From an N-Heterocyclic Silacyclopropene to Donor-Supported Silacyclopropenylium Cations

Addition of equimolar amounts of B(C₆F₅)₃ to the N-heterocyclic silacyclopropenes [LSi(C₂H₂)] (2; L = CH{(CCH₂)(CMe)(2,6-ⁱPr₂C₆H₃N)₂}) affords the first isolable, zwitterionic silacyclopropenylium−boranide compounds 3. Protonation of 2 with the convenient Brønsted acid H(OEt₂)₂⁺B(C₆F₅)₄⁻ leads to quantitative formation of the corresponding silacyclopropenylium salt [4-B(C₆F₅)₄].