N-heterocyclic olefins (NHOs), IPrCH2 (1) and SIPrCH2 (2) (IPrCH2 = {N(2,6-iPr2C6H3)CH}2CCH2 and SIPrCH2 = {N(2,6-iPr2C6H3)CH2}2CCH2), react with HSiCl3 and afford IPrCH(SiHCl2) (3) and SIPrCH(SiHCl2) (4), respectively. Compounds 3 and 4 have been isolated in almost quantitative yield. Interestingly, treatment of the silylene IPr·SiCl2 with 1 also affords 3, where silylene insertion into a C–H bond is observed. Computational analysis shows a high energy barrier for silylene insertion, therefore a protonation–deprotonation mechanism is more likely.