A Dialkyl Calcium Carbene Adduct: Synthesis, Structure, and Catalytic Cross-Dehydrocoupling of Silanes with Amines

Eleven neutral ligands were investigated in promoting the calcium-catalyzed cross-dehydrocoupling reaction between phenylsilane and diisopropylamine. Among them, N-heterocyclic carbene (NHC) ligand IiPr(2)Me(2) (1,3-di-isopropyl-4,5- dimethylimidazol-2-ylidene) displayed superior activity and selectivity. The first neutral NHC-supported alkyl calcium complex {(IiPr(2)Me(2))(2)Ca[CH(SiMe3)(2)](2)} (4) was subsequently synthesized and characterized by NMR spectroscopy and X-ray crystallography. Complex 4 displayed high activity and excellent chemoselectivity in the catalytic cross-dehydrocoupling reactions between bulky amines and silanes under mild conditions. The asymmetric version was also achieved by combining Ca[CH(SiMe3)(2)](2) with a chiral NHC ligand, which afforded an optically active silicon stereogenic silazane in 26 % ee.