The new terphenyl trifluorosilanes Mes 2 C 6 H 3 SiF 3 ( 1 ) and Tip 2 C 6 H 3 SiF 3 ( 2 ) have been synthesized, and their reduction behavior has been investigated in detail. Reduction with sodium in both cases results in insertion of the silicon center into C−C bonds of the substituent. The reactive intermediates giving rise to the C−C insertion most likely involve fluorosilylene or disilyne species. The final product is a bis-silafluorenyl ( 3 ) in the case of 1 and a silafluorenyl anion in the case of 2 . The anion can be protonated to give a stable silafluorene. The reduction of 1 and 2 with potassium gives a completely different result, and radical species are formed instead. The different reaction pathway is probably caused by the existence of a poorly soluble intermediate [2Mes 2 C 6 H 3 SiF 3 ·3KF] ( 10 ) that lowers the concentration of the starting material and therefore influences the reaction kinetics. Crystal structures are presented for 1, 2, the insertion product 3, and the intermediate adduct 10 .
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Pietschnig et al. (2000) studied this question.