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].