Reduction of terphenyltrifluorosilanes: C-C insertion products and possible formation of a disilyne

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.