1
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Pascual-Borràs M, Arca E, Yoshikawa H, Penfold T, Waddell PG, Errington RJ. Mechanochemical Polyoxometalate Super-Reduction with Lithium Metal. J Am Chem Soc 2024; 146:26485-26496. [PMID: 39255382 PMCID: PMC11440509 DOI: 10.1021/jacs.4c09998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2024]
Abstract
In this first systematic investigation of mechanochemical polyoxometalate (POM) reduction, (TBA)3[PMo12O40] was reacted with n equiv of lithium metal (n = 1-24) to generate PMo12/n products which were shown to be mixtures of electron-rich PMo12Lix species. FTIR analysis revealed the lengthening/weakening of terminal Mo═O bonds with increasing levels of reduction, while EXAFS spectra indicated the onset of Mo-Mo bond formation at n ∼ 8 and a significant structural change at n > 12. Successive MoVI reductions were monitored by XANES and XPS, and at n = 24, results were consistent with the formation of at least one MoIV-MoIV bonded {MoIV3} triad together with MoV. Upon dissolution, the PMo12Lix species present in the solid PMo12/n products undergo electron exchange and single-peak 31P NMR spectra were observed for n = 1-12. For n ≥ 16, changes in solid state and solution 31P NMR spectra coincided with the emergence of features in the UV-vis spectra associated with MoV-MoV and {MoIV3} bonding in an ε-Keggin structure. Bonding between {Li(NCMe)}+ and 2-electron-reduced PMo12 in (TBA)4[PMo12O40{Li(NCMe)}] suggests that super-reduction gives rise to more extensive Li-O bonding that ultimately causes lithium-oxide-promoted TBA cation decomposition and POM degradation, which might explain the appearance of XPS peaks for Mo2C at n ≥ 16. This work has revealed some of the complex, unexplored chemistry of super-reduced POMs and establishes a new, solvent-free approach in the search for a better fundamental understanding of the electronic properties and reactivity of electron-rich nanoscale metal oxides.
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Affiliation(s)
- Magda Pascual-Borràs
- NUPOM Lab, Chemistry, School of Natural & Environmental Sciences, Newcastle University, NE1 7RU Newcastle Upon Tyne, U.K
| | - Elisabetta Arca
- School of Mathematics, Statistics and Physics, Newcastle University, NE1 7RU Newcastle Upon Tyne, U.K
| | - Hirofumi Yoshikawa
- Department of Materials Science, Kwansei Gakuin University, Sanda, Hyogo 669-1330, Japan
| | - Thomas Penfold
- NUPOM Lab, Chemistry, School of Natural & Environmental Sciences, Newcastle University, NE1 7RU Newcastle Upon Tyne, U.K
| | - Paul G Waddell
- NUPOM Lab, Chemistry, School of Natural & Environmental Sciences, Newcastle University, NE1 7RU Newcastle Upon Tyne, U.K
| | - R John Errington
- NUPOM Lab, Chemistry, School of Natural & Environmental Sciences, Newcastle University, NE1 7RU Newcastle Upon Tyne, U.K
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2
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Maji M, Sousa-Silva A, Solans-Monfort X, Schrock RR, Conley MP, Farias P, Carta V. Thermal Formation of Metathesis-Active Tungsten Alkylidene Complexes from Cyclohexene. J Am Chem Soc 2024; 146:18661-18671. [PMID: 38917446 DOI: 10.1021/jacs.4c05256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
A 7-tungstabicyclo[4.3.0]nonane complex forms slowly upon addition of cyclohexene to the ethylene complex, W(NAr)(OSiPh3)2(C2H4), at 22 °C. A single-crystal X-ray study showed its structure to be closest to a square pyramid (τ = 0.23). At 22 °C, loss of cyclohexene or ring contraction of the 7-tungstabicyclo[4.3.0]nonane complex is slow. Above ∼80 °C, cyclohexene is ejected to give W(NAr)(OSiPh3)2(C2H4), but a sufficient amount of 7-tungstabicyclo[4.3.0]nonane complex remains in the presence of cyclohexene and the ring contracts to yield methylenecyclohexane and a methylidene complex or ethylene and a cyclohexylidene complex. Other complexes that have been observed include an 8-tungstabicyclo[4.3.0]nonane complex formed from 1,7-octadiene, a 7-tungstabicyclo[4.2.0]octane complex (formed from a methylidene complex and cyclohexene), and a methylenecyclohexane complex. 13C-Labeling studies show that the exo-methylene group in methylenecyclohexane and the α positions in the 8-tungstabicyclo[4.3.0]nonane come from ethylene. An alternative ring contraction of a tungstacyclopentane made from two molecules of cyclohexene cannot be excluded when concentrations of ethylene are low. A cyclohexylidene complex could also form from two cyclohexenes via a newly proposed "alkyl/allyl" mechanism. The results reported here are the first experimental confirmations that a tungstacyclopentane can ring-contract thermally at a substituted WCα position to form a tungstacyclobutane and therefore metathesis-active alkylidenes.
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Affiliation(s)
- Milan Maji
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
| | | | | | - Richard R Schrock
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
| | - Matthew P Conley
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
| | - Phillip Farias
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
| | - Veronica Carta
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
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3
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Skoda D, Zhu R, Hanulikova B, Styskalik A, Vykoukal V, Machac P, Simonikova L, Kuritka I, Poleunis C, Debecker DP, Román-Leshkov Y. Propylene Metathesis over Molybdenum Silicate Microspheres with Dispersed Active Sites. ACS Catal 2023; 13:12970-12982. [PMID: 37822857 PMCID: PMC10563125 DOI: 10.1021/acscatal.3c02045] [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: 05/05/2023] [Revised: 07/31/2023] [Indexed: 10/13/2023]
Abstract
In this work, we demonstrate that amorphous and porous molybdenum silicate microspheres are highly active catalysts for heterogeneous propylene metathesis. Homogeneous molybdenum silicate microspheres and aluminum-doped molybdenum silicate microspheres were synthesized via a nonaqueous condensation of a hybrid molybdenum biphenyldicarboxylate-based precursor solution with (3-aminopropyl)triethoxysilane. The as-prepared hybrid metallosilicate products were calcined at 500 °C to obtain amorphous and porous molybdenum silicate and aluminum-doped molybdenum silicate microspheres with highly dispersed molybdate species inserted into the silicate matrix. These catalysts contain mainly highly dispersed MoOx species, which possess high catalytic activity in heterogeneous propylene metathesis to ethylene and butene. Compared to conventional silica-supported MoOx catalysts prepared via incipient wetness impregnation (MoIWI), the microspheres with low Mo content (1.5-3.6 wt %) exhibited nearly 2 orders of magnitude higher steady-state propylene metathesis rates at 200 °C, approaching site time yields of 0.11 s-1.
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Affiliation(s)
- David Skoda
- Centre
of Polymer Systems, Tomas Bata University
in Zlin, tr. Tomase Bati 5678, Zlin CZ-76001, Czech Republic
| | - Ran Zhu
- Department
of Chemical Engineering, Massachusetts Institute
of Technology (MIT), 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Barbora Hanulikova
- Centre
of Polymer Systems, Tomas Bata University
in Zlin, tr. Tomase Bati 5678, Zlin CZ-76001, Czech Republic
| | - Ales Styskalik
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kotlarska
2, Brno CZ-61137, Czech Republic
| | - Vit Vykoukal
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kotlarska
2, Brno CZ-61137, Czech Republic
- Central
European Institute of Technology, Masaryk
University, Kamenice
5, Brno CZ 62500, Czech Republic
| | - Petr Machac
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kotlarska
2, Brno CZ-61137, Czech Republic
| | - Lucie Simonikova
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kotlarska
2, Brno CZ-61137, Czech Republic
| | - Ivo Kuritka
- Centre
of Polymer Systems, Tomas Bata University
in Zlin, tr. Tomase Bati 5678, Zlin CZ-76001, Czech Republic
| | - Claude Poleunis
- Institute
of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCLouvain), Place Louis Pasteur 1, 1348 Louvain-la-Neuve, Belgium
| | - Damien P. Debecker
- Institute
of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCLouvain), Place Louis Pasteur 1, 1348 Louvain-la-Neuve, Belgium
| | - Yuriy Román-Leshkov
- Department
of Chemical Engineering, Massachusetts Institute
of Technology (MIT), 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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4
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Liu Y, Agarwal A, Kratish Y, Marks TJ. Single-Site Carbon-Supported Metal-Oxo Complexes in Heterogeneous Catalysis: Structure, Reactivity, and Mechanism. Angew Chem Int Ed Engl 2023; 62:e202304221. [PMID: 37142561 DOI: 10.1002/anie.202304221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/06/2023]
Abstract
When early transition metal complexes are molecularly grafted onto catalyst supports, well-defined, surface-bound species are created, which are highly active and selective single-site heterogeneous catalysts (SSHCs) for diverse chemical transformations. In this minireview, we analyze and summarize a less conventional type of SSHC in which molybdenum dioxo species are grafted onto unusual carbon-unsaturated scaffolds, such as activated carbon, reduced graphene oxide, and carbon nanohorns. The choice of earth-abundant, low-toxicity, versatile metal constituents, and various carbon supports illustrates "catalyst by design" principles and yields insights into new catalytic systems of both academic and technological interest. Here, we summarize experimental and computational investigations of the bonding, electronic structure, reaction scope, and mechanistic pathways of these unusual catalysts.
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Affiliation(s)
- Yiqi Liu
- Department of Chemistry and the, Institute for Catalysis in Energy Processes (ICEP), 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Amol Agarwal
- Department of Material Science and Engineering and the, Institute for Catalysis in Energy Processes (ICEP), 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Yosi Kratish
- Department of Chemistry and the, Institute for Catalysis in Energy Processes (ICEP), 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Tobin J Marks
- Department of Chemistry and the, Institute for Catalysis in Energy Processes (ICEP), 2145 Sheridan Road, Evanston, IL 60208, USA
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5
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Berkson ZJ, Zhu R, Ehinger C, Lätsch L, Schmid SP, Nater D, Pollitt S, Safonova OV, Björgvinsdóttir S, Barnes AB, Román-Leshkov Y, Price GA, Sunley GJ, Copéret C. Active Site Descriptors from 95Mo NMR Signatures of Silica-Supported Mo-Based Olefin Metathesis Catalysts. J Am Chem Soc 2023. [PMID: 37256723 DOI: 10.1021/jacs.3c02201] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The olefin metathesis activity of silica-supported molybdenum oxides depends strongly on metal loading and preparation conditions, indicating that the nature and/or amounts of the active sites vary across compositionally similar catalysts. This is illustrated by comparing Mo-based (pre)catalysts prepared by impregnation (2.5-15.6 wt % Mo) and a model material (2.3 wt % Mo) synthesized via surface organometallic chemistry (SOMC). Analyses of FTIR, UV-vis, and Mo K-edge X-ray absorption spectra show that these (pre)catalysts are composed predominantly of similar isolated Mo dioxo sites. However, they exhibit different reaction properties in both liquid and gas-phase olefin metathesis with the SOMC-derived catalyst outperforming a classical catalyst of a similar Mo loading by ×1.5-2.0. Notably, solid-state 95Mo NMR analyses leveraging state-of-the-art high-field (28.2 T) measurement conditions resolve four distinct surface Mo dioxo sites with distributions that depend on the (pre)catalyst preparation methods. The intensity of a specific deshielded 95Mo NMR signal, which is most prominent in the SOMC-derived catalyst, is linked to reducibility and catalytic activity. First-principles calculations show that 95Mo NMR parameters directly manifest the local strain and coordination environment: acute (SiO-Mo(O)2-OSi) angles and low coordination numbers at Mo lead to highly deshielded 95Mo chemical shifts and small quadrupolar coupling constants, respectively. Natural chemical shift analyses relate the 95Mo NMR signature of strained species to low LUMO energies, which is consistent with their high reducibility and corresponding reactivity. The 95Mo chemical shifts of supported Mo dioxo sites are thus linked to their specific electronic structures, providing a powerful descriptor for their propensity toward reduction and formation of active sites.
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Affiliation(s)
- Zachariah J Berkson
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
| | - Ran Zhu
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Christian Ehinger
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
| | - Lukas Lätsch
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
| | - Stefan P Schmid
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
| | - Darryl Nater
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
| | - Stephan Pollitt
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
- PSI, CH-5232 Villigen, Switzerland
| | | | - Snædís Björgvinsdóttir
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
| | - Alexander B Barnes
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
| | - Yuriy Román-Leshkov
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Gregory A Price
- Applied Sciences, bp Innovation & Engineering, BP plc, Saltend, Hull HU12 8DS, U.K
| | - Glenn J Sunley
- Applied Sciences, bp Innovation & Engineering, BP plc, Saltend, Hull HU12 8DS, U.K
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
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6
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Gani TZH, Berkson ZJ, Zhu R, Kang JH, Di Iorio JR, Chan KW, Consoli DF, Shaikh SK, Copéret C, Román-Leshkov Y. Promoting active site renewal in heterogeneous olefin metathesis catalysts. Nature 2023; 617:524-528. [PMID: 37198312 DOI: 10.1038/s41586-023-05897-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/28/2023] [Indexed: 05/19/2023]
Abstract
As an atom-efficient strategy for the large-scale interconversion of olefins, heterogeneously catalysed olefin metathesis sees commercial applications in the petrochemical, polymer and speciality chemical industries1. Notably, the thermoneutral and highly selective cross-metathesis of ethylene and 2-butenes1 offers an appealing route for the on-purpose production of propylene to address the C3 shortfall caused by using shale gas as a feedstock in steam crackers2,3. However, key mechanistic details have remained ambiguous for decades, hindering process development and adversely affecting economic viability4 relative to other propylene production technologies2,5. Here, from rigorous kinetic measurements and spectroscopic studies of propylene metathesis over model and industrial WOx/SiO2 catalysts, we identify a hitherto unknown dynamic site renewal and decay cycle, mediated by proton transfers involving proximal Brønsted acidic OH groups, which operates concurrently with the classical Chauvin cycle. We show how this cycle can be manipulated using small quantities of promoter olefins to drastically increase steady-state propylene metathesis rates by up to 30-fold at 250 °C with negligible promoter consumption. The increase in activity and considerable reduction of operating temperature requirements were also observed on MoOx/SiO2 catalysts, showing that this strategy is possibly applicable to other reactions and can address major roadblocks associated with industrial metathesis processes.
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Affiliation(s)
- Terry Z H Gani
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - Zachariah J Berkson
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - Ran Zhu
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
| | - Jong Hun Kang
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
| | - John R Di Iorio
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
| | - Ka Wing Chan
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - Daniel F Consoli
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
| | - Sohel K Shaikh
- Research & Development Center, Saudi Aramco, Dhahran, Saudi Arabia
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland.
| | - Yuriy Román-Leshkov
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA.
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7
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Nishi K, Tsurugi H, Mashima K. Chromium-catalyzed olefination of arylaldehydes with haloforms assisted by 2,3,5,6-tetramethyl- N, N'-bis(trimethylsilyl)-1,4-dihydropyrazine. Chem Commun (Camb) 2023; 59:908-911. [PMID: 36594831 DOI: 10.1039/d2cc06104j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Chromium-catalyzed olefination of arylaldehydes with haloforms was achieved using 2,3,5,6-tetramethyl-N,N'-bis(trimethylsilyl)-1,4-dihydropyrazine (1a) as an organic reducing agent, giving β-halostyrene derivatives in a trans-selective manner. The reaction required no metal powders, such as zinc and manganese, as reductants, thereby minimizing metal-based reaction waste.
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Affiliation(s)
- Kohei Nishi
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
| | - Hayato Tsurugi
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
| | - Kazushi Mashima
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka 565-0871, Japan.
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8
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Nater DF, Kaul CJ, Lätsch L, Tsurugi H, Mashima K, Copéret C. Olefin Metathesis Catalysts Generated In Situ from Molybdenum(VI)-Oxo Complexes by Tuning Pendant Ligands. Chemistry 2022; 28:e202200559. [PMID: 35234311 PMCID: PMC9313794 DOI: 10.1002/chem.202200559] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Indexed: 12/01/2022]
Abstract
Tailored molybdenum(VI)-oxo complexes of the form MoOCl2 (OR)2 (OEt2 ) catalyse olefin metathesis upon reaction with an organosilicon reducing agent at 70 °C, in the presence of olefins. While this reactivity parallels what has recently been observed for the corresponding classical heterogeneous catalysts based on supported metal oxide under similar conditions, the well-defined nature of our starting molecular systems allows us to understand the influence of structural, spectroscopic and electronic characteristics of the catalytic precursor on the initiation and catalytic proficiency of the final species. The catalytic performances of the pre-catalysts are determined by the highly electron withdrawing (σ-donation) character of alkoxide ligands, Ot BuF9 being the best. This activity correlates with both the 95 Mo chemical shift and the reduction potential that follows the same trend: Ot BuF9 >Ot BuF6 >Ot BuF3 .
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Affiliation(s)
- Darryl F. Nater
- Department of Chemistry and Applied BiosciencesETH ZürichVladimir-Prelog-Weg 1–58093ZürichSwitzerland
| | - Christoph J. Kaul
- Department of Chemistry and Applied BiosciencesETH ZürichVladimir-Prelog-Weg 1–58093ZürichSwitzerland
| | - Lukas Lätsch
- Department of Chemistry and Applied BiosciencesETH ZürichVladimir-Prelog-Weg 1–58093ZürichSwitzerland
| | - Hayato Tsurugi
- Department of ChemistryGraduate School of Engineering ScienceOsaka University1-3, Machikaneyama-choToyonakaOsaka560-8531Japan
| | - Kazushi Mashima
- Department of ChemistryGraduate School of Engineering ScienceOsaka University1-3, Machikaneyama-choToyonakaOsaka560-8531Japan
| | - Christophe Copéret
- Department of Chemistry and Applied BiosciencesETH ZürichVladimir-Prelog-Weg 1–58093ZürichSwitzerland
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9
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Berkson Z, Bernhardt M, Schlapansky SL, Benedikter MJ, Buchmeiser MR, Price GA, Sunley GJ, Copéret C. Olefin-Surface Interactions: A Key Activity Parameter in Silica-Supported Olefin Metathesis Catalysts. JACS AU 2022; 2:777-786. [PMID: 35373213 PMCID: PMC8969997 DOI: 10.1021/jacsau.2c00052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 02/24/2022] [Accepted: 02/24/2022] [Indexed: 06/02/2023]
Abstract
Molecularly defined and classical heterogeneous Mo-based metathesis catalysts are shown to display distinct and unexpected reactivity patterns for the metathesis of long-chain α-olefins at low temperatures (<100 °C). Catalysts based on supported Mo oxo species, whether prepared via wet impregnation or surface organometallic chemistry (SOMC), exhibit strong activity dependencies on the α-olefin chain length, with slower reaction rates for longer substrate chain lengths. In contrast, molecular and supported Mo alkylidenes are highly active and do not display such dramatic dependence on the chain length. State-of-the-art two-dimensional (2D) solid-state nuclear magnetic resonance (NMR) spectroscopy analyses of postmetathesis catalysts, complemented by Fourier transform infrared (FT-IR) spectroscopy and molecular dynamics calculations, evidence that the activity decrease observed for supported Mo oxo catalysts relates to the strong adsorption of internal olefin metathesis products because of interactions with surface Si-OH groups. Overall, this study shows that in addition to the nature and the number of active sites, the metathesis rates and the overall catalytic performance depend on product desorption, even in the liquid phase with nonpolar substrates. This study further highlights the role of the support and active site composition and dynamics on activity as well as the need for considering adsorption in catalyst design.
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Affiliation(s)
- Zachariah
J. Berkson
- Department
of Chemistry and Applied Bioscience, ETH
Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland
| | - Moritz Bernhardt
- Department
of Chemistry and Applied Bioscience, ETH
Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland
| | - Simon L. Schlapansky
- Department
of Chemistry and Applied Bioscience, ETH
Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland
| | - Mathis J. Benedikter
- Institute
of Polymer Chemistry, Universität
Stuttgart, Pfaffenwaldring 55, Stuttgart 70569, Germany
| | - Michael R. Buchmeiser
- Institute
of Polymer Chemistry, Universität
Stuttgart, Pfaffenwaldring 55, Stuttgart 70569, Germany
| | - Gregory A. Price
- Applied
Sciences, BP Innovation & Engineering, BP plc, Saltend, Hull HU12 8DS, U.K.
| | - Glenn J. Sunley
- Applied
Sciences, BP Innovation & Engineering, BP plc, Saltend, Hull HU12 8DS, U.K.
| | - Christophe Copéret
- Department
of Chemistry and Applied Bioscience, ETH
Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland
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10
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Myradova M, Węgrzynowicz A, Węgrzyniak A, Gierada M, Jodlowski P, Łojewska J, Handzlik J, Michorczyk P. Tuning metathesis performance of molybdenum oxide-based catalyst by silica support acidity modulation and high temperature pretreatment. Catal Sci Technol 2022. [DOI: 10.1039/d1cy02064a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molybdenum oxide-based catalysts containing 5 wt. % of Mo obtained by simple impregnation of silica mesoporous support were studied in olefin metathesis reaction at 50 °C. Effect of support modification...
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11
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Sahoo P, Majumdar M. Reductively disilylated N-heterocycles as versatile organosilicon reagents. Dalton Trans 2021; 51:1281-1296. [PMID: 34889336 DOI: 10.1039/d1dt03331j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The reductively disilylated N-heterocyclic systems 1,4-bis(trimethylsilyl)-1-aza-2,5-cyclohexadiene (1Si), 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (2Si) and its methyl derivatives (3Si and 4Si), and 1,1'-bis(trimethylsilyl)-4,4'-bipyridinylidene (5Si) are proficient organosilicon reagents owing to their low first vertical ionization potentials and the heterophilicity of the polarized N-Si bonds. These have prompted their reactivity as two-electron reductants or reductive silylations. These reactions benefit from the concomitant rearomatization of the N-heterocycles and liberation of trimethylsilyl halides or (Me3Si)2O, which are mostly volatile or easily removable byproducts. In this perspective, we have discussed the utilization of these reductively disilylated N-heterocyclic systems as versatile reagents in the salt-free reduction of transition metals (A) and main-group halides (B), in organic transformations (C) and in materials syntheses (D).
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Affiliation(s)
- Padmini Sahoo
- Department of Chemistry, Indian Institute of Science Education and Research, Pune-411008, Maharashtra, India.
| | - Moumita Majumdar
- Department of Chemistry, Indian Institute of Science Education and Research, Pune-411008, Maharashtra, India.
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12
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Zhizhko PA, Bushkov NS, Pichugov AV, Zarubin DN. Oxo/imido heterometathesis: From molecular stoichiometric studies to well-defined heterogeneous catalysts. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214112] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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13
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Handzlik J, Kurleto K, Gierada M. Computational Insights into Active Site Formation during Alkene Metathesis over a MoO x/SiO 2 Catalyst: The Role of Surface Silanols. ACS Catal 2021. [DOI: 10.1021/acscatal.1c03912] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Jarosław Handzlik
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, ul. Warszawska 24, Kraków 31-155, Poland
| | - Kamil Kurleto
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, ul. Warszawska 24, Kraków 31-155, Poland
| | - Maciej Gierada
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, ul. Warszawska 24, Kraków 31-155, Poland
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14
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Copéret C, Berkson ZJ, Chan KW, de Jesus Silva J, Gordon CP, Pucino M, Zhizhko PA. Olefin metathesis: what have we learned about homogeneous and heterogeneous catalysts from surface organometallic chemistry? Chem Sci 2021; 12:3092-3115. [PMID: 34164078 PMCID: PMC8179417 DOI: 10.1039/d0sc06880b] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 02/08/2021] [Indexed: 11/21/2022] Open
Abstract
Since its early days, olefin metathesis has been in the focus of scientific discussions and technology development. While heterogeneous olefin metathesis catalysts based on supported group 6 metal oxides have been used for decades in the petrochemical industry, detailed mechanistic studies and the development of molecular organometallic chemistry have led to the development of robust and widely used homogeneous catalysts based on well-defined alkylidenes that have found applications for the synthesis of fine and bulk chemicals and are also used in the polymer industry. The development of the chemistry of high-oxidation group 5-7 alkylidenes and the use of surface organometallic chemistry (SOMC) principles unlocked the preparation of so-called well-defined supported olefin metathesis catalysts. The high activity and stability (often superior to their molecular analogues) and molecular-level characterisation of these systems, that were first reported in 2001, opened the possibility for the first direct structure-activity relationships for supported metathesis catalysts. This review describes first the history of SOMC in the field of olefin metathesis, and then focuses on what has happened since 2007, the date of our last comprehensive reviews in this field.
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Affiliation(s)
- Christophe Copéret
- ETH Zürich, Department of Chemistry and Applied Biosciences Vladimir Prelog Weg 2 CH-8093 Zürich Switzerland
| | - Zachariah J Berkson
- ETH Zürich, Department of Chemistry and Applied Biosciences Vladimir Prelog Weg 2 CH-8093 Zürich Switzerland
| | - Ka Wing Chan
- ETH Zürich, Department of Chemistry and Applied Biosciences Vladimir Prelog Weg 2 CH-8093 Zürich Switzerland
| | - Jordan de Jesus Silva
- ETH Zürich, Department of Chemistry and Applied Biosciences Vladimir Prelog Weg 2 CH-8093 Zürich Switzerland
| | - Christopher P Gordon
- ETH Zürich, Department of Chemistry and Applied Biosciences Vladimir Prelog Weg 2 CH-8093 Zürich Switzerland
| | - Margherita Pucino
- ETH Zürich, Department of Chemistry and Applied Biosciences Vladimir Prelog Weg 2 CH-8093 Zürich Switzerland
| | - Pavel A Zhizhko
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences Vavilov Str. 28 119991 Moscow Russia
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15
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Chakraborty S, Matson EM. Reductive silylation of polyoxovanadate surfaces using Mashima's reagent. Inorg Chem Front 2021. [DOI: 10.1039/d1qi00920f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mechanistic insights into the reductive silylation of metal oxide surfaces.
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Affiliation(s)
- Sourav Chakraborty
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | - Ellen M. Matson
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
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16
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Wu J, Ramanathan A, Kersting R, Jystad A, Zhu H, Hu Y, Marshall CP, Caricato M, Subramaniam B. Enhanced Olefin Metathesis Performance of Tungsten and Niobium Incorporated Bimetallic Silicates: Evidence of Synergistic Effects. ChemCatChem 2020. [DOI: 10.1002/cctc.201902131] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jian‐Feng Wu
- State Key Laboratory of Applied Organic Chemistry Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province College of Chemistry and Chemical EngineeringLanzhou University Lanzhou 730000 P. R. China
- Center for Environmentally Beneficial CatalysisThe University of Kansas Lawrence KS-66047 USA
| | - Anand Ramanathan
- Center for Environmentally Beneficial CatalysisThe University of Kansas Lawrence KS-66047 USA
| | | | - Amy Jystad
- Department of ChemistryThe University of Kansas Lawrence KS-66045 USA
| | - Hongda Zhu
- Center for Environmentally Beneficial CatalysisThe University of Kansas Lawrence KS-66047 USA
- Department of Chemical and Petroleum EngineeringThe University of Kansas Lawrence KS-66045 USA
| | - Yongfeng Hu
- Canadian Light Source Inc.University of Saskatchewan Saskatoon Saskatchewan S7 N 2 V3 Canada
| | - Craig P. Marshall
- Department of ChemistryThe University of Kansas Lawrence KS-66045 USA
- Department of GeologyThe University of Kansas Lawrence KS-66045 USA
| | - Marco Caricato
- Department of ChemistryThe University of Kansas Lawrence KS-66045 USA
| | - Bala Subramaniam
- Center for Environmentally Beneficial CatalysisThe University of Kansas Lawrence KS-66047 USA
- Department of Chemical and Petroleum EngineeringThe University of Kansas Lawrence KS-66045 USA
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17
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Herndon JW. The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2018. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2019.213051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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18
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Chan KW, Mance D, Safonova OV, Copéret C. Well-Defined Silica-Supported Tungsten(IV)-Oxo Complex: Olefin Metathesis Activity, Initiation, and Role of Brønsted Acid Sites. J Am Chem Soc 2019; 141:18286-18292. [PMID: 31618022 DOI: 10.1021/jacs.9b09493] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite the importance of the heterogeneous tungsten-oxo-based olefin metathesis catalyst (WO3/SiO2) in industry, understanding of its initiation mechanism is still very limited. It has been proposed that reduced W(IV)-oxo surface species act as precatalysts. In order to understand the reactivity and initiation mechanism of surface W(IV)-oxo species, we synthesized a well-defined silica-supported W(IV)-oxo species, (≡SiO)WO(OtBuF6)(py)3 (F6@SiO2-700; OtBuF6 = OC(CH3)(CF3)2; py = pyridine), via surface organometallic chemistry (SOMC). F6@SiO2-700 was shown to be highly active in olefin metathesis upon removal of pyridine ligands through the addition of tris(pentafluorophenyl)borane (B(C6F5)3) or thermal treatment under high vacuum. The metathesis activity toward olefins with and without allylic C-H groups, namely β-methylstyrene and styrene, respectively, was investigated. In the case of styrene, we demonstrated the role of surface OH groups in initiating metathesis activity. We proposed that the presence of strong Brønsted acidic OH sites, which likely arises from the presence of adjacent W sites in the catalyst as revealed by 15N-labeled pyridine adsorption, can assist styrene metathesis. In contrast, initiation of olefins with allylic C-H groups (e.g., β-methylstyrene) is independent of the surface OH density and likely involves an allylic C-H activation mechanism, like the molecular W(IV)-oxo species. This study indicates that initiation mechanisms depend on the olefinic substrates and reveals the synergistic effect of Brønsted acidic surface sites and reduced W(IV) sites in the initiation of olefin metathesis.
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Affiliation(s)
- Ka Wing Chan
- Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
| | - Deni Mance
- Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
| | | | - Christophe Copéret
- Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
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19
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Samantaray MK, D'Elia V, Pump E, Falivene L, Harb M, Ould Chikh S, Cavallo L, Basset JM. The Comparison between Single Atom Catalysis and Surface Organometallic Catalysis. Chem Rev 2019; 120:734-813. [PMID: 31613601 DOI: 10.1021/acs.chemrev.9b00238] [Citation(s) in RCA: 133] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Single atom catalysis (SAC) is a recent discipline of heterogeneous catalysis for which a single atom on a surface is able to carry out various catalytic reactions. A kind of revolution in heterogeneous catalysis by metals for which it was assumed that specific sites or defects of a nanoparticle were necessary to activate substrates in catalytic reactions. In another extreme of the spectrum, surface organometallic chemistry (SOMC), and, by extension, surface organometallic catalysis (SOMCat), have demonstrated that single atoms on a surface, but this time with specific ligands, could lead to a more predictive approach in heterogeneous catalysis. The predictive character of SOMCat was just the result of intuitive mechanisms derived from the elementary steps of molecular chemistry. This review article will compare the aspects of single atom catalysis and surface organometallic catalysis by considering several specific catalytic reactions, some of which exist for both fields, whereas others might see mutual overlap in the future. After a definition of both domains, a detailed approach of the methods, mostly modeling and spectroscopy, will be followed by a detailed analysis of catalytic reactions: hydrogenation, dehydrogenation, hydrogenolysis, oxidative dehydrogenation, alkane and cycloalkane metathesis, methane activation, metathetic oxidation, CO2 activation to cyclic carbonates, imine metathesis, and selective catalytic reduction (SCR) reactions. A prospective resulting from present knowledge is showing the emergence of a new discipline from the overlap between the two areas.
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Affiliation(s)
- Manoja K Samantaray
- King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia
| | - Valerio D'Elia
- School of Molecular Science and Engineering (MSE) , Vidyasirimedhi Institute of Science and Technology (VISTEC) , Wang Chan, Payupnai , 21210 Rayong , Thailand
| | - Eva Pump
- King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia
| | - Laura Falivene
- King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia
| | - Moussab Harb
- King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia
| | - Samy Ould Chikh
- King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia
| | - Luigi Cavallo
- King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia
| | - Jean-Marie Basset
- King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia
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20
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Ghaffari B, Mendes‐Burak J, Chan KW, Copéret C. Silica‐Supported MnIISites as Efficient Catalysts for Carbonyl Hydroboration, Hydrosilylation, and Transesterification. Chemistry 2019; 25:13869-13873. [DOI: 10.1002/chem.201903638] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Behnaz Ghaffari
- Department of Chemistry and Applied BiosciencesETH Zürich Vladimir-Prelog-Weg 1–5 8093 Zürich Switzerland
| | - Jorge Mendes‐Burak
- Department of Chemistry and Applied BiosciencesETH Zürich Vladimir-Prelog-Weg 1–5 8093 Zürich Switzerland
| | - Ka Wing Chan
- Department of Chemistry and Applied BiosciencesETH Zürich Vladimir-Prelog-Weg 1–5 8093 Zürich Switzerland
| | - Christophe Copéret
- Department of Chemistry and Applied BiosciencesETH Zürich Vladimir-Prelog-Weg 1–5 8093 Zürich Switzerland
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21
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Beagan DM, Huerfano IJ, Polezhaev AV, Caulton KG. Reductive Silylation Using a Bis-silylated Diaza-2,5-cyclohexadiene. Chemistry 2019; 25:8105-8111. [PMID: 30994211 DOI: 10.1002/chem.201900879] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Indexed: 11/06/2022]
Abstract
1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene, 1, was tested as a reagent for the reductive silylation of various unsaturated functionalities, including N-heterocycles, quinones, and other redox-active moieties in addition to deoxygenation of main group oxides. Whereas most reactions tested are thermodynamically favorable, based on DFT calculations, a few do not occur, perhaps giving limited insight on the mechanism of this very attractive reductive process. Of note, reductive silylation reactions show a strong solvent dependence where a polar solvent facilitates conversions.
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Affiliation(s)
- Daniel M Beagan
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
| | - I J Huerfano
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
| | | | - Kenneth G Caulton
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
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22
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Copéret C. Single-Sites and Nanoparticles at Tailored Interfaces Prepared via Surface Organometallic Chemistry from Thermolytic Molecular Precursors. Acc Chem Res 2019; 52:1697-1708. [PMID: 31150207 DOI: 10.1021/acs.accounts.9b00138] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Heterogeneous catalysts are complex by nature, making particularly difficult to assess the structure of their active sites. Such complexity is inherited in part from their mode of preparation, which typically involves coprecipitation or impregnation of metal salts in aqueous solution, and the associated complex surface chemistries. In this context, surface organometallic chemistry (SOMC) has emerged as a powerful approach to generate well-defined surface species, where the metal sites are introduced by grafting tailored molecular precursors. When combined with thermolytic molecular precursors (TMPs) that can lose their organic moieties quite readily upon thermal treatment, SOMC provides access to supported isolated metal sites with defined oxidation state and nuclearity inherited from the precursor. The resulting surface species bear unusual coordination imposed by the surface that provides them high reactivity in comparison with their molecular precursor. In addition, these molecularly defined species bare strong resemblance with the active sites of supported metal oxides. However, they typically contain a higher proportion of active sites making structure-activity relationship possible. They thus constitute ideal models for this important class of industrial catalysts that are used in numerous applications such as olefin epoxidation (Shell process), olefin metathesis (triolefin process), ethylene polymerization (Phillips catalysts), or propane dehydrogenation (Catofin and related processes). This SOMC/TMP approach can thus provide detailed information about the structure of active sites in industrial catalysts, their mode of initiation and deactivation, as well as the role of the support and specific thermal treatment on the final activity of the catalysts. Nonetheless, these structurally characterized surface sites still exhibit heterogeneous environments borrowed from the support itself, that explain the intrinsic complexity of heterogeneous catalysis. Furthermore, SOMC/TMP can also be used to generate and investigate supported metal nanoparticles. Starting from the well-defined isolated sites, that also contain adjacent surface OH groups, one can graft a second metal and then generate after treatment under hydrogen small and narrowly dispersed alloys or nanoparticles with tailored interfaces that can show improved catalytic performances and are amiable to detailed structure-activity relationships. This approach is illustrated by two case studies: (1) formation of supported copper nanoparticles at tailored interfaces that contain isolated metal sites for the selective hydrogenation of carbon dioxide to methanol, allowing for a detailed understanding of the role of dopants and supports in heterogeneous catalysis, and (2) preparation of highly selective and productive propane dehydrogenation catalysts based on silica-supported Pt xGa y alloy. Overall, this Account shows how the combination of SOMC and TMP helps to generate catalysts, particularly suited for elucidating structural characterization of active sites at a molecular-level which in turn enables structure-activity relationship to be drawn. Such detailed information obtained on well-defined catalysts can then be used to understand complex effects observed in industrial catalysts (effects of supports, additives, dopants, etc.), and to extract information that can then be used to improve them in a more rational way.
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Affiliation(s)
- Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg. 1-5, CH-8093 Zürich, Switzerland
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23
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Tsurugi H, Mashima K. Salt-Free Reduction of Transition Metal Complexes by Bis(trimethylsilyl)cyclohexadiene, -dihydropyrazine, and -4,4'-bipyridinylidene Derivatives. Acc Chem Res 2019; 52:769-779. [PMID: 30794373 DOI: 10.1021/acs.accounts.8b00638] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Chemical reduction of transition metals provides the corresponding low-valent transition metal species as a key step for generating catalytically active species in metal-assisted organic transformations and is a fundamental unit reaction for preparing organometallic complexes. A variety of metal-based reductants, such as metal powders and organometallic reagents of alkali and alkaline-earth metals, have been developed to date to access low-valent metal species. During the reduction, however, reductant-derived metal salts are formed as reaction waste, some of which often interact with the reactive low-valent metal center, thereby disrupting the catalytic performance and hampering the isolation of organometallic complexes as a result of salt coordination to the coordinatively unsaturated vacant and active sites and the formation of thermally unstable ate complexes. In this Account, we emphasize the synthetic utility and versatility of organic reductants containing two trimethylsilyl groups, i.e., 1,4-bis(trimethylsilyl)cyclohexa-2,5-diene (1a) and its methyl derivative (1b), 1,4-bis(trimethylsilyl)dihydropyrazine (2a) and its dimethyl (2b) and tetramethyl (2c) derivatives, and 1,1'-bis(trimethylsilyl)-4,4'-bipyridinylidene (3), leading to the reduction of various kinds of metal compounds in a salt-free fashion by release of two electrons together with the coproduction of easily removable (hetero)aromatics and trimethylsilyl derivatives from these organic reductants 1-3. When homoleptic chlorides of group 5 and 6 metals are treated with 1a and 1b, in situ-generated highly reactive low-valent metal species react with redox-active molecules such as ethylene, α-diimines, and α-diketones to produce metallacyclopentane, (ene-diamido)metal, and (ene-diolato)metal complexes, respectively. The advantage of the salt-free protocol is further exemplified in the low-valent titanocene-catalyzed Reformatsky-type reaction when 2c is used as a reductant: the yield of the product using the organosilicon reductant is higher than that when manganese powder is used as the reductant for the catalytic Reformatsky-type reaction of ethyl 2-bromoisobutyrate and its derivatives with various aldehydes. Moreover, when halides, carboxylates, and acetylacetonate compounds of late transition metals and main-group elements are treated with the organosilicon reductant 2c, metal(0) particles are smoothly precipitated under mild conditions. Among them, metallic nickel(0) nanoparticles are applicable to reductive biaryl formation and reductive cross-coupling of aryl halides/aryl aldehydes. In addition, reduction of the heterogeneous catalysts on a solid supporting matrix was also achieved by this salt-free reduction method; volatile byproducts are easily removed from the catalyst surface without suppressing the catalytic performance. Thus, the salt-free reduction strategy is a very powerful synthetic method that can be extended to various metals throughout the periodic table.
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Affiliation(s)
- Hayato Tsurugi
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Kazushi Mashima
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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24
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Seo J, Cabelof AC, Chen CH, Caulton KG. Selective deoxygenation of nitrate to nitrosyl using trivalent chromium and the Mashima reagent: reductive silylation. Chem Sci 2019; 10:475-479. [PMID: 30746094 PMCID: PMC6335631 DOI: 10.1039/c8sc02979b] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 10/15/2018] [Indexed: 01/26/2023] Open
Abstract
1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene is an effective silyl transfer reagent towards the oxygen of nitrate coordinated to Cr(iii) in a pincer complex.
1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene is an effective silyl transfer reagent towards the oxygen of nitrate coordinated to Cr(iii) in a pincer complex. Two nitrate oxygens are removed to give the 17 valence electron octahedral complex (H2L)Cr(NO3)2(NO). This is shown by a variety of spectroscopic methods, together with DFT, to be a Cr(i) complex with a linear CrNO unit. This work also identifies future applications of this reductive silylation process.
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Affiliation(s)
- Junghee Seo
- Indiana University , Department of Chemistry , 800 E. Kirkwood Ave. , Bloomington , IN 47401 , USA .
| | - Alyssa C Cabelof
- Indiana University , Department of Chemistry , 800 E. Kirkwood Ave. , Bloomington , IN 47401 , USA .
| | - Chun-Hsing Chen
- Indiana University , Department of Chemistry , 800 E. Kirkwood Ave. , Bloomington , IN 47401 , USA .
| | - Kenneth G Caulton
- Indiana University , Department of Chemistry , 800 E. Kirkwood Ave. , Bloomington , IN 47401 , USA .
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25
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Chan KW, Lam E, D'Anna V, Allouche F, Michel C, Safonova OV, Sautet P, Copéret C. C-H Activation and Proton Transfer Initiate Alkene Metathesis Activity of the Tungsten(IV)-Oxo Complex. J Am Chem Soc 2018; 140:11395-11401. [PMID: 30110534 DOI: 10.1021/jacs.8b06603] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In alkene metathesis, while group 6 (Mo or W) high-oxidation state alkylidenes are accepted to be key reaction intermediates for both homogeneous and heterogeneous catalysts, it has been proposed that low valent species in their +4 oxidation state can serve as precatalysts. However, the activation mechanism for these latter species-generating alkylidenes-is still an open question. Here, we report the syntheses of tungsten(IV)-oxo bisalkoxide molecular complexes stabilized by pyridine ligands, WO(OR)2py3 (R = CMe(CF3)2 (2a), R = Si(O tBu)3 (2b), and R = C(CF3)3 (2c); py = pyridine), and show that upon activation with B(C6F5)3 they display alkene metathesis activities comparable to W(VI)-oxo alkylidenes. The initiation mechanism is examined by kinetic, isotope labeling and computational studies. Experimental evidence reveals that the presence of an allylic CH group in the alkene reactant is crucial for initiating alkene metathesis. Deuterium labeling of the allylic C-H group shows a primary kinetic isotope effect on the rate of initiation. DFT calculations support the formation of an allyl hydride intermediate via activation of the allylic C-H bond and show that formation of the metallacyclobutane from the allyl "hydride" involves a proton transfer facilitated by the coordination of a Lewis acid (B(C6F5)3) and assisted by a Lewis base (pyridine). This proton transfer step is rate determining and yields the metathesis active species.
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Affiliation(s)
- Ka Wing Chan
- ETH Zürich , Department of Chemistry and Applied Biosciences , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
| | - Erwin Lam
- ETH Zürich , Department of Chemistry and Applied Biosciences , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
| | - Vincenza D'Anna
- Univ Lyon, Ens de Lyon , CNRS UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie , F-69342 Lyon , France
| | - Florian Allouche
- ETH Zürich , Department of Chemistry and Applied Biosciences , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
| | - Carine Michel
- Univ Lyon, Ens de Lyon , CNRS UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie , F-69342 Lyon , France
| | | | - Philippe Sautet
- Univ Lyon, Ens de Lyon , CNRS UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie , F-69342 Lyon , France.,Department of Chemical and Biomolecular Engineering , University of California, Los Angeles , Los Angeles , California 90095 , United States.,Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095 , United States
| | - Christophe Copéret
- ETH Zürich , Department of Chemistry and Applied Biosciences , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
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26
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Noguchi M, Suzuki K, Kobayashi J, Yurino T, Tsurugi H, Mashima K, Yamashita M. Planar and Bent BN-Embedded p-Quinodimethanes Synthesized by Transmetalation of Bis(trimethylsilyl)-1,4-dihydropyrazines with Chloroborane. Organometallics 2018. [DOI: 10.1021/acs.organomet.8b00294] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Mao Noguchi
- Department of Applied Chemistry, Graduate School of Science and Engineering, Chuo University, 1-23-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Katsunori Suzuki
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho,
Chikusa-ku, Nagoya 464-8603, Japan
| | - Jun Kobayashi
- Department of Applied Chemistry, Graduate School of Science and Engineering, Chuo University, 1-23-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Taiga Yurino
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Hayato Tsurugi
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Kazushi Mashima
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Makoto Yamashita
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho,
Chikusa-ku, Nagoya 464-8603, Japan
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