Iminosilylene LSiCp L bis 2,6-diisopropylphenyl imidazolin-2-iminato, Cp MesCs

2 Iminosilylene LSiCp L = bis(2,6-diisopropylphenyl)-imidazolin-2-iminato, Cp = MesCs  

N-Heterocyclic silylenes have the advantage of kinetic as well as thermodynamic stahilization achieved through the coordination of silicon to the nitrogen atoms possessing bulky aryl substituents as well as with rr-donation from nitrogen to silicon. 

An imidazolin-2-iminato substituent can act as a two 8- and either a two rr- or a four rr-electron donor, which can result in multiple-bond character in the interaction between nitrogen and the silylene thus providing additional stability. As well as the steric bulk at the NHC moiety may provide sufficient stability to the resulting silylene. 

To a cooled ( 78°C) suspension of [Cp Si] [B(C6F5)4] (0.247 g, 0.293 mmol) in Et20/hexane (0.5 mL/5 mL) was added a cooled (-78°C) suspension of LiL salt (0.120 g, 0.293 mmol) in Et20/hex-ane (0.5 mL/5 mL). Reaction mixture was warmed to room temperature over 3h and stirred overnight. All volatiles were evaporated under vacuum and the residue was treated with hexane (2x7 mL). After filtration the hexane phase was concentrated to 0.5 mL and left for crystallization at 5°C. The iminosilylene was isolated as colorless crystals. Yield 57% (94 m. Mp 70—72°C. 

The first step is the synthesis of dihromosilane LSiBr2 by the treatment of imidazolin-2-iminato lithium LiL with Cp SiBr3. The dihromosilane is afterward subjected to reduction to yield the iminosilylene. 

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