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Updated: Jan 21, 2026
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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Isolation of a Square-Planar Th(III) Complex: Synthesis and Structure of [Th(OC6H2tBu2-2,6-Me-4)4]1
Daniel N Huh1, Saswata Roy1, Joseph W Ziller1
1Department of Chemistry , University of California , Irvine , California 92697 , United States.
Abstract:
Reduction 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 6d character with 7s Rydberg admixture.
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