Unusual mechanistic pathways. The novel chemistry of compounds with tris(trimethylsilyl) methyl or related ligands on silicon

This review is concerned with compounds containing the very bulky tris(trimethylsilyl)methyl or closely related ligands in which three organosilyl substituents are attached to the central carbon atom. The prototype tris(trimethylsilyl)methyl ligand, (Me3Si)3C, is referred to as the 'trisyl' ligand and commonly denoted by Tsi. A Dalton Perspective dealing with compounds in which such groups are attached to metal or metalloid elements from all groups of the Periodic Table except 18 appeared recently, but the chemistry of compounds in which such ligands are attached to functional silicon centres was considered to be too extensive for inclusion in that general survey, and so is reviewed here. It will become clear that much chemistry previously unobservable because of the great ease of nucleophilic attack at functional centres in 'normal' organosilicon compounds can be revealed by using the very bulky ligand to hinder that attack. Other unusual reactions appear to arise from the relief of the steric strain in the crowded compounds. The compounds under consideration are usually made by reaction of appropriate silicon or organosilicon halides, e.g. SiCl4 or Ph2SiF2,2 with organolithium reagents of the types (Me3Si)3CLi, (XMe2Si)3CLi (e.g. X = Ph), (Me3Si)(XMe2Si)2CLi (e.g. X = Ph), or (Me3Si)2(XMe2Si)CLi (e.g. X = OMe). The range of such ligands is described in ref. 1. Since there is space available to summarize only a small part of the new chemistry developed during this programme a complete list (with titles) of the author's papers in the field is given as ESI.