Facile Skeletal Rearrangement of Polycyclic Disilenes with Bicyclo[1.1.1]pentasilanyl Groups

The unexpected formations of fused polycyclic disilenes 2 a and ( E ),( Z )‐ 3 b by the reduction of the 1,2‐dibromodisilanes 5 a (R=Me) and 5 b (R= i Pr) bearing bicyclo[1.1.1]pentasilanyl (BPS) groups is reported. The disilenes 2 a and ( E ),( Z )‐ 3 b were characterized by a combination of NMR spectroscopy and X‐ray diffraction analysis (XRD). The reduction of 5 b in the presence of 2,3‐dimethyl‐1,3‐butadiene provided an ene adduct of the disilene 1 b bearing BPS groups, which suggested that an initial product of the reduction of 5 b was the disilene 1 b . Thermal reactions of 2 a and ( E ),( Z )‐ 3 b afforded the highly strained saturated silicon clusters 4 a and 4 b . A computational study suggested that the transformation of 1 to 2 , 3 , or 4 can involve silyldisilene–disilanylsilylene rearrangement reactions and insertion reactions of a silylene into a Si−Si bond.