Trapping a Silicon(I) Radical with Carbenes: A Cationic cAAC–Silicon(I) Radical and an NHC–Parent‐Silyliumylidene Cation

Abstract

The trapping of a silicon(I) radical with N-heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAAC_Me ] (cAAC_Me =:C(CMe₂ )₂ (CH₂ )NAr, Ar=2,6-iPr₂ C₆ H₃ ) with H₂ SiI₂ in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAAC_Me )₂ Si:^. ]⁺ I^- (1), which features a cationic cAAC-silicon(I) radical, and [cAAC_Me -H]⁺ I^- . In addition, the reaction of the NHC-iodosilicon(I) dimer [I_Ar (I)Si:]₂ (I_Ar =:C{N(Ar)CH}₂ ) with 4 equiv of I_Me (:C{N(Me)CMe}₂ ), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(I_Me )₂ SiH]⁺ I^- (2) comprising the first NHC-parent-silyliumylidene cation. Its further reaction with fluorobenzene afforded the C_Ar -H bond activation product [1-F-2-I_Me -C₆ H₄ ]⁺ I^- (3). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1. Compounds 1-3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X-ray crystallography.