Synthesis of NHC-Stabilized Silole Silylene

The NHC-stabilized silole silylene was prepared by the reaction of 1-H-l-chloro-l-silacyclopentadiene with two equiv of liPr. These two precursors were synthesized according to published procedures (6,7). 

Schlenk flask, magnetic stirrer, vacuum pump, low-temperature reactor, constant pressure funnel, safety glasses, laboratory coat, and protective gloves. 

Since silylenes are air and moisture sensitive, the synthetic operations were carried out under an atmosphere of dry argon or nitrogen by using modified Schlenk line and glovebox techniques. Solvents THF and toluene were freshly distilled from sodium 

A solution of hPr (0.72 g, 4.0 mmol) in THF (30 mL) was added dropwise to a solution of 1-H-l-chloro-tetraphenylsilacyclopenta-diene (0.84 g, 2.0 mmol) in THF (60 mL) at 78°C. After the addition was complete, the mixture was allowed to warm up to room temperature and was stirred overnight. The solvents were removed under vacuum, and the remaining residual was extracted with toluene (100 mL). It was filtered, and the filtrate was concentrated (ca. 10 mL) and stored at -30°C overnight to yield orange yellow crystals (yield 0.60 g, 53%). 

The base-stabilized silole silylene is highly nucleophilic and reacted with a number of substrates to give either silole ring expansion products or new silole derivatives with different substituents on the silicon atom. These compounds are not easily accessible by other methods. 

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