Investigations into Accessible and Efficient Precatalysts for Silicon-Nitrogen Heterodehydrocoupling
Date of Completion
2024
Document Type
Honors College Thesis
Department
Chemistry
Thesis Type
Honors College, College of Arts and Science Honors
First Advisor
Rory Waterman
Keywords
catalysis, chemistry, organometallics, silane, amine
Abstract
Silicon–nitrogen compounds such as aminosilanes and silylamines are utilized in a wide range of applications from materials science to synthetic chemistry. These compounds are materials precursors for ceramics and in chemical vapor deposition, and in chemical synthesis, they play important roles as ligands and protecting groups. Silicon–nitrogen heterodehydrocoupling is a versatile catalytic method to form the Si–N bonds of aminosilane and silylamine products. The atom-economy and greenness of heterodehydrocoupling makes this reaction attractive, and as such, the search for effective catalysts has been ongoing. Commercially available catalysts with non-toxic and abundant metals have been found to be effective silicon-nitrogen heterodehydrocoupling precatalysts from broad categories of compounds including alkyl lithium alkoxide, and Grignard reagents. Substrate scope for examples of catalyst type, nBuLi, KOtAmyl, and MeMgBr, was explored showing a general trend of high activity under mild conditions. Organolithium compounds were shown to be highly active for primary, secondary, and tertiary silanes with amines although reactivity began to stagnate with tertiary silanes and less basic or more sterically hindered amines. Reactivity and Hammett study is suggestive of a nucleophilic-type mechanism. Group I amylates and alkoxides were proven to be highly active catalysts for traditionally challenging substrates such as tertiary silanes and anilines. The reactivity did not resemble nucleophilic or electrophilic-type mechanisms and electron paramagnetic resonance spectroscopy indicated the generation of radicals suggestive of a radical based mechanism. Methyl magnesium bromide showed high activity for primary silanes with amines although reactivity dropped significantly with tertiary silanes. Less basic amines such as aniline were inaccessible, consistent with a nucleophilic mechanism. Bulkier amines and primary silanes with MeMgBr showed increased selectivity for less substituted aminosilane products. These investigations have led to highly active, accessible, and cost-efficient catalysts for silicon–nitrogen heterodehydrocoupling providing new facile routes to aminosilane products.
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Recommended Citation
Bushey, Claire E., "Investigations into Accessible and Efficient Precatalysts for Silicon-Nitrogen Heterodehydrocoupling" (2024). UVM Patrick Leahy Honors College Senior Theses. 618.
https://scholarworks.uvm.edu/hcoltheses/618