Quantifying Actinide–Carbon Bond Covalency in a Uranyl–Aryl Complex Utilizing Solution ¹³C NMR Spectroscopy

Abstract

Reaction of [UO 2 Cl 2 (THF) 2 ] 2 with in situ generated LiFmes (FmesH = 1,3,5-(CF 3 ) 3 C 6 H 3 ) in Et 2 O resulted in the formation of the uranyl aryl complexes [Li(THF) 3 ][UO 2 (Fmes) 3 ] ([Li(THF) 3 ][1]) and [Li-(Et 2 O) 3 (THF)][UO 2 (Fmes) 3 ] ([Li(Et 2 O) 3 (THF)][1]) in good to moderate yields after crystallization from hexanes and Et 2 O, respectively. Both complexes were characterized by X-ray crystallography and NMR spectroscopy. DFT calculations reveal that the C ispo resonance in [1] − exhibits a deshielding of 51 ppm from spin− orbit coupling effects originating at uranium, which indicates an appreciable covalency in the U−C bonding interaction.

Ligand–Metal Complementarity in Rare-Earth and Actinide Chemistry

“…This provides an experimental grounding to calculated results, and it has allowed Autschbach, Hayton, and co-workers to explore U−C aryl bonding in rare U VI organometallic species 49 They find appreciable covalent character in the U−C aryl bond and were able to excellently reproduce the experimental data, allowing them to describe trends in the 5f contribution to the bonding in these complexes and to compare this to other U VI organometallic complexes. 49 Continuing the theme of actinide-ligand covalency, the groups of Zi, Ding, and Walter reported a comparative tour de force case study between thorium(IV) and uranium(IV) imido complexes, [An(Cp ttt ) 2 (=NC 6 H 4 -4-Me)] (An = Th, U). 50 In this work, small structural differences, such as the uranium complex being slightly more sterically congested due to increased covalency, and hence tighter ligand binding, and the smaller size of U IV versus Th IV , are used to rationalize a substantial body of divergent reactivity.…”

Contemporary Assessment of Energy Degeneracy in Orbital Mixing with Tetravalent f-Block Compounds

“…Along with this development of f-block chemistry, improvements in the spectral resolution of X-ray techniques is expected to improve the fundamental understanding of bonding in Ln IV and An IV systems by revealing absorption structures not seen before, as demonstrated in recent reports on the XANES of f-block compounds through high-energy-resolution fluorescence-detected XANES. − Utilizing other more accessible techniques to quantify covalency will not only compliment XANES characterization but also help to close the gap between theory and experiment. NMR and electron paramagnetic resonance spectroscopy are emerging as reliable techniques for this purpose. − Finally, the advancement of accurate, computationally economical modeling methods will also make f-block bonding theory more accessible and standardized, such as the marriage of multireference wave function theory with DFT through multiconfigurational pair density functional theory. , …”

Exploring Spin‐Orbit Effects in a [Cu6Tl]+ Nanocluster Featuring an Uncommon Tl−H Interaction

“…[4,6,15] Similar SO effects are also seen in lanthanide and actinide organometallics, where they have been used to study Ln/AnÀ L bonding. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] In contrast to the progress made with Hg and Pb hydrides, Tl hydrides are almost unknown. In fact, we are aware of only two complexes with structurally characterized TlÀ H bonds, [31] namely, [CpRu(η 2 -HTl)(PP)][PF 6 ] (PP = dppm, dppe).…”