The Inverse Trans Influence in a Family of Pentavalent Uranium Complexes

Systematic ligand variation in a
structurally conserved framework
of pentavalent uranium complexes of the formulas UVX2[N­(SiMe3)2]3 (X = F, Cl,
Br, N3, NCS, 2-naphthoxide) and UVOX­[N­(SiMe3)2]3– (X = −CCPh,
−CN) allowed an investigation into the role of the inverse
trans influence in pentavalent uranium complexes. The −CCPh
and −CN derivatives were only stable in the presence of the trans-UO multiple bond, implicating the inverse
trans influence in stabilizing these complexes. Spectroscopic, structural,
and density functional theory calculated electronic structural data
are explored. Near-IR data of all complexes is presented, displaying vibronic coupling of 5f1 electronic transitions along the primary axis. Electrochemical characterization
allowed assessment of the relative donating ability of the various
axial ligands in this framework. Electron paramagnetic resonance data
presented display axial spectra, with hyperfine coupling along the
primary axis.