Reaction of Bis(alkynyl)silanes with Tris(pentafluorophenyl)borane: Synthesis of Bulky Silole Derivatives by Means of 1,1-Carboboration under Mild Reaction Conditions

The strong Lewis acid tris(pentafluorophenyl)borane [B(C6F5)(3)] reacts rapidly with dimethylbis(phenylethynyl)silane (1c) at room temperature In toluene by shift of a pentafluorophenyl (C6F5) group and formation of a new carbon-bis(pentafluorophenyl)boron linkage [C-B(C6F5)(2)] in a sequence of 1,1-carboboration reactions to yield the 4-bis(pentafluorophenyl)boryl/3-pentafluorophenyl- substituted 1,1-dimethyl-2,5-diphenylsilole derivative 7c. The analogous reaction of bis(trimethylsilylethynyl)diphenylsilane (1d) with tris(pentafluorophenyl)borane gave the corresponding boryl-substituted silole derivative (7d) featuring six bulky substituents attached at the central heterocyclic frarnework. Both the starting materials (1c, 1d) and the products (7c, 7d) were characterized by X-ray crystal structure analyses.