The smaller, the better? How the aggregate size affects the reactivity of (trimethylsilyl)methyllithium.

Weighting both the basicity and nucleophilicity of an organolithium compound is crucial for an effective use of these reagents in syntheses. To achieve this, an aggregate of optimal size and reactivity has to be formed by adding suitable donating agents. Against usual expectations, this is not inevitably the smallest possible aggregate. In this work, we show that the monomeric complex of (trimethylsilyl)methyllithium stabilized by the bidentate ligand (R,R)-TMCDA shows no significant reactivity. In contrast, two dimeric aggregates stabilized by monodentate quinuclidine were obtained, exhibiting enhanced reactivity compared to the parent compound and to the monomeric complex.