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Bauer M, Cadge J, Davies D, Durand DJ, Eisenstein O, Ess D, Fey N, Gallarati S, George M, Hamilton A, Harvey J, Hintermair U, Hulme AN, Ishii Y, Jensen VR, Lloyd-Jones G, Love J, Lynam J, Macgregor S, Marder TB, Meijer EJ, Morgan P, Morris RH, Mwansa J, Odom A, Perutz R, Reiher M, Schafer L, Slattery J, Young T. Computational and theoretical approaches for mechanistic understanding: general discussion. Faraday Discuss 2019; 220:464-488. [DOI: 10.1039/c9fd90073j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Boyt SM, Jenek NA, Hintermair U. Synthesis of organometallic pentalenide complexes. Dalton Trans 2019; 48:5107-5124. [PMID: 30897189 DOI: 10.1039/c9dt00689c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
While a number of reports have established the unique structures and electronic properties of mono- and dinuclear pentalenide complexes of s, p, d and f block elements, access to these intriguing compounds is restricted by synthetic challenges. Here we review various strategies for the synthesis, functionalisation and (trans)metalation of pentalenide complexes from a practical point of view, pointing out promising avenues for future research that may allow wider access to novel pentalenide complexes for application in many different areas.
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Sackville EV, Marken F, Hintermair U. Cover Feature: Electrochemical and Kinetic Insights into Molecular Water Oxidation Catalysts Derived from Cp*Ir(pyridine‐alkoxide) Complexes (ChemCatChem 19/2018). ChemCatChem 2018. [DOI: 10.1002/cctc.201801528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Sackville EV, Marken F, Hintermair U. Electrochemical and Kinetic Insights into Molecular Water Oxidation Catalysts Derived from Cp*Ir(pyridine-alkoxide) Complexes. ChemCatChem 2018; 10:4280-4291. [PMID: 31007774 PMCID: PMC6470865 DOI: 10.1002/cctc.201800916] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Indexed: 01/04/2023]
Abstract
We report the solution-phase electrochemistry of seven half-sandwich iridium(III) complexes with varying pyridine-alkoxide ligands to quantify electronic ligand effects that translate to their activity in catalytic water oxidation. Our results unify some previously reported electrochemical data of Cp*Ir complexes by showing how the solution speciation determines the electrochemical response: cationic complexes show over 1 V higher redox potentials that their neutral forms in a distinct demonstration of charge accumulation effects relevant to water oxidation. Building on previous work that analysed the activation behaviour of our pyalk-ligated Cp*Ir complexes 1-7, we assess their catalytic oxygen evolution activity with sodium periodate (NaIO4) and ceric ammonium nitrate (CAN) in water and aqueous tBuOH solution. Mechanistic studies including H/D kinetic isotope effects and reaction progress kinetic analysis (RPKA) of oxygen evolution point to a dimer-monomer equilibrium of the IrIV resting state preceding a proton-coupled electron transfer (PCET) in the turnover-limiting step (TLS). Finally, true electrochemically driven water oxidation is demonstrated for all catalysts, revealing surprising trends in activity that do not correlate with those obtained using chemical oxidants.
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Hall AMR, Broomfield-Tagg R, Camilleri M, Carbery DR, Codina A, Whittaker DTE, Coombes S, Lowe JP, Hintermair U. Online monitoring of a photocatalytic reaction by real-time high resolution FlowNMR spectroscopy. Chem Commun (Camb) 2018; 54:30-33. [PMID: 29139489 DOI: 10.1039/c7cc07059d] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate how FlowNMR spectroscopy can readily be applied to investigate photochemical reactions that require sustained input of light and air to yield mechanistic insight under realistic conditions. The Eosin Y mediated photo-oxidation of N-allylbenzylamine is shown to produce imines as primary reaction products from which undesired aldehydes form after longer reaction times. Facile variation of reaction conditions during the reaction in flow allows for probe experiments that give information about the mode of action of the photocatalyst.
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Sackville EV, Kociok-Köhn G, Hintermair U. Ligand Tuning in Pyridine-Alkoxide Ligated Cp*IrIII Oxidation Catalysts. Organometallics 2017. [DOI: 10.1021/acs.organomet.7b00492] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Naeem A, Ting VP, Hintermair U, Tian M, Telford R, Halim S, Nowell H, Hołyńska M, Teat SJ, Scowen IJ, Nayak S. Mixed-linker approach in designing porous zirconium-based metal–organic frameworks with high hydrogen storage capacity. Chem Commun (Camb) 2016; 52:7826-9. [DOI: 10.1039/c6cc03787a] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New zirconium based metal–organic framework (UBMOF-31) synthesised using mixed-linker strategy showing permanent porosity, excellent hydrogen uptake, and high selectivity for adsorption of CO2 over N2.
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Hall AMR, Chouler JC, Codina A, Gierth PT, Lowe JP, Hintermair U. Practical aspects of real-time reaction monitoring using multi-nuclear high resolution FlowNMR spectroscopy. Catal Sci Technol 2016. [DOI: 10.1039/c6cy01754a] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
FlowNMR spectroscopy is an excellent technique for non-invasive real-time reaction monitoring under relevant conditions that avoids many of the limitations that bedevil other reaction monitoring techniques.
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Franciò G, Hintermair U, Leitner W. Unlocking the potential of supported liquid phase catalysts with supercritical fluids: low temperature continuous flow catalysis with integrated product separation. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:rsta.2015.0005. [PMID: 26574523 PMCID: PMC4650014 DOI: 10.1098/rsta.2015.0005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Solution-phase catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of homogeneous catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow homogeneous catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.
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Thomsen JM, Sheehan SW, Hashmi SM, Campos J, Hintermair U, Crabtree RH, Brudvig GW. Electrochemical Activation of Cp* Iridium Complexes for Electrode-Driven Water-Oxidation Catalysis. J Am Chem Soc 2014; 136:13826-34. [DOI: 10.1021/ja5068299] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Wesselbaum S, vom Stein T, Hintermair U, Klankermayer J, Leitner W. Continuous-Flow Hydrogenation of CO 2Using Molecular Catalysts. CHEM-ING-TECH 2014. [DOI: 10.1002/cite.201450069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Campos J, Hintermair U, Brewster TP, Takase MK, Crabtree RH. Catalyst Activation by Loss of Cyclopentadienyl Ligands in Hydrogen Transfer Catalysis with Cp*IrIII Complexes. ACS Catal 2014. [DOI: 10.1021/cs401138f] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Hintermair U, Campos J, Brewster TP, Pratt LM, Schley ND, Crabtree RH. Hydrogen-Transfer Catalysis with Cp*IrIII Complexes: The Influence of the Ancillary Ligands. ACS Catal 2013. [DOI: 10.1021/cs400834q] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Ingram AJ, Wolk AB, Flender C, Zhang J, Johnson CJ, Hintermair U, Crabtree RH, Johnson MA, Zare RN. Modes of Activation of Organometallic Iridium Complexes for Catalytic Water and C–H Oxidation. Inorg Chem 2013; 53:423-33. [DOI: 10.1021/ic402390t] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Graeupner J, Hintermair U, Huang DL, Thomsen JM, Takase M, Campos J, Hashmi SM, Elimelech M, Brudvig GW, Crabtree RH. Probing the Viability of Oxo-Coupling Pathways in Iridium-Catalyzed Oxygen Evolution. Organometallics 2013; 32:5384-5390. [PMID: 24474842 PMCID: PMC3902142 DOI: 10.1021/om400658a] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A series of Cp*IrIII dimers have been synthesized to elucidate the mechanistic viability of radical oxo-coupling pathways in iridium-catalyzed O2 evolution. The oxidative stability of the precursors toward nanoparticle formation and their oxygen evolution activity have been investigated and compared to suitable monomeric analogues. We found that precursors bearing monodentate NHC ligands degraded to form nanoparticles (NPs), and accordingly their O2 evolution rates were not significantly influenced by their nuclearity or distance between the two metals in the dimeric precursors. A doubly chelating bis-pyridine-pyrazolide ligand provided an oxidation-resistant ligand framework that allowed a more meaningful comparison of catalytic performance of dimers with their corresponding monomers. With sodium periodate (NaIO4) as the oxidant, the dimers provided significantly lower O2 evolution rates per [Ir] than the monomer, suggesting a negative interaction instead of cooperativity in the catalytic cycle. Electrochemical analysis of the dimers further substantiates the notion that no radical oxyl-coupling pathways are accessible. We thus conclude that the alternative path, nucleophilic attack of water on high-valent Ir-oxo species, may be the preferred mechanistic pathway of water oxidation with these catalysts, and bimolecular oxo-coupling is not a valid mechanistic alternative as in the related ruthenium chemistry, at least in the present system.
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Hintermair U, Sheehan SW, Parent AR, Ess DH, Richens DT, Vaccaro PH, Brudvig GW, Crabtree RH. Precursor Transformation during Molecular Oxidation Catalysis with Organometallic Iridium Complexes. J Am Chem Soc 2013; 135:10837-51. [DOI: 10.1021/ja4048762] [Citation(s) in RCA: 181] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Hintermair U, Franciò G, Leitner W. Cover Picture: A Fully Integrated Continuous-Flow System for Asymmetric Catalysis: Enantioselective Hydrogenation with Supported Ionic Liquid Phase Catalysts Using Supercritical CO 2as the Mobile Phase (Chem. Eur. J. 14/2013). Chemistry 2013. [DOI: 10.1002/chem.201390045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Hintermair U, Franciò G, Leitner W. A Fully Integrated Continuous-Flow System for Asymmetric Catalysis: Enantioselective Hydrogenation with Supported Ionic Liquid Phase Catalysts Using Supercritical CO2as the Mobile Phase. Chemistry 2013; 19:4538-47. [DOI: 10.1002/chem.201204159] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Indexed: 11/06/2022]
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44
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Zhou M, Hintermair U, Hashiguchi BG, Parent AR, Hashmi SM, Elimelech M, Periana RA, Brudvig GW, Crabtree RH. Cp* Iridium Precatalysts for Selective C–H Oxidation with Sodium Periodate As the Terminal Oxidant. Organometallics 2013. [DOI: 10.1021/om301252w] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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45
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Wesselbaum S, Hintermair U, Leitner W. Continuous‐Flow Hydrogenation of Carbon Dioxide to Pure Formic Acid using an Integrated scCO
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Process with Immobilized Catalyst and Base. Angew Chem Int Ed Engl 2012; 51:8585-8. [DOI: 10.1002/anie.201203185] [Citation(s) in RCA: 159] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 05/31/2012] [Indexed: 11/05/2022]
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Wesselbaum S, Hintermair U, Leitner W. Continuous‐Flow Hydrogenation of Carbon Dioxide to Pure Formic Acid using an Integrated scCO
2
Process with Immobilized Catalyst and Base. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201203185] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hintermair U, Hashmi SM, Elimelech M, Crabtree RH. Particle Formation during Oxidation Catalysis with Cp* Iridium Complexes. J Am Chem Soc 2012; 134:9785-95. [DOI: 10.1021/ja3033026] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Hintermair U, Roosen C, Kaever M, Kronenberg H, Thelen R, Aey S, Leitner W, Greiner L. A Versatile Lab to Pilot Scale Continuous Reaction System for Supercritical Fluid Processing. Org Process Res Dev 2011. [DOI: 10.1021/op200053w] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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49
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Hintermair U, Englert U, Leitner W. Distinct Reactivity of Mono- and Bis-NHC Silver Complexes: Carbene Donors versus Carbene–Halide Exchange Reagents. Organometallics 2011. [DOI: 10.1021/om101056y] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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50
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Hintermair U, Franciò G, Leitner W. Continuous flow organometallic catalysis: new wind in old sails. Chem Commun (Camb) 2011; 47:3691-701. [DOI: 10.1039/c0cc04958a] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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