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

Alasdair Formanuik; Fabrizio Ortu; Christopher J Inman; Andrew Kerridge; Ludovic Castro; Laurent Maron; David P Mills

doi:10.1002/chem.201604622

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

Chemistry. 2016 Dec 12;22(50):17976-17979. doi: 10.1002/chem.201604622. Epub 2016 Oct 27.

Authors

Alasdair Formanuik¹, Fabrizio Ortu¹, Christopher J Inman², Andrew Kerridge³, Ludovic Castro⁴, Laurent Maron⁴, David P Mills¹

Affiliations

¹ School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK.
² Department of Chemistry and Biochemistry, School of Life Sciences, University of Sussex, Brighton, BN1 9QL, UK.
³ Department of Chemistry, Lancaster University, Lancaster, LA1 4YB, UK.
⁴ LPCNO, CNRA and INSA, Université Paul Sabatier, 135 Avenue de Rangeuil, Toulouse, 31077, France.

Abstract

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''={C₅ H₃ (SiMe₃ )₂ -1,3}), reacts with CO₂ to give the mixed oxalate-carboxylate thorium(IV) complex [{Th(Cp'')₂ [κ² -O₂ C{C₅ H₃ -3,3'-(SiMe₃ )₂ }]}₂ (μ-κ² :κ² -C₂ O₄ )] (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.

Keywords: actinides; reduction; small molecule activation; subvalent compounds; thorium.