The synthesis and several reactions of the stable silylene 1 (1,3-di-tert-butyl-2,3-dihydro-1H-1,3,2-diazasilol-2-ylidene) are described. X-ray crystal structures are given for two intermediates in the synthesis of 1, the diimine 7 and its dilithium salt 8, and for a byproduct, the spiro compound 10. 1 reacts with ethanol and water by inserting into the O-H bond, and with iodomethane by insertion into the C-I bond. The silanol from reaction of 1 with water condenses to a disiloxane, 13. From 1 and sulfur and selenium, cyclic compounds containing Si2E2 rings are obtained (E = S or Se). Crystal structures are presented for disiloxane 13 and for the sulfur and selenium cycloadducts, 15 and 17.