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Álvarez-Ruiz E, Sancho I, Navarro M, Fernández I, Santamaría C, Hernán-Gómez A. A Mixed-Valence Ti(II)/Ti(III) Inverted Sandwich Compound as a Regioselective Catalyst for the Uncommon 1,3,5-Alkyne Cyclotrimerization. Inorg Chem 2024; 63:8642-8653. [PMID: 38690944 PMCID: PMC11094787 DOI: 10.1021/acs.inorgchem.4c00149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 04/19/2024] [Accepted: 04/23/2024] [Indexed: 05/03/2024]
Abstract
The synthesis, structure, and catalytic activity of a Ti(II)/Ti(III) inverted sandwich compound are presented in this study. Synthesis of the arene-bridged dititanium compound begins with the preparation of the titanium(IV) precursor [TiCl2(MesPDA)(thf)2] (MesPDA = N,N'-bis(2,4,6-trimethylphenyl)-o-phenylenediamide) (2). The reduction of 2 with sodium metal results in species [{Ti(MesPDA)(thf)}2(μ-Cl)3{Na}] (3) in oxidation state III. To achieve the lower oxidation state II, 2 undergoes reduction through alkylation with lithium cyclopentyl. This alkylation approach triggers a cascade of reactions, including β-hydride abstraction/elimination, hydrogen evolution, and chemical reduction, to generate the Ti(II)/Ti(III) compound [Li(thf)4][(TiMesPDA)2(μ-η6: η6-C6H6)] (4). X-ray and EPR characterization confirms the mixed-valence states of the titanium species. Compound 4 catalyzes a mild, efficient, and regiospecific cyclotrimerization of alkynes to form 1,3,5-substituted arenes. Kinetic data support a mechanism involving a binuclear titanium arene compound, similar to compound 4, as the resting state. The active catalyst promotes the oxidative coupling of two alkynes in the rate-limiting step, followed by a rapid [4 + 2] cycloaddition to form the arene product. Computational analysis of the resting state for the cycloaddition of trimethylsilylacetylene indicates a thermodynamic preference for stabilizing the 1,3,5-arene within the space between the two [TiMesPDA] fragments, consistent with the observed regioselectivity.
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Affiliation(s)
- Elena Álvarez-Ruiz
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus Universitario, Alcalá de Henares, Madrid E-28805, Spain
| | - Ignacio Sancho
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus Universitario, Alcalá de Henares, Madrid E-28805, Spain
| | - Marta Navarro
- Departamento
de Química Inorgánica, Orgánica y Bioquímica,
Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Ciudad Real 13071, Spain
| | - Israel Fernández
- Departamento
de Química Orgánica I, Facultad de Ciencias Químicas
and Centro de Innovación en Química Avanzada (ORFEO−CINQA), Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Cristina Santamaría
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus Universitario, Alcalá de Henares, Madrid E-28805, Spain
| | - Alberto Hernán-Gómez
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus Universitario, Alcalá de Henares, Madrid E-28805, Spain
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2
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Lai Q, Mason AH, Agarwal A, Edenfield WC, Zhang X, Kobayashi T, Kratish Y, Marks TJ. Rapid Polyolefin Hydrogenolysis by a Single-Site Organo-Tantalum Catalyst on a Super-Acidic Support: Structure and Mechanism. Angew Chem Int Ed Engl 2023; 62:e202312546. [PMID: 37948306 DOI: 10.1002/anie.202312546] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Indexed: 11/12/2023]
Abstract
The novel electrophilic organo-tantalum catalyst AlS/TaNpx (1) (Np=neopentyl) is prepared by chemisorption of the alkylidene Np3 Ta=CHt Bu onto highly Brønsted acidic sulfated alumina (AlS). The proposed catalyst structure is supported by EXAFS, XANES, ICP, DRIFTS, elemental analysis, and SSNMR measurements and is in good agreement with DFT analysis. Catalyst 1 is highly effective for the hydrogenolysis of diverse linear and branched hydrocarbons, ranging from C2 to polyolefins. To the best of our knowledge, 1 exhibits one of the highest polyolefin hydrogenolysis activities (9,800 (CH2 units) ⋅ mol(Ta)-1 ⋅ h-1 at 200 °C/17 atm H2 ) reported to date in the peer-reviewed literature. Unlike the AlS/ZrNp2 analog, the Ta catalyst is more thermally stable and offers multiple potential C-C bond activation pathways. For hydrogenolysis, AlS/TaNpx is effective for a wide variety of pre- and post-consumer polyolefin plastics and is not significantly deactivated by standard polyolefin additives at typical industrial concentrations.
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Affiliation(s)
- Qingheng Lai
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL-60208-3113, USA
| | - Alexander H Mason
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL-60208-3113, USA
| | - Amol Agarwal
- Department of Materials Science & Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL-60208-3113, USA
| | - Wilson C Edenfield
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL-60208-3113, USA
| | - Xinrui Zhang
- Department of Materials Science & Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL-60208-3113, USA
| | - Takeshi Kobayashi
- U.S. DOE Ames National Laboratory, IOWA State University, Ames, IA50011-3020, USA
| | - Yosi Kratish
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL-60208-3113, USA
| | - Tobin J Marks
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL-60208-3113, USA
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Sancho I, Navarro M, Montilla M, Salvador P, Santamaría C, Luis JM, Hernán-Gómez A. Ti(III) Catalysts for CO 2/Epoxide Copolymerization at Unusual Ambient Pressure Conditions. Inorg Chem 2023; 62:14873-14887. [PMID: 37651747 PMCID: PMC10521022 DOI: 10.1021/acs.inorgchem.3c01249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Indexed: 09/02/2023]
Abstract
Titanium compounds in low oxidation states are highly reducing species and hence powerful tools for the functionalization of small molecules. However, their potential has not yet been fully realized because harnessing these highly reactive complexes for productive reactivity is generally challenging. Advancing this field, herein we provide a detailed route for the formation of titanium(III) orthophenylendiamido (PDA) species using [LiBHEt3] as a reducing agent. Initially, the corresponding lithium PDA compounds [Li2(ArPDA)(thf)3] (Ar = 2,4,6-trimethylphenyl (MesPDA), 2,6-diisopropylphenyl (iPrPDA)) are combined with [TiCl4(thf)2] to form the heterobimetallic complexes [{TiCl(ArPDA)}(μ-ArPDA){Li(thf)n}] (n = 1, Ar = iPr 3 and n = 2, Ar = Mes 4). Compound 4 evolves to species [Ti(MesPDA)2] (6) via thermal treatment. In contrast, the transformation of 3 into [Ti(iPrPDA)2] (5) only occurs in the presence of [LiNMe2], through a lithium-assisted process, as revealed by density functional theory (DFT). Finally, the Ti(IV) compounds 3-6 react with [LiBHEt3] to give rise to the Ti(III) species [Li(thf)4][Ti(ArPDA)2] (Ar = iPr 8, Mes 9). These low-valent compounds in combination with [PPN]Cl (PPN = bis(triphenylphosphine)iminium) are proved to be highly selective catalysts for the copolymerization of CO2 and cyclohexene epoxide. Reactions occur at 1 bar pressure with activity/selectivity levels similar to Salen-Cr(III) compounds.
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Affiliation(s)
- Ignacio Sancho
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus
Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Marta Navarro
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus
Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Marc Montilla
- Institute
of Computational Chemistry and Catalysis and Department of Chemistry, University of Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain
| | - Pedro Salvador
- Institute
of Computational Chemistry and Catalysis and Department of Chemistry, University of Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain
| | - Cristina Santamaría
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus
Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Josep M. Luis
- Institute
of Computational Chemistry and Catalysis and Department of Chemistry, University of Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain
| | - Alberto Hernán-Gómez
- Departamento
de Química Orgánica y Química Inorgánica,
Instituto de Investigación Química “Andrés
M. del Río” (IQAR), Universidad
de Alcalá, Campus
Universitario, E-28805 Alcalá de Henares, Madrid, Spain
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Carbó JJ, Gómez M, Hernández-Prieto C, Hernán-Gómez A, Martín A, Mena M, Puiggalí-Jou J, Ricart JM, Santamaría C. Reductive Hydrogenation of Sulfido-Bridged Tantalum Alkyl Complexes: A Mechanistic Insight. Inorg Chem 2023. [PMID: 37319404 DOI: 10.1021/acs.inorgchem.3c00043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Hydrogenolysis of a series of alkyl sulfido-bridged tantalum(IV) dinuclear complexes [Ta(η5-C5Me5)R(μ-S)]2 [R = Me, nBu (1), Et, CH2SiMe3, C3H5, Ph, CH2Ph (2), p-MeC6H4CH2 (3)] has led quantitatively to the Ta(III) tetrametallic sulfide cluster [Ta(η5-C5Me5)(μ3-S)]4 (4) along with the corresponding alkane. Mechanistic information for the formation of the unique low-valent tetrametallic compound 4 was gathered by hydrogenation of the phenyl-substituted precursor [Ta(η5-C5Me5)Ph(μ-S)]2, which proceeds through a stepwise hydrogenation process, disclosing the formation of the intermediate tetranuclear hydride sulfide [Ta2(η5-C5Me5)2(H)Ph(μ-S)(μ3-S)]2 (5). Extending our studies toward tantalum alkyl precursors containing functional groups susceptible to hydrogenation, such as the allyl-and benzyl-substituted compounds [Ta(η5-C5Me5)(η3-C3H5)(μ-S)]2 and [Ta(η5-C5Me5)(CH2Ph)(μ-S)]2 (2), enables alternative reaction pathways en route to the formation of 4. In the former case, the dimetallic system undergoes selective hydrogenation of the unsaturated allyl moiety, forming the asymmetric complex [{Ta(η5-C5Me5)(η3-C3H5)}(μ-S)2{Ta(η5-C5Me5)(C3H7)}] (6) with only one propyl fragment. Species 2, in addition to the hydrogenation of one benzyl fragment and concomitant toluene release, also undergoes partial hydrogenation and dearomatization of the phenyl ring on the vicinal benzyl unity to give a η5-cyclohexadienyl complex [Ta2(η5-C5Me5)2(μ-CH2C6H6)(μ-S)2] (7). The mechanistic implications of the latter hydrogenation process are discussed by means of DFT calculations.
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Affiliation(s)
- Jorge J Carbó
- Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, C/ Marcel.lí Domingo, s/n, 43007 Tarragona, Spain
| | - Manuel Gómez
- Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, Campus Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Cristina Hernández-Prieto
- Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, Campus Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Alberto Hernán-Gómez
- Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, Campus Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Avelino Martín
- Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, Campus Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Miguel Mena
- Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, Campus Universitario, E-28805 Alcalá de Henares, Madrid, Spain
| | - Jordi Puiggalí-Jou
- Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, C/ Marcel.lí Domingo, s/n, 43007 Tarragona, Spain
| | - Josep M Ricart
- Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, C/ Marcel.lí Domingo, s/n, 43007 Tarragona, Spain
| | - Cristina Santamaría
- Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, Campus Universitario, E-28805 Alcalá de Henares, Madrid, Spain
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Panda S, Dhara S, Singh A, Dey S, Kumar Lahiri G. Metal-coordinated azoaromatics: Strategies for sequential azo-reduction, isomerization and application potential. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.214895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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