Synthesis of a Dimeric Base-Stabilized Cobaltosilylene Complex for Catalytic C-H Bond Functionalization and C-C Bond Formation.

The synthesis of a dimeric base-stabilized cobaltosilylene complex and its catalytic reactions are described. Treatment of the amidinato silicon(I) dimer [LSi:]2 (1; L=PhC(NtBu)2 ) with CoBr2 in toluene for 10 days afforded the dimeric amidinato cobaltosilylene [(LSi)μ-{CoBr(LSiBr)}]2 (2), which is speculated to proceed via "LSiCoBr" and "LSiBr" intermediates in the reaction. Compound 2 is paramagnetic, with an effective magnetic moment of 2.8 μB. Its electronic structure was elucidated by single-crystal X-ray crystallography and DFT studies. It was capable of catalyzing C-H bond functionalization, in which a combination of 2, phosphine and MeMgI can regio- and stereoselectively promoted the addition of the C≡C triple bonds in alkynes to the ortho-C-H position in arylpyridines. In addition, compound 2 catalyzed Kumada-type coupling reactions between aryl chlorides and the Grignard reagent 2-mesitylmagnesium bromide.