ (Ce), 10.878(2) Ĺ (Pr); V = 1074.9(1) Ĺ3 (Ce), 1066.2(2) Ĺ3 (Pr); Z = 2). Ln atoms are coordinated by nine fluorine atoms in the shape of the tri-capped trigonal prism and are further connected in threedimensional framework via trans bridging AsF6 units. Three fluorine atoms are provided by AsF3 (capped positions) and six by AsF6 units. X-ray powder analysis of Ln(AsF3)3(AsF6)3 (Ln = La, Nd, Sm, Eu, Gd, Tb, Er, Tm) show that they are isostructural with corresponding Ce and Pr compounds.