1,2-Dihydrosilenes were synthesized by the photolysis of silyldiazomethane derivatives bearing one bulky trialkylsilyl group SiR[CH(SiMe3)(2)](2) (R = Me and i-Pr) and two hydrogen atoms on the silicon atom. The selective migration of the hydrogen atom to the carbene center occurred, leading to stable trans-1,2-hydrosilenes, which were characterized by their spectroscopic data. An X-ray analysis of the Diels-Alder adduct demonstrated the trans geometry of the 1,2-dihydrosilene.