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

• Published in: Chemistry : a European journal 2018-09, Vol.24 (54), p.14329-14334
• Main Authors: Khoo, Sabrina, Cao, Jiajia, Yang, Ming‐Chung, Shan, Yu‐Liang, Su, Ming‐Der, So, Cheuk‐Wai
• Format: Article
• Language: English
• Subjects: Alkynes; Aromatic compounds; carbene homologue; Catalysis; Chemical reactions; Chemical synthesis; Chemistry; cobalt; Coupling (molecular); Crystal structure; Crystallography; C−C bond functionalization; C−H activation; Dimers; Electronic structure; Hydrogen bonds; Intermediates; Magnetic moments; Phosphine; Reagents; silicon; Toluene
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201803410

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. Cobalt causes bonding! A combination of the dimeric amidinato cobaltosilylene, phosphine, and MeMgI can regio‐ and stereoselectively catalyze the addition the C≡C triple bonds of alkynes to the ortho‐C−H position in arylpyridines.