Synthesis of a Base-Free N-Heterocyclic Silanimine

N-heterocyclic silylene (HCNAr)2Si and terphenyl azide Ai N3 were synthesized according to published procedures (7,8). 

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

N-heterocyclic 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. THF and n-hexane were freshly distilled from sodium. 

THF (50 mL) was added to a mixture containing the N-heterocyclic silylene (HCNAr)2Si (0.81 g, 2 mmol) and the ter-phenyl azide Ar Na (0.71 g, 2 mmol) at -78°C. The mixture was warmed to room temperature and stirred for 1 h. The solvents were removed, and the remaining solid was recrystallized from n-hexane at —40°C to yield yellow crystals of (HCNAr)2Si=NAr (yield 1.25 g, 85%). 

This compound represents the first isolable base-free silanimine with an almost linear Si=N—C skeleton, and is of interest for the understanding of bonding nature of silicon—nitrogen multiple bonds. In addition, the Si=N double bond is synthetically useful for cyclic silicon compounds. 

---