1
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Chen X, Peng M, Xiao D, Liu H, Ma D. Fully Exposed Metal Clusters: Fabrication and Application in Alkane Dehydrogenation. ACS Catal 2022. [DOI: 10.1021/acscatal.2c04008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Xiaowen Chen
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, People’s Republic of China
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China
| | - Mi Peng
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People’s Republic of China
| | - Dequan Xiao
- Center for Integrative Materials Discovery, Department of Chemistry and Chemical and Biomedical Engineering, University of New Haven, West Haven, Connecticut 06516, United States
| | - Hongyang Liu
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, People’s Republic of China
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China
| | - Ding Ma
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People’s Republic of China
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2
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Trzmiel SPO, Langmann J, Maichle-Mössmer C, Anwander R. Chromous siloxides of variable nuclearity and magnetism. Dalton Trans 2022; 51:5072-5081. [PMID: 35262151 DOI: 10.1039/d2dt00354f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Treatment of Cr[N(SiMe3)2]2(thf)2 with HOSiR3 (R = Et, iPr) in THF afforded the bridged CrII siloxide complexes Cr3(OSiEt3)2(μ-OSiEt3)4(thf)2 and Cr2(OSiiPr3)2(μ-OSiiPr3)2(thf)2 in high yield. Exposure of these compounds to vacuum in aliphatic solvents led to the loss of coordinated THF and to the formation of the homoleptic chromous siloxides Cr4(μ-OSiEt3)8 and Cr3(OSiiPr3)2(μ-OSiiPr3)4, respectively, in moderate to high yield. Use of TMEDA as a potentially bidentate donor molecule gave the monomeric cis-coordinated siloxide Cr(OSiiPr3)2(tmeda) (tmeda = N,N,N',N'-tetramethylethane-1,2-diamine). Oxidation of Cr2(OSiiPr3)2(μ-OSiiPr3)2(thf)2 with CHI3 and C2Cl6 produced the trigonal bipyramidal chromic compound CrIII(OSiiPr)3(thf)2 and asymmetrically coordinated Cr2Cl3(OSiiPr3)3(thf)3, respectively. Magnetic measurements (Evans and SQUID) hinted at (a) antiferromagnetic interactions between the CrII centres, (b) revealed higher effective magnetic moments (μeff) for cis-coordinated monomeric heteroleptic complexes compared to trans-coordinated ones, and (c) pointed out the highest (μeff) for the tetranuclear complex Cr4(μ-OSiEt3)8 (6.26μB, SQUID, 300 K; Cr⋯Cradjacent avg. 2.535 A).
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Affiliation(s)
- Simon P O Trzmiel
- Institute of Inorganic Chemistry, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany.
| | - Jan Langmann
- Institut für Physik, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany
| | - Cäcilia Maichle-Mössmer
- Institute of Inorganic Chemistry, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany.
| | - Reiner Anwander
- Institute of Inorganic Chemistry, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany.
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Trummer D, Searles K, Algasov A, Guda SA, Soldatov AV, Ramanantoanina H, Safonova OV, Guda AA, Copéret C. Deciphering the Phillips Catalyst by Orbital Analysis and Supervised Machine Learning from Cr Pre-edge XANES of Molecular Libraries. J Am Chem Soc 2021; 143:7326-7341. [PMID: 33974429 DOI: 10.1021/jacs.0c10791] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Unveiling the nature and the distribution of surface sites in heterogeneous catalysts, and for the Phillips catalyst (CrO3/SiO2) in particular, is still a grand challenge despite more than 60 years of research. Commonly used references in Cr K-edge XANES spectral analysis rely on bulk materials (Cr-foil, Cr2O3) or molecules (CrCl3) that significantly differ from actual surface sites. In this work, we built a library of Cr K-edge XANES spectra for a series of tailored molecular Cr complexes, varying in oxidation state, local coordination environment, and ligand strength. Quantitative analysis of the pre-edge region revealed the origin of the pre-edge shape and intensity distribution. In particular, the characteristic pre-edge splitting observed for Cr(III) and Cr(IV) molecular complexes is directly related to the electronic exchange interactions in the frontier orbitals (spin-up and -down transitions). The series of experimental references was extended by theoretical spectra for potential active site structures and used for training the Extra Trees machine learning algorithm. The most informative features of the spectra (descriptors) were selected for the prediction of Cr oxidation states, mean interatomic distances in the first coordination sphere, and type of ligands. This set of descriptors was applied to uncover the site distribution in the Phillips catalyst at three different stages of the process. The freshly calcined catalyst consists of mainly Cr(VI) sites. The CO-exposed catalyst contains mainly Cr(II) silicates with a minor fraction of Cr(III) sites. The Phillips catalyst exposed to ethylene contains mainly highly coordinated Cr(III) silicates along with unreduced Cr(VI) sites.
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Affiliation(s)
- David Trummer
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Keith Searles
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Alexander Algasov
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178/24, Rostov-on-Don, Russia, 344090.,Institute of Mathematics, Mechanics and Computer Science, Southern Federal University, Milchakova 8a, Rostov-on-Don, Russia, 344090
| | - Sergey A Guda
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178/24, Rostov-on-Don, Russia, 344090.,Institute of Mathematics, Mechanics and Computer Science, Southern Federal University, Milchakova 8a, Rostov-on-Don, Russia, 344090
| | - Alexander V Soldatov
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178/24, Rostov-on-Don, Russia, 344090
| | | | | | - Alexander A Guda
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178/24, Rostov-on-Don, Russia, 344090
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
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4
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Werner D, Anwander R. Unveiling the Takai Olefination Reagent via Tris( tert-butoxy)siloxy Variants. J Am Chem Soc 2018; 140:14334-14341. [PMID: 30213182 DOI: 10.1021/jacs.8b08739] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The elusive Takai olefination reagent, namely, the iodo-methylidene Cr(III) complex [Cr2Cl4(CHI)(thf)4], has been isolated by careful handling of the reaction between CrCl2 and CHI3 in THF at -35 °C. Alternatively, treatment of [Cr(OSi(O tBu)3)2] with CHI3 gave the mixed-valent dihalido-methanide complex [CrII/III2I2(OSi(O tBu)3)2(CHI2)], featuring a Cr(III)-CHI2 moiety. In the presence of TMEDA nucleophilic attack at CHI2 occurred generating the zwitterionic species [CrIII(OSi(O tBu)3)2(tmeda-CHI)][I]. Complexes [Cr2Cl4(CHI)(thf)4] and [CrII/III2I2(OSi(O tBu)3)2(CHI2)] were screened for their ability to induce monohalido olefination of benzaldehyde. Remarkably, both complexes promote olefination, with [Cr2Cl4(CHI)(thf)4] accomplishing the same E selectivity as Takai 's original mixture. Complex [CrII/III2I2(OSi(O tBu)3)2(CHI2)], however, appeared to give preferentially Z isomer, corroborating the monoiodo-methylidene species Cr(III)-CHI-Cr(III) as the active olefination component of the original in situ generated Takai reagent mixture.
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Affiliation(s)
- Daniel Werner
- Institut für Anorganische Chemie , Eberhard Karls Universität Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Reiner Anwander
- Institut für Anorganische Chemie , Eberhard Karls Universität Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
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5
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Docherty SR, Estes DP, Copéret C. Facile Synthesis of Unsymmetrical Trialkoxysilanols: (RO) 2
(R′O)SiOH. Helv Chim Acta 2018. [DOI: 10.1002/hlca.201700298] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Scott R. Docherty
- Department of Chemistry and Applied Biology; ETH Zürich; Vladimir-Prelog-Weg 1-5 CH-8093 Zürich Switzerland
| | - Deven P. Estes
- Department of Chemistry and Applied Biology; ETH Zürich; Vladimir-Prelog-Weg 1-5 CH-8093 Zürich Switzerland
| | - Christophe Copéret
- Department of Chemistry and Applied Biology; ETH Zürich; Vladimir-Prelog-Weg 1-5 CH-8093 Zürich Switzerland
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Friedrich J, Qiao Y, Maichle-Mössmer C, Schelter EJ, Anwander R. Redox-enhanced hemilability of a tris(tert-butoxy)siloxy ligand at cerium. Dalton Trans 2018; 47:10113-10123. [DOI: 10.1039/c8dt01878b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Combined structural/electrochemical/computational studies of ceric Ce[OSi(OtBu)3]4 and cerous [Ce{OSi(OtBu)3}4][K(2.2.2-crypt)] suggest a redox-modulated coordination switch of a tris(tert-butoxy)siloxy ligand.
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Affiliation(s)
- Jochen Friedrich
- Institut für Anorganische Chemie
- Eberhard Karls Universität Tübingen
- 72076 Tübingen
- Germany
| | - Yusen Qiao
- P. Roy and Diana T. Vagelos Laboratories
- Department of Chemistry
- University of Pennsylvania
- Philadelphia
- USA
| | | | - Eric J. Schelter
- P. Roy and Diana T. Vagelos Laboratories
- Department of Chemistry
- University of Pennsylvania
- Philadelphia
- USA
| | - Reiner Anwander
- Institut für Anorganische Chemie
- Eberhard Karls Universität Tübingen
- 72076 Tübingen
- Germany
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Lorenz V, Ehle S, Liebing P, Engelhardt F, Hashemi-Haeri H, Oehler F, Hinderberger D, Busse S, Urbaschok J, Edelmann FT. High-yield synthesis of a unique Mn(iii) siloxide complex through KMnO 4 oxidation of a Mn(ii) precursor. Dalton Trans 2017; 47:62-66. [PMID: 29226937 DOI: 10.1039/c7dt03500d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A unique trivalent manganese siloxide complex, blue-violet MnIIILi2Cl[(Ph2SiO)2O]2(THF)4·2THF (3) has been prepared by a straightforward two-step synthetic protocol. Lithiation of (Ph2SiOH)2O (1) followed by reaction with MnCl2(THF)2 gave the structurally remarkable Mn(ii) precursor MnIILi4Cl2[(Ph2SiO)2O]2(THF)5·2THF (2). Surprisingly, the final oxidation step could be achieved using KMnO4 in THF to provide the Mn(iii) species 3 in high yield (91%). Both title compounds were structurally characterized by single-crystal X-ray diffraction.
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Affiliation(s)
- Volker Lorenz
- Chemisches Institut der Otto-von-Guericke-Universität, 39106 Magdeburg, Germany.
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8
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Estes DP, Siddiqi G, Allouche F, Kovtunov KV, Safonova OV, Trigub AL, Koptyug IV, Copéret C. C–H Activation on Co,O Sites: Isolated Surface Sites versus Molecular Analogs. J Am Chem Soc 2016; 138:14987-14997. [DOI: 10.1021/jacs.6b08705] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Deven P. Estes
- Department of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Georges Siddiqi
- Department of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Florian Allouche
- Department of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Kirill V. Kovtunov
- International Tomography Center, SB RAS, 3A Institutskaya
St., Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Olga V. Safonova
- General Energy Research Department, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Alexander L. Trigub
- National Research Centre “Kurchatov Institute”, 1 Akademika Kurchatova Pl., 123182 Moscow, Russia
| | - Igor V. Koptyug
- International Tomography Center, SB RAS, 3A Institutskaya
St., Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
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Dettenrieder N, Dietrich HM, Maichle-Mössmer C, Anwander R. Yttrium Siloxide Complexes Bearing Terminal Methyl Ligands: Molecular Models for Ln−CH3Terminated Silica Surfaces. Chemistry 2016; 22:13189-200. [DOI: 10.1002/chem.201602424] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Indexed: 12/20/2022]
Affiliation(s)
- Nicole Dettenrieder
- Institute of Inorganic Chemistry; Eberhard Karls Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
| | - H. Martin Dietrich
- Institute of Inorganic Chemistry; Eberhard Karls Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Cäcilia Maichle-Mössmer
- Institute of Inorganic Chemistry; Eberhard Karls Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Reiner Anwander
- Institute of Inorganic Chemistry; Eberhard Karls Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
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