Reactions of organometallic compounds containing silicon. Part V. Reactions of triphenyl- and methyldiphenyl-silylsodium with fluorene in tetrahydrofuran

Abstract

Previous studies of the reactions of triphenyl-, methyldiphenyl-, and dimethylphenyl-silyl-lithium with fluorene in tetrahydrofuran by the stopped-flow method have been extended by following the reaction of fluorene with triphenyl- and methyldiphenyl-silylsodium in tetrahydrofuran. It has been shown that in the change from Na⁺ to Li⁺ the increase in solvation of the initial state is more important than that of the transition state. A study of the equilibrium between contact ion pairs and solvent-separated ion pairs in the case of triphenylsilyl-lithium in dimethoxyethane has yielded the following thermodynamic constants: ΔG°= 1·98 kJ mol^–1, ΔH°=–23·1 kJ mol^–1, ΔS°=–86·0 J K^–1 mol^–1, at 20 °C.