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

Abstract

A tetrahomoleptic, pseudotetrahedral U⁴⁺ imidophosphorane complex, [U(NP(pip)₃)₄], <b>1-U(PN)</b>, 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], <b>2-U(PN)NMes</b>, exhibits a unique square pyramidal geometry in contrast to the expected trigonal bipyramidal geometry of the oxo complex [U(O)(NP(pip)₃)₄], <b>2-U(PN)O</b>. The bonding driving the structural dichotomy of these structures and the absence of a structurally observable inverse <i>trans</i>-influence in <b>2-U(PN)NMes</b> were examined by DFT and natural bonding orbital analysis.