Uranium-mediated reductive conversion of CO2 to CO and carbonate in a single-vessel, closed synthetic cycle.

The new neopentyl (Neop)-substituted tris(aryloxide) U(III) complex [(((Neop,Me)ArO)(3)tacn)U(III)] reacts with CO(2) to form CO and the bridging carbonate complex [{(((Neop,Me)ArO)(3)tacn)U(IV)}(2)(μ-CO(3))]. The uranium(IV) bridging oxo [{(((Neop,Me)ArO)(3)tacn)U(IV)}(2)(μ-O)] has been determined to be the intermediate in this reaction. For the first time, both U(iv) complexes can be reduced back to the U(III) starting material. Thus, with KC(8) as reductant, [(((Neop,Me)ArO)(3)tacn)U(III)] engages in a synthetic cycle, in which CO(2) is converted to CO and CO(3)(2-).