The pentamethylcyclopentadienylsilicon(II) cation: synthesis, characterization, and reactivity.

In the flourishing chemistry of divalent silicon, π-complex formation between silicon and the pentamethylcyclopentadienyl (Cp*) group is one of the successful strategies for thermodynamic and/or kinetic stabilization. Here, the diverse reactivity of the [Cp*Si](+) ion is described. Its chemistry is characterized by the addition of anionic and neutral nucleophiles and by the easy hapticity change and the leaving-group character of the Cp* group. Several novel sandwich and half-sandwich π-complexes of divalent silicon were synthesized, and a novel access to the class of cyclotrisilenes was found. A reversible adduct formation is the basis for the catalytic activity of the [Cp*Si](+) ion in the specific oligoether degradation. Homo- or heterolytic Cp*-Si bond cleavage allows the use of the cation as a source of silicon atoms in silicon cluster synthesis and in nanoparticle formation.