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.