ja9b04399_si_001.cif (2.39 MB)
Isolation of a Square-Planar Th(III) Complex: Synthesis and Structure of [Th(OC6H2tBu2‑2,6-Me-4)4]1–
dataset
posted on 2019-07-31, 15:42 authored by Daniel
N. Huh, Saswata Roy, Joseph W. Ziller, Filipp Furche, William J. EvansReduction
of Th(OC6H2tBu2-2,6-Me-4)4 using either KC8 or Li in THF forms
a new example of a crystallographically characterizable Th(III) complex
in the salts [K(THF)5(Et2O)][Th(OC6H2tBu2-2,6-Me-4)4] and
[Li(THF)4][Th(OC6H2tBu2-2,6-Me-4)4]. Surprisingly, in each structure the
four aryloxide ligands are arranged in a square-planar geometry, the
first example of this coordination mode for an f element complex.
The Th(III) ion and four oxygen donor atoms are coplanar to within
0.05 Å with O–Th–O angles of 89.27(8) to 92.02(8)°
between cis ligands. The ligands have Th–O–C(ipso) angles
of 173.9(2) to 178.6(4)°, and the aryl rings make angles of 58.5
to 65.1° with the ThO4 plane. The effect of the eight tert-butyl substituents in generating the unusual structure
through packing and/or dispersion forces is discussed. EPR spectroscopy
reveals an axial signal consistent with a metal-based radical in a
planar complex. DFT calculations yield a C4-symmetric structure that accommodates a low-lying SOMO of 6dz2 character with 7s Rydberg admixture.