In-plane Thorium(IV), Uranium(IV), and Neptunium(IV) Expanded Porphyrin Complexes.

Abstract

Here, we report a first series of in-plane thorium(IV), uranium(IV), and neptunium(IV) expanded porphyrin complexes. These actinide (An) complexes were synthesized using a hexa-aza porphyrin analogue, termed dipyriamethyrin, and the non-aqueous An(IV) precursors: ThCl4(DME)2, UCl4, and NpCl4(DME)2 under conditions of in situ sodium bis(trimethylsilyl)amide deprotonation. The molecular and electronic structure of the ligand, each An(IV) complex, and a corresponding uranyl(VI) complex were characterized using NMR and UV-vis spectroscopies, as well as single crystal X-ray diffraction analysis. Computational analyses of these complexes, coupled with their structural features, provide support for the conclusion that a greater degree of covalency in the ligand-cation orbital interactions arises as the early actinide series is traversed from Th(IV) to U(IV) and Np(IV). The axial ligands in the present An(IV) complexes proved labile, allowing for the electronic features of these complexes to be further modified.