Di-tert-butylsilylene, generated by photolysis of hexa-tert-butylcyclotrisilane, reacts with the triple bond of adamantane-1-carbonitrile to furnish the 1,3-diaza-2,5-disilacyclohexa-3,6-diene 5. However, treatment of 2,2-dimethylpropanenitrile with dimesitylsilylene affords the azadisilacyclobutene ring system 6. The structures of 5 and 6 were determined by X-ray crystallography.Key words: silicon, silylene, silaheterocycles, X-ray crystallography.