XeF${}_2$ coordination to La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Y in rare-earth metal(III) tetrafluoridoborates

Removal of volatiles at 243 K from solutions of completely dissolved LnF${}_3$ (Ln=La-Dy and Y) and XeF${}_2$ (molar ratio 1 : 3) in anhydrous HF acidified with an excess of BF${}_3$ resulted in [Ln (XeF${}_2$)${}_3$](BF${}_4$)${}_3$ salts. Isolated solids are stable at 298 K and give similar Raman spectra. [La(XeF${}_2$)${}_3$](BF${}_4$)${}_3$ crystallizes in the monoclinic space group C2/m at 150 K. Each La atom is coordinated with three XeF${}_2$ ligands. Six F atoms provided by six bridging BF${}_4$ units, that connect the neighboring La${}^{3+}$ atoms into columns, complete the nine-fold coordination of each La atom. Chemical reactions carried out in the same way but with molar ratio LnF${}_3$:XeF${}_2$ = 1:1 yielded [Ln (XeF${}_2$)](BF${}_4$)${}_3$ salts (La - Nd). Crystal structures of La and Nd salts are isotypic and crystallize in the monoclinic space group P2${}_1$/m at 150 K (La) and 200 K (Nd). Each Ln center is coordinated by nine fluorine atoms provided by eight BF${}_4$ units and one XeF${}_2$ ligand. The BF${}_4$ groups interconnect the Ln atoms into two-dimensional layers. With molar ratio LnF${}_3$:XeF${}_2$ = 1:2 and the same synthetic approach, only La yielded [La(XeF${}_2$)${}_2$](BF${}_4$)${}_3$ salt. Prolonged pumping of [Ln (XeF${}_2$)${}_n$](BF${}_4$)${}_3$ (n=3, 2, 1) at 298 K or attempts of the isolation at 298 K resulted in products with lower content of XeF${}_2$ or in mixtures of various products. In addition to [Ln (XeF${}_2$)](BF${}_4$)${}_3$ and LnF${}_3$/BF${}_3$ products, the [Ln (XeF${}_2$)]F(BF${}_4$)${}_2$ salts (Ln=La, Nd, Sm, Eu, Tb, Dy and Y) also formed. The crystal structures of LaF(HF)(BF${}_4$)${}_2$ and LaF (BF${}_4$)${}_2$ side products were determined. (© 2021 Wiley‐VCH GmbH)