Rare earths(III) fluorides as donors of F− in the presence of superacids

Synthesis and Characterization of LnF(HF)(BF4)2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy), and Crystal Structures of LnF(HF)(BF4)2 (Ln = Pr, Nd) and La(BF4)3

“…The evaporation of the solvent from these solutions was carried out by maintaining a temperature gradient corresponding to about less then 10 K between both tubes for 4-5 months. The effect of this treatment was to enable aHF and the excess of BF 3 to be slowly evaporated from a narrower into a wider tube leaving colorless crystals of La(BF 4 ) 3 and green crystals of PrF(HF)(BF 4 ) 2 . Single violet crystals of NdF(HF)(BF 4 ) 2 were grown from the solution, obtained by reacting of Nd 2 O 3 with BF 3 in aHF and slowly evaporated for 3 months.…”

“…Single crystals were immersed in perfluorinated oil (ABCR, FO5960) in the dry-box, selected under the microscope and afterwards transferred into the cold nitrogen stream of the diffractometer. Some crystals of LnF(HF)(BF 4 ) 2 (Ln = Pr, Nd) and La(BF 4 ) 3 were selected in the dry-box and placed inside 0.3 mm quartz capillaries and heat-sealed. Raman spectra could be obtained only for La(BF 4 ) 3 .…”

“…Structure drawings were generated by Balls & Sticks, freely available software [13]. X-ray crystallographic files in CIF format have been sent to Fach- 3 ], and can be obtained by contacting FIZ (quoting the article details and corresponding SUP number). Crystal and structure refinement data are given in Table 2.…”

“…On the contrary, other authors [2] claimed for better solubility of praseodymium(III) and neodymium(III) fluoroborates and electronic spectra of solutions containing these rare earth ions were measured. The preparation of solid LnF 3 ·nBF 3 was reported first in 1991 and later in 1995 [3,4]. Although the extensive research of LnF 3 /BF 3 /aHF system has been done by different investigators [5][6][7], the proper composition of isolated products stayed unknown.…”

“…The preparation of single crystals and structure determination of LnF(HF)(BF 4 ) 2 (Ln = Pr, Nd) provided the key infor-ces are significantly shorter [2.2489(6) Å for Pr and 2.234(1) Å for Nd] than Ln-F(BF 4 -) and Ln-F(HF) ones [Pr: 2.461(4)-2.528(5) Å, Nd : 2.446(7)-2.511(9) Å]. In La(BF 4 ) 3 , the lanthanum atoms are coordinated by nine fluorine atoms with seven shorter La-F distances [2.410(2)-2.485(2) Å] and two elongated ones [2.600(2) Å]. The vibrational spectra of isolated rare earth tetrafluoroborates show strong deviations of the [BF 4 ]anions from ideal T d symmetry.…”