Synthesis and Structure of a 2,4‐Unsubstituted cis/trans ‐1,3‐Disilacyclobutane by Dehydrofluorination of a Highly Hindered Fluorosilane

The preparation, molecular structure, and metalation behavior of a sterically highly congested fluorosilane ( t BuTipMeSiF) are described. This silane is subjected to dehydrofluorination under thermally mild conditions. A C ‐unsubstituted transient intermediate — either the silene or the corresponding silenoid — is generated in a metalation/elimination sequence at low temperatures, and this intermediate dimerizes to give the corresponding 1,3‐disilacyclobutane exclusively, even in the presence of a trapping agent. The significant steric hindrance in the starting fluorosilane and the final 1,3‐disilacyclobutane is corroborated by their crystal structures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)