Electric Deflection of Molecular Beams of the Lanthanide Di- and Trifluorides, ScF3 and YF3

Abstract

Electric-deflection studies on molecular beams of the lanthanide trifluorides have been carried out in the temperature range 1000–1200°C. Substantial refocussing, indicative of polar distortions, has been observed for LaF3, GdF3, and LuF3. Weaker refocussing was present in TmF3. CeF3 and ErF3 showed refocussing barely above the noise level. Defocussing was observed in PrF3, NdF3, TbF3, DyF3, and HoF3. Observations on SmF3, EuF3, and YbF3 were inconclusive due to sample reduction in the oven but showed no refocussing attributable to the respective trifluorides. ScF3 and YF3 showed refocussing of a magnitude similar to the trifluorides of La, Gd, and Lu. Deflection studies on the three known lanthanide difluorides revealed that SmF2, EuF2, and YbF2 are strongly polar molecules in the vapor phase and must, therefore, have highly bent structures.

Inorganic Compounds

“…The thermodynamic functions of the gaseous ScX, ScX 2 and ScX 3 molecules, where X = F, Cl, Br and I, were calculated by Krasnov and Danilova (1969) from 298-15-3000°K. Electron deflection studies by Kaiser et al (1972) on ScF 3 (g) indicate that it is very similar to gaseous LaF 3 and YF 3 and probably has a D 2h symmetry.…”

Molecular Structure of Metal Halides

“…There is conflicting information in the literature about the shape of these molecules, just as for the transition metal dihalides. ScF 3 was found to be pyramidal by molecular beam deflection, 352 planar by matrix isolation IR, 353 and also planar by quantum chemical calculations. [354][355][356] Chromium trifluoride is planar according to ESR, 357,252b IR, and Raman spectroscopy 255 and a recent quantum chemical calculation, 358 while it is pyramidal by other quantum chemical studies.…”

“…359 Most other trihalides are found to be planar, either by spectroscopy or by computation, except YF 3 , which is found to be pyramidal by molecular beam deflection. 352 YCl 3 was reported to be pyramidal by gas-phase IR spectroscopy 360 but planar by computation 361 and by a joint ED/computational study. 362 The computed infrared intensities point to a problem in the deconvolution used for the interpretation of the broad lines in the vapor-phase spectra.…”

How an Inert‐Gas Matrix Can Modify the Molecular Properties of Lanthanide Trifluoride

“…[10,11,12,13,14,15] All calculations so far reported agree in predicting a pyramidal equilibrium structure for the isolated LnF 3 molecules with a very shallow minimum, in agreement with most of the molecularbeam electric deflection data. [16] Recently, we showed that for the LnF 3 ·IG and LnF 3 ·IG 2 (IG = Ne, Ar, Kr, Xe and N 2 ) model complexes, LnF 3 -IG interactions are strong, and a possible LnF 3 planar structure may be found in contrast to the results on isolated molecules. [17,18] Herein, LaF 3 ·Ar n (n = 1-21) van der Waals complexes are proposed as models to account for the argon-matrix effects on the molecular properties of the LaF 3 molecule trapped in solid matrices at cryogenic temperatures.…”

“…Analogously to group A, the La-Ar eq distances are longer, and the Ar-Ar interactions become the main stabilizing effect. After that, three argon atoms locate on both sides of the LaF 3 molecule with the formation of the LaF 3 ·Ar 16 and LaF 3 ·Ar 19 complexes.…”