Preparation, Structure, and Reactions of a Lattice-Framework Disilene

Reduction of tri-tert-butyl-3-(tribromosilyl)cyclopropene with potassium graphite yielded
a unique lattice-framework disilene, a racemate of (4R,6R,4‘R,6‘R)- and (4S,6S,4‘S,6‘S)-2,3,4,6,7,8,2‘,3‘,4‘,6‘,7‘,8‘-dodeca-tert-butyl-[5,5‘]bi{1,5-disilatricyclo[4.2.0.01,4]octylidene}-2,7,2‘,7‘-tetraene (dl-2). Oxidation of dl-2 gave the corresponding 1,3,2,4-dioxadisiletane
derivative stereospecifically. Trapping experiments revealed that a thermal equilibrium
between dl-2 and the corresponding silylene, 2,3,4,6,7,8-hexa-tert-butyl-1,5-disilatricyclo[4.2.0.01,4]octa-2,7-diene-5,5-diyl (6), existed in solution at room temperature. Thus, the
intermediate 6 reacted with methanol, halides, and acetylenes to give the corresponding
methoxysilane, dihalosilanes, and silacyclopropenes, respectively. The reactions were
accelerated by irradiation. DFT calculations of dl-2 and the related compounds well
reproduced the experimental results of the thermal equilibrium between dl-2 and 6. TD-DFT calculations of dl-2 revealed that an intramolecular through-space interaction exists
between the π*SiSi and π*CC orbitals in the LUMO of dl-2, contributing to the stabilization
of the LUMO.