Michelle Chretien - Dalhousie University

Placement: McMaster University
Supervisor: Dr. Willie Leigh
Current Position:  Graduate student, Dept. of Chemistry, University of Ottawa

The Chemistry of Reactive Silenes Derived from a-Silylketenes

Phenyldimethylsilyl- and phenylmethylsilacyclopropyl ketene (1 and 2) were synthesized as possible photochemical precursors of reactive silenes. Photolysis of 1 in the presence of t-butanol with 214-nm light led to the formation of two alkoxysilanes (3 and 4), which are the result of addition of the alcohol to the two silenes derived from methyl- and phenyl-migration in the a-silyl carbene obtained from decarbonylation of the ketene. Laser flash photolysis at 193 nm led to the formation of extremely weak transient species, which were assigned to the silenes from their absorption spectra and reactivity toward alcohols. However, the signals were so weak that further study of the silenes was unwarranted.

Surprisingly, steady state photolysis of the compound in the presence of t-butanol with 254- or 300-nm light did not lead to the formation of the silene-derived products, but led instead to the formation of ester 5, by photochemical addition of the alcohol to an excited state of the ketene.

Further investigation into the wavelength dependence of various a-silyl ketenes is warranted. This wavelength dependent photoesterification could be significant for materials science applications. Continued investigation into transient silene chemistry should focus on the analogous diazo compounds as more efficient presursors for carbene-derived silenes.

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