A Comparative Study of Oxo‐Ligand Effects in the Gas‐Phase Chemistry of Atomic Lanthanide and Actinide Cations

Abstract

The effects of 0x0 ligands on lanthanide and actinide cations have been examined for the mono-and dioxocations MO' and MO; of cerium, neodymium, thorium, and uranium by probing C-H and C-C bond activation of hydrocarbons in an FT-ICR mass spectrometer. The metal monoxide cations are readily available by reaction of the "bare" metal cations with 0,, CO,, N,O, or H,O. In the ensuing oxidation of MO', UO: is obtained by each of these oxidants, while CeO' could only be oxidized by N,O.NO, was necessary for the generation of Tho;, and NdOz could not be prepared at all. The monoxides are rather unreactive and only dehydrogenate reactive substrates such as 1-butene and 1,4-cyclohexadiene to generate the corresponding butadiene or benzene complexes. In con-

Preparation and Reactions of Base-Free Bis(1,2,4-tri-tert-butylcyclopentadienyl)uranium Oxide, Cp‘2UO

“…The bipyridyl complex, Cp' 2 U(bipy) (6), reacts with p-tolylazide to give Cp' 2 U=N(p-tolyl) (7) and N 2 , Scheme 2. The imide 7, is soluble in pentane from which it may be crystallized, gives a monomeric molecular ion in its mass spectrum, and is a monomer in the solid state as shown by the ORTEP diagram in Figure 4.…”

“…[6][7][8][9] In addition to providing reactivity patterns, these gas phase studies yield useful thermodynamic bond disruption enthalpies for the U-O bonds which lie in the range of 120-190 kcal mol -1 . [6][7][8][9] This paper describes the synthesis of base-free [η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 ] 2 UO (10), Cp' 2 UO, and some of its reactions with silyl-and alkylhalides. These reactions provide a molecular model for the heterogeneous reaction of solid U 3 O 8 and chlorocarbons that results in complete destruction of the latter to CO x and HCl.…”

Energy levels of Th+between 7.3 and 8.3 eV

“…and hydrocarbons [27][28][29]. In the presence of oxygen, the ThO + molecule is formed, characterized by a double bond of 9.1 eV dissociation energy [8].…”

How Can Uranium Ions (U+, U2+) Activate the OH Bond of Water in the Gas Phase?

“…In the QIT-MS experiments, [5] the minor product UOH + was also detected with a branching ratio close to 10:1, in agreement with the ion-beam experiments. In Fourier transform ion cyclotron mass spectrometry (FTICR-MS) experiments, on the other hand, [7,8] reaction (2) was not observed. UOH + was formed only under conditions where thermalization was not effective.…”

“…[5,6] The calculated exothermicity for the dehydrogenation reaction fairly agrees with the experimental estimation (about 315 kJ mol À1 ). [7] In addition to the previously mentioned dehydrogenation path, which involves the formation of the (H 2 )UO + intermediate, we also considered the formation of a dihydride uranium oxo ion, (H) 2 UO + . However, in a quite large inspection of the potential energy surfaces, we could localize this species only for U + doublet states.…”