• Login
    View Item 
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UA Campus RepositoryCommunitiesTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournalThis CollectionTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournal

    My Account

    LoginRegister

    About

    AboutUA Faculty PublicationsUA DissertationsUA Master's ThesesUA Honors ThesesUA PressUA YearbooksUA CatalogsUA Libraries

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Synthesis and reactivity of tantalum and tungsten alkyne complexes: Models for alkyne cyclization.

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_td_9108428_sip1_m.pdf
    Size:
    3.911Mb
    Format:
    PDF
    Description:
    azu_td_9108428_sip1_m.pdf
    Download
    Author
    Wexler, Pamela Andrea.
    Issue Date
    1990
    Keywords
    Chemistry
    Advisor
    Wigley, David E.
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    Intermediates in the cyclization reaction of alkynes have been isolated using the group 5 tantalum phenoxide reagents, Ta(DIPP)₂Cl₃(OEt₂) and Ta(DIPP)₃Cl₂(OEt₂) (DIPP = O-2,6-C₆H₃-i-Pr₂). The extent of cyclization has been effected by controlling the sterics at the metal center or the alkyne itself. Reducing the less congested bis phenoxide complex, Ta(DIPP)₂Cl₃(OEt₂), by two electrons in the presence of 2-butyne or 3-hexyne allowed the isolation of an arene complex, (C₆R₆)Ta(DIPP)₂Cl (R = Me, Et), which is formally classified as a 7-metallanorbornadiene. This complex can also be reduced by one more electron to produce a tanatalum (II) species that readily undergoes a one-electron addition reaction with halogenated reagents. This complex also underwent an intramolecular C-H activation of one of the alkyl groups on the arene ring. Attempts were made to try and generalize this cyclization and C-H activation chemistry to the group 6 metals. Tungsten phenoxide and mixed phenylimido-phenoxide reagents were synthesized for use in subsequent cyclization reactions. Reducing the bis phenoxide complex, W(DIPP)₂Cl₄, by two electrons in the presence of a variety of alkynes afforded the alkyne complexes W(DIPP)₂Cl₂(RC≡CR') (R = R' = Me, Et, Ph; R = CMe₃, R' = H). The mixed phenylimido-phenoxide complexes, W(NAr)(DMP)ₓCl₃₋ₓ (x = 1 or 2; NAr = N-2,6-C₆H₃-i-Pr₂; DMP = O-2,6-C₆H₃Me₂), were also reduced by two electrons in the presence of alkynes to afford adducts (i.e. W(NAr)(DMP)₂(EtC≡CEt)). These alkyne adduct complexes failed to undergo any cycloaddition reactions. Reduction of the tantalum tris phenoxide complex, Ta(DIPP)₃Cl₂(OEt₂), by two electrons in the presence of the bulky alkynes diphenylacetylene or trimethylsilyl-1-propyne afforded the isolation of the alkyne adducts (DIPP)₃Ta(PhC≡CPh) and (DIPP)₃Ta(Me₃SiC≡CMe) respectively. The alkyne adduct (DIPP)₃Ta(Me₃SiC≡CMe) undergoes regioselective cross-coupling reactions with smaller alkynes to afford metallacyclopentadienes. Metallacyclopentadienes can be formed directly from the reduction of the tris phenoxide complex in the presence of smaller alkynes (i.e. (DIPP)₃Ta(CEt=CEtCEt=CEt)). The alkyne adduct undergoes cyclization reactions with nitriles that contain α-hydrogens to yield metallacycloenamine complexes (DIPP)₃Ta(CSiMe₃=CMeC(=CHR)NH). The adduct also reacts with ketones to produce metallacyclic complexes with the formulation (DIPP)₃Ta(CSiMe₃=CMeC(RR')O).
    Type
    text
    Dissertation-Reproduction (electronic)
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Chemistry
    Graduate College
    Degree Grantor
    University of Arizona
    Collections
    Dissertations

    entitlement

     
    The University of Arizona Libraries | 1510 E. University Blvd. | Tucson, AZ 85721-0055
    Tel 520-621-6442 | repository@u.library.arizona.edu
    DSpace software copyright © 2002-2017  DuraSpace
    Quick Guide | Contact Us | Send Feedback
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.