The reactions of organometallic compounds containing silicon. Part I. Reactions of dimethylphenyl-, methyldiphenyl-, and triphenyl-silyllithium with 1,1-diphenylethylene

Abstract

Dimethylphenyl-, methyldiphenyl-, and triphenyl-silyl-lithium react very rapidly with 1,1-diphenylethylene in tetrahydrofuran but the reaction can be followed at low temperature using a stop-flow technique. The thermodynamic constants of activation at –40° for this reaction (R₃SiLi + H₂C:CPh₂→ R₃Si·CH₂·CPh₂^– Li⁺) with Ph₃SiLi, MePh₂SiLi, and Me₂PhSiLi, respectively, are : ΔG^‡= 12·8, 12·3, and 12·4 kcal. mole^–1; ΔH^‡= 3·4, 3·05, and 3·4 kcal. mole^–1; ΔS^‡=–40·3, –39·8, and –38·7 cal. mole^–1 deg.^–1. The addition products show an absorption maximum at 506 mµ(ε= 2·7 × 10⁴).