1
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Reyna JA, Krishnan VM, Silva Villatoro R, Arman HD, Stoian SA, Tonzetich ZJ. Square-planar imido complexes of cobalt: synthesis, reactivity and computational study. Dalton Trans 2024; 53:12128-12137. [PMID: 38979933 DOI: 10.1039/d4dt01483a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Treatment of [Co(N2)(tBuPNP)] (tBuPNP = anion of 2,5-bis(di-tert-butylphosphinomethyl)pyrrole) with one equivalent of an aryl azide generates the four-coordinate imido complexes [Co(NAr)(tBuPNP)] (Ar = mesityl, phenyl, or 4-tBu-phenyl). X-ray crystallographic analysis of the compounds shows an unusual square-planar geometry about cobalt with nearly linear imido units. In the presence of the hydrogen atom donor, TEMPOH, [Co(NPh)(tBuPNP)] undergoes addition of the H atom to the imido nitrogen to generate the corresponding amido complex, [Co(NHPh)(tBuPNP)], whose structure and composition were verified by independent synthesis. Despite the observation of H atom transfer reactivity with TEMPOH, the imido complexes do not show catalytic activity for C-H amination or aziridination for several substrates examined. In the case of [Co(NPh)(tBuPNP)], addition of excess azide produced the tetrazido complex, [Co(N4Ph2)(tBuPNP)], whose bond metrics were most consistent with an anionic Ph2N4 ligand. Density Functional Theory (DFT) investigations of the imido and tetrazido species suggest that they adopt a ground state best described as possessing a low-spin cobalt(II) ion ferromagnetically coupled to an iminyl radical.
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Affiliation(s)
- Jackson A Reyna
- Department of Chemistry, University of Texas at San Antonio (UTSA), San Antonio, TX 78249, USA.
| | - V Mahesh Krishnan
- Department of Chemistry, University of Texas at San Antonio (UTSA), San Antonio, TX 78249, USA.
| | - Roberto Silva Villatoro
- Department of Chemistry, University of Texas at San Antonio (UTSA), San Antonio, TX 78249, USA.
| | - Hadi D Arman
- Department of Chemistry, University of Texas at San Antonio (UTSA), San Antonio, TX 78249, USA.
| | | | - Zachary J Tonzetich
- Department of Chemistry, University of Texas at San Antonio (UTSA), San Antonio, TX 78249, USA.
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2
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Malik DD, Ryu W, Kim Y, Singh G, Kim JH, Sankaralingam M, Lee YM, Seo MS, Sundararajan M, Ocampo D, Roemelt M, Park K, Kim SH, Baik MH, Shearer J, Ray K, Fukuzumi S, Nam W. Identification, Characterization, and Electronic Structures of Interconvertible Cobalt-Oxygen TAML Intermediates. J Am Chem Soc 2024; 146:13817-13835. [PMID: 38716885 PMCID: PMC11216523 DOI: 10.1021/jacs.3c14346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
The reaction of Li[(TAML)CoIII]·3H2O (TAML = tetraamido macrocyclic tetraanionic ligand) with iodosylbenzene at 253 K in acetone in the presence of redox-innocent metal ions (Sc(OTf)3 and Y(OTf)3) or triflic acid affords a blue species 1, which is converted reversibly to a green species 2 upon cooling to 193 K. The electronic structures of 1 and 2 have been determined by combining advanced spectroscopic techniques (X-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), X-ray absorption spectroscopy/extended X-ray absorption fine structure (XAS/EXAFS), and magnetic circular dichroism (MCD)) with ab initio theoretical studies. Complex 1 is best represented as an S = 1/2 [(Sol)(TAML•+)CoIII---OH(LA)]- species (LA = Lewis/Brønsted acid and Sol = solvent), where an S = 1 Co(III) center is antiferromagnetically coupled to S = 1/2 TAML•+, which represents a one-electron oxidized TAML ligand. In contrast, complex 2, also with an S = 1/2 ground state, is found to be multiconfigurational with contributions of both the resonance forms [(H-TAML)CoIV═O(LA)]- and [(H-TAML•+)CoIII═O(LA)]-; H-TAML and H-TAML•+ represent the protonated forms of TAML and TAML•+ ligands, respectively. Thus, the interconversion of 1 and 2 is associated with a LA-associated tautomerization event, whereby H+ shifts from the terminal -OH group to TAML•+ with the concomitant formation of a terminal cobalt-oxo species possessing both singlet (SCo = 0) Co(III) and doublet (SCo = 1/2) Co(IV) characters. The reactivities of 1 and 2 at different temperatures have been investigated in oxygen atom transfer (OAT) and hydrogen atom transfer (HAT) reactions to compare the activation enthalpies and entropies of 1 and 2.
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Affiliation(s)
- Deesha D Malik
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Wooyeol Ryu
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Yujeong Kim
- Western Seoul Center, Korea Basic Science Institute, Seoul 03759, Korea
| | - Gurjot Singh
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Jun-Hyeong Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science, Daejeon 34141, Korea
| | | | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Mi Sook Seo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Mahesh Sundararajan
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science, Daejeon 34141, Korea
- Theoretical Chemistry Section, Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - Daniel Ocampo
- Department of Chemistry, Trinity University, San Antonio, Texas 78212-7200, United States
| | - Michael Roemelt
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Kiyoung Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Sun Hee Kim
- Western Seoul Center, Korea Basic Science Institute, Seoul 03759, Korea
- Department of Chemistry, Chung-Ang University, Seoul 06974, Korea
| | - Mu-Hyun Baik
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science, Daejeon 34141, Korea
| | - Jason Shearer
- Department of Chemistry, Trinity University, San Antonio, Texas 78212-7200, United States
| | - Kallol Ray
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
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3
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Scott JS, Schneider JE, Tewelde EG, Gardner JG, Anferov SW, Filatov AS, Anderson JS. Combining Donor Strength and Oxidative Stability in Scorpionates: A Strongly Donating Fluorinated Mesoionic Tris(imidazol-5-ylidene)borate Ligand. Inorg Chem 2023; 62:21224-21232. [PMID: 38051936 DOI: 10.1021/acs.inorgchem.3c03251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Strongly donating scorpionate ligands support the study of high-valent transition metal chemistry; however, their use is frequently limited by oxidative degradation. To address this concern, we report the synthesis of a tris(imidazol-5-ylidene)borate ligand featuring trifluoromethyl groups surrounding its coordination pocket. This ligand represents the first example of a chelating poly(imidazol-5-ylidene) mesoionic carbene ligand, a scaffold that is expected to be extremely donating. The {NiNO}10 complex of this ligand, as well as that of a previously reported strongly donating tris(imidazol-2-ylidene)borate, has been synthesized and characterized. This new ligand's strong donor properties, as measured by the υNO of its {NiNO}10 complex and natural bonding orbital second-order perturbative energy analysis, are at par with those of the well-studied alkyl-substituted tris(imidazol-2-ylidene)borates, which are known to effectively stabilize high-valent intermediates. The good donor properties of this ligand, despite the electron-withdrawing trifluoromethyl substituents, arise from the strongly donating imidazol-5-ylidene mesoionic carbene arms. These donor properties, when combined with the robustness of trifluoromethyl groups toward oxidative decomposition, suggest this ligand scaffold will be a useful platform in the study of oxidizing high-valent transition-metal species.
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Affiliation(s)
- Joseph S Scott
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Joseph E Schneider
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Eyob G Tewelde
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Joel G Gardner
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Sophie W Anferov
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Alexander S Filatov
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - John S Anderson
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
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4
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Moore SM, Sun C, Steele JL, Laaker EM, Rheingold AL, Doerrer LH. HAA by the first {Mn(iii)OH} complex with all O-donor ligands. Chem Sci 2023; 14:8187-8195. [PMID: 37538819 PMCID: PMC10395311 DOI: 10.1039/d3sc01971c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 07/05/2023] [Indexed: 08/05/2023] Open
Abstract
There is considerable interest in MnOHx moieties, particularly in the stepwise changes in those O-H bonds in tandem with Mn oxidation state changes. The reactivity of aquo-derived ligands, {MOHx}, is also heavily influenced by the electronic character of the other ligands. Despite the prevalence of oxygen coordination in biological systems, preparation of mononuclear Mn complexes of this type with all O-donors is rare. Herein, we report several Mn complexes with perfluoropinacolate (pinF)2- including the first example of a crystallographically characterized mononuclear {Mn(iii)OH} with all O-donors, K2[Mn(OH)(pinF)2], 3. Complex 3 is prepared via deprotonation of K[Mn(OH2)(pinF)2], 1, the pKa of which is estimated to be 18.3 ± 0.3. Cyclic voltammetry reveals quasi-reversible redox behavior for both 1 and 3 with an unusually large ΔEp, assigned to the Mn(iii/ii) couple. Using the Bordwell method, the bond dissociation free energy (BDFE) of the O-H bond in {Mn(ii)-OH2} is estimated to be 67-70 kcal mol-1. Complex 3 abstracts H-atoms from 1,2-diphenylhydrazine, 2,4,6-TTBP, and TEMPOH, the latter of which supports a PCET mechanism. Under basic conditions in air, the synthesis of 1 results in K2[Mn(OAc)(pinF)2], 2, proposed to result from the oxidation of Et2O to EtOAc by a reactive Mn species, followed by ester hydrolysis. Complex 3 alone does not react with Et2O, but addition of O2 at low temperature effects the formation of a new chromophore proposed to be a Mn(iv) species. The related complexes K(18C6)[Mn(iii)(pinF)2], 4, and (Me4N)2[Mn(ii)(pinF)2], 5, have also been prepared and their properties discussed in relation to complexes 1-3.
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Affiliation(s)
- Shawn M Moore
- Boston University, Chemistry Department 590 Commonwealth Avenue Boston Massachusetts 02215 USA
| | - Chen Sun
- Boston University, Chemistry Department 590 Commonwealth Avenue Boston Massachusetts 02215 USA
| | - Jennifer L Steele
- Boston University, Chemistry Department 590 Commonwealth Avenue Boston Massachusetts 02215 USA
| | - Ellen M Laaker
- Boston University, Chemistry Department 590 Commonwealth Avenue Boston Massachusetts 02215 USA
| | - Arnold L Rheingold
- University of California, San Diego Department of Chemistry and Biochemistry 9500 Gilman Drive La Jolla California 92093 USA
| | - Linda H Doerrer
- Boston University, Chemistry Department 590 Commonwealth Avenue Boston Massachusetts 02215 USA
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5
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Homuth PA, McNeely J, Doerrer LH. Extra-long C C single bonds via negative hyperconjugation in perfluoropinacolate complexes. Polyhedron 2022. [DOI: 10.1016/j.poly.2022.116040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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6
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Heinemann J, Klüfers P. [Ti(fpin)
3
]
2−
: a structurally characterized transition metal tris(perfluoropinacolato) complex. Z Anorg Allg Chem 2021. [DOI: 10.1002/zaac.202000449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jan Heinemann
- Ludwig-Maximilians-Universität Department Chemie Butenandtstraße 5–13 81377 München Germany
| | - Peter Klüfers
- Ludwig-Maximilians-Universität Department Chemie Butenandtstraße 5–13 81377 München Germany
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7
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Elinburg JK, Carter SL, Nelson JJM, Fraser DG, Crockett MP, Beeler AB, Nordlander E, Rheingold AL, Doerrer LH. Reversible PCET and Ambient Catalytic Oxidative Alcohol Dehydrogenation by {V=O} Perfluoropinacolate Complexes. Inorg Chem 2020; 59:16500-16513. [PMID: 33119300 DOI: 10.1021/acs.inorgchem.0c02367] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new air-stable catalyst for the oxidative dehydrogenation of benzylic alcohols under ambient conditions has been developed. The synthesis and characterization of this compound and the related monomeric and dimeric V(IV)- and V(V)-pinF (pinF = perfluoropinacolate) complexes are reported herein. Monomeric V(IV) complex (Me4N)2[V(O)(pinF)2] (1) and dimeric (μ-O)2-bridged V(V) complex (Me4N)2[V2(O)2(μ-O)2(pinF)2] (3a) are prepared in water under ambient conditions. Monomeric V(V) complex (Me4N)[V(O)(pinF)2] (2) may be generated via chemical oxidation of 1 under an inert atmosphere, but dimerizes to 3a upon exposure to air. Complexes 1 and 2 display a perfectly reversible VIV/V couple at 20 mV (vs Ag/AgNO3), whereas a quasi-reversible VIV/V couple at -865 mV is found for 3a. Stoichiometric reactions of 3a with both fluorenol and TEMPOH result in the formation of (Me4N)2[V2(O)2(μ-OH)2(pinF)2] (4a), which contains two V(IV) centers that display antiferromagnetic coupling. In order to structurally characterize the dinuclear anion of 4a, {K(18C6)}+ countercations were employed, which formed stabilizing K···O interactions between the counterion and each terminal oxo moiety and H-bonding between the oxygen atoms of the crown ether and μ-OH bridges of the dimer, resulting in {K(18C6)}2[V2(O)2(μ-OH)2(pinF)2] (4b). The formal storage of H2 in 4a is reversible and proton-coupled electron transfer (PCET) from crystals of 4a regenerates 3a upon exposure to air over the course of several days. Furthermore, the reaction of 3a (2%) under ambient conditions with excess fluorenol, cinnamyl alcohol, or benzyl alcohol resulted in the selective formation of fluorenone (82% conversion), cinnamaldehyde (40%), or benzaldehyde (7%), respectively, reproducing oxidative alcohol dehydrogenation (OAD) chemistry known for VOx surfaces and demonstrating, in air, the thermodynamically challenging selective oxidation of alcohols to aldehydes/ketones.
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Affiliation(s)
- Jessica K Elinburg
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Samantha L Carter
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Joshua J M Nelson
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Douglas G Fraser
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Michael P Crockett
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - Aaron B Beeler
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Ebbe Nordlander
- Chemical Physics, Department of Chemistry, Lund University, Lund SE-221 00, Sweden
| | - Arnold L Rheingold
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, MC 0332, La Jolla, California 92093, United States
| | - Linda H Doerrer
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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8
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Elinburg JK, Doerrer LH. Synthesis, structure, and electronic properties of late first-row transition metal complexes of fluorinated alkoxides and aryloxides. Polyhedron 2020. [DOI: 10.1016/j.poly.2020.114765] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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9
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Elinburg JK, Hyre AS, McNeely J, Alam TM, Klenner S, Pöttgen R, Rheingold AL, Doerrer LH. Formation of monomeric Sn(ii) and Sn(iv) perfluoropinacolate complexes and their characterization by 119Sn Mössbauer and 119Sn NMR spectroscopies. Dalton Trans 2020; 49:13773-13785. [PMID: 33000834 DOI: 10.1039/d0dt02837a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis and characterization of a series of Sn(ii) and Sn(iv) complexes supported by the highly electron-withdrawing dianionic perfluoropinacolate (pinF) ligand are reported herein. Three analogs of [SnIV(pinF)3]2- with NEt3H+ (1), K+ (2), and {K(18C6)}+ (3) counter cations and two analogs of [SnII(pinF)2]2- with K+ (4) and {K(15C5)2}+ (5) counter cations were prepared and characterized by standard analytical methods, single-crystal X-ray diffraction, and 119Sn Mössbauer and NMR spectroscopies. The six-coordinate SnIV(pinF) complexes display 119Sn NMR resonances and 119Sn Mössbauer spectra similar to SnO2 (cassiterite). In contrast, the four-coordinate SnII(pinF) complexes, featuring a stereochemically-active lone pair, possess low 119Sn NMR chemical shifts and relatively high quadrupolar splitting. Furthermore, the Sn(ii) complexes are unreactive towards both Lewis bases (pyridine, NEt3) and acids (BX3, Et3NH+). Calculations confirm that the Sn(ii) lone pair is localized within the 5s orbital and reveal that the Sn 5px LUMO is energetically inaccessible, which effectively abates reactivity.
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Affiliation(s)
- Jessica K Elinburg
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA.
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10
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Brazeau SE, Pope F, Huang VL, Anklin C, Rheingold AL, Doerrer LH. Phosphine ligands as protecting groups for 3d complexes in oxidation by O2. Polyhedron 2020. [DOI: 10.1016/j.poly.2020.114609] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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11
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Brazeau SEN, Doerrer LH. Cu(i)-O 2 oxidation reactions in a fluorinated all-O-donor ligand environment. Dalton Trans 2019; 48:4759-4768. [PMID: 30869674 DOI: 10.1039/c8dt05028g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Investigation of Cu-O2 oxidation reactivity is important in biological and anthropogenic chemistry. Zeolites are one of the most promising Cu/O based oxidation catalysts for development of industrial-scale CH4 to CH3OH conversion. Their oxidation mechanisms are not well understood, however, highlighting the importance of the investigation of molecular Cu(i)-O2 reactivity with O-donor complexes. Herein, we give an overview of the synthesis, structural properties, and O2 reactivity of three different series of O-donor fluorinated Cu(i) alkoxides: K[Cu(OR)2], [(Ph3P)Cu(μ-OR)2Cu(PPh3)], and K[(R3P)Cu(pinF)], in which OR = fluorinated monodentate alkoxide ligands and pinF = perfluoropinacolate. This breadth allowed for the exploration of the influence of the denticity of the ligand, coordination number, the presence of phosphine, and KF/O interactions on their O2 reactivity. KF/O interactions were required to activate O2 in the monodentate-ligand-only family, whereas these connections did not affect O2 activation in the bidentate complexes, potentially due to the presence of phosphine. Both families formed trisanionic, trinuclear cores of the form {Cu3(μ3-O)2}3-. Intramolecular and intermolecular substrate oxidation were also explored and found to be influenced by the fluorinated ligand. Namely, {Cu3(μ3-O)2}3- from K[Cu(OR)2] could perform both monooxygenase reactivity and oxidase catalysis, whereas those from K[(R3P)Cu(pinF)] could only perform oxidase catalysis.
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Affiliation(s)
- Sarah E N Brazeau
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA.
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