Huh, Daniel N. Roy, Saswata W. Ziller, Joseph Furche, Filipp Evans, William J. Isolation of a Square-Planar Th(III) Complex: Synthesis and Structure of [Th(OC<sub>6</sub>H<sub>2</sub><sup>t</sup>Bu<sub>2</sub>‑2,6-Me-4)<sub>4</sub>]<sup>1–</sup> Reduction of Th­(OC<sub>6</sub>H<sub>2</sub><sup>t</sup>Bu<sub>2</sub>-2,6-Me-4)<sub>4</sub> using either KC<sub>8</sub> or Li in THF forms a new example of a crystallographically characterizable Th­(III) complex in the salts [K­(THF)<sub>5</sub>(Et<sub>2</sub>O)]­[Th­(OC<sub>6</sub>H<sub>2</sub><sup>t</sup>Bu<sub>2</sub>-2,6-Me-4)<sub>4</sub>] and [Li­(THF)<sub>4</sub>]­[Th­(OC<sub>6</sub>H<sub>2</sub><sup>t</sup>Bu<sub>2</sub>-2,6-Me-4)<sub>4</sub>]. 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 ThO<sub>4</sub> plane. The effect of the eight <i>tert</i>-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 <i>C</i><sub>4</sub>-symmetric structure that accommodates a low-lying SOMO of 6d<sub><i>z</i><sup>2</sup></sub> character with 7s Rydberg admixture. Bu;butyl substituents;THF forms;EPR spectroscopy;square-planar geometry;Rydberg admixture;ThO 4 plane;z 2 character;oxygen donor atoms;aryl rings;SOMO;KC 8;aryloxide ligands;coordination mode;cis ligands;C 4;0.05 Å;f element;DFT calculations 2019-07-31
    https://acs.figshare.com/articles/dataset/Isolation_of_a_Square-Planar_Th_III_Complex_Synthesis_and_Structure_of_Th_OC_sub_6_sub_H_sub_2_sub_sup_t_sup_Bu_sub_2_sub_2_6-Me-4_sub_4_sub_sup_1_sup_/9199742
10.1021/jacs.9b04399.s001