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(Iµ= 2·7 × 104).