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NEUTRON AND X-RAY CRYSTALLOGRAPHIC STUDIES ON METAL
HYDRIDE COMPELXES AND ORGANIC RING INVERSION
by
Timothy James Stewart
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
August 2009
Copyright 2009 Timothy James Stewart
Object Description
| Title | Neutron and x-ray crystallographic studies on metal hydride compelxes and organic ring inversion |
| Author | Stewart, Timothy James |
| Author email | tim.stewart@usc.edu; gon41st@gmail.com |
| Degree | Doctor of Pharmacy / Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2009-06-24 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-08-06 |
| Advisor (committee chair) | Prakash, Surya |
| Advisor (committee member) |
Hogen-Esch, Thieo Petruska, John |
| Abstract | Chapter 1 gives a brief description about neutron diffraction and how neutrons are used to locate hydrogen atoms, an importance over X-rays, especially in the case of metal hydride complexes. Listed individually are 5 different neutron diffraction instruments that have made my research possible.; Chapter 2 describes our single–crystal neutron diffraction results that unambiguously reveal a four-coordinate H atom located in the center of a soluble organometallic tetrahedral complex [Li(THF)4][(C5Me4SiMe3)4 Dy4(u-Cl)(u-H)8]. The core of the molecule consists of a tetranuclear cluster with one interstitial, two face-bridging and five edge-bridging hydride ligands. Neutron data were collected on the Quasi-Laue diffractometer VIVALDI at Institut Laue-Langevin (ILL) (Grenoble, France). The existence of a 4-coordinate hydrogen reinforces previous results observed with a series of high-connectivity hydride ligands located at the interstitial cavities of molecular clusters. Interestingly, the 4-coordinate yttrium allows us to analyze simultaneously three different types of hydride coordination in the same molecule (M2(u2 – H), M3(u3 – H), and M4(u4 – H)).; Chapter 3 describes the structures of (Cp’-Y)4H11[Cp*WPMe3] (1) and (Cp’-Y)4H11[Cp*W] (2) [Cp’= C5Me4(SiMe3)] which have been determined by single-crystal neutron diffraction on the monochromatic four-circle diffractometer D19 (for 1) and the quasi-Laue diffractometer VIVALDI (for 2) at ILL. A highly distorted 4-coordinate tetrahedral hydrogen and an unprecedented 5-coordinate trigonal bipyramidal hydrogen have been unambiguously located in the complexes cores, for the first time.; Chapter 4 describes our studies to accurately measure the length of the U-H single bond by single crystal neutron diffraction in the molecular complex [(C5Me5)2U(H)(u-H2)]2. Presented here is the first accurate covalent bond measurement between the lightest and heaviest naturally occurring elements. Successful single-crystal neutron diffraction has accurately determined both terminal U-H and bridging U-H-U hydride distances on two instruments, VIVALDI of ILL, and SXD of ISIS.; Chapter 5 describes two chiral tetraphenylenes, 2,15-dideuteriotetraphenylene (7) and 2,7-dimethyltetraphenylene (15). They were synthesized and resolved to address the tetraphenylene inversion barrier problem. Neutron diffraction investigation of enantiopure 7 showed that the molecule retained its chirality integrity during its synthesis from enantiopure precursors and rules out the possibility of tetraphenylene framework possessing a very low-energy barrier to its inversion. |
| Keyword | diffraction; single crystal; neutron; x-ray |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m2488 |
| Rights | Stewart, Timothy James |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Stewart-3087 |
| Archival file | uscthesesreloadpub_Volume26/etd-Stewart-3087.pdf |
Description
| Title | Page 1 |
| Full text | NEUTRON AND X-RAY CRYSTALLOGRAPHIC STUDIES ON METAL HYDRIDE COMPELXES AND ORGANIC RING INVERSION by Timothy James Stewart A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (CHEMISTRY) August 2009 Copyright 2009 Timothy James Stewart |
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