1
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Almquist CC, Rajeshkumar T, Jayaweera HDAC, Removski N, Zhou W, Gelfand BS, Maron L, Piers WE. Oxidation-induced ambiphilicity triggers N-N bond formation and dinitrogen release in octahedral terminal molybdenum(v) nitrido complexes. Chem Sci 2024; 15:5152-5162. [PMID: 38577349 PMCID: PMC10988598 DOI: 10.1039/d4sc00090k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 02/16/2024] [Indexed: 04/06/2024] Open
Abstract
Coupling of octahedral, terminal d1 molybdenum(v) nitrido complexes supported by a dianionic pentadentate ligand via N-N bond formation to give μ-dinitrogen complexes was found to be thermodynamically feasible but faces significant kinetic barriers. However, upon oxidation, a kinetically favored nucleophilic/electrophilic N-N bond forming mechanism was enabled to give monocationic μ-dinitrogen dimers. Computational and experimental evidence for this "oxidation-induced ambiphilic nitrido coupling" mechanism is presented. The factors influencing release of dinitrogen from the resulting μ-dinitrogen dimers were also probed and it was found that further oxidation to a dicationic species is required to induce (very rapid) loss of dinitrogen. The mechanistic path discovered for N-N bond formation and dinitrogen release follows an ECECC sequence (E = "electrochemical step"; C = "chemical step"). Experimental evidence for the intermediacy of a highly electrophilic, cationic d0 molybdenum(vi) nitrido in the N-N bond forming mechanism via trapping with an isonitrile reagent is also discussed. Together these results are relevant to the development of molecular catalysts capable of mediating ammonia oxidation to dihydrogen and dinitrogen.
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Affiliation(s)
- C Christopher Almquist
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | | | - H D A Chathumal Jayaweera
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Nicole Removski
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Wen Zhou
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Benjamin S Gelfand
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Laurent Maron
- LPCNO, Université de Toulouse, INSA UPS Toulouse France
| | - Warren E Piers
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
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2
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Beh DW, Cuellar De Lucio AJ, del Rosal I, Maron L, Spasyuk D, Gelfand BS, Li JB, Piers WE. Organotitanium Complexes Supported by a Dianionic Pentadentate Ligand. Organometallics 2023. [DOI: 10.1021/acs.organomet.2c00609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2023]
Affiliation(s)
- Daniel W. Beh
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | | | - Iker del Rosal
- LPCNO, Université de Toulouse, INSA, UPS, LPCNO, 135 avenue de Rangueil, F-31077 Toulouse, France
- CNRS, LPCNO, F-31077 Toulouse, France
| | - Laurent Maron
- LPCNO, Université de Toulouse, INSA, UPS, LPCNO, 135 avenue de Rangueil, F-31077 Toulouse, France
- CNRS, LPCNO, F-31077 Toulouse, France
| | - Denis Spasyuk
- Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, Saskatchewan S7N 2V3, Canada
| | - Benjamin S. Gelfand
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Jian-Bin Li
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Warren E. Piers
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
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3
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Guzmán J, Urriolabeitia A, Padilla M, García-Orduña P, Polo V, Fernández-Alvarez FJ. Mechanism Insights into the Iridium(III)- and B(C 6F 5) 3-Catalyzed Reduction of CO 2 to the Formaldehyde Level with Tertiary Silanes. Inorg Chem 2022; 61:20216-20221. [PMID: 36472385 PMCID: PMC10468102 DOI: 10.1021/acs.inorgchem.2c03330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Indexed: 12/12/2022]
Abstract
The catalytic system [Ir(CF3CO2)(κ2-NSiMe)2] [1; NSiMe = (4-methylpyridin-2-yloxy)dimethylsilyl]/B(C6F5)3 promotes the selective reduction of CO2 with tertiary silanes to the corresponding bis(silyl)acetal. Stoichiometric and catalytic studies evidenced that species [Ir(CF3COO-B(C6F5)3)(κ2-NSiMe)2] (3), [Ir(κ2-NSiMe)2][HB(C6F5)3] (4), and [Ir(HCOO-B(C6F5)3)(κ2-NSiMe)2] (5) are intermediates of the catalytic process. The structure of 3 has been determined by X-ray diffraction methods. Theoretical calculations show that the rate-limiting step for the 1/B(C6F5)3-catalyzed hydrosilylation of CO2 to bis(silyl)acetal is a boron-promoted Si-H bond cleavage via an iridium silylacetal borane adduct.
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Affiliation(s)
- Jefferson Guzmán
- Facultad
de Ciencias, Departamento de Química Inorgánica, Instituto
de Síntesis Química y Catálisis Homogénea, Universidad de Zaragoza, CSIC, Zaragoza 50009, Spain
| | - Asier Urriolabeitia
- Facultad
de Ciencias, Departamento de Química Física, BIFI, Universidad de Zaragoza, Zaragoza 50009, Spain
| | - Marina Padilla
- Facultad
de Ciencias, Departamento de Química Inorgánica, Instituto
de Síntesis Química y Catálisis Homogénea, Universidad de Zaragoza, CSIC, Zaragoza 50009, Spain
| | - Pilar García-Orduña
- Facultad
de Ciencias, Departamento de Química Inorgánica, Instituto
de Síntesis Química y Catálisis Homogénea, Universidad de Zaragoza, CSIC, Zaragoza 50009, Spain
| | - Víctor Polo
- Facultad
de Ciencias, Departamento de Química Física, BIFI, Universidad de Zaragoza, Zaragoza 50009, Spain
| | - Francisco J. Fernández-Alvarez
- Facultad
de Ciencias, Departamento de Química Inorgánica, Instituto
de Síntesis Química y Catálisis Homogénea, Universidad de Zaragoza, CSIC, Zaragoza 50009, Spain
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4
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Shinohara K, Tsurugi H, Mashima K. N-Methylation of Aniline Derivatives with CO 2 and Phenylsilane Catalyzed by Lanthanum Hydridotriarylborate Complexes bearing a Nitrogen Tridentate Ligand. ACS Catal 2022. [DOI: 10.1021/acscatal.2c01658] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Koichi Shinohara
- 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
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5
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Esarte Palomero O, Jones RA. Ferrocene tethered boramidinate frustrated Lewis pairs: stepwise capture of CO 2 and CO. Dalton Trans 2022; 51:6275-6284. [PMID: 35379999 DOI: 10.1039/d2dt00691j] [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
The synthesis and reactivity of novel ferrocene tethered boramidinate frustrated Lewis pairs (FLPs), capable of the sequential capture of small molecules, is reported. Reactions of 1,1'-dicarbodiimidoferrocenes with different boranes provides access to metallocene tethered FLPs. The reactivity of the boramidinate moieties can be tuned by the nature of the carbodiimido substituents (alkyl vs. aryl) and the borane used in the reduction (9-borabicyclo[3.3.1]nonane [(C8H14)2BH]2vs. bis-pentafluorophenyl borane [(C6F5)2BH]2). The boramidinate FLP arms do not engage in intramolecular reactions, allowing for independent small molecule capture by each FLP. By careful synthetic control, sequential capture of different gaseous small molecules (CO2 and CO or CO2 and CNtBu) by the same bis(boramidinate)ferrocene molecule has been demonstrated.
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Affiliation(s)
- Orhi Esarte Palomero
- Department of Chemistry - The University of Texas at Austin, 105 E 24th St., Austin, TX 78712, USA.
| | - Richard A Jones
- Department of Chemistry - The University of Texas at Austin, 105 E 24th St., Austin, TX 78712, USA.
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6
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Patrick EA, Yang Y, Piers WE, Maron L, Gelfand BS. A monoanionic pentadentate ligand platform for scandium-pnictogen multiple bonds. Chem Commun (Camb) 2021; 57:8640-8643. [PMID: 34369525 DOI: 10.1039/d1cc03481b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A new monoanionic pentadentate ligand is designed to accommodate Sc = E bonds (E = N, P). The imido complex is stable enough to isolate and characterize, and reacts rapidly with CO2. The phosphinidene, on the other hand, is highly reactive and induces C-C bond cleavage to yield a phosphido-pyridyl complex which also undergoes rapid reacton with CO2.
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Affiliation(s)
- Evan A Patrick
- Department of Chemistry, University of Calgary, 2500 University Drive N.W., Calgary, Alberta T2N 1N4, Canada.
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7
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Chang K, Del Rosal I, Zheng X, Maron L, Xu X. Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity. Dalton Trans 2021; 50:7804-7809. [PMID: 34100492 DOI: 10.1039/d1dt01074c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An efficient tandem hydrosilylation of CO2, which uses a combination of a simple, homoleptic lanthanum aryloxide and B(C6F5)3, was performed. Use of a less sterically hindered silane led to an exclusive reduction of CO2 to CH4, with a turnover frequency of up to 6000 h-1 at room temperature. The catalytic system is robust, and 19 400 turnovers could be achieved with 0.005 mol% loading of lanthanum. The reaction outcome depended highly on the nature of the silane reductant used. Selective production of the formaldehyde equivalent, i.e., bis(silyl)acetal, without over-reduction, was observed when a sterically bulky silane was used. The reaction mechanism was elucidated by stoichiometric reactions and DFT calculations.
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Affiliation(s)
- Kejian Chang
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China.
| | - Iker Del Rosal
- LPCNO, CNRS & INSA, Université Paul Sabatier, 135 Avenue de Rangueil, 31077 Toulouse, France.
| | - Xizhou Zheng
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China.
| | - Laurent Maron
- LPCNO, CNRS & INSA, Université Paul Sabatier, 135 Avenue de Rangueil, 31077 Toulouse, France.
| | - Xin Xu
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China.
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8
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Ghosh D, Kumar GR, Subramanian S, Tanaka K. More Than Just a Reagent: The Rise of Renewable Organohydrides for Catalytic Reduction of Carbon Dioxide. CHEMSUSCHEM 2021; 14:824-841. [PMID: 33369102 DOI: 10.1002/cssc.202002660] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 12/06/2020] [Indexed: 06/12/2023]
Abstract
Stoichiometric carbon dioxide reduction to highly reduced C1 molecules, such as formic acid (2e- ), formaldehyde (4e- ), methanol (6e- ) or even most-reduced methane (8e- ), has been successfully achieved by using organosilanes, organoboranes, and frustrated Lewis Pairs (FLPs) in the presence of suitable catalyst. The development of renewable organohydride compounds could be the best alternative in this regard as they have shown promise for the transfer of hydride directly to CO2 . Reduction of CO2 by two electrons and two protons to afford formic acid by using renewable organohydride molecules has recently been investigated by various groups. However, catalytic CO2 reduction to ≥2e- -reduced products by using renewable organohydride-based molecules has rarely been explored. This Minireview summarizes important findings in this regard, encompassing both stoichiometric and catalytic CO2 reduction.
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Affiliation(s)
- Debashis Ghosh
- Department of Chemistry, St. Joseph's College (Autonomous), Bangalore, 560027, Karnataka, India
| | - George Rajendra Kumar
- Department of Applied Chemistry, Karunya Institute of Technology and Sciences, Coimbatore, 641114, Tamil Nadu, India
| | - Saravanan Subramanian
- Inorganic Materials and Catalysis Division, CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, 364002, Gujarat, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Koji Tanaka
- Institute for Integrated Cell-Material Sciences (KUIAS/iCeMS), Kyoto University, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan
- Department of Applied Chemistry, College of Life Science, Ritsumeikan University, 525-8577 Noji-higashi, 1-1-1, Kusatsu, Shiga, Japan
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9
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Caise A, Hicks J, Ángeles Fuentes M, Goicoechea JM, Aldridge S. Partnering a Three-Coordinate Gallium Cation with a Hydroborate Counter-Ion for the Catalytic Hydrosilylation of CO 2. Chemistry 2021; 27:2138-2148. [PMID: 33169886 DOI: 10.1002/chem.202004408] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/08/2020] [Indexed: 12/16/2022]
Abstract
A novel β-diketiminate stabilized gallium hydride, (Dipp L)Ga(Ad)H (where (Dipp L)={HC(MeCDippN)2 }, Dipp=2,6-diisopropylphenyl and Ad=1-adamantyl), has been synthesized and shown to undergo insertion of carbon dioxide into the Ga-H bond under mild conditions. In this case, treatment of the resulting κ1 -formate complex with triethylsilane does not lead to regeneration of the hydride precursor. However, when combined with B(C6 F5 )3 , (Dipp L)Ga(Ad)H catalyses the reductive hydrosilylation of CO2 . Under stoichiometric conditions, the addition of one equivalent of B(C6 F5 )3 to (Dipp L)Ga(Ad)H leads to the formation of a 3-coordinate cationic gallane complex, partnered with a hydroborate anion, [(Dipp L)Ga(Ad)][HB(C6 F5 )3 ]. This complex rapidly hydrometallates carbon dioxide and catalyses the selective reduction of CO2 to the formaldehyde oxidation level at 60 °C in the presence of Et3 SiH (yielding H2 C(OSiEt3 )2 ). When catalysis is undertaken in the presence of excess B(C6 F5 )3 , appreciable enhancement of activity is observed, with a corresponding reduction in selectivity: the product distribution includes H2 C(OSiEt3 )2 , CH4 and O(SiEt3 )2 . While this system represents proof-of-concept in CO2 hydrosilylation by a gallium hydride system, the TOF values obtained are relatively modest (max. 10 h-1 ). This is attributed to the strength of binding of the formatoborate anion to the gallium centre in the catalytic intermediate (Dipp L)Ga(Ad){OC(H)OB(C6 F5 )3 }, and the correspondingly slow rate of the turnover-limiting hydrosilylation step. In turn, this strength of binding can be related to the relatively high Lewis acidity measured for the [(Dipp L)Ga(Ad)]+ cation (AN=69.8).
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Affiliation(s)
- Alexa Caise
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Jamie Hicks
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - M Ángeles Fuentes
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Jose M Goicoechea
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Simon Aldridge
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
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10
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Nurdin L, Yang Y, Neate PGN, Piers WE, Maron L, Neidig ML, Lin JB, Gelfand BS. Activation of ammonia and hydrazine by electron rich Fe(ii) complexes supported by a dianionic pentadentate ligand platform through a common terminal Fe(iii) amido intermediate. Chem Sci 2020; 12:2231-2241. [PMID: 34163989 PMCID: PMC8179247 DOI: 10.1039/d0sc06466a] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
We report the use of electron rich iron complexes supported by a dianionic diborate pentadentate ligand system, B2Pz4Py, for the coordination and activation of ammonia (NH3) and hydrazine (NH2NH2). For ammonia, coordination to neutral (B2Pz4Py)Fe(ii) or cationic [(B2Pz4Py)Fe(iii)]+ platforms leads to well characterized ammine complexes from which hydrogen atoms or protons can be removed to generate, fleetingly, a proposed (B2Pz4Py)Fe(iii)–NH2 complex (3Ar-NH2). DFT computations suggest a high degree of spin density on the amido ligand, giving it significant aminyl radical character. It rapidly traps the H atom abstracting agent 2,4,6-tri-tert-butylphenoxy radical (ArO˙) to form a C–N bond in a fully characterized product (2Ar), or scavenges hydrogen atoms to return to the ammonia complex (B2Pz4Py)Fe(ii)–NH3 (1Ar-NH3). Interestingly, when (B2Pz4Py)Fe(ii) is reacted with NH2NH2, a hydrazine bridged dimer, (B2Pz4Py)Fe(ii)–NH2NH2–Fe(ii)(B2Pz4Py) ((1Ar)2-NH2NH2), is observed at −78 °C and converts to a fully characterized bridging diazene complex, 4Ar, along with ammonia adduct 1Ar-NH3 as it is allowed to warm to room temperature. Experimental and computational evidence is presented to suggest that (B2Pz4Py)Fe(ii) induces reductive cleavage of the N–N bond in hydrazine to produce the Fe(iii)–NH2 complex 3Ar-NH2, which abstracts H˙ atoms from (1Ar)2-NH2NH2 to generate the observed products. All of these transformations are relevant to proposed steps in the ammonia oxidation reaction, an important process for the use of nitrogen-based fuels enabled by abundant first row transition metals. Synopsis: a highly reactive Fe(iii)–NH2 complex is generated via activation of ammonia or hydrazine in reactions of relevance to fundamental steps in ammonia oxidation processes mediated by an abundant, first row transition metal.![]()
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Affiliation(s)
- Lucie Nurdin
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Yan Yang
- LPCNO, Université de Toulouse, INSA, UPS Toulouse France
| | - Peter G N Neate
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Warren E Piers
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Laurent Maron
- LPCNO, Université de Toulouse, INSA, UPS Toulouse France
| | - Michael L Neidig
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Jian-Bin Lin
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Benjamin S Gelfand
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
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11
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Huang W, Roisnel T, Dorcet V, Orione C, Kirillov E. Reduction of CO2 by Hydrosilanes in the Presence of Formamidinates of Group 13 and 12 Elements. Organometallics 2020. [DOI: 10.1021/acs.organomet.9b00853] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Weiheng Huang
- Organometallics: Materials and Catalysis laboratories, Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35700 Rennes, France
| | - Thierry Roisnel
- Centre de diffraction X, Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35700 Rennes, France
| | - Vincent Dorcet
- Centre de diffraction X, Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35700 Rennes, France
| | - Clement Orione
- CRMPO, Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35700 Rennes, France
| | - Evgueni Kirillov
- Organometallics: Materials and Catalysis laboratories, Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35700 Rennes, France
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12
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Bayer U, Anwander R. Carbonyl group and carbon dioxide activation by rare-earth-metal complexes. Dalton Trans 2020; 49:17472-17493. [PMID: 33232414 DOI: 10.1039/d0dt03578e] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The rare-earth elements (Ln = Sc, Y, La-Lu) are widely used in stoichiometric and catalytic carbonyl group transformations. Sufficient availability, non-toxicity, high oxophilicity, tunable ion size/Lewis acidity and enhanced ligand exchangeability have been major driving factors for their successful implementation. Routinely employed reagents for stoichiometric carbonyl group transformations are divalent ytterbium and samarium compounds (e.g., ketone reduction), bimetallic CeCl3/LiR (C-C coupling), or ceric ammonium nitrate CAN (cyclic ketone oxidation). Rare-earth-metal triflates, and in particular Sc(OTf)3, are prominent examples of Lewis acid catalysts for versatile use in organic synthesis (e.g., Aldol and Michael reactions). Moreover, Ln(ii) and Ln(iii) complexes efficiently catalyze the (co)polymerization of carbonyl group-containing monomers including lactones, lactides, acrylates, and carbon dioxide. Featuring the most notorious greenhouse gas, CO2 is currently assessed as a cheap, abundant, and non-toxic C1 building block. Ln(iii) complexes are not only capable of efficient CO2 capture via reversible insertion but also of CO2 activation for catalytic conversions (copolymerization/cycloaddition with epoxides). This perspective focuses on structurally elucidated Ln complexes resulting from ketone or carbonyl derivative activation/insertion as well as carbon dioxide insertion products. The respective compounds will be sorted by structural motifs and, if applicable, details on reactivity and feasibility of catalytic reactions are presented. The article is subdivided in three parts: (i) donor and insertion products of ketones and aldehydes, (ii) redox-enhanced activation of carbonyl derivatives, and (iii) CO2 insertion/redox products and homogeneous catalytic conversion.
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Affiliation(s)
- Uwe Bayer
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen (EKUT), Auf der Morgenstelle 18, 72076 Tübingen, Germany.
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