Phosphazides as ancillary ligands in uranium and thorium coordination chemistry

Abstract

The synthesis of uranium(IV) and thorium(IV) phosphazide complexes is described herein. Two new series of ancillary ligands featuring phosphazide groups are presented, leveraging potassium ion stabilization of the phosphazides to facilitate salt metathesis transfer of the ligands to uranium and thorium. These complexes and their precursors were prepared and characterized by multi-nuclear (1H, 13C and 31P) NMR spectroscopy, single crystal X-ray diffraction experiments and elemental analysis. Step wise N2 elimination from the diphosphazide ligands was observed and, in some cases, the asymmetric mixed phosphazide/phosphinimine system was isolated and characterized. The complexes bearing diphosphazide ligands were compared to the analogous complexes containing phosphinimines, and, in the pyrrole-based system, the phosphazides were shown to allow for reactivity that is not available to their phosphinimine counterparts.