Crystallographically-characterizable Th(III) complexes are rare and most contain cyclopentadienyl ancillary ligands. However, the first crystallographically-characterizable Th(III) complex with aryloxide ligands can be synthesized by reduction of tetrahedral ThIV(OC6H2tBu2-2,6-Me-4)4 using either KC8 or Li in THF. These reactions form the salts [K(THF)5(Et2O)][Th(OC6H2tBu2-2,6-Me-4)4] and [Li(THF)4][Th(OC6H2tBu2-2,6-Me-4)4]. In each structure, the four aryloxide ligands are arranged in a square planar geometry, which is the first example of this coordination mode for an f element complex. EPR spectroscopy reveals an axial signal consistent with a metal-based radical in a planar complex. DFT calculations by F. Furche and R. Saswata indicate that the SOMO is predominantly a Th 6dz2 orbital.

Synthesis of an unusual square planar Th(III) complex

2019 Fall National Meeting

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