Insights into the making of a stable silylene

Abstract

Reduction of Cl₂Si[(NR)₂C₆H₄-1,2] (R = CH₂Bu^t) with potassium is known to lead to the stable silylene Si[(NR)₂C₆H₄-1,2] (1). However, silylene 1 is now shown to react further with an alkali metal (Na or K) to yield the (1)₂²⁻, c-(1)₃⁻˙, c-(1)₃²⁻ or c-(1)₄²⁻ derivatives. Reduction of Cl₂Si[(NR)₂C₆H₄-1,2] (R = CH₂CH₃ or CH₂CHMe₂) with potassium does not lead to an isolable silylene, but such a silylene is proposed to be an intermediate and, as for 1, reacts further to afford the potassium salts of c-[Si{(NR)₂C₆H₄-1,2}]₄⁻˙ and c-[Si{(NR)₂C₆H₄-1,2}]₄²⁻. The pathways leading to the anionic cyclotri- and cyclotetrasilanes are discussed and supported experimentally; including by X-ray structures of relevant intermediates.