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Synthetic, structural, and mechanistic studies in early transition metal and actinide chemistry

Citation

Nelson, Janet E. (1991) Synthetic, structural, and mechanistic studies in early transition metal and actinide chemistry. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-07192007-074200

Abstract

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A series of permethyltantalocene thioaldehyde hydride complexes is prepared by treatment of Cp*2Ta([eta superscript 2]-C6H4)H with thiols. The X-ray structure of Cp*2Ta([eta superscript 2]-S=CHCH2Ph)H is reported. These permethyltantalocene thioaldehyde hydride complexes are shown to be in rapid equilibrium with a 16 electron thiolate species through a beta-H elimination/migration process. Upon heating, the permethyltantalocene thioaldehyde hydride complexes undergo an a-alkyl migration to the thermodynamically favored tautomer, the permethyltantalocene sulfido alkyl, Cp*2Ta(=S)CH2R. Derivatives of the permethyltantalocene phenethylthioaldehyde hydride have been prepared from the erythro- and threo-phenethyl-d2 mercaptan to elucidate the mechanism of this migration. The migration has been found to proceed primarily with retention of stereochemistry at carbon for the migrating alkyl.

In contrast to the extremely specific regioselectivity and stereoselectivity normally demonstrated by Schwartz's reagent (Cp2ZrHCl), hydrozirconation of styrene shows two unusual behaviors. First, treatment of Cp2ZrHCl with styrene leads to a mixture of terminal (85%) and internal (15%) insertion products. The benzylic insertion product is stable, and does not undergo migration to a terminal organozirconium product, even when heated. Second, attempts to prepare stereospecifically labeled deutero organozirconium derivatives result in scrambling of the 6 positions of both isomers, yielding a statistical distribution of isotopomers. The features of this scrambling process are described and a mechanism involving an organozirconium alkyl hydride species is proposed.

[K(THF)2]2[U(NHAr)5] [...] THF, (Ar = 2,6-diisopropylphenyl) is prepared by treatment of Ul3(THF)4 with five equivalents of potassium 2,6-diisopropylanilide (KNHAr) in THF. Electronic absorption spectra reveal internal f-f transitions characteristic of trivalent uranium. A single crystal X-ray study revealed that the dianion is a monomer containing a trigonal bipyramidal five-coordinate uranium center. The potassium cations each interact in an [eta]6 and [eta]4 fashion with two arene rings of the arylamido ligands, and two THF molecules. Crystal data (at -70[degrees] C): Monoclinic space group P2[1]/C, with a = [...], and Z = 4.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Bercaw, John E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:22 April 1991
Record Number:CaltechETD:etd-07192007-074200
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-07192007-074200
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2930
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:02 Aug 2007
Last Modified:26 Dec 2012 02:55

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