Degree Type

Dissertation

Date of Award

1993

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

John G. Verkade

Abstract

This dissertation describes synthesis and reactivity patterns, and the spectral and structural characterization of a series of the group 13 azatranes: (M(RNCH[subscript]2CH[subscript]2)[subscript]3N) [subscript] n (M = B, Al, Ga; R = H, Me, SiMe[subscript]3, SiMe[subscript]2-tert-Bu; n = 1, 2). These azatranes display an oligomeric behavior depending on the nature of the central atom M and the size of the substituents R. Bulky substituents such as SiMe[subscript]3 and SiMe[subscript]2-tert-Bu stabilize monomers with a three-fold molecular symmetry. Single-crystal X-ray diffraction studies on monomeric Al(Me[subscript]3SiNCH[subscript]2CH[subscript]2)[subscript]3N revealed a rare trigonal monopyramidal (TMP) geometry of the aluminum center. The C[subscript]3 propeller-like conformation of these molecules implies the presence of two enantiomers, [delta] and [lambda], whose interconversion (racemization) was observed by variable temperature [superscript]1H NMR spectroscopy in solution for B(Me[subscript]3SiNCH[subscript]2CH[subscript]2)[subscript]3N;Azatranes of Al and Ga possessing smaller equatorial groups form dimers as was shown by multinuclear and two-dimensional NMR spectroscopy experiments. The curious cis configuration of the substituents on the central (M-N)[subscript]2 ring was verified by single-crystal X-ray diffraction studies of three azatranes. The presence of the trans isomer or an interconversion process between the two isomers in solution was ruled out by [superscript]1H and [superscript]13 C NMR spectroscopies in all cases. A series of [superscript]27 Al NMR chemical shifts of monomeric aluminum amides and monomeric and dimeric azaalumatranes containing aluminum ligated exclusively by nitrogens and coordination coordination numbers from three to five displayed a trend toward higher shielding with increasing coordination number;Monomeric and dimeric azaalumatranes and trimethylazaboratrane were found to take part in interesting transmetallation reactions with main-group and transition metal alkoxides and Ga(acac)[subscript]3. By this method, main-group and transition metal azatranes were prepared. Azatranes were also shown to convert to corresponding atranes in a transligation reaction with triethanolamine;The tetrameric nature of alumatrane in solution was substantiated by [superscript]27 Al, [superscript]1 H COSY, and variable temperature [superscript]13 C NMR spectroscopy experiments. The compound displays a complex dynamic behavior including racemization and rotation of the peripheral units.

DOI

https://doi.org/10.31274/rtd-180813-12957

Publisher

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

Copyright Owner

Jiri Pinkas

Language

en

Proquest ID

AAI9414013

File Format

application/pdf

File Size

208 pages

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