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Beagan DM, Rivera C, Szymczak NK. Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II). J Am Chem Soc 2024; 146:12375-12385. [PMID: 38661576 DOI: 10.1021/jacs.3c12399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
We disclose a suite of Ni(II) complexes featuring secondary sphere Lewis acids of varied Lewis acidity and tether lengths. Several of these complexes feature atypical behavior of Ni(II): reactivity with O2 that occurs only in the presence of a tethered Lewis acid. In situ UV-vis spectroscopy revealed that, although adducts are stable at -40 °C, complexes containing 9-borabicyclo[3.3.1]nonane (9-BBN) Lewis acids underwent irreversible oxidative deborylation when warmed to room temperature. We computationally and experimentally identified that oxidative instability of appended 9-BBN moieties can be mitigated using weaker Lewis acids such as pinacolborane (BPin). These insights enabled the realization of catalytic reactions: hydrogen atom abstraction from phenols and room temperature oxygen atom transfer to PPh3.
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Affiliation(s)
- Daniel M Beagan
- University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, United States
| | - Carolina Rivera
- University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, United States
| | - Nathaniel K Szymczak
- University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, United States
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Durfy CS, Zurakowski JA, Jobin G, Drover MW. An Investigation of Allyl-Substituted Bis(Diphosphine) Iron Complexes: Towards Precursors for Cooperative CO 2 Activation. Chemistry 2024; 30:e202302721. [PMID: 37724786 DOI: 10.1002/chem.202302721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 09/18/2023] [Accepted: 09/19/2023] [Indexed: 09/21/2023]
Abstract
In developing homogenous catalysts capable of CO2 activation, interaction with a metal center is often imperative. This work provides primary efforts towards the cooperative activation of CO2 using a Lewis acidic secondary coordination sphere (SCS) and iron via a paired theoretical/experimental approach. Specifically, this study reports efforts towards [Fe(diphosphine)2 (N2 )] as a CO2 -coordinated synthon where diphosphine=1,2-bis(di(3-cyclohexylboranyl)propylphosphino)ethane) (P2 BCy 4 ) or its precursor, 1,2-bis(diallylphosphino)ethane (tape). Initial efforts toward the {Fe(0)-N2 } complex were focused on deprotonation reactions of [Fe(diphosphine)2 (H)(NCCH3 )]+ and reduction of [Fe(tape)2 Cl2 ]. In the latter case, a mixture of intramolecularly π-bonded alkene and associated metallacyclic Fe(II)-H species were produced - heating this mixture provided the hydride as the major product. Notably, the interconversion of this pair counters that of related intermolecular reactions between [Fe(depe)2 ] (depe=1,2-bis(diethylphosphino)ethane) and ethylene, where hydride formation occurs subsequent to π-coordination; this has been probed by theoretical calculations. Finally, reactivity of the metallacyclic {Fe(II)-H} complex with CO2 was probed, resulting in a pair of isomeric ferra(II)lactones.
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Affiliation(s)
- Connor S Durfy
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada
- Department of Chemistry, Western University, 1151 Richmond Street, London, ON, N6A 3K7, Canada
| | - Joseph A Zurakowski
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada
- Department of Chemistry, Western University, 1151 Richmond Street, London, ON, N6A 3K7, Canada
| | - Gabriel Jobin
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada
- Department of Chemistry, Western University, 1151 Richmond Street, London, ON, N6A 3K7, Canada
| | - Marcus W Drover
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada
- Department of Chemistry, Western University, 1151 Richmond Street, London, ON, N6A 3K7, Canada
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Wang B, Seo CSG, Zhang C, Chu J, Szymczak NK. A Borane Lewis Acid in the Secondary Coordination Sphere of a Ni(II) Imido Imparts Distinct C-H Activation Selectivity. J Am Chem Soc 2022; 144:15793-15802. [PMID: 35973127 PMCID: PMC10276360 DOI: 10.1021/jacs.2c06662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Two borane-functionalized bidentate phosphine ligands that vary in tether length have been prepared to examine cooperative metal-substrate interactions. Ni(0) complexes react with aryl azides at low temperatures to form structurally unusual κ2-(N,N)-N3Ar adducts. Warming these adducts affords products of N2 extrusion and in one case, a Ni-imido compound that is capped by the appended borane. Reactions with 1-azidoadamantane (AdN3) provide a distinct outcome, where a proposed nickel imido intermediate activates the sp2 C-H bonds of arenes, even in the presence of benzylic C-H sites. Combined experimental and computational mechanistic studies demonstrate that the unique reactivity is a consequence of Lewis-acid-induced polarization of the Ni-NR bond, potentially providing a synthetic strategy for chemoselective reaction engineering.
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Affiliation(s)
- Baolu Wang
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 10049, P. R. China
| | - Chris S. G. Seo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Cuijuan Zhang
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 10049, P. R. China
| | - Jiaxiang Chu
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 10049, P. R. China
| | - Nathaniel K. Szymczak
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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