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

Graphical A five-coordinate samarium(II) monoalkyl complex is synthesized and structurally characterized. This complex shows high catalytic activity and high stereo- and regioselectivity in the hydrosilylation of various aryl and methyl-substituted unsymmetrical internal alkynes with secondary hydrosilanes under mild conditions (see scheme). 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(SiMe 3 ) 2 ] (L=[MeC(NDipp)CHC(Me)NCH 2 CH 2 N(Me)CH 2 CH 2 NMe 2 ] − , Dipp=2,6-( i Pr) 2 C 6 H 3 ). This complex is synthesized by the salt metathesis reaction of samarium iodide [LSm( μ -I)] 2 and KCH(SiMe 3 ) 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.