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Summary: Thermal and Photochemical [2+2] Cycloreversion of a
1,2-Disilacyclobutane and a 1,2-Digermacyclobutane
Yitzhak Apeloig,*, Dmitry Bravo-Zhivotovskii, Ilya Zharov, Vladislav Panov,
William J. Leigh, and Gregory W. Sluggett,§
Contribution from the Department of Chemistry and the Lise Meitner-MinerVa Center for Computational
Quantum Chemistry, TechnionsIsrael Institute of Technology, Haifa 32 000, Israel, and Department of
Chemistry, McMaster UniVersity, 1280 Main St. West, Hamilton, Ontario, Canada L8S 4M1
ReceiVed August 22, 1997
Abstract: Upon heating of the highly sterically congested 1,1,2,2-tetrakis(trimethylsilyl)dispiro[3,3,4,4-
biadamantane-1,2-disilacyclobutane] (2) in solution in the presence of trapping reagents, such as 1,3-butadienes,
styrene, phenylacetylene, and methanol, the trapping products of the silene bis(trimethylsilyl)adamantyl-
idenesilene (1) are formed with high regioselectivity and good yields. Photolysis of 2 at -196 °C in
methylcyclohexane in the absence of trapping agents produces tetrakis(trimethylsilyl)disilene (3). Photolysis
of 2 in solution in the presence of 1,3-butadiene leads to a 2:1 mixture of 1,1,2,2-tetrakis(trimethylsilyl)-1,2-
disilacyclohex-4-ene (10)sthe trapping product of the disilene 3sand of 1,1-bis(trimethylsilyl)-1-silacyclopent-
3-ene (11)sthe trapping product of bis(trimethylsilyl)silylene (4)stogether with 2,2-biadamantylidene. The
results of laser flash photolysis and of additional trapping experiments suggest that the sole primary product
in the photolysis of 2 is the disilene 3, which dissociates under further irradiation to produce the silylene 4.
Heating of 1,1,2,2-tetrakis(trimethylsilyl)dispiro[3,3,4,4-biadamantane-1,2-digermacyclobutane] (14) in solution
results in the quantitative formation of 2,2-biadamantylidene and of germanium-containing oligomers, while
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