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.