The insertion of carbon dioxide into actinide alkyl and hydride bonds

This contribution reports on the insertion of CO₂ into actinide methyl and hydride bonds to yield acetate and formate complexes, respectively. Thus, addition of excess CO₂ to Cp′₂MMe₂ (Cp′ = η⁵- C₅Me₅, M = Th, U) results in the formation of Cp′₂- M(OAc)₂ complexes in high yield. These new complexes, which could also be prepared from Cp′₂- MCl₂ and 2 equiv. of NaOAc, were characterized by standard techniques. On the basis of infrared data and molecular weight measurements the bis(acetate) compounds are suggested to be monomeric with two bidentate acetate ligands, thus achieving a 10-coordinate geometry about the metal ion. The addition of only 1 equiv. of CO₂ to Cp′₂MMe₂ yields Cp′₂MMe(OAc) complexes exclusively, suggesting that the formation of the bis(acetate) complexes proceeds sequentially. These complexes could also be prepared via metathesis of the corresponding Cp′₂MMeCl complexes with NaOAc. Although the reaction of CO₂ with [Cp′₂Th(μ-H)(H)]₂ produces a variety of uncharacterizable products, Cp′₂Th(O₂CH)(OCH-t-Bu) was formed upon treatment of Cp′₂Th(H)(OCH-t-Bu) with CO₂.