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

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.