Synthesis and Characterization of Thorium(IV) and Uranium(IV) Corrole Complexes

The first examples of actinide complexes incorporating corrole ligands are presented. Thorium(IV) and uranium(IV) macrocycles of Mes(2)(p-OMePh)corrole were synthesized via salt metathesis with the corresponding lithium corrole in remarkably high yields (93% and 83%, respectively). Characterization by single-crystal X-ray diffraction revealed both complexes to be dimeric, having two metal centers bridged via bis(mu-chlorido) linkages. In each case, the corrole ring showed a large distortion from planarity, with the Th(IV) and U(IV) ions residing unusually far (1.403 and 1.330 angstrom, respectively) from the N-4 plane of the ligand. H-1 NMR spectroscopy of both the Th and U dimers revealed dynamic solution behavior. In the case of the diamagnetic thorium corrole, variable-temperature, DOSY (diffusion-ordered) and EXSY (exhange) H-1 NMR spectroscopy was employed and supported that this behavior was due to an intrinsic pseudorotational mode of the corrole ring about the M-M axis. Additionally, the electronic structure of the actinide corroles was assessed using UV-vis spectroscopy, cyclic voltammetry, and variable-temperature magnetic susceptibility. This novel class of macrocyclic complexes provides a rich platform in an underdeveloped area for the study of nonaqueous actinide bonding and reactivity.