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DeLucia AA, Kelly KA, Herrera KA, Gray DL, Olshansky L. Intramolecular Hydrogen-Bond Interactions Tune Reactivity in Biomimetic Bis(μ-hydroxo)dicobalt Complexes. Inorg Chem 2021; 60:15599-15609. [PMID: 34606250 DOI: 10.1021/acs.inorgchem.1c02210] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Active site hydrogen-bond (H-bond) networks represent a key component by which metalloenzymes control the formation and deployment of high-valent transition metal-oxo intermediates. We report a series of dinuclear cobalt complexes that serve as structural models for the nonheme diiron enzyme family and feature a Co2(μ-OH)2 diamond core stabilized by intramolecular H-bond interactions. We define the conditions required for the kinetically controlled synthesis of these complexes: [Co2(μ-OH)2(μ-OAc)(κ1-OAc)2(pyR)4][PF6] (1R), where OAc = acetate and pyR = pyridine with para-substituent R, and we describe a homologous series of 1R in which the para-R substituent on pyridine is modulated. The solid state X-ray diffraction (XRD) structures of 1R are similar across the series, but in solution, their 1H NMR spectra reveal a linear free energy relationship (LFER) where, as R becomes increasingly electron-withdrawing, the intramolecular H-bond interaction between bridging μ-OH and κ1-acetate ligands results in increasingly "oxo-like" μ-OH bridges. Deprotonation of the bridging μ-OH results in the quantitative conversion to corresponding cubane complexes: [Co4(μ-O)4(μ3-OAc)4(pyR)4] (2R), which represent the thermodynamic sink of self-assembly. These reactions are unusually slow for rate-limiting deprotonation events, but rapid-mixing experiments reveal a 6000-fold rate acceleration on going from R = OMe to R = CN. These results suggest that we can tune reactivity by modulating the μ-OH pKa in the presence of intramolecular H-bond interactions to maintain stability as the octahedral d6 centers become increasingly acidic. Nature may similarly employ dynamic carboxylate-mediated H-bond interactions to control the reactivity of acidic transition metal-oxo intermediates.
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Affiliation(s)
- Alyssa A DeLucia
- Department of Chemistry, University of Illinois, Urbana-Champaign, 600 S. Mathews Ave. Urbana, Illinois 61801, United States
| | - Kimberly A Kelly
- Department of Chemistry, University of Illinois, Urbana-Champaign, 600 S. Mathews Ave. Urbana, Illinois 61801, United States
| | - Kevin A Herrera
- Department of Chemistry, University of Illinois, Urbana-Champaign, 600 S. Mathews Ave. Urbana, Illinois 61801, United States
| | - Danielle L Gray
- Department of Chemistry, University of Illinois, Urbana-Champaign, 600 S. Mathews Ave. Urbana, Illinois 61801, United States
| | - Lisa Olshansky
- Department of Chemistry, University of Illinois, Urbana-Champaign, 600 S. Mathews Ave. Urbana, Illinois 61801, United States
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Kephart JA, Hecht Z, Livesay BN, Bhowmick I, Shores MP, Popescu VC, Arulsamy N, Hulley EB. Self-assembly of an organometallic Fe 9O 6 cluster from aerobic oxidation of (tmeda)Fe(CH 2tBu) 2. Chem Commun (Camb) 2020; 56:4994-4997. [PMID: 32239066 DOI: 10.1039/d0cc00011f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Aerobic oxidation of (tmeda)Fe(CH2tBu)2 in toluene or THF solution leads to the self-assembly of a magic-sized all-ferrous oxide cluster containing the Fe9O6 subunit and bearing organometallic and diamine ligands. Mössbauer studies of the cluster are consistent with an all-ferrous assignment and magnetometry reveals complex intracluster and intercluster magnetic interactions.
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Li Y, Handunneththige S, Farquhar ER, Guo Y, Talipov MR, Li F, Wang D. Highly Reactive Co III,IV2(μ-O) 2 Diamond Core Complex That Cleaves C-H Bonds. J Am Chem Soc 2019; 141:20127-20136. [PMID: 31794198 DOI: 10.1021/jacs.9b09531] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The selective activation of strong sp3 C-H bonds at mild conditions is a key step in many biological and synthetic transformations and an unsolved challenge for synthetic chemists. In nature, soluble methane monooxygenase (sMMO) is one representative example of nonheme dinuclear iron-dependent enzymes that activate strong sp3 C-H bonds by a high-valent diiron(IV) intermediate Q. To date, synthetic model complexes of sMMO-Q have shown limited abilities to oxidize strong C-H bonds. In this work, we generated a high-valent CoIII,IV2(μ-O)2 complex 3 supported by a tetradentate tris(2-pyridylmethyl)amine (TPA) ligand via one-electron oxidation of its CoIII2(μ-O)2 precursor 2. Characterization of 2 and 3 using X-ray absorption spectroscopy and DFT calculations showed that both species possess a diamond core structure with a short Co···Co distance of 2.78 Å. Furthermore, 3 is an EPR active species showing an S = 1/2 signal with clearly observable hyperfine splittings originated from the coupling of the 59Co nuclear spin with the electronic spin. Importantly, 3 is a highly reactive oxidant for sp3 C-H bonds, and an oxygenation reagent. 3 has the highest rate constant (1.5 M-1 s-1 at -60 °C) for oxidizing 9,10-dihydroanthracene (DHA) compared to diamond core complexes of other first-row transition metals including Mn, Fe and Cu reported previously. Specifically, 3 is about 4-5 orders of magnitude more reactive than the diiron analogs FeIII,IV2(μ-O)2 and FeIV2(μ-O)2 supported by TPA and related ligands. These findings shed light on future development of more reactive approaches for C-H bond activation by bioinspired dicobalt complexes.
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Affiliation(s)
- Yan Li
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics , University of Montana , Missoula , Montana 59803 , United States
| | - Suhashini Handunneththige
- Department of Chemistry and Biochemistry , New Mexico State University , Las Cruces , New Mexico 88003 , United States
| | - Erik R Farquhar
- CWRU Center for Synchrotron Biosciences, NSLS-II , Brookhaven National Laboratory , Upton , New York 11973 , United States.,School of Medicine , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Yisong Guo
- Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Marat R Talipov
- Department of Chemistry and Biochemistry , New Mexico State University , Las Cruces , New Mexico 88003 , United States
| | - Feifei Li
- Department of Chemistry and Biochemistry , New Mexico State University , Las Cruces , New Mexico 88003 , United States
| | - Dong Wang
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics , University of Montana , Missoula , Montana 59803 , United States
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Bukhryakov KV, Schrock RR, Hoveyda AH, Müller P, Becker J. Synthesis of 2,6-Hexa-tert-butylterphenyl Derivatives, 2,6-(2,4,6-t-Bu 3C 6H 2) 2C 6H 3X, where X = I, Li, OH, SH, N 3, or NH 2. Org Lett 2017; 19:2607-2609. [PMID: 28459588 PMCID: PMC5811262 DOI: 10.1021/acs.orglett.7b01062] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A "double benzyne" reaction between 1,3-dichloro-2-iodobenzene and 2,4,6-t-Bu3C6H2MgBr followed by the addition of iodine led to 2,6-(2,4,6-t-Bu3C6H2)2C6H3I (HTBTI) in 65% yield. Lithiation of HTBTI with Li-t-Bu gave Li(Et2O)2HTBT from which HTBTSH, HTBTN3, HTBTNH2, and HTBTOH were prepared. An X-ray structure of W(OHTBT)2Cl4 shows that the two HTBTO ligands are trans to one another with the t-Bu3C6H2 groups on one HTBTO interdigitated with the t-Bu3C6H2 groups on the other HTBTO.
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Affiliation(s)
- Konstantin V. Bukhryakov
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Richard R. Schrock
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Amir H. Hoveyda
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Peter Müller
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Jonathan Becker
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Lake BRM, Shaver MP. Iron(ii) β-ketiminate complexes as mediators of controlled radical polymerisation. Dalton Trans 2016; 45:15840-15849. [DOI: 10.1039/c6dt01208f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A series of novel iron(ii) β-ketiminate complexes have been prepared and screened in styrene and methyl methacrylate CRP.
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