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Development of Copper Catalysts for the Reduction of Polar Bonds

Chakraborty, Arundhoti
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479814963555246

Abstract Details

2016, PhD, University of Cincinnati, Arts and Sciences: Chemistry.
This thesis focuses on the synthesis of new transition metal complexes that show metal–metal cooperativity and metal-ligand cooperativity. Late-late and early-late heterobimetallic complexes have been synthesized and employed in important chemical transformations like benzaldehyde (PhCHO) reduction under water-gas shift reaction (WGSR) conditions and reduction of an imine moiety respectively. A bifunctional hexameric copper hydride complex has also been isolated and utilized in the catalytic hydrogenation of aldehydes, ketones and CO2. I have synthesized late-late heterobimetallic complexes containing Fe–Cu bonds where the iron center is supported by a Knolker-type cyclopentadienone ligand and the copper center is ligated to a N-heterocyclic carbene. Reactions between the Knolker’s iron tricarbonyl complexes (SiMe3 and tBu derivatives) and (IPr)CuOH lead to the formation of new Fe/Cu heterobimetallic complexes that contain a bridging hydride in the solid state. Solution IR, &sup1&sup3C{&sup1H} NMR analysis and variable temperature NMR suggest a dominant terminal iron hydride structure in solution for the SiMe3 derivative. Stoichiometric reactions of these Fe/Cu complexes with alkyl halides lead to the formation of new Fe/Cu halide complexes. Under a CO atmosphere, these Fe/Cu complexes generate the corresponding iron tricarbonyl species and the dimeric (IPr)CuH complex. Reduction of PhCHO to PhCH2OH was successfully performed under water-gas shift reaction conditions. Both metal centers are necessary to carry out the reaction demonstrating the importance of metal-metal cooperativity. Isotope labelling studies performed with &sup1&sup3CO confirmed that the Fe/Cu catalyst is indeed active in WGSR. In my second project I have synthesized and isolated a new copper hydride supported by a bis(phosphine)amine [iPrPN(H)P] ligand with a hexameric copper core. The assignment of the hydride peak in the &sup1H NMR spectrum was confirmed by comparing the &sup1H NMR spectrum of the related copper deuteride complex. Benzaldehyde and acetophenone insert into the Cu-H bond to afford the corresponding copper alkoxide products. CO2 also undergoes a facile insertion into the Cu-H bond to form the corresponding copper formate species. Isotope labelling study indicates that the insertion is reversible but favors the formation of copper formate. Hydrogenation of aldehydes, ketones and CO2 has been carried out with the copper bromide precursor under mild conditions. The copper hydride complex also serves as an effective catalyst in the hydrogenation of benzaldehyde implying its direct involvement in the catalytic reaction. Catalytic inactivity of the copper bromide species containing the [iPr(PN(Me)P] ligand in the hydrogenation reaction implies a bifunctional mechanism; however, further investigation is needed to support this mechanism. My third project focuses on the synthesis of early-late heterobimetallic complexes containing Cr–Cu bonds and the respective metal centers are supported by bulky Cp* (Cp* = 1,2,3,4,5-cyclopentadienyl) and N-heterocyclic carbene ligands. It was hypothesized that the polarity of the Cr-Cu bond and the steric crowding at the metal centers could assist in the activation of small molecules. Although activation of a variety of substrates such as H2, CO2 etc. proved unsuccessful, catalytic hydrogenation of an imine substrate led to the formation of the corresponding amine at higher temperature and pressure.
Hairong Guan, Ph.D. (Committee Chair)
William Connick, Ph.D. (Committee Member)
David Smithrud, Ph.D. (Committee Member)
175 p.
Chemistry
Organometallic Chemistry; cooperativity; heterobimetallic complexes; iron and copper catalysis; Water-Gas Shift Reaction; hydrogenation

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Citations

  • Chakraborty, A. (2016). Development of Copper Catalysts for the Reduction of Polar Bonds [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479814963555246

    APA Style (7th edition)

  • Chakraborty, Arundhoti. Development of Copper Catalysts for the Reduction of Polar Bonds. 2016. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479814963555246.

    MLA Style (8th edition)

  • Chakraborty, Arundhoti. "Development of Copper Catalysts for the Reduction of Polar Bonds." Doctoral dissertation, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479814963555246

    Chicago Manual of Style (17th edition)

ucin1479814963555246
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This open access ETD is published by University of Cincinnati and OhioLINK.