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Bennett MT, Park KA, Musgrave CB, Brubaker JW, Dickie DA, Goddard WA, Gunnoe TB. Hexa-Fe(III) Carboxylate Complexes Facilitate Aerobic Hydrocarbon Oxidative Functionalization: Rh Catalyzed Oxidative Coupling of Benzene and Ethylene to Form Styrene. ACS Catal 2024; 14:10295-10316. [PMID: 38988649 PMCID: PMC11232027 DOI: 10.1021/acscatal.4c02355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2024] [Revised: 06/04/2024] [Accepted: 06/05/2024] [Indexed: 07/12/2024]
Abstract
Fe(II) carboxylates react with dioxygen and carboxylic acid to form Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 (X = acetate or pivalate), which is an active oxidant for Rh-catalyzed arene alkenylation. Heating (150-200 °C) the catalyst precursor [(η2-C2H4)2Rh(μ-OAc)]2 with ethylene, benzene, Fe(II) carboxylate, and dioxygen yields styrene >30-fold faster than the reaction with dioxygen in the absence of the Fe(II) carboxylate additive. It is also demonstrated that Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 is an active oxidant under anaerobic conditions, and the reduced material can be reoxidized to Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 by dioxygen. At optimized conditions, a turnover frequency of ∼0.2 s-1 is achieved. Unlike analogous reactions with Cu(II) carboxylate oxidants, which undergo stoichiometric Cu(II)-mediated production of phenyl esters (e.g., phenyl acetate) as side products at temperatures ≥150 °C, no phenyl ester side product is observed when Fe carboxylate additives are used. Kinetic isotope effect experiments using C6H6 and C6D6 give k H/k D = 3.5(3), while the use of protio or monodeutero pivalic acid reveals a small KIE with k H/k D = 1.19(2). First-order dependencies on Fe(II) carboxylate and dioxygen concentration are observed in addition to complicated kinetic dependencies on the concentration of carboxylic acid and ethylene, both of which inhibit the reaction rate at a high concentration. Mechanistic studies are consistent with irreversible benzene C-H activation, ethylene insertion into the formed Rh-Ph bond, β-hydride elimination, and reaction of Rh-H with Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 to regenerate a Rh-carboxylate complex.
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Affiliation(s)
- Marc T. Bennett
- Department
of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Kwanwoo A. Park
- Department
of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Charles B. Musgrave
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - Jack W. Brubaker
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - Diane A. Dickie
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - William A. Goddard
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - T. Brent Gunnoe
- Department
of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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Reid C, Gunnoe TB. Rhodium-Catalyzed Oxidative Alkenylation of Anisole: Control of Regioselectivity. Organometallics 2024; 43:1362-1376. [PMID: 38938896 PMCID: PMC11200324 DOI: 10.1021/acs.organomet.4c00155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 05/26/2024] [Accepted: 05/30/2024] [Indexed: 06/29/2024]
Abstract
We report the conversion of anisoles and olefins to alkenyl anisoles via a transition-metal-catalyzed arene C-H activation and olefin insertion mechanism. The catalyst precursor, [(η2-C2H4)2Rh(μ-OAc)]2, and the in situ oxidant Cu(OPiv)2 (OPiv = pivalate) convert anisoles and olefins (ethylene or propylene) to alkenyl anisoles. When ethylene is used as the olefin, the o/m/p ratio varies between approximately 1:3:1 (selective for 3-methoxystyrene) and 1:5:10 (selective for 4-methoxystyrene). When propylene is the olefin, the o/m/p regioselectivity varies between approximately 1:8:20 and 1:8.5:5. The o/m/p ratios depend on the concentration of pivalic acid and olefin. For example, when using ethylene, at relatively high pivalic acid concentrations and low ethylene concentrations, the o/m/p regioselectivity is 1:3:1. Conversely, again for use of ethylene, at relatively low pivalic acid concentrations and high ethylene concentrations, the o/m/p regioselectivity is 1:5:10. Mechanistic studies of the conversion of anisoles and olefins to alkenyl anisoles provide evidence that the regioselectivity is likely under Curtin-Hammett conditions.
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Affiliation(s)
- Christopher
W. Reid
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - T. Brent Gunnoe
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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Ketcham H, Zhu W, Gunnoe TB. Highly Anti-Markovnikov Selective Oxidative Arene Alkenylation Using Ir(I) Catalyst Precursors and Cu(II) Carboxylates. Organometallics 2024; 43:774-786. [PMID: 38606203 PMCID: PMC11005047 DOI: 10.1021/acs.organomet.4c00030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 02/21/2024] [Accepted: 03/04/2024] [Indexed: 04/13/2024]
Abstract
The Ir(I) complex [Ir(μ-Cl)(coe)2]2 (coe = cis-cyclooctene) is a catalyst precursor for benzene alkenylation using Cu(II) carboxylate salts. Using [Ir(μ-Cl)(coe)2]2, propenylbenzenes are formed from the reaction of benzene, propylene, and CuX2 (X = acetate, pivalate, or 2-ethylhexanoate). The Ir-catalyzed reactions selectively produce anti-Markovnikov products, trans-β-methylstyrene, cis-β-methylstyrene, and allylbenzene, along with minor amounts of the Markovnikov product, α-methylstyrene. The selectivity for the anti-Markovnikov products changed as the reaction progressed. For example, in a reaction that uses 240 equiv of Cu(OHex)2 (related to Ir), the selectivity for the anti-Markovnikov products increases from 18:1 at 3 h to 42:1 at 42 h with 30 psig of propylene at 150 °C. Studies of product stability have revealed that the increase in the selectivity for anti-Markovnikov products is not the result of an isomerization process or the selective decomposition of specific products. Rather, the change in selectivity correlates with the ratio of Cu(II) to Cu(I) in the solution, which decreases as the reaction progresses. We propose that the identity of the active catalyst changes as Cu(I) is accumulated, resulting in the formation of an active catalyst that is more selective for anti-Markovnikov products. Using a 4:1 Cu(I)/Cu(II) ratio at the start of the reaction, a 65(3):1 anti-Markovnikov/Markovnikov ratio is observed.
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Affiliation(s)
- Hannah Ketcham
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Weihao Zhu
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - T. Brent Gunnoe
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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Bennett MT, Jia X, Musgrave CB, Zhu W, Goddard WA, Gunnoe TB. Pd(II) and Rh(I) Catalytic Precursors for Arene Alkenylation: Comparative Evaluation of Reactivity and Mechanism Based on Experimental and Computational Studies. J Am Chem Soc 2023. [PMID: 37392467 DOI: 10.1021/jacs.3c04295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/03/2023]
Abstract
We combine experimental and computational investigations to compare and understand catalytic arene alkenylation using the Pd(II) and Rh(I) precursors Pd(OAc)2 and [(η2-C2H4)2Rh(μ-OAc)]2 with arene, olefin, and Cu(II) carboxylate at elevated temperatures (>120 °C). Under specific conditions, previous computational and experimental efforts have identified heterotrimetallic cyclic PdCu2(η2-C2H4)3(μ-OPiv)6 and [(η2-C2H4)2Rh(μ-OPiv)2]2(μ-Cu) (OPiv = pivalate) species as likely active catalysts for these processes. Further studies of catalyst speciation suggest a complicated equilibrium between Cu(II)-containing complexes containing one Rh or Pd atom with complexes containing two Rh or Pd atoms. At 120 °C, Rh catalysis produces styrene >20-fold more rapidly than Pd. Also, at 120 °C, Rh is ∼98% selective for styrene formation, while Pd is ∼82% selective. Our studies indicate that Pd catalysis has a higher predilection toward olefin functionalization to form undesired vinyl ester, while Rh catalysis is more selective for arene/olefin coupling. However, at elevated temperatures, Pd converts vinyl ester and arene to vinyl arene, which is proposed to occur through low-valent Pd(0) clusters that are formed in situ. Regardless of arene functionality, the regioselectivity for alkenylation of mono-substituted arenes with the Rh catalyst gives an approximate 2:1 meta/para ratio with minimal ortho C-H activation. In contrast, Pd selectivity is significantly influenced by arene electronics, with electron-rich arenes giving an approximate 1:2:2 ortho/meta/para ratio, while the electron-deficient (α,α,α)-trifluorotoluene gives a 3:1 meta/para ratio with minimal ortho functionalization. Kinetic intermolecular arene ethenylation competition experiments find that Rh reacts most rapidly with benzene, and the rate of mono-substituted arene alkenylation does not correlate with arene electronics. In contrast, with Pd catalysis, electron-rich arenes react more rapidly than benzene, while electron-deficient arenes react less rapidly than benzene. These experimental findings, in combination with computational results, are consistent with the arene C-H activation step for Pd catalysis involving significant η1-arenium character due to Pd-mediated electrophilic aromatic substitution character. In contrast, the mechanism for Rh catalysis is not sensitive to arene-substituent electronics, which we propose indicates less electrophilic aromatic substitution character for the Rh-mediated arene C-H activation.
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Affiliation(s)
- Marc T Bennett
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Xiaofan Jia
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Charles B Musgrave
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States
| | - Weihao Zhu
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - William A Goddard
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States
| | - T Brent Gunnoe
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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Ketcham HE, Bennett MT, Reid CW, Gunnoe TB. Advances in arene alkylation and alkenylation catalyzed by transition metal complexes based on ruthenium, nickel, palladium, platinum, rhodium and iridium. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2023. [DOI: 10.1016/bs.adomc.2023.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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Kong F, Chen S, Chen J, Liu C, Zhu W, Dickie DA, Schinski WL, Zhang S, Ess DH, Gunnoe TB. Cu(II) carboxylate arene C─H functionalization: Tuning for nonradical pathways. SCIENCE ADVANCES 2022; 8:eadd1594. [PMID: 36001664 PMCID: PMC9401614 DOI: 10.1126/sciadv.add1594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 07/11/2022] [Indexed: 06/15/2023]
Abstract
We report carbon-hydrogen acetoxylation of nondirected arenes benzene and toluene, as well as related functionalization with pivalate and 2-ethylhexanoate ester groups, using simple copper(II) [Cu(II)] salts with over 80% yield. By changing the ratio of benzene and Cu(II) salts, 2.4% conversion of benzene can be reached. Combined experimental and computational studies results indicate that the arene carbon-hydrogen functionalization likely occurs by a nonradical Cu(II)-mediated organometallic pathway. The Cu(II) salts used in the reaction can be isolated, recycled, and reused with little change in reactivity. In addition, the Cu(II) salts can be regenerated in situ using oxygen and, after the removal of the generated water, the arene carbon-hydrogen acetoxylation and related esterification reactions can be continued, which leads to a process that enables recycling of Cu(II).
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Affiliation(s)
- Fanji Kong
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Shusen Chen
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84604, USA
| | - Junqi Chen
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Chang Liu
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Weihao Zhu
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Diane A. Dickie
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | | | - Sen Zhang
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Daniel H. Ess
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84604, USA
| | - T. Brent Gunnoe
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
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Musgrave CB, Bennett MT, Ellena JF, Dickie DA, Gunnoe TB, Goddard WA. Reaction Mechanism Underlying Pd(II)-Catalyzed Oxidative Coupling of Ethylene and Benzene to Form Styrene: Identification of a Cyclic Mono-Pd II Bis-Cu II Complex as the Active Catalyst. Organometallics 2022. [DOI: 10.1021/acs.organomet.2c00183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Charles B. Musgrave
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States
| | - Marc T. Bennett
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Jeffrey F. Ellena
- Biomolecular Magnetic Resonance Facility, School of Medicine, University of Virginia, Charlottesville, Virginia 22908, United States
| | - Diane A. Dickie
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - T. Brent Gunnoe
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - William A. Goddard
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States
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Ghosh S, Shilpa S, Athira C, Sunoj RB. Role of Additives in Transition Metal Catalyzed C–H Bond Activation Reactions: A Computational Perspective. Top Catal 2021. [DOI: 10.1007/s11244-021-01527-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Sciortino G, Maseras F. Computational Study of Homogeneous Multimetallic Cooperative Catalysis. Top Catal 2021. [DOI: 10.1007/s11244-021-01493-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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