• Login
    View Item 
    •   etd@IISc
    • Division of Chemical Sciences
    • Inorganic and Physical Chemistry (IPC)
    • View Item
    •   etd@IISc
    • Division of Chemical Sciences
    • Inorganic and Physical Chemistry (IPC)
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Mapping The Reaction Coordinate For The Oxidative Addition Of Molecular Hydrogen To A Metal Center

    View/Open
    G22328.pdf (3.573Mb)
    Date
    2010-07-15
    Author
    Dutta, Saikat
    Metadata
    Show full item record
    Abstract
    The binding of molecular hydrogen to a metal center leads to the elongation of the H−H bond and subsequently to its cleavage along the reaction coordinate for the oxidative addition of H2. There has been considerable interest in the study of the activation of dihydrogen and map out the reaction coordinate for the homolysis of H2 on a metal center. A large number of H2 complexes reported to date possess H−H distances ranging from 0.8 to 1.0 Å. A relatively fewer examples of elongated dihydrogen complexes wherein the H−H distances fall in the range of 1.0 to 1.5 Å, are known. Study of the elongated dihydrogen complexes is of great significance because of its relevance in important catalytic processes such as hydrogenation, hydrogenolysis, and hydroformylation. Objectives The objectives of this work are as follows: (a) Synthesis and characterization of elongated dihydrogen complexes with chelating phosphine coligands by varying the electron donor ability. (b) Trap the various intermediate states in the process of oxidative addition of H2 to a metal center. (c) Map the reaction coordinate for the oxidative addition for the oxidative addition of H2 to a metal center. Results We have synthesized and characterized two new elongated dihydrogen complexes cis-[Ir(H)(η2-S2CH)(η2-H2)(PR3)2][BF4] (PR3 = PCy3, PPh3) wherein hydrogen atom undergoes site exchange between the H2 and the hydride sites. The dynamics of the exchange was studied using NMR spectroscopy. In addition, a series of ruthenium dihydrogen complexes of the type trans-[Ru(Cl)(η2-H2)(PP)][BF4] (PP = 1,2- Synopsis bis(diarylphosphino)ethane) has been synthesized and characterized wherein the aryl group is a benzyl moiety with a substituent (p-fluoro, H, m-methyl, p-methyl, p-isopropyl); in this series of complexes, a small increment in the electron donor ability (decrease in Hammett substituent constants) of the chelating phosphine ligand resulted in an elongation of the H−H bond by a small, yet significant amount. We also synthesized a series of 16-electron dicationic dihydrogen complexes bearing elongated dihydrogen ligand. In addition, we prepared a series of dihydrogen complexes of the type [RuCp/Cp*(PP)(η2-H2)][OTf] (PP = 1,2-bis(diarylphosphino)ethane, 1,2-bis(diarylphosphino)methane, 1,2-bis(dialkylphosphino)methane) bearing elongated H2 ligand (dHH = 1.0 to 1.17 Å); in this series of complexes as well, we found that the H−H bond distances increased as the donor ability of the chelating phosphines increased in small increments, along the reaction coordinate for the oxidative addition of H2 to a metal center. This investigation therefore, has established a very nice correlation between the H−H bond lengths and the Hammett substitutent constants (donor properties) resulting in the construction of dihydrogen complexes along the reaction coordinate for the oxidative addition of H2 to a metal center.
    URI
    https://etd.iisc.ac.in/handle/2005/754
    Collections
    • Inorganic and Physical Chemistry (IPC) [300]

    Related items

    Showing items related by title, author, creator and subject.

    • Utilization Of Small Molelcules In C1 Chemistry 

      Thirumanavelan, G (2011-10-25)
    • Influence Of The Bite Angles Of Chelating Diphosphine Ligands In The Chemistry Of Ruthenium Hydride And Dihydrogen Complexes 

      Sivakumar, V (Indian Institute of Science, 2007-06-22)
      The bite angle of a diphosphine ligand plays an important role in determining the reactivity of a transition metal complex. The coordinated dihydrogen on a transition metal center can be activated toward homolysis or ...
    • Chemistry of Ru(II) Complexes Bearing N-heterocyclic Carbene, Hydride, and Dihydrogen Ligands : Synthesis, Mechanistic Insights, and Applications 

      Mala, Deep
      Introduction N-heterocyclic carbenes (NHC) are strong  donors and weak acceptors. Also, NHC forms strong metal-carbon bonds in metal complexes and hence complexes bearing NHC ligands are in general, thermally stable. ...

    etd@IISc is a joint service of SERC & J R D Tata Memorial (JRDTML) Library || Powered by DSpace software || DuraSpace
    Contact Us | Send Feedback | Thesis Templates
    Theme by 
    Atmire NV
     

     

    Browse

    All of etd@IIScCommunities & CollectionsTitlesAuthorsAdvisorsSubjectsBy Thesis Submission DateThis CollectionTitlesAuthorsAdvisorsSubjectsBy Thesis Submission Date

    My Account

    LoginRegister

    etd@IISc is a joint service of SERC & J R D Tata Memorial (JRDTML) Library || Powered by DSpace software || DuraSpace
    Contact Us | Send Feedback | Thesis Templates
    Theme by 
    Atmire NV