Synthesis of (O₂CEPh)^1- Ligands (E = S, Se) by CO₂ Insertion into Lanthanide Chalcogen Bonds and Their Utility in Forming Crystallographically Characterizable Organoaluminum Complexes [Me₂Al(μ-O₂CEPh)]₂

CO₂ inserts into the Sm−S and Sm−Se bonds of [(C₅Me₅)₂Sm(μ-EPh)]₂ (E = S, Se) to form the first crystallographically characterized (O₂CEPh)^1- complexes, [(C₅Me₅)₂Sm(μ-O₂CEPh)]₂. These complexes are structurally analogous to [(C₅Me₅)₂Sm(μ-O₂CR)]₂ complexes, but they are less soluble. This feature was utilized in the reaction of Me₂AlCl with [(C₅Me₅)₂Sm(μ-O₂CEPh)]₂, which forms crystallographically characterizable [Me₂Al(μ-O₂CEPh)]₂ complexes. Such complexes could not be isolated from an analogous carboxylate reaction. [(C₅Me₅)₂Sm(μ-O₂CSePh)]₂ decarboxylates in THF to form (C₅Me₅)₂Sm(SePh)(THF). The loss of CO₂ rather than COSe with formation of (C₅Me₅)₂Sm(OPh)(THF) was established by ¹³CO₂ studies and independent synthesis of (C₅Me₅)₂Sm(OPh)(THF) from (C₅Me₅)₂Sm[N(SiMe₃)₂] and PhOH.