1
|
Evans MJ, Jones C. Low oxidation state and hydrido group 2 complexes: synthesis and applications in the activation of gaseous substrates. Chem Soc Rev 2024; 53:5054-5082. [PMID: 38595211 DOI: 10.1039/d4cs00097h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Numerous industrial processes utilise gaseous chemical feedstocks to produce useful chemical products. Atmospheric and other small molecule gases, including anthropogenic waste products (e.g. carbon dioxide), can be viewed as sustainable building blocks to access value-added chemical commodities and materials. While transition metal complexes have been well documented in the reduction and transformation of these substrates, molecular complexes of the terrestrially abundant alkaline earth metals have also demonstrated promise with remarkable reactivity reported towards an array of industrially relevant gases over the past two decades. This review covers low oxidation state and hydrido group 2 complexes and their role in the reduction and transformation of a selection of important gaseous substrates towards value-added chemical products.
Collapse
Affiliation(s)
- Matthew J Evans
- School of Chemistry, Monash University, PO Box 23, Melbourne, Victoria, 3800, Australia.
| | - Cameron Jones
- School of Chemistry, Monash University, PO Box 23, Melbourne, Victoria, 3800, Australia.
| |
Collapse
|
2
|
Evans MJ, Mullins J, Mondal R, Jones C. Reductions of Arenes using a Magnesium-Dinitrogen Complex. Chemistry 2024:e202401005. [PMID: 38622992 DOI: 10.1002/chem.202401005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/15/2024] [Accepted: 04/16/2024] [Indexed: 04/17/2024]
Abstract
In this contribution, we present "Birch-type", and other reductions of simple arenes by the potassium salt of an anionic magnesium dinitrogen complex, [{K(TCHPNON)Mg}2(μ-N2)] (TCHPNON=4,5-bis(2,4,6-tricyclohexylanilido)-2,7-diethyl-9,9-dimethyl-xanthene), which acts as a masked dimagnesium(I) diradical in these reactions. This reagent is non-hazardous, easy-to-handle, and in some cases provides access to 1,4-cyclohexadiene reduction products under relatively mild reaction conditions. This system works effectively to reduce benzene, naphthalene and anthracene through magnesium-bound "Birch-type" reduction intermediates. Cyclohexadiene products can be subsequently released from the magnesium centres by protonolysis with methanol. In contrast, the reduction of substituted arenes is less selective and involves competing reaction pathways. For toluene and 1,3,5-triphenylbenzene, the structural authentication of "Birch-type" reduction intermediates is conclusive, although the formation of corresponding 1,4-cyclohexadiene derivatives was low yielding. Reduction of anisole did not yield an isolable "Birch-type" intermediate, but instead gave a C-O activation product. Treating triphenylphosphine with [{K(TCHPNON)Mg}2(μ-N2)] resulted in the extrusion of both biphenyl and dinitrogen to afford a magnesium(II) phosphanide [{K(TCHPNON)Mg(μ-PPh2)}2]. Reduction of fluorobenzene proceeded via C-F activation of the arene, and isolation of the magnesium(II) fluoride [{K(TCHPNON)Mg(μ-F)}2]. Finally, the two-electron reduction of 1,3,5,7-cyclooctatetraene (COT) with [{K(TCHPNON)Mg}2(μ-N2)] yielded a complex, [{K(TCHPNON)Mg}2(μ-COT)], incorporating the aromatic dianion (COT2-).
Collapse
Affiliation(s)
- Matthew J Evans
- School of Chemistry, Monash University, PO Box 23, 3800, Melbourne, Victoria, Australia
| | - Jeremy Mullins
- School of Chemistry, Monash University, PO Box 23, 3800, Melbourne, Victoria, Australia
| | - Rahul Mondal
- School of Chemistry, Monash University, PO Box 23, 3800, Melbourne, Victoria, Australia
| | - Cameron Jones
- School of Chemistry, Monash University, PO Box 23, 3800, Melbourne, Victoria, Australia
| |
Collapse
|
3
|
Czernetzki C, Arrowsmith M, Endres L, Krummenacher I, Braunschweig H. Tricoordinate Beryllium Radicals and Their Reactivity. Inorg Chem 2024; 63:2670-2678. [PMID: 38259240 DOI: 10.1021/acs.inorgchem.3c04014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The one-electron reduction of [(CAAC)Be(Dur)Br] (CAAC = cyclic alkyl(amino)carbene, Dur = 2,3,5,6-tetramethylphenyl = duryl) with lithium sand in diethyl ether yields the first neutral, tricoordinate, and moderately stable beryllium radical, [(CAAC)(Et2O)BeDur]• (2-Et2O), which undergoes a facile second one-electron reduction concomitant with the insertion of the beryllium center into the endocyclic C-NCAAC bond and a cyclopropane-forming C-H bond activation of an adjacent methyl group. In situ generation of 2-Et2O and addition of PMe3 yield the stable analogue, [(CAAC)(Me3P)BeDur]• (2-PMe3), which serves as a platform for PMe3-ligand exchange with stronger donors, generating the radicals [(CAAC)LBeDur]• (2-L, L = isocyanides, pyridines, and N-heterocyclic carbenes). X-ray structural analyses show trigonal-planar beryllium centers and strong π backbonding from the metal to the CAAC ligand. The EPR signals of all six isolated [(CAAC)LBeDur]• radicals display significant, albeit small, hyperfine coupling to the 9Be nucleus. DFT calculations show that the spin density is mostly delocalized over the CAAC π framework and, where present, the isocyanide CN moiety, with only a small proportion (3-6%) on the beryllium center. 2-PMe3 proved thermally unstable at 80 °C, first undergoing radical hydrogen abstraction with the solvent, followed by insertion of beryllium into the endocyclic C-NCAAC bond and PMe3 transfer to the former carbene carbon atom. The reactions with diphenyl disulfide and phenyl azide occur at the beryllium center and yield the corresponding Be(II) phenyl sulfide and amino complexes, respectively, the latter concomitant with radical transfer and hydrogen abstraction by the beryllium-bound nitrogen center.
Collapse
Affiliation(s)
- Corinna Czernetzki
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Merle Arrowsmith
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Lukas Endres
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Ivo Krummenacher
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Holger Braunschweig
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
| |
Collapse
|
4
|
Lachguar A, Pichugov AV, Neumann T, Dubrawski Z, Camp C. Cooperative activation of carbon-hydrogen bonds by heterobimetallic systems. Dalton Trans 2024; 53:1393-1409. [PMID: 38126396 PMCID: PMC10804807 DOI: 10.1039/d3dt03571a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 11/24/2023] [Indexed: 12/23/2023]
Abstract
The direct activation of C-H bonds has been a rich and active field of organometallic chemistry for many years. Recently, incredible progress has been made and important mechanistic insights have accelerated research. In particular, the use of heterobimetallic complexes to heterolytically activate C-H bonds across the two metal centers has seen a recent surge in interest. This perspective article aims to orient the reader in this fast moving field, highlight recent progress, give design considerations for further research and provide an optimistic outlook on the future of catalytic C-H functionalization with heterobimetallic complexes.
Collapse
Affiliation(s)
- Abdelhak Lachguar
- Université de Lyon, Institut de Chimie de Lyon, Laboratory of Catalysis, Polymerization, Processes & Materials, CP2M UMR 5128 CNRS-UCB Lyon 1-CPE Lyon, 43 Bd du 11 Novembre 1918, F-69616 Villeurbanne, France.
| | - Andrey V Pichugov
- Université de Lyon, Institut de Chimie de Lyon, Laboratory of Catalysis, Polymerization, Processes & Materials, CP2M UMR 5128 CNRS-UCB Lyon 1-CPE Lyon, 43 Bd du 11 Novembre 1918, F-69616 Villeurbanne, France.
| | - Till Neumann
- Université de Lyon, Institut de Chimie de Lyon, Laboratory of Catalysis, Polymerization, Processes & Materials, CP2M UMR 5128 CNRS-UCB Lyon 1-CPE Lyon, 43 Bd du 11 Novembre 1918, F-69616 Villeurbanne, France.
| | - Zachary Dubrawski
- Université de Lyon, Institut de Chimie de Lyon, Laboratory of Catalysis, Polymerization, Processes & Materials, CP2M UMR 5128 CNRS-UCB Lyon 1-CPE Lyon, 43 Bd du 11 Novembre 1918, F-69616 Villeurbanne, France.
| | - Clément Camp
- Université de Lyon, Institut de Chimie de Lyon, Laboratory of Catalysis, Polymerization, Processes & Materials, CP2M UMR 5128 CNRS-UCB Lyon 1-CPE Lyon, 43 Bd du 11 Novembre 1918, F-69616 Villeurbanne, France.
| |
Collapse
|