A Linear, O-Coordinated η ¹ -CO ₂ Bound to Uranium

Abstract

The electron-rich, six-coordinate tris-aryloxide uranium(III) complex [((AdArO)3tacn)U(III)] [where (AdArOH)3tacn = 1,4,7-tris(3-adamantyl-5-tert-butyl-2-hydroxybenzyl)1,4,7-triazacyclononane] reacts rapidly with CO2 to yield [((AdArO)3tacn)U(IV)(CO2)], a complex in which the CO(2) ligand is linearly coordinated to the metal through its oxygen atom (eta1-OCO). The latter complex has been crystallographically and spectroscopically characterized. The inequivalent O-C-O bond lengths [1.122 angstroms (A) for the O-C bond adjacent to uranium and 1.277 A for the other], considered together with magnetization data and electronic and vibrational spectra, support the following bonding model: U(IV)=O=C*-O- <--> U(IV)-OC-O-. In these charge-separated resonance structures, the uranium center is oxidized to uranium(IV) and the CO2 ligand reduced by one electron.

Formation of unprecedented actinidecarbon triple bonds in uranium methylidyne molecules

“…Although the chemistry of these species prepared and isolated in a low-temperature noble-gas matrix is difficult to investigate experimentally, these unique diamagnetic X 3 U'CR molecules might be synthesized by coordination of U with highly electronwithdrawing ligands and steric protection of the U'C bonds with bulky ligands, possibly with pseudo-threefold local symmetry. The ability of fluorine-substituted or sterically encumbering ligands (25) to generate new types of metal-ligand multiple bonds might be extended to the still-elusive actinide-carbon multiple-bond alkylidyne and arylidyne systems. The discovery of these actinide complexes with An'C triple bonds is potentially important for organosynthesis, catalysis, interstellar chemistry, atmospheric chemistry, and actinide chemistry under extreme conditions.…”

“…Whereas numerous organic and inorganic compounds with multiple bonds are known (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), f elements (lanthanides and actinides) with multiple bonds are relatively rare, except for early actinides. Such bonding has aroused great interest recently in the search for actinide complexes with multiple bonds between two actinide metals (18)(19)(20)(21) and between actinide (An) and main-group ligands (L) (22)(23)(24)(25)(26)(27)(28).…”

“…Among the actinide complexes with An-L multiple bonds, the importance of first-row elements to bond to actinide metal centers has been highlighted by Burns (22), and molecular complexes containing metal-nitride units have been prepared recently (24)(25)(26). Uranium as the leading example forms a plethora of UϭO bonds and a handful of UϭNR and UϭCR 2 (R ϭ organic groups) bonds.…”

Radical ligand-containing single-molecule magnets

“…The U III complex bearing the hexadentate ligand (1,4,7-tris(3-adamantyl-5-tert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclonane) (( Ad ArO) 3 tacn) was shown to reduce CO 2 by one electron to form the U IV radical complex (( Ad ArO) 3 tacn)U IV (CO 2 −• ) (42; Fig. 38) [367]. Variable-temperature magnetic susceptibility data for 42 were compared with the analogous data of the U IV azide complex, (( Ad ArO) 3 tacn)U IV (N 3 ).…”

On the multi-reference nature of plutonium oxides: PuO22+, PuO2, PuO3 and PuO2(OH)2

“…With the 5f and 6d orbitals being in the primary valence shell, actinides are able to form unique bonds and interact with other compounds in ways that no other elements are able to. [55][56][57][58][59][60] In plutonium dioxides, the 5f and 6d orbitals of the plutonium center interact with the valence orbitals on the oxygen atoms, with the exception of four pairwise degenerate nonbonding orbitals: the doubly degenerate δ u , φ u and δ g orbitals. [55].…”