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-dibro-modisilanes 5 a (R = Me) and 5 b (R = iPr) bearing bicy-clo[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-buta-diene 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 silyldisi-lene–disilanylsilylene rearrangement reactions and insertion reactions of a silylene into a Si Si bond.