which isprotected kinetically by the bulky helmet substituent1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl, does notdimerize to the corresponding disilene either in solution orin the solid state. During our efforts to obtain compoundstethering two dialkyl silylene moieties,we have achievedunexpectedly the synthesis of fused tricyclic disilenes with twodialkyl silylene units, trans- and cis-2. Neither cis-2nor trans-2dissociates into the corresponding silylene. Instead,uponheating, trans-2 undergoes unprecedented intramolecular[2