Base-Stabilized 1-Hydrosilaimine: Reactivity of Diaminochlorosilane toward N-Heterocyclic Carbenes

Studies on the formation of silaimines are among the most fascinating topics in organosilicon chemistry. The first route to silaimine via eliminaition of Me3SiCl from diaminochlorosilanes is reported. Reaction of aminodichlorosilane ArN(SiMe3)SiHCl2 (1) (Ar=2,6-i-Pr2C6H3) with ArN(SiMe3)Li in Et2O at -78 degrees C followed by stirring the mixture for 5 h at room temperature afforded diaminochlorosilane [ArN(SiMe3)](2)SiHCl (2). Compound 2 has been fully characterized by H-1 NMR, C-13 NMR, Si-29 NMR, IR and elemental analysis. Reactivity of 2 with different N-heterocyclic carbenes has been examined. It was found that 2 did not react with sterically hindered N-heterocyclic carbenes (NHC), 3-tert-butylimidazol-2-ylidene (ItBu) and 1,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene (IiPr) at room temperature or under reflux conditions. However, compound 2 could react with one equivalent of 1,3,4,5-tetramethyl-imidazol-2-ylidene (IMe4) to give base-stabilized 1-hydrosilaimine 3. Compound 3 can be viewed as the elimination product from 2 through loss of Me3SiCl, as the small IMe4 coordinate to 2 to form a hypervalent silicon species.