Rare-Earth Metal Complexes Bearing Electrophilic Carbon and Strongly Polarized Metallacyclopropane Moiety: Synthesis and Diverse Reactivity toward Small Molecules

Metallacyclopropanes are highly strained and very reactive organometallics; the rare-earth metal complexes bearing both highly reactive electrophilic carbon and strongly polarized metallacyclopropanes are extremely rare. This type of rare-earth metal complexes (κ²-L)RE(η²-C₂B₁₀H₁₀)·(THF)₃ [L = 1-(2-N-C₅H₁₀NCH₂CH₂)-3-(2,6-ⁱPr₂C₆H₃NCH)–C₈H₄N, RE = Lu(1a), Yb(1b), Er(1c), Y(1d), Dy(1e)] bearing the indol-2-yl electrophilic carbon and carboryne-based strongly polarized metallacyclopropanes have been synthesized. Structures of complexes 1 are further confirmed by single-crystal X-ray diffraction and DFT theoretical calculations. It is found that complexes 1 have remarkable reactivity toward different polar unsaturated small molecules, elemental sulfur, and selenium to provide different products (2–15) through the selective reactions of the RE–C_cage, and RE–C_2‑ind bonds with the given small molecules, respectively. The reactivities of these complexes are different from those of the reported rare-earth metallacyclopropenes and d-block metal–carborynes.