Concomitant Carboxylate and Oxalate Formation From the Activation of CO2 by a Thorium(III) Complex.

Improving our comprehension of diverse CO₂ activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO₂ activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO₂ is readily reduced to CO, but isolated thorium(III) CO₂ activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′)₃] ( 1, Cp′′={C₅H₃(SiMe₃)₂-1,3}), reacts with CO₂ to give the mixed oxalate-carboxylate thorium(IV) complex [{Th(Cp′′)₂[κ²-O₂C{C₅H₃-3,3′-(SiMe₃)₂}]}₂(μ-κ²:κ²-C₂O₄)] ( 3). The concomitant formation of oxalate and carboxylate is unique for CO₂ activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO₂ activation can differ from better understood uranium(III) chemistry. [ABSTRACT FROM AUTHOR]