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Synthesis and Reactivity of Cyclopentadienone Metal Complexes

Lydon, Evan
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1636029076230597

Abstract Details

2021, PhD, University of Cincinnati, Arts and Sciences: Chemistry.
Cyclopentadienone/hydroxycyclopentadienyl metal complexes have been of great interest to the homogenous catalysis community for their application as bifunctional hydrogenation/dehydrogenation catalysts. The stable pairing of a Lewis-acidic/basic site next to a reactive hydride or metal center creates a catalytic ‘pocket’ that can stabilize reaction transition states. Group 8 cyclopentadienone metal complexes have been extensively studied and applied to numerous organic and inorganic transformations; however, the reactivity of group 7 and 9 cyclopentadienone complexes remain comparatively less understood. Additionally, cyclopentadienone complexes have primarily been studied as standalone metal complexes, and only recently has interest in their application to bimetallic and tandem catalytic reactions emerged. Here, I will present research into newly synthesized cyclopentadienone metal complexes and their unique reactivities. Cobalt cyclopentadienone complexes have been reported in the literature; however, their synthesis has been plagued by poor yields and unwanted side products and their applications remain sparse. Novel cobalt(I) cyclopentadienone complexes were synthesized and their unique reactivity was studied. These compounds showed fast hydride transfer reactivity with triphenyl carbenium tetrafluoroborate in acetonitrile, transferring the acidic OH proton and two electrons in an unusual umpolung type reaction. This reaction was shown to be highly sensitive to solvent conditions, ligand backbone and the presence of exogenous bases and electron donors, giving some insights to its mechanism. The hydride transfer reaction was optimized to yield a class of previously uncharacterized cationic cobalt(I) cyclopentadienone complexes which were shown to be highly diversifiable with three labile coordination sites. These newly synthesized cationic cobalt complexes were screened for their reactivity in organic transformations. Manganese-based cyclopentadienone complexes are far less known; only one report was found in the literature for a manganese cyclopentadienone complex and no modern characterization data was present. A series of novel manganese(I) cyclopentadienone complexes were synthesized with increasing electron density on the metal and their reactivity with electrophiles was studied. In contrast to the cobalt system, pure manganese cyclopentadienone complexes were much less capable of umpolung hydride transfer to triphenyl carbenium tetrafluoroborates without greatly increasing the electron density on the manganese center. However, manganese cyclopentadienone complexes proved to be much more diversifiable than the cobalt analogs and a series of new ligands were installed on the manganese which allowed access to a unique manganese(III) hydride complex and an efficient manganese(I) hydride transfer reagent. Iron-nickel bimetallic complexes have been studied extensively as model complexes for the FeNi-hydrogenases found in nature. However, increasingly in homogenous catalysis, bimetallic complexes are seeing increased attention for their application in organic transformations in which two metal centers can cooperate within a catalytic cycle. A novel series of iron-nickel bimetallic complexes were synthesized and characterized. They displayed varying stabilities and reactivities dependent on the steric and electronic properties of the coordinating ligands and represent an interesting starting point for new research.
Hairong Guan, Ph.D. (Committee Chair)
Allan Pinhas (Committee Member)
Michael Baldwin, Ph.D. (Committee Member)
103 p.
Chemistry
Cyclopentadienone; Trityl Cation; Knolker; Hydroxocyclopentadiene; Masked Hydride; Tetracyclone

Recommended Citations

Citations

  • Lydon, E. (2021). Synthesis and Reactivity of Cyclopentadienone Metal Complexes [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1636029076230597

    APA Style (7th edition)

  • Lydon, Evan. Synthesis and Reactivity of Cyclopentadienone Metal Complexes. 2021. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1636029076230597.

    MLA Style (8th edition)

  • Lydon, Evan. "Synthesis and Reactivity of Cyclopentadienone Metal Complexes." Doctoral dissertation, University of Cincinnati, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1636029076230597

    Chicago Manual of Style (17th edition)

ucin1636029076230597
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© 2021, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.
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