Concomitant Carboxylate and Oxalate Formation From the Activation of CO 2 by a Thorium(III) Complex

Improving our comprehension of diverse CO 2 activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO 2 activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO 2 is readily reduced to CO, but isolated thorium(III) CO 2 activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′) 3 ] ( 1 , Cp′′={C 5 H 3 (SiMe 3 ) 2 ‐1,3}), reacts with CO 2 to give the mixed oxalate‐carboxylate thorium(IV) complex [{Th(Cp′′) 2 [κ 2 ‐O 2 C{C 5 H 3 ‐3,3′‐(SiMe 3 ) 2 }]} 2 (μ‐κ 2 :κ 2 ‐C 2 O 4 )] ( 3 ). The concomitant formation of oxalate and carboxylate is unique for CO 2 activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO 2 activation can differ from better understood uranium(III) chemistry.