C–H Bond Activation via U(II) in the Reduction of Heteroleptic Bis(trimethylsilyl)amide U(III) Complexes
Justin C. Wedal, Samuel Bekoe, Joseph W. Ziller, Filipp Furche, William J. Evans
Abstract
Reduction of (C5Me5)2UIII(NR2) and (C5Me5)UIII(NR2)2 (R = SiMe3) with potassium graphite in the presence of 2.2.2-cryptand (crypt) generates dark solutions that have UV–visible spectra consistent with time-dependent density functional theory (TDDFT) calculations on the U(II) products, [(C5Me5)2UII(NR2)]− and [(C5Me5)UII(NR2)2]−. However, the solutions quickly change color and form the U(III) C–H bond activation products [K(crypt)][(C5Me5)2UIII(CH2SiMe2NSiMe3-κC,κN)] (1) and [K(crypt)][(C5Me5)UIII(NR2)(CH2SiMe2NSiMe3-κC,κN)] (2), which were identified by X-ray crystallography. DFT calculations on the putative [(C5Me5)2UII(NR2)]− and [(C5Me5)UII(NR2)2]− complexes revealed 5f36d1 ground-state electron configurations, as previously found in isolable [(C5H4SiMe3)3UII]−, which indicated that these low-symmetry heteroleptic complexes are reasonable precursors for new U(II) complexes.