Synthesis, structure, and reactivity of crystalline molecular complexes of the {[CH(SiMe)]Th} anion containing thorium in the formal +2 oxidation state.

Reduction of the Th complex Cp''3Th, [Cp'' = CH(SiMe)], with potassium graphite in THF in the presence of 2.2.2-cryptand generates [K(2.2.2-cryptand)][Cp''3Th], , a complex containing thorium in the formal +2 oxidation state. Reaction of with KC in the presence of 18-crown-6 generates the analogous Th compound, [K(18-crown-6)(THF)][Cp''3Th], . Complexes and form dark green solutions in THF with = 23 000 M cm, but crystallize as dichroic dark blue/red crystals. X-ray crystallography revealed that the anions in and have trigonal planar coordination geometries, with 2.521 and 2.525 Å Th-(Cp'' ring centroid) distances, respectively, equivalent to the 2.520 Å distance measured in . Density functional theory analysis of (Cp''3Th) is consistent with a 6d ground state, the first example of this transition metal electron configuration. Complex reacts as a two-electron reductant with cyclooctatetraene to make Cp''2Th(CH), , and [K(18-crown-6)]Cp''.