Samarium(II) Monoalkyl Complex Supported by a β-Diketiminato-Based Tetradentate Ligand: Synthesis, Structure, and Catalytic Hydrosilylation of Internal Alkynes

Abstract

The synthesis and catalytic applications of trivalent rare-earth metal alkyl complexes have been well developed, but the chemistry of divalent rare-earth metal alkyl complexes lagged much behind. Herein, we report the synthesis, structure, and catalytic applications of a samarium(II) monoalkyl complex supported by a β-diketiminato-based tetradentate ligand, [LSmCH(SiMe₃ )₂ ] (L=[MeC(NDipp)CHC(Me)NCH₂ CH₂ N(Me)CH₂ CH₂ NMe₂ ]^- , Dipp=2,6-(iPr)₂ C₆ H₃ ). This complex is synthesized by the salt metathesis reaction of samarium iodide [LSm(μ-I)]₂ and KCH(SiMe₃ )₂ in 63 % yield. Its structure is characterized by single-crystal X-ray diffraction, showing a distorted square-pyramid coordination geometry. This samarium(II) monoalkyl complex exhibits high catalytic activity in the hydrosilylation of aryl and methyl-substituted unsymmetrical internal alkynes with secondary hydrosilanes, selectively providing the α-(E) products in high yields.

Keywords: alkyl complex; alkynes; homogeneous catalysis; hydrosilylation; samarium.