Degree Type

Dissertation

Date of Award

1990

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Thomas J. Barton

Abstract

The generation of silathiones is shown to be possible by the retroene elimination of propene from allylthiodimethylsilane and 1-allylthio-1-hydrido-1,2,2,2-tetramethyldisilane. This retroene reaction of allylthiodimethylsilane has a very low activation energy (E[subscript] a = 36.3 kcal/mol, log A = 11.3), when compared with carbon, oxygen or nitrogen homologs. The low activation energy is probably due to the strong Si-S [pi] bond and the weak S-C bond. The low log A indicates that the formation of propene and silathione is via a 1,5-hydrogen shift from a six-centered transition state.;The trapping of (trimethylsilyl)methylsilathione by butadiene afforded a 5-membered ring (1-trimethylthio)-1-methyl-1-silacyclopent-3-ene) which is presumably due to the migration of a silyl group of silathione from silicon to sulfur to generate a silylene which was trapped by butadiene. This is the first example of a silathione-silylene isomerization.;Another route demonstrated to generate silathione was the reaction of a silylene, Me[subscript]2Si:, with carbon disulfide. Dimethylsilylene is thought to form a transient 3-membered ring with CS[subscript]2 and the elimination of carbon sulfide produces dimethylsilathione.;The other method to produce silathione was the [beta]-elimination of bis(trimethylsilythio)dimethylsilane. The [beta]-elimination has an activation energy (E[subscript] a = 33.8 kcal/mol, log A = 10.5).;The second example of a silathione-silylene isomerization was observed in the pyrolysis of 1,1-bis(trimethylsilythio)-1,2,2,2-tetramethyldisilane. The [beta]-elimination of hexamethyldisilathiane initially produced trimethylsilylmethylsilathione whose trimethyl silyl group migrated from silicon to sulfur to give a corresponding silylene. This silylene was trapped by butadiene to yield a 5-membered ring. The possibility of formation of silylene via [alpha]-elimination was ruled out by the result that the [alpha]-elimination of methylthiopentamethyldisilane had a high activation energy (E[subscript] a = 53.0 kcal/mol, log A = 14.2), while the [beta]-elimination of bis(trimethylsilythio)dimethylsilane had a low activation energy (E[subscript] a = 33.8 kcal/mol, log A = 10.5).

DOI

https://doi.org/10.31274/rtd-180813-11820

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Chong Bok Kim

Language

en

Proquest ID

AAI9110518

File Format

application/pdf

File Size

98 pages

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