62462-55-9Relevant academic research and scientific papers
Temperature dependent rate constants for the reactions of gas phase lanthanides with N2O
Campbell, Mark L.
, p. 562 - 566 (2007/10/03)
The reactivity of gas phase lanthanide (Ln) atoms (Ln=La-Yb with the exception of Pm) with N2O from 298 to 623 K is reported. Lanthanide atoms were produced by the photodissociation of Ln(TMHD)3 (TMHD=2,2,6,6-tetramethyl-3,5-heptanat
Temperature-Dependent Rate Constants for the Reactions of Gas-Phase Lanthanides with O2
Campbell, Mark L.
, p. 7274 - 7279 (2007/10/03)
The reactivity of the gas-phase lanthanide atoms Ln (Ln = La-Yb with the exception of Pm) with O2 is reported. Lanthanide atoms were produced by the photodissociation of [Ln(TMHD)3] and detected by laser-induced fluorescence. For all the lanthanides studied with the exception of Yb, the reaction mechanism is bimolecular abstraction of an oxygen atom. The bimolecular rate constants (in molecule-1 cm3 s-1) are described in Arrhenius form by k[Ce(1G4)] = (3.0 ± 0.4) × 10-10 exp(-3.4 ± 1.3 kJ mol-1/RT); Pr(4I9/2), (3.1 ± 0.7) × 10-10 exp(-5.3 ± 1.5 kJ mol-1/RT); Nd(5I4), (3.6 ± 0.3) × 10-10 exp(-6.2 ± 0.4 kJ mol-1/RT); Sm(7F0), (2.4 ± 0.4) × 10-10 exp(-6.2 ± 1.5 kJ mol-1/RT); Eu(8S7/2), (1.7 ± 0.3) × 10-10 exp(-9.6 ± 0.7 kJ mol-1/RT); Gd(9D2), (2.7 ± 0.3) × 10-10 exp(-5.2 ± 0.8 kJ mol-1/RT); Tb(6H15/2), (3.5 ± 0.6) × 10-10 exp(-7.2 ± 0.8 kJ mol-1/RT); Dy(5I8), (2.8 ± 0.6) × 10-10 exp(-9.1 ± 0.9 kJ mol-1/RT); Ho(4I15/2), (2.4 ± 0.4) × 10-10 exp(-9.4 ± 0.8 kJ mol-1/RT); Er(3H6), (3.0 ± 0.8) × 10-10 exp(-10.6 ± 1.1 kJ mol-1/RT); Tm(2F7/2), (2.9 ± 0.2) × 10-10 exp(-11.1 ± 0.4 kJ mol-1/RT), where the uncertainties represent ±2σ. The reaction barriers are found to correlate to the energy required to promote an electron out of the 6s subshell. The reaction of Yb(1S0) with O2 reacts through a termolecular mechanism. The limiting low-pressure third-order rate constants are described in Arrhenius form by k0[Yb(1S0)] = (2.0 ± 1.3) × 10-28 exp(-9.5 ± 2.8 kJ mol-1/RT) molecule-2 cm6 s-1.
Hydrocarbon Activation by Gas-Phase Lanthanide Cations: Interaction of Pr+, Eu+, and Gd+ with Small Alkanes, Cycloalkanes, and Alkenes
Schilling, J. Bruce,Beauchamp, J. L.
, p. 15 - 24 (2007/10/02)
We describe ion beam studies of the interaction of gas-phase lanthanide ions, praseodymium (Pr+), europium (Eu+), and gadolinium (Gd+), with small alkanes, cycloalkanes, alkenes, and several oxygen-containing compounds.Only Gd+ is seen to activate C-H and C-C bonds of alkanes.The ground-state electronic configuration of Gd+ (4f75d16s1) is different from those of Pr+ (4f36s1) and Eu+ (4f76s1), leading to the conclusion that the f electrons play little part in the metal ion reactivity.Gd+ can be thought of as having two valence electrons, and indeed it reacts similarly to Sc+ and the other group 3 metal ions Y+ and La+, yielding products corresponding to elimination of hydrogen, alkanes, and alkenes.The elimination of neutral alkenes in the reaction of Gd+ with alkanes results in the formation of metal dialkyl or hydrido-alkyl complexes.This finding leads to estimates for the sum of two Gd+ ? bond dissociation energies of between 110 and 130 kcal/mol.Gd+ and Pr+ react readily with alkenes, yielding mostly dehydrogenation products along with smaller amounts of C-C bond cleavage products.Reactions of Gd+ and Pr+ with oxyen-containing species such as nitric oxide, formaldehyde, acetaldehyde, and acetone yield primarily the metal oxide ions and provide a lower limit for D(M+-O) of 179 kcal/mol, in good agreement with literature values of D(Pr+-O) = 188.4 +/- 5.2 kcal/mol and D(Gd+-O) = 181.0 +/- 4.4 kcal/mol.In keeping with the strong metal ? bonds, Gd+ is also seen to readily react with formaldehyde to eliminate CO and form GdH2+.
SYNTHESIS OF RARE EARTH MONOXIDES.
Leger,Yacoubi,Loriers
, p. 261 - 270 (2008/10/09)
The standard Gibbs energy changes for the formulation of an ionic or metallic monoxide from rare earth metal and sesquioxide have been calculated. Under high pressures ionic ytterbium monoxide and lighter rare earth metallic monoxides should be obtained, which is confirmed by experiments in a belt-type apparatus in the range 15-80 kbar and 500-1200 degree C. For Ln equals La, Ce, Pr, Nd, Sm, a face-centered cubic compound is obtained from each reaction. The cell parameters are respectively 5. 144, 5. 089, 5. 031, 4. 994, and 4. 943 plus or minus 0. 005 A. The compounds appear golden yellow with a metallic luster. From chemical analysis and cell parameter consideration it is concluded that these compounds are the rare earth monoxides. For Ln equals Gd, Dy, Tm, no reaction is observed at 50 kbar and 1000 degree C.
