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Krämer F. Aluminum in Frustrated Lewis Pair Chemistry. Angew Chem Int Ed Engl 2024; 63:e202405207. [PMID: 38826040 DOI: 10.1002/anie.202405207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2024] [Revised: 04/30/2024] [Accepted: 05/02/2024] [Indexed: 06/04/2024]
Abstract
This review article describes the development of the use of aluminum compounds in the chemistry of frustrated Lewis pairs (FLPs) over the last 14 years. It also discusses the synthesis, reactivity and catalytic applications of intermolecular, intramolecular and so-called hidden FLPs with phosphorus, nitrogen and carbon Lewis bases. The intrinsically higher acidity of aluminum compounds compared to their boron analogs opens up different reaction pathways. The results are presented in a more or less chronological order. It is shown that Al FLPs react with a variety of polar and non-polar substrates and form both stable adducts and reversibly activate bonds. Consequently, some catalytic applications of the title compounds were presented such as dimerization of alkynes, hydrogenation of tert-butyl ethylene and imines, C-F bond activation, reduction of CO2, dehydrogenation of amine borane and transfer of ammonia. In addition, various Al FLPs were used as initiators in polymerization reactions.
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Affiliation(s)
- Felix Krämer
- C1 Green Chemicals AG, Am Studio 2a, 12489, Berlin, Germany
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Werner L, Hagn J, Walpuski J, Radius U. Aluminum(III) Cations [(NHC) ⋅ AlMes 2 ] + : Synthesis, Characterization, and Application in FLP-Chemistry. Angew Chem Int Ed Engl 2023:e202312111. [PMID: 37877231 DOI: 10.1002/anie.202312111] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 10/24/2023] [Accepted: 10/25/2023] [Indexed: 10/26/2023]
Abstract
The three-coordinate aluminum cations ligated by N-heterocyclic carbenes (NHCs) [(NHC) ⋅ AlMes2 ]+ [B(C6 F5 )4 ]- (NHC=IMeMe 4, IiPrMe 5, IiPr 6, Mes=2,4,6-trimethylphenyl) were prepared via hydride abstraction of the alanes (NHC) ⋅ AlHMes2 (NHC=IMeMe 1, IiPrMe 2, IiPr 3) using [Ph3 C]+ [B(C6 F5 )4 ]- in toluene as hydride acceptor. If this reaction was performed in diethyl ether, the corresponding four-coordinate aluminum etherate cations [(NHC) ⋅ AlMes2 (OEt2 )]+ [B(C6 F5 )4 ]- 7-9 (NHC=IMeMe 7, IiPrMe 8, IiPr 9) were isolated. According to a theoretical and experimental assessment of the Lewis-acidity of the [(IMeMe ) ⋅ AlMes2 ]+ cation is the acidity larger than that of B(C6 F5 )3 and of similar magnitude as reported for Al(C6 F5 )3 . The reaction of [(IMeMe ) ⋅ AlMes2 ]+ [B(C6 F5 )4 ]- 4 with the sterically less demanding, basic phosphine PMe3 afforded a mixed NHC/phosphine stabilized cation [(IMeMe ) ⋅ AlMes2 (PMe3 )]+ [B(C6 F5 )4 ]- 10. Equimolar mixtures of 4 and the sterically more demanding PCy3 gave a frustrated Lewis-pair (FLP), i.e., [(IMeMe ) ⋅ AlMes2 ]+ [B(C6 F5 )4 ]- /PCy3 FLP-11, which reacts with small molecules such as CO2 , ethene, and 2-butyne.
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Affiliation(s)
- Luis Werner
- Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Julika Hagn
- Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Janis Walpuski
- Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Udo Radius
- Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
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Federmann P, Müller R, Beckmann F, Lau C, Cula B, Kaupp M, Limberg C. Synthesis of Intramolecular P/Al‐Based Frustrated Lewis Pairs via Aluminum‐Tin‐Exchange and their Reactivity toward CO
2. Chemistry 2022; 28:e202200404. [PMID: 35213074 PMCID: PMC9314872 DOI: 10.1002/chem.202200404] [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: 02/08/2022] [Indexed: 11/07/2022]
Abstract
Frustrated Lewis pairs (FLPs) composed of acidic alane and basic phosphane functions, separated by a xanthene linker, can be prepared through the corresponding Me3Sn derivative and methyl aluminum compounds with elimination of Me4Sn. This way MeClAl‐, Cl2Al‐ and (C6F5)2Al‐ moieties could be introduced and the resulting FLPs are stabilized by a further equivalent of the alane precursors. In contact with the FLPs CO2 is bound via the C atom at the phosphane functions and the two O atoms at the Al centers. The residues at the latter determine the binding strength. Hence, in case of MeClAl CO2 capture occurs at higher pressure and under ambient conditions CO2 is released again, while for Cl2Al and (C6F5)2Al CO2 binding becomes irreversible. The results of DFT calculations rationalize these findings by the high thermodynamic stabilization in case of more electronegative residues, which concomitantly lead to higher barriers, and in case of (C6F5)2Al further stabilization is achieved through a low reorganization energy.
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Affiliation(s)
- Patrick Federmann
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Robert Müller
- Institut für ChemieTheoretische Chemie/QuantenchemieSekr. C7Technische Universität BerlinStraße des 17. Juni 13510623BerlinGermany
| | - Fabian Beckmann
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Caroline Lau
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Beatrice Cula
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Martin Kaupp
- Institut für ChemieTheoretische Chemie/QuantenchemieSekr. C7Technische Universität BerlinStraße des 17. Juni 13510623BerlinGermany
| | - Christian Limberg
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
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Haider W, Calvin-Brown MD, Bischoff IA, Huch V, Morgenstern B, Müller C, Sergeieva T, Andrada DM, Schäfer A. Diarylpnictogenyldialkylalanes─Synthesis, Structures, Bonding Analysis, and CO 2 Capture. Inorg Chem 2022; 61:1672-1684. [PMID: 34985262 DOI: 10.1021/acs.inorgchem.1c03494] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several new diphenylamino- and diphenylphosphanyldialkylalanes are reported, which were characterized in solution and in the solid state, assisted by in-depth bonding analysis within the DFT framework. In the case of bulky alkyl substituents on the aluminum atom, the species are stable in their monomeric form and were structurally characterized by single crystal X-ray diffraction, expanding the relatively small field of monomeric pnictogenylalanes. In the case of oligomeric diphenylpnictogenyldimethylalanes, their reactivity toward different σ-donor ligands was studied, and several examples of monomeric adducts could be structurally characterized, including the first cyclic(alkyl)(amino)carbene complexes. The reactivity of these CAAC complexes, their oligomeric precursors, and an unstabilized monomeric aminoalane toward CO2 was probed, leading to different insertion products that could be characterized. Additionally, the mechanism was elucidated by DFT calculations.
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Affiliation(s)
- Wasim Haider
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - Marces Devonne Calvin-Brown
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - Inga-Alexandra Bischoff
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - Volker Huch
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - Bernd Morgenstern
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - Carsten Müller
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - Tetiana Sergeieva
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - Diego M Andrada
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
| | - André Schäfer
- Saarland University, Faculty of Natural Sciences and Technology, Department of Chemistry, Campus Saarbrücken, 66123 Saarbrücken, Federal Republic of Germany
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