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Nicholls TP, Jia Z, Chalker JM. Electrochemical Synthesis of Gold-N-Heterocyclic Carbene Complexes. Chemistry 2024; 30:e202303161. [PMID: 37876029 DOI: 10.1002/chem.202303161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2023] [Revised: 10/23/2023] [Accepted: 10/24/2023] [Indexed: 10/26/2023]
Abstract
An electrochemical synthesis of gold(I)-N-heterocyclic carbene (Au-NHC) complexes has been developed. The electrochemical methodology uses only imidazolium salts, gold metal electrodes, and electricity to produce these complexes with hydrogen gas as the only by-product. This high-yielding and operationally simple procedure has been used to produce eight mononuclear and three dinuclear Au-NHC complexes. The electrochemical procedure facilitates a clean reaction with no by-products. As such, Au-NHC complexes can be directly transferred to catalytic reactions without work-up or purification. The Au-NHC complexes were produced on-demand and tested as catalysts in a vinylcyclopropanation reaction. All mononuclear Au-NHC complexes performed similarly to or better than the isolated complexes.
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Affiliation(s)
- Thomas P Nicholls
- Institute for Nanoscale Science and Technology, College of Science and Engineering, Flinders University, Bedford Park, South Australia, 5042, Australia
| | - Zhongfan Jia
- Institute for Nanoscale Science and Technology, College of Science and Engineering, Flinders University, Bedford Park, South Australia, 5042, Australia
| | - Justin M Chalker
- Institute for Nanoscale Science and Technology, College of Science and Engineering, Flinders University, Bedford Park, South Australia, 5042, Australia
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Thompson ES, Olivas EM, Torres A, Arreaga BC, Alarcon HL, Dolberry D, Brannon JP, Stieber SCE. Effect of methyl-ene versus ethyl-ene linkers on structural properties of tert-butyl and mesityl bis-(imidazolium) bromide salts. Acta Crystallogr E Crystallogr Commun 2022; 78:905-911. [PMID: 36072516 PMCID: PMC9443804 DOI: 10.1107/s2056989022008003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 08/08/2022] [Indexed: 11/17/2022]
Abstract
The crystal structures of ligand precursor bis-(imidazolium) salts 1,1'-methyl-enebis(3-tert-butyl-imidazolium) dibromide monohydrate, C15H26N4 +·2Br-·H2O or [ tBuNHC2Me][Br]2·H2O, 1,1'-(ethane-1,2-di-yl)bis-(3-tert-butyl-imidazolium) dibromide dihydrate, C16H28N4 +·2Br-·2H2O or [ tBuNHC2Et][Br]2·2H2O, 1,1'-methyl-enebis[3-(2,4,6-tri-methyl-phen-yl)imidazolium] dibromide dihydrate, C25H30N4 2+·2Br-·2H2O or [MesNHC2Me][Br]2·2H2O, and 1,1'-(ethane-1,2-di-yl)bis-[3-(2,4,6-tri-methyl-phen-yl)imidazolium] dibromide tetra-hydrate, C26H32N4 2+·2Br-·4H2O or [MesNHC2Et][Br]2·4H2O, are reported. At 293 K, [ tBuNHC2Me][Br]2·H2O crystallizes in the P21/c space group, while [ tBuNHC2Et][Br]2·2H2O crystallizes in the P21/n space group at 100 K. At 112 K, [MesNHC2Me][Br]2·2H2O crystallizes in the ortho-rhom-bic space group Pccn while [MesNHC2Et][Br]2·4H2O crystallizes in the P21/c space group at 100 K. Bond distances and angles within the imidazolium rings are generally comparable among the four structures. All four bis-(imidazolium) salts co-crystallize with one to four mol-ecules of water.
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Affiliation(s)
- Emily S. Thompson
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
| | - Elisa M. Olivas
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
| | - Adrian Torres
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
| | - Briana C. Arreaga
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
| | - Hector L. Alarcon
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
| | - Deandrea Dolberry
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
| | - Jacob P. Brannon
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
| | - S. Chantal E. Stieber
- Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, 3801 W. Temple Ave., Pomona, CA 91768, USA
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Vanston CR, Nicholls TP, Bissember AC, Gardiner MG, Ho CC. Cationic Charge-Appended Abnormal Carbenes: Synthesis and Study of Electronically Modified Abnormal N-Heterocyclic Carbenes. Inorg Chem 2021; 61:622-632. [PMID: 34941242 DOI: 10.1021/acs.inorgchem.1c03336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A range of palladium complexes featuring electronically modified, imidazole-based abnormal N-heterocyclic carbene (aNHC) ligands have been prepared in the hopes of accessing a new class of cationic aNHC ligands electronically distinct from normal NHCs and aNHCs. These palladium complexes represent the first examples of transition metal-ligated aNHC complexes featuring a cationic moiety adjacent to the abnormal carbene center. It was anticipated that these design principles could facilitate electron transfer between the imidazolinylidene and the cationic heterocycle, thus reducing the electron density at the abnormal carbene center. However, this case study suggests that greater conformational restrictions that allow for heterocycle coplanarity are necessary to achieve significant electron transfer and enable access to a new class of cationic charge-appended aNHCs with unique electronic properties.
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Affiliation(s)
- Catriona R Vanston
- School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Thomas P Nicholls
- School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Alex C Bissember
- School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Michael G Gardiner
- School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Curtis C Ho
- School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
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Nicholls TP, Williams JR, Willans CE. Reactivities of N-heterocyclic carbenes at metal centers. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2021. [DOI: 10.1016/bs.adomc.2021.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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