Electrophilic Behavior of the "Nucleophilic" Pyramidane: Reactivity of Ge-Pyramidane towards Organolithium Reagents

The particular reactivity of the recently discovered class of the main group element polyhedral clusters, pyramidanes, remains largely unexplored. In this communication, we report the reaction of the germapyramidane with tert-butyllithium leading to the rather unusual organogermanium compound [Li⁺(thf)₂]⋅2^-, as the product of the formal insertion of a Ge-apex into the C-Li bond. This reactivity mode exemplifies unusual electrophilic behaviour of a pyramidane, which is a priori considered as a nucleophilic reagent. Being highly reactive, [Li⁺(thf)₂]⋅2^- readily undergoes reactions with electrophiles (MeI, EtBr), initially forming intermediate germahousenes, which isomerize to the thermodynamically more favourable germoles.