Two-Electron Oxidative Atom Transfer at a Homoleptic, Tetravalent Uranium Complex

A tetrahomoleptic, pseudotetrahedral
U4+ imidophosphorane
complex, [U­(NP­(pip)3)4], 1-U­(PN), is reported. This complex can be oxidized by two electrons with
either mesityl azide or nitrous oxide. This two-electron atom/group
transfer oxidation is the first example observed at a homoleptic,
tetravalent uranium complex. The mesityl imido compound [U­(NMes)­(NP­(pip)3)4], 2-U­(PN)­NMes, exhibits a unique
square pyramidal geometry in contrast to the expected trigonal bipyramidal
geometry of the oxo complex [U­(O)­(NP­(pip)3)4], 2-U­(PN)­O. The bonding driving the structural dichotomy
of these structures and the absence of a structurally observable inverse trans-influence in 2-U­(PN)­NMes were examined
by DFT and natural bonding orbital analysis.