Silyl group migration in a P-silylated phosphonium ylide derived from dppm — A combined experimental and theoretical study

摘要

The lithium complex [(Et2O)2Li{(Ph2P)2CH}] (2) was synthesized by recrystallization of the corresponding solvent-free complex in diethyl ether. The kinetic product of the reaction of 2 and Me3SiCl, Ph2PCHP(SiMe3) Ph2 (3), was isolated under appropriate conditions and characterized by NMR measurement at 228 K. Both, reversible P-to-P and irreversible P-to-C migration of the silyl group were observed at higher temperatures and investigated by NMR techniques and quantum chemical calculations. The thermodynamic product Ph2_ PCH(SiMe3)PPh2 (t) was found to be 84 kJ mol~(-1) (B97-D/TZVPP) lower in energy than the kinetic product 3. The molecular structures of 1-3 were determined by X-ray diffraction measurement.