Density Functional Theory Analysis of the Importance of Coordination Geometry for 5f<sup>3</sup>6d<sup>1</sup> versus 5f<sup>4</sup> Electron Configurations in U(II) Complexes
Justin C. Wedal, Filipp Furche, William J. Evans
Abstract
Density functional theory (DFT) calculations on four known and seven hypothetical U(II) complexes indicate the importance of coordination geometry in favoring 5f 3 6d 1 versus 5f 4 electronic ground states. The known [Cp″ 3 U] −, [Cp tet 3 U] −, and [U(NR 2 ) 3 ] − [Cp″ = C 5 H 3 (SiMe 3 ) 2, Cp tet = C 5 Me 4 H, and R = SiMe 3 ] anions were found to have 5f 3 6d 1 ground states, while a 5f 4 ground state was found for the known compound (NHAr i Pr 6 ) 2 U. The UV–visible spectra of the known 5f 3 6d 1 compounds were simulated via time-dependent DFT and are in qualitative agreement with the experimental spectra. For the hypothetical U(II) compounds, the 5f 3 6d 1 configuration is predicted for [U(CHR 2 ) 3 ] −, [U(H 3 BH) 3 ] −, [U(OAr′) 4 ] 2–, and [(C 8 H 8 )U] 2– (OAr′ = O-C 6 H 2 t Bu 2 -2,6-Me-4). In the case of [U(bnz′) 4 ] 2– (bnz′ = CH 2 -C 6 H 4 t Bu-4), a 5f 3 configuration with a ligand-based radical was found as the ground state.