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

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(CMe 2 ) 2 (CH 2 )NAr, Ar=2,6‐ i Pr 2 C 6 H 3 ) with H 2 SiI 2 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 ‐C 6 H 4 ] + 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.