Structural studies of some molybdenum complexes of pyrazolylborate and of the enzyme, Staphylococcal nuclease /
| Main Author: | |
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
[College Station, Tex.] :
Stanislowski,
1976.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=760481911&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Abstract: | The molecular structure of (diethyldi-l-pyrazolylborato)(pyrazylato) (trihapto-allyl)(dicarbonyl)molybdenum, 1 , and (diethyldi-l-pyrazolylborato) (trihapto-2 -phenylallyl)(dicarbonyl)molybdenum, 2 were studied by x-ray crystallography in order to examine the coordination sphere on the molybdenum atom. An unstrained Mo-N-N-B-N-N ring and no interaction with Mo atom of any atoms attached to the boron atom were found in 1. In comparison, the chelate ring in 2 is far more buckled bringing a hydrogen from the carbon α to the boron into the coordination sphere of the molybdenum atom. This serves to give the metal an effective 18 electron configuration. The H-Mo distance in 2 is 2.27(8) A, the shortest found for an aliphatic C-H bond and a transition metal. The energy of the C-H***Mo bond was calculated from the variable temperature proton nmr of 2 and of (diethyldi-l-pyrazolylborato) (trihapto-allyl)(dicarbonyl)molybdenum, 3. Both molecules undergo two different conformational changes. The one at low temperatures, involving the interconversion between the enantiomers, was calculated to have an Arrhenius activation energy of 14 kcal*mole. In the high temperature process, the C-H***Mo bond is severed completely and the activation energy of this interaction (17-20 kcal*mole⁻¹) probably approximates the strength of the C-H***Mo interaction. The high resolution 1.5 A x-ray data were collected on a single crystal of the native Staphylococcal nuclease. The 2.0 A electron density maps of the native enzyme were derived by using the native amplitudes and the phases from: a) isomorphous replacement b) the Fourier transform of the modified map of the inhibited enzyme, i.e., S. nuclease- Ca²⁺- pdTp.. |
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| Item Description: | Vita. "Major Subject: Chemistry." |
| Physical Description: | xv, 218 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references (leaves 205-215). |