Date of Award
2009
Degree Type
Thesis
Degree Name
Doctor of Philosophy
Program
Chemistry
Supervisor
Dr. Kim Baines
Abstract
In this thesis, various aspects of E=C compound reactivity are reported. Alkyne addition to three different phosphaalkenes and a germene has been investigated. The results were compared to those reported from previous work on the addition of alkynes to silenes. Formal [2+2] cycloaddition does not appear to be a general pathway for the addition of alkynes to E=C compounds. Some cycloadducts were observed; however, ene-addition and CH-insertion of the terminal alkynyl bond across the E=C bond were also prominent. The favoured pathway of addition depends heavily on the polarity of the E=C bond, which varies with the main group element (E) and the electronic nature of the substituents.
Alkyne cycloaddition and CH-insertion pathways were modeled for silenes and germenes using computational chemistry. Cycloaddition involving the formation of a diradical intermediate was found to be the lowest energy pathway for both silenes and germenes.
Addition polymerization o f a silene, Mes2Si=C(H)CH2® u , and germene, Mes2Ge=C(H)CH2fBu, has also been investigated. The use of anionic and radical initiators is reported. The polymers contain a regularly alternating metalloid-carbon backbone.
Conditions for the living anionic polymerization of Mes2Ge=C(H)CH2iBu have been explored. Low molecular weight polygermene can be synthesized in a controlled fashion in an ether-THF cosolvent using iBuLi as the initiator. The conditions developed
for the radical polymerization of Mes2Ge=C(H)CH2tBu have been applied to the synthesis of germene-styrene copolymers.
m
Addition Polymerization Alkyne Addition CH-Insertion Copolymer Cycloaddition 1,2-Dihydrophosphinine DFT
Ene-addition Germacyc lobutene Germene Germylacetylene Inorganic Polymer Mechanism Phosphaalkene Polycarbogermane Polycarbosilane Silacyclobutene Silene
Recommended Citation
Pavelka, Laura C., "A Study of E=C Compound Reactivity: Alkyne Addition and Polymerization" (2009). Digitized Theses. 3779.
https://ir.lib.uwo.ca/digitizedtheses/3779