Formation of unprecedented actinidecarbon triple bonds in uranium methylidyne molecules

Abstract

Chemistry of the actinide elements represents a challenging yet vital scientific frontier. Development of actinide chemistry requires fundamental understanding of the relative roles of actinide valence-region orbitals and the nature of their chemical bonding. We report here an experimental and theoretical investigation of the uranium methylidyne molecules X 3U'CH (X ‫؍‬ F, Cl, Br), F2ClU'CH, and F 3U'CF formed through reactions of laser-ablated uranium atoms and trihalomethanes or carbon tetrafluoride in excess argon. By using matrix infrared spectroscopy and relativistic quantum chemistry calculations, we have shown that these actinide complexes possess relatively strong U'C triple bonds between the U 6d-5f hybrid orbitals and carbon 2s-2p orbitals. Electron-withdrawing ligands are critical in stabilizing the U(VI) oxidation state and sustaining the formation of uranium multiple bonds. These unique U'C-bearing molecules are examples of the long-sought actinide-alkylidynes. This discovery opens the door to the rational synthesis of triple-bonded actinide-carbon compounds.actinide multiple bond ͉ heavy element ͉ laser ablation ͉ matrix isolation ͉ relativistic quantum chemistry

Defect Induced Electronic Structure of Uranofullerene

“…A significant advantage of DFT calculations is that accounting for the electron correlation does not increase the CPU time considerably. Therefore, DFT has been widely used in the calculation of actinides31323334. Relativistic pseudopotential method is able to incorporate relativistic effects with a small increase in computational time3536.…”

Reactions of Thorium Atoms with Polyhalomethanes: Infrared Spectra of the CH2=ThX2, HC÷ThX3, and XC÷ThX3 Molecules

“…One of the SOMOs is illustrated in Figure 10: notice that the SOMO has slight contact with Th and extends past C and even H. However, when two more electrons are added to the system, as in the FCϵUF 3 and HCϵUF 3 (methylidyne)uranium molecules, the six-electron CϵU triple bonds are computed to be substantially shorter, 2.007 Å and 1.941 Å, respectively. [33] In this (methylidyne)-uranium system, there is more HOMO contact with U and only slight extension past C. bonds are longer in the thorium complexes, which suggests that the C-F conjugation with the CϬTh bond offered to justify the very high C-F stretching frequency [11] is decreased in the (methylidyne)thorium complexes. Indeed, the observed spectrum for the FCϬThFCl 2 complex shows that this is the case.…”

Structures, spectroscopic and thermodynamic properties of U2On (n = 0 ∼ 2, 4) molecules: a density functional theory study

“…Lyon et al [27] used ADF to study the formation of unprecedented actinide≡carbon triple bonds. Zhang et al [28] investigated the molecular structures and vibrational frequencies for uranium hexahalides UX 6 (X=F, Cl, Br and I) with the same software.…”

“…Their results were in good agreement with recent experimental data. Previously, DFT has been applied with great success to determining the physical and chemical properties of uranium and plutonium compounds [27,29,30]. We employed spin-polarized generalized gradient approximation (GGA) with OPTX [31] exchange with PBE correlation (OPBE) [32] functional for the exchange and correlation (XC) interaction, and TZP basis sets (contains valence triple zeta and one polarization function) [33].…”