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
Mes2(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(μ-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
Å, respectively) from the N4 plane of the ligand. 1H 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) 1H 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.