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

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 Ph2PCH(SiMe3)PPh2 (1) 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.