| Research Abstract |
Reduction of tri-tert-butyl-3-(tnribromosilyl)cyclopropene with potassiumn graphite yielded a unique lattice-framework disilene, a racemate of (4R,6R.,4R,6R) - and (4S,6S,4S,6S) -2,3,4,6,7,8,2,3,4,6,7,8-dodeca-tert-buty1-[5,5]bi{1,5-disilatricyclo[4,2.0.01,4]octylidene}-2,7,2,7-tetraene (dl-1). Oxidation of dl-1 gave the corresponding 1,3,2,4-dioxadisiletane derivative stereospecifically. Trapping experiments revealed that a thermal equilibrium between d1-1 and the corresponding silylene, 2,3,4,6,7,8-hexa-tert-buty1-1,5-disilatricyclo[4.2.0.01,4]octa-2,7-diene-5,5-diyl (2), existed in solution at room temperature. Thus, the intermediate 2 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-1 and the related compounds well reproduced the experimental results of the thermal equilibrium between dl-1 and 2 TD-DFT calculations of dl-1 revealed that an intramolecular through-space interaction mists between the π*Si-Si and π*C-C orbitals in the LUMO of dl-1, contributing to the stabilization of the LUMO. The n-p transition of the lattice-framework silylene 2 is observed by differential transmission spectroscopy at 764 nm The significantly red-shifled n-p transition of the silylene is caused by the planar four-mernbered Si2C2 ring containing the divalent aeon atom.
Reduction ofI,I-dichloro-l-silacyclobutane using potassiurn graphite gives hexasila[6.5]coronane (3) as the first silicon analog of coromne. Compound 3 would be formed by sequential rearrangements ofa plausible initial product, hocasaa[6.4]rotane. X-Ray crystallographic analysis shows the cyclohexasilane ring of 3 is fixed to be planer by sextuple trimethylene light bridges, while [6.5]coronane was reported to haw a chair-formed cyclohexane ring. Bea, er of the unique planer structure, 3 shows phosphorescence at 425 nm at77K.
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