Stability Trends for the Lanthanides on Dowex A-1 Chelating Resin

Distribution coefficients have been determined for a number of trivalent lanthanide ions on an ion exchange resin containing N-benzyliminodiacetic acid groups. At pH 2.00, μ=0.100 and 25.00°C. the relative stability trends for lanthanum through neodymium were found to be in agreement with trends previously observed with iminodiacetic acid N-methyliminodiacetic acid and N-benzyliminodiacetic acid. Beyond neodymium the distribution coefficient sequence of lanthanide-resin chelates is inverted. On the basis of the distribution coefficients, the inverted elution sequences previously reported in the literature for lanthanum and lutetium on the resin can be explained. A number of plausible explanations for the trends observed can be offered, among which are steric effects, changes in coordination number and electrostatic repulsive effects. Infrared spectral data indicate the existence of a zwitterionic lanthanide chelate species which may contribute to the latter effect

MÖSSBAUER SPECTROSCOPY OF KRYPTON COMPOUNDS

Les spectres Mössbauer de KrF2 et des composés α et β, KrF+AsF-6 et KrF+SbF-6, ont été obtenus à partir de la transition à 9,3 keV de l'isotope 83Kr obtenu à partir d'une source de 83RbF. Les valeurs de l'effet quadrupolaire et du déplacement isomérique indiquent que les liaisons Kr-F sont similaires dans tous les composés étudiés. Une legère augmentation de l'effet quadrupolaire dans la série KrF2, (α, β) KrF+AsF6, KrF+SbF-6 peut provenir d'une réduction de la longueur des liaisons Kr-F. On a obtenu une valeur très précise du rapport Qex/Qgr des moments quadrupolaires dans l'état excité 9,3 keV et l'état fondamental.Mössbauer spectra of KrF2 and the recently synthesized compounds α- and β-KrF+AsF-6 and KrF+SbF-6 have been measured using the 9.3 keV transition of 83Kr populated by the decay of an 83RbF source. The results for the quadrupole coupling and the isomer shifts indicate that the Kr-F bonding in all compounds studied is very similar. A slight increase of the quadrupole coupling in the sequence KrF2, (α-, β-) KrF+AsF-6, KrF+SbF-6 can be interpreted in terms of a shortening of the average Kr-F bond length. A very accurate value, Qex/Qgr = 1.958 0 ± 0.002 4 for the ratio of the quadrupole moments of the 9.3 keV state and the ground state has been derived from the measurements

Mössbauer spectroscopy of KrF2 and KrF2⋅MF5 (M=As, Sb)

Mössbauer spectra of KrF2 and the recently synthesized compounds α‐ and β‐ [KrF]+[AsF6]− and [KrF]+[SbF6]− have been measured using the 9.4 keV transition of 83Kr produced in the decay of an 83RbF source. The results for the values of quadrupole coupling strengths and the isomer shifts indicate that the Kr–F bonding in all compounds studied is very similar. A slight increase of the quadrupole coupling in going from KrF2 to F–Kr–F–MF5 can be interpreted in terms of a shortening of the average Kr–F bond length. A very accurate value, Qex/Qgr=1.958±0.002 for the ratio of the quadrupole moments of the 9.4 keV state and the ground state has also been derived from the measurements

Stable Chloro- and Bromoxenate Cage Anions; [X₃(XeO₃)₃]^3– and [X₄(XeO₃)₄]^4– (X = Cl or Br)

The number of isolable compounds which contain different noble-gas–element bonds is limited for xenon and even more so for krypton. Examples of Xe–Cl bonds are rare, and prior to this work, no Xe–Br bonded compound had been isolated in macroscopic quantities. The syntheses, isolation, and characterization of the first compounds to contain Xe–Br bonds and their chlorine analogues are described in the present work. The reactions of XeO₃ with [N­(CH₃)₄]Br and [N­(C₂H₅)₄]­Br have provided two bromo­xenate salts, [N­(C₂H₅)₄]₃[Br₃(XeO₃)₃] and [N(CH₃)₄]₄[Br₄(XeO₃)₄], in which the cage anions have Xe–Br bond lengths that range from 3.0838(3) to 3.3181(8) Å. The isostructural chloroxenate anions (Xe–Cl bond lengths, 2.9316(2) to 3.101(4) Å) were synthesized by analogy with their bromine analogues. The bromo- and chloroxenate salts are stable in the atmosphere at room temperature and were characterized in the solid state by Raman spectroscopy and low-temperature single-crystal X-ray diffraction, and in the gas phase by quantum-chemical calculations. They are the only known examples of cage anions that contain a noble-gas element. The Xe–Br and Xe–Cl bonds are very weakly covalent and can be viewed as σ-hole interactions, similar to those encountered in halogen bonding. However, the halogen atoms in these cases are valence electron lone pair donors, and the σ*_Xe–O orbitals are lone pair acceptors