Syntheses and Reactivity of Yb and Sm Inverse Sandwich Arene Complexes

Inverse sandwich arene complexes of rare earth metals have gained notable interest due to their unique electronic properties. In these complexes, an arene ligand bridges two metal centres, storing 0, 2, or 4 electrons, which is the basis for unique reactivity. Herein, we report on the reactivity of [(^DIPePBDI)Ln]₂(η⁶,η⁶-benzene) (II-Ln, Ln = Yb or Sm) and in situ reduced [(^DIPePBDI)SmI]₂ (V) (^DIPePBDI = HC[C(Me)N-DIPeP]₂, DIPeP = 2,6-CHEt₂-phenyl). The Yb^II-benzene^2--Yb^II complex (II-Yb) reacted smoothly with biphenyl, naphthalene, anthracene, and COT, giving a range of new Yb^II complexes with bridging arene or COT ligands. However, due to much stronger Sm-arene bonding in II-Sm, which should be regarded as a Sm^III-benzene^4--Sm^III complex, this reagent only reacted with substrates that can be reduced easily (anthracene and COT). Interestingly, reaction with anthracene gave a Sm^II-anthracene^2--Sm^II complex, showing that the benzene^4- is able to reduce Sm^III to Sm^II. In situ reduced [(^DIPePBDI)SmI]₂ (V) can be considered a (^DIPePBDI)Sm^I synthon, which reacted smoothly with toluene, biphenyl, or 1,3,5-triphenyl-benzene and affords a series of Sm^III-arene^4--Sm^III complexes. However, reaction with pyrene gave an Sm^II-pyrene^2--Sm^II product. All complexes have been fully characterized with X-ray diffraction.