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Metal-Ligand Cooperative Small Molecule Activation and Catalysis by a Tetradentate Bis(amido)bis(phosphine) Fe(II) Complex

Stevens, Jeremiah Edward
http://orcid.org/0000-0002-9419-5835
http://rave.ohiolink.edu/etdc/view?acc_num=osu1700665830499664

Abstract Details

2023, Doctor of Philosophy, Ohio State University, Chemistry.
Over the past several decades, the noble metals (Au, Pt, Ru, Rh, Pd, Os, and Ir) have proliferated in many industrially relevant processes. With steady growth in world population, increases in anthropogenic climate change, and negative socioeconomic impacts of sustained use of noble metals, the necessity for catalysts based on readily available, earth-abundant frst-row transition metals has grown considerably in recent years. Despite their clear sustainability advantage, the frst-row metals suffer from a reduced proclivity toward the productive two-electron processes upon which the mechanisms of their precious metal counterparts are based. Metal-ligand cooperativity (MLC) has emerged as a strategy to counteract the frst-row metals’ propensity toward one-electron processes by appending a non-innocent ligand to the metal center to mitigate the redox burden associated with substrate activation. The MLC examples most relevant to the present work involve activation of substrates across metal–ligand bonds. Often, this activation event brings about a chemical change in the ligand—e.g., the conversion of amides to amines. Herein, substrate activation across the Fe–Namide bond in a square planar S = 1 FeII complex supported by an aryl-linked bis(amido)bis(phosphine) ligand is described. In a previous work, this (PNNP)Fe complex was shown activate B–H bonds across each Fe–N linkage, producing an iron dihydride species that maintained its FeII oxidation state by virtue of MLC. Expanding on this previous result, the work herein reports activation of Si–H and C–H bonds across the Fe–N linkage in addition to functionalization of the Fe–P linkage. Upon treatment of (PNNP)Fe with a slight excess of primary silanes, a unique bridging structure in which two of the Si–H bonds of the primary silanes are activated across the Fe–N bonds of two different (PNNP)Fe units is obtained. Treatment with manifold excess primary silane, however, is shown to result in the formation of a Si–Si bond across the Fe–N bond via a dehydrogenative coupling reaction. In a similar fashion, treatment of (PNNP)Fe with two equivalents of terminal aryl alkynes results in C–H activation across the Fe–N bond to yield an iron bis(acetylide) complex. If excess alkyne is introduced to a solution of either (PNNP)Fe or the iron bis(acetylide) complex, the substrate is catalytically dimerized to form the Z-isomer of the 1,3-conjugated enyne in moderate to excellent yields. Finally, in stark contrast to the E–H (E = B, Si, C) activation observed across the Fe–N bond in the aforementioned examples, treatment of (PNNP)Fe with the nitrene transfer reagent 2,4,6-trimethylphenyl azide results in structures with one or more formally oxidized phosphine fragments. The mechanism of this transformation is proposed to involve formal FeIV––NR intermediates that intramolecularly attack the PIII donors of the (PNNP) ligand scaffold to convert them to PV donors to return the FeII oxidation state.
Christine Thomas (Advisor)
Shiyu Zhang (Committee Member)
Christopher Hadad (Committee Member)
208 p.
Chemistry
inorganic chemistry, chemistry, organometallic chemistry, computational chemistry

Recommended Citations

Citations

  • Stevens, J. E. (2023). Metal-Ligand Cooperative Small Molecule Activation and Catalysis by a Tetradentate Bis(amido)bis(phosphine) Fe(II) Complex [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1700665830499664

    APA Style (7th edition)

  • Stevens, Jeremiah. Metal-Ligand Cooperative Small Molecule Activation and Catalysis by a Tetradentate Bis(amido)bis(phosphine) Fe(II) Complex. 2023. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1700665830499664.

    MLA Style (8th edition)

  • Stevens, Jeremiah. "Metal-Ligand Cooperative Small Molecule Activation and Catalysis by a Tetradentate Bis(amido)bis(phosphine) Fe(II) Complex." Doctoral dissertation, Ohio State University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=osu1700665830499664

    Chicago Manual of Style (17th edition)

osu1700665830499664
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This open access ETD is published by The Ohio State University and OhioLINK.
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