Degree Type

Dissertation

Date of Award

1994

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

John G. Verkade

Abstract

This dissertation describes novel and interesting chemistry of azasilatranes and azagermatranes. Herein are described the synthesis and characterization of approximate forty new compounds, including a series of aminoazasilatranes RN[subscript]2Si(R[superscript]'NCH[subscript]2CH[subscript]2)[subscript]3N (R[superscript]' = H, R = H (5), CH[subscript]3(6), CH[subscript]2CH[subscript]3 (7), Si(CH[subscript]3)[subscript]3) (8); R[superscript]' = CH[subscript]3, R = H (9), R = CH[subscript]3 (10), R = CH[subscript]3CH[subscript]3 (11), R = Si(CH[subscript]3)[subscript]3 (12)) as attractive candidates for potential Si[subscript]3N[subscript]4 precursors. Interestingly, the plane defined by the N(Si(CH[subscript]3)[subscript]3)[subscript]2 moiety in 8 is found to be fixed at the apical position of the azatrane, but the counterpart in 12 rotates freely around the apical Si-N bond due to steric homogeneity;The reactivities of chloroazasilatranes ClSi(R[superscript]'NCH[subscript]2CH[subscript]2)[subscript]3N (R[superscript]' = H (2), R[superscript]' = CH[subscript]3 (4)) toward various nucleophilic reagents are described, and are found to be higher compared with the acyclic tetracoordinate analog ClSi(N(CH[subscript]3)[subscript]2)[subscript]3. This is in accord with previously established results that the reactivity of extra-coordinated silicon species is higher than that of their tetravalent analogs. The equatorial NR[superscript]' functionalities were found in this dissertation to significantly influence the reaction pathways. Compound 2 reacted with NaNH[subscript]2, LiN(CH[subscript]3)[subscript]2 and LiN(Si(CH[subscript]3)[subscript]3)[subscript]2 giving 5, 6 and 8, respectively. With stronger bases, lithiation of the equatorial NH hydrogens was observed to be the main pathway. However, the product(s) of 4 with nucleophiles and their relative ratios depend substantially on stereoelectronic factors, the nature of the nucleophilic reagents and the reaction conditions. In the case of the reaction of 4 with C[subscript]6F[subscript]5Li, three products, namely, C[subscript]6F[subscript]5Si(CH[subscript]3NCH[subscript]2CH[subscript]2)[subscript]3N (13), C[subscript]6F[subscript]5Si(CH[subscript]3NCH[subscript]2CH[subscript]2)[subscript]2- (C[subscript]6F[subscript]4CH[subscript]3NCH[subscript]2CH[subscript]2)N (14) and FSi(CH[subscript]3NCH[subscript]2CH[subscript]2)[subscript]3N (15) formed in an approximate ratio of 1:1:2. The formation of 14 is attributed to perfluorobenzyne insertion into a Si-N bond of 13. An X-ray diffraction analysis shows that the transannular Si-N bond (2.246 A) is maintained despite the presence of a seven-membered ring in 14;In the course of repeating a literature procedure, the new compound Si[subscript]2Cl (N(CH[subscript]3)[subscript]2][subscript]5 was discovered, which can also be synthesized by reacting Si[subscript]2Cl[subscript]6 with excess HN(CH[subscript]3)[subscript]2 in ether. Five azagermatranes have also been synthesized. Interconversions between azagermatranes and less sterically hindered tripodal ligands to give less sterically hindered atrane systems were observed and accounted for with the aid of two molecular structures of azagermatranes.

DOI

https://doi.org/10.31274/rtd-180813-12477

Publisher

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

Copyright Owner

Yanjian Wan

Language

en

Proquest ID

AAI9424271

File Format

application/pdf

File Size

218 pages

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