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 =¿-C8H6(tBuMe2Si)2-1,4) by potassium yields the anionic compound {Th[COT(TBS)2]2}(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.