Reactions at silicon centres bearing the bulky tris(phenyldimethylsilyl)methyl ligand

Abstract

Metallation of (PhMe₂Si)₃CH with MeLi in tetrahydrofuran gives (PhMe₂Si)₃CLi, which reacts with Mel to give (PhMe₂Si)₃CMe, and also with Me₂SiHCl and MeSiHCl₂, to give (PhMe₂Si)₃CSiMe₂H and (PhMe₂Si)₃CSiMe(H)Cl, respectively, but not with Me₃SiCl or a range of other organosilicon halides. The (PhMe₂Si)₃CSiMe₂H gives the halides (PhMe₂Si)₃CSiMe₂X (X =Cl, Br, and I) upon treatment with halogens, and the iodide is converted into various (PhMe₂Si)₃CSiMe₂Y species (Y =F, OH, O₂CMe, O₂CCF₃, OSO₂CF₃, OCN, NCO, NCS) by treatment with appropriate silver salts. The iodide reacts with NaN₃in (MeOCH₂CH₂)₂O and with KSCN in MeCN to give (PhMe₂Si)₃CSiMe₂N₃ and (PhMe₂Si)₃CSiMe₂NCS₃respectively, the reactions with KSCN in this solvent and in MeOH being fairly similar in rate to those of (Me₃Si)₃CSiMe₂l. In contrast, the latter is markedly less reactive than (PhMe₂Si)₃CSiMe₂l in reactions with silver salts and in methanolysis, and this is tentatively attributed to greater anchimeric assistance (in 1,3 Si to Si bridging) by a Ph than by an Me group.