The chemistry of low-valent metal complexes containing ligands capable of Pi-donation : creating and stabilizing unsaturation /
The synthesis of several group 6 low-valent metal carbonyl complexes stabilized by a variety of ancillary 7c-donor ligands has been accomplished in good yields. The relative strength of each 7r-donor has been examined through reactivity and structural studies. The lability of the carbonyl ligands...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=737704261&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The synthesis of several group 6 low-valent metal carbonyl complexes stabilized by a variety of ancillary 7c-donor ligands has been accomplished in good yields. The relative strength of each 7r-donor has been examined through reactivity and structural studies. The lability of the carbonyl ligands on such complexes has been monitored by infrared and 1 3 C NMR spectroscopy. These investigations have focused on the related systems specified below. Tungsten pentacarbonyl complexes of asymmetrically substituted phenoxide ligands, including 2-tert-butylphenoxide, have been synthesized in order to examine the steric influences of these ligands on the insertion Of C02 and COS into a metalphenoxide bond. The interactions of the SALEN ligand, a tetradentate ligand prevalent in coordination chemistry, with chromium and prevalent in coordination chemistry, with chromium and tungsten carbonyl derivatives has been examined to determine-nine the degree to which SALEN may interact with a low-valent metal center and labilize the carbonyl ligands. Amino- and phosphino-acid derivatives of Cr(O) and W(o) tetracarbonyl complexes have been synthesized, and their solid-state structures have been determined. In select amino solid-state structures have been determined. In select amino is proposed to occur via a substitutionally labile amino transient species formed by base-assisted removal of a proton from the amine functionality. The isotope effect (kil/kD) and activation parameters are consistent with this suggestion. For comparison the [Et4N]2[W(CO)4(orotate)] derivative, where the nitrogen atom is deprotonated, has been synthesized and the rates of CO dissociation determined via 13 CO exchange studies. Eighteen- and sixteen-electron derivatives of tungsten(O) and chromium(O) carbonyl complexes were synthesized using a series of 1,2-disubstituted benzene rings with varying series of 1,2-disubstituted benzene rings with varying species the geometry of the metal anion is that of a distorted trigonal bipyramid consisting of three carbonyl ligands and a five-membered chelate ring bound through the 7r-donor atoms at an equatorial and an axial position, with the stronger 7r-donor atom in the equatorial site. Investigations illustrating that the relative stability of the 16- vs. the 18-electron species varies as a function of metal and donor atoms have been carried out. Inter- and intramolecular CO-exchange processes have been probed via intramolecular CO-exchange processes have been probed via |
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| Item Description: | Vita. "Major Subject: Chemistry". In title, Greek letter Pi is a symbol. |
| Physical Description: | xiv, 184 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 140-144. |