Synthesis and Characterization of the First Sandwich Complex of Trivalent Thorium:  A Structural Comparison with the Uranium Analogue

Reduction of the bulky 8-annulene thorium complex [Th{COT(TBS)₂}₂] (COT(TBS)₂ = η-C₈H₆(tBuMe₂Si)₂-1,4) by potassium yields the anionic compound {Th[COT(TBS)₂]₂}K·(DME)₂, which was crystallographically characterized and is the first sandwich complex of Th(III). EPR spectroscopy indicates that the molecule possesses a 6d¹ ground state. A structural comparison is made with the isostructural uranium(III) complex and the thorium(IV) parent compound.