Gas-Phase f-Element Organometallic Chemistry:  Reactions of Cyclic Hydrocarbons with Th⁺, U⁺, ThO⁺, UO⁺, and Lanthanide Ions, Ln⁺

Abstract

The extent of reaction of metal ions, M+, with organic molecules depends upon the electronic structure of the metal ion; in particular, the degree to which laser-ablated lanthanide ions, Ln+, dehydrogenate hydrocarbons is known to reflect the energy needed to excite ground state Ln+ to a divalent configuration. Reported here are gas-phase reactions of Ln+ and AnO n + (An = Th or U; n = 0 or 1) with C6 and C8 cyclic hydrocarbons. The reactivities of Ln+ with c-C8H8+2 m (m = 0, 2, or 4) were consistent with previous results for Ln+ + c-C6H6+2 m , in that the relative dehydrogenation efficiencies reflected the metal ion electronic structure and excitation energy. Additionally, the relatively strong bonding between Ln+ and cyclooctatetraene (COT) was manifested as abundant condensation adduct, Ln+−COT. The dehydrogenation reactivities of Th+ and U+ with both C6 and C8 cyclic hydrocarbons were found to be comparable to that of Ce+, the most reactive Ln+, consistent with divalent An+ electronic configurations and a dehydrogenation mechanism initiated by oxidative insertion of An+ into a C−H bond. The most conspicuous discrepancy between the actinide and lanthanide results was the significant dehydrogenation reactivities of the AnO+, this in sharp contrast to essentially inert behavior of all LnO+ studied. In view of the similarity between Ce and Th, the substantial reactivity of ThO+ in light of the inert behavior of CeO+ is particularly intriguing and suggests a central role of the metal center in the dehydrogenation process. The activity of the AnO+ may reflect the distinctive nature of the 5f valence orbitals and could be partly attributable to relativistic effects. An ancillary result of the present investigation was the identification of several metal oxide clusters comprising uranium in multiple valence states.

Molecular Uranates: Laser Synthesis of Uranium Oxide Anions in the Gas Phase

“…This type of clusters has been previously obtained in several studies using either fast-atom bombardment (FAB) [28,29] or LDI [30][31][32][33][34][35]. Figure 3 shows a representative mass spectrum obtained from a powdered anhydrous UO 3 sample, in which the highly abundant UO + and UO 2 + ions were ejected prior to detection; no UO 3 + was ever detected.…”

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

“…[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.…”

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry

“…Many of these studies have focused on the reactions of U ϩ and UO ϩ with alkanes [6,7], alkenes [8], alcohols, thiols and ethers [9], arenes [10], and other small molecules [11][12][13][14][15][16]. Recently, the hydration reactivities of UO ϩ , UO 2 ϩ , and UO 2 2ϩ were examined using secondary ion mass spectrometry [17].…”