301
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Lee YY, Zseng HW, Tsai ZH, Su YS, Hu CH, Lee HM. Isomeric Palladium Complexes Bearing Imidazopyridine-Based Abnormal Carbene Ligands: Synthesis, Characterization, and Catalytic Activity in Direct C–H Arylation Reaction. Organometallics 2019. [DOI: 10.1021/acs.organomet.8b00806] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Yan-Yi Lee
- Department of Chemistry, National Changhua University of Education, Changhua, Taiwan 50058
| | - Han-Wei Zseng
- Department of Chemistry, National Changhua University of Education, Changhua, Taiwan 50058
| | - Zong-Han Tsai
- Department of Chemistry, National Changhua University of Education, Changhua, Taiwan 50058
| | - Yong-Siang Su
- Department of Chemistry, National Changhua University of Education, Changhua, Taiwan 50058
| | - Ching-Han Hu
- Department of Chemistry, National Changhua University of Education, Changhua, Taiwan 50058
| | - Hon Man Lee
- Department of Chemistry, National Changhua University of Education, Changhua, Taiwan 50058
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302
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Halder P, SantaLucia DJ, Park SV, Berry JF. From Pincer to Paddlewheel: C-H and C-S Bond Activation at Bis(2-pyridylthio)methane by Palladium(II). Inorg Chem 2019; 58:2270-2274. [PMID: 30698431 DOI: 10.1021/acs.inorgchem.8b03568] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The bis(2-pyridylthio)methanidopalladium(II) pincer complex (1), containing a Pd-C bond, was obtained from the reaction of bis(2-pyridylthio)methane (H2L) with palladium(II) acetate in toluene under reflux. When palladium(II) trifluoroacetate was used, H2L reacted to generate the tetrakis(pyridine-2-thiol)palladium(II) complex (2). Complex 2 was converted to a heterobimetallic palladium(II)-iron(II) paddlewheel complex (3) upon treatment with iron(II) triflate in the presence of a base in acetonitrile at room temperature.
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Affiliation(s)
- Partha Halder
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - Daniel J SantaLucia
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - Sungho V Park
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - John F Berry
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
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303
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Keim M, Maas G. Terminal Acetylenic Iminium Salts: Cycloaddition Reactions with Azides Leading to 1,2,3-Triazoles and Bicyclic 1,2,3-Triazolium Salts. European J Org Chem 2019. [DOI: 10.1002/ejoc.201801749] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Michael Keim
- Institute of Organic Chemistry I; Ulm University; Albert-Einstein-Allee 11 89081 Ulm Germany
| | - Gerhard Maas
- Institute of Organic Chemistry I; Ulm University; Albert-Einstein-Allee 11 89081 Ulm Germany
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304
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AL-Shnani F, Guisado-Barrios G, Sainz D, Peris E. Tris-triazolium Salts as Anion Receptors and as Precursors for the Preparation of Cylinder-like Coordination Cages. Organometallics 2019. [DOI: 10.1021/acs.organomet.8b00874] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Fadi AL-Shnani
- Departament de Química Inorgànica i Orgànica, Universitat de Barcelona, Marti i Franquès 1, Barcelona, E-08028, Spain
| | - Gregorio Guisado-Barrios
- Institute of Advanced Materials (INAM), Centro de Innovación en Química Avanzada (ORFEO−CINQA), Universitat Jaume I, Av. Vicente Sos Baynat s/n, Castellón, E-12071, Spain
| | - Daniel Sainz
- Departament de Química Inorgànica i Orgànica, Universitat de Barcelona, Marti i Franquès 1, Barcelona, E-08028, Spain
| | - Eduardo Peris
- Institute of Advanced Materials (INAM), Centro de Innovación en Química Avanzada (ORFEO−CINQA), Universitat Jaume I, Av. Vicente Sos Baynat s/n, Castellón, E-12071, Spain
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305
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Aucamp D, Kumar SV, Liles DC, Fernandes MA, Harmse L, Bezuidenhout DI. Synthesis of heterobimetallic gold(i) ferrocenyl-substituted 1,2,3-triazol-5-ylidene complexes as potential anticancer agents. Dalton Trans 2019; 47:16072-16081. [PMID: 30276400 DOI: 10.1039/c8dt03116a] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
1,2,3-Triazol-5-ylidene (trz) complexes of gold(i) containing a ferrocenyl substituent on the C4-position of the trz ring were synthesized to yield the neutral heterobimetallic gold(i) trz chlorido (2), gold(i) trz phenyl (3), and the cationic gold(i) trz triphenylphospine (5) complexes. In order to compare the effect of silver(i) as central metal vs. gold(i), [Ag(trz)2]+ (4) was also prepared, while variation of the C4-1,2,3-triazol-5-ylidene substituent from a ferrocenyl to a phenyl group was done to prepare the monometallic analogue of 5, namely the cationic Au(i) trz triphenylphosphine complex 6. The complexes were characterised with spectroscopic and electrochemical methods, and the single crystal X-ray structures of 2-6 were determined. NMR stability studies of 5 as a representative example of the series of complexes were performed to confirm the stability of the complexes in the solvent dimethylsulfoxide and in aqueous solution. The anti-cancer potential of 5 was evaluated against the lung cancer cell lines A549 and H1975, and the human embryonic kidney cell line (HEK-293) was used as a non-cancer model. IC50 values of 0.89, 0.23 and 5.43 μM, respectively, were obtained for A549, H1975 and HEK-293, respectively, indicating the activity and selectivity of 5 for cancer cells. Fluorescence microscopy experiments as a preliminary mode-of-action study evidenced an apoptotic cell death mechanism rather than necrotic cell death.
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Affiliation(s)
- Danielle Aucamp
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa.
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306
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Chadwick FM, Curchod BFE, Scopelliti R, Fadaei Tirani F, Solari E, Severin K. Azo‐MICs: Redox‐Active Mesoionic Carbene Ligands Derived from Azoimidazolium Dyes. Angew Chem Int Ed Engl 2019; 58:1764-1767. [DOI: 10.1002/anie.201813780] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Indexed: 11/06/2022]
Affiliation(s)
- F. Mark Chadwick
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | | | - Rosario Scopelliti
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Farzaneh Fadaei Tirani
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Euro Solari
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Kay Severin
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
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307
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Chadwick FM, Curchod BFE, Scopelliti R, Fadaei Tirani F, Solari E, Severin K. Azo‐MICs: Redox‐Active Mesoionic Carbene Ligands Derived from Azoimidazolium Dyes. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201813780] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- F. Mark Chadwick
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | | | - Rosario Scopelliti
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Farzaneh Fadaei Tirani
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Euro Solari
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Kay Severin
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
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308
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Byrne JP, Musembi P, Albrecht M. Carbohydrate-functionalized N-heterocyclic carbene Ru(ii) complexes: synthesis, characterization and catalytic transfer hydrogenation activity. Dalton Trans 2019; 48:11838-11847. [DOI: 10.1039/c9dt02614b] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Triazolylidene NHCs decorated with a carbohydrate wingtip group were complexed to a ruthenium(ii) center. Deprotection of the carbohydrate in the metal complex affords a carbohydrate–NHC hybrid system for use as a transfer hydrogenation catalyst.
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Affiliation(s)
- Joseph P. Byrne
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern
- Switzerland
| | - Pauline Musembi
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern
- Switzerland
| | - Martin Albrecht
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern
- Switzerland
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309
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Baltrun M, Watt FA, Schoch R, Wölper C, Neuba AG, Hohloch S. A new bis-phenolate mesoionic carbene ligand for early transition metal chemistry. Dalton Trans 2019; 48:14611-14625. [DOI: 10.1039/c9dt03099a] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A new chelating mesoionic carbene ligand, derived from 1,2,3-triazoles, with two redox-active tert-butyl-phenolate linkers has been synthesized and explored towards its reactivity and electrochemical properties in early transition metal chemistry.
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Affiliation(s)
- Marc Baltrun
- Universität Paderborn
- Fakultät für Naturwissenschaften
- Department Chemie Warburger Straße 100
- 33098 Paderborn
- Germany
| | - Fabian A. Watt
- Universität Paderborn
- Fakultät für Naturwissenschaften
- Department Chemie Warburger Straße 100
- 33098 Paderborn
- Germany
| | - Roland Schoch
- Universität Paderborn
- Fakultät für Naturwissenschaften
- Department Chemie Warburger Straße 100
- 33098 Paderborn
- Germany
| | | | - Adam G. Neuba
- Universität Paderborn
- Fakultät für Naturwissenschaften
- Department Chemie Warburger Straße 100
- 33098 Paderborn
- Germany
| | - Stephan Hohloch
- Universität Paderborn
- Fakultät für Naturwissenschaften
- Department Chemie Warburger Straße 100
- 33098 Paderborn
- Germany
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310
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Pinto MF, Olivares M, Vivancos Á, Guisado-Barrios G, Albrecht M, Royo B. (Di)triazolylidene manganese complexes in catalytic oxidation of alcohols to ketones and aldehydes. Catal Sci Technol 2019. [DOI: 10.1039/c9cy00685k] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A robust bimetallic manganese complex with a mesoionic 1,2,3,-triazolylidene ligand for efficient oxidation of alcohols with tert-butylhydroperoxide.
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Affiliation(s)
- Mara F. Pinto
- Instituto de Tecnologia Química e Biológica António Xavier
- ITQB NOVA
- Universidade Nova de Lisboa
- 2780-157 Oeiras
- Portugal
| | - Marta Olivares
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern
- Switzerland
| | - Ángela Vivancos
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern
- Switzerland
| | | | - Martin Albrecht
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern
- Switzerland
| | - Beatriz Royo
- Instituto de Tecnologia Química e Biológica António Xavier
- ITQB NOVA
- Universidade Nova de Lisboa
- 2780-157 Oeiras
- Portugal
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311
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Malan FP, Singleton E, van Rooyen PH, Landman M. Tandem transfer hydrogenation–epoxidation of ketone substrates catalysed by alkene-tethered Ru( ii)–NHC complexes. NEW J CHEM 2019. [DOI: 10.1039/c9nj01220f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Eight novel alkene-tethered Ru(ii)–NHC complexes were employed as catalysts in tandem transfer hydrogenation–epoxidation reactions using phenacyl bromide derivatives as substrates.
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Affiliation(s)
| | - Eric Singleton
- Department of Chemistry
- University of Pretoria
- Hatfield
- South Africa
| | | | - Marilé Landman
- Department of Chemistry
- University of Pretoria
- Hatfield
- South Africa
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312
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Yan X, Yang X. Mechanistic insights and computational design of half-sandwich iridium and rhodium complexes for hydrogenation of quinoline. NEW J CHEM 2019. [DOI: 10.1039/c9nj00835g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
DFT calculations reveal a stepwise proton and hydride transfer mechanism for the hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline catalysed by half-sandwich Cp*Ir(NHC) complexes.
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Affiliation(s)
- Xiuli Yan
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory for Structural Chemistry of Unstable and Stable Species
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
| | - Xinzheng Yang
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory for Structural Chemistry of Unstable and Stable Species
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
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313
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Xu X, Zhang Z, Huang S, Cao L, Liu W, Yan X. 4-Halo-1,2,3-triazolylidenes: stable carbenes featuring halogen bonding. Dalton Trans 2019; 48:6931-6941. [PMID: 31038514 DOI: 10.1039/c9dt01018a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Synthesis and coordination of 4-halo-1,2,3-triazolylidenes have been developed. These novel ligands featured the character with σ-donation at carbon and a σ-hole at the halogen. Halogen bonding was observed by single crystal X-ray diffraction in their coinage metal complexes. The electronic properties of 4-iodo-1,2,3-triazolylidene were studied by both Ir-CO frequencies of the Tolman electronic parameter (TEP) and Huynh's electronic parameter (HEP) method, which suggested similar electronic properties to those of imidazolylidenes. During HEP tests, an interesting tunability was observed when different electron donors were employed.
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Affiliation(s)
- Xingyu Xu
- Department of Chemistry, Renmin University of China, Beijing 100872, People's Republic of China.
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314
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Simler T, Feuerstein TJ, Yadav R, Gamer MT, Roesky PW. Access to divalent lanthanide NHC complexes by redox-transmetallation from silver and CO 2 insertion reactions. Chem Commun (Camb) 2018; 55:222-225. [PMID: 30525155 DOI: 10.1039/c8cc08120d] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Through a redox-transmetallation procedure, divalent NHC-LnII (NHC = N-heterocyclic carbene; Ln = Eu, Yb) complexes were obtained from the corresponding NHC-AgI. The lability of the NHC-LnII bond was investigated and treatment with CO2 led to insertion reactions without oxidation of the metal centre. The EuII complex [EuI2(IMes)(THF)3] (IMes = 1,3-dimesitylimidazol-2-ylidene) exhibits photoluminescence with a quantum yield reaching 53%.
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Affiliation(s)
- Thomas Simler
- Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, Engesserstr. 15, 76131 Karlsruhe, Germany.
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315
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Guisado-Barrios G, Soleilhavoup M, Bertrand G. 1 H-1,2,3-Triazol-5-ylidenes: Readily Available Mesoionic Carbenes. Acc Chem Res 2018; 51:3236-3244. [PMID: 30417642 DOI: 10.1021/acs.accounts.8b00480] [Citation(s) in RCA: 133] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Classical carbenes are usually described as neutral compounds featuring a divalent carbon with only six electrons in their valence shell. It was only in 1988 that our group prepared the first isolable example, in which the carbene center was stabilized by a push-pull effect, using a phosphino and a silyl substituent. In the last 30 years, a myriad of acyclic and cyclic push-pull and push-push carbenes, bearing different heteroatom substituents, have been isolated. Among them, the so-called N-heterocyclic carbenes (NHCs), which include cyclic (alkyl)(amino)carbenes (CAACs), are arguably the most popular. They have found a vast number of applications ranging from catalysis to material science, and even in medicine. In this Account, we focus on the synthesis, structure, electronic properties, coordination, and applications of a different class of stable cyclic carbenes, namely, 1 H-1,2,3-triazol-5-ylidenes. In contrast with NHCs and CAACs, these compounds have no reasonable canonical resonance forms that can be drawn showing a carbene without additional charges. According to the IUPAC, they belong to the family of mesoionic compounds and thus they are named mesoionic carbenes (MICs). In 2010, we prepared the first stable 1,2,3-triazol-5-ylidene, via a CuAAC reaction, followed by alkylation of the resulting 1,2,3-triazole, and deprotonation. Later, we synthesized more robust N3-arylated counterparts from 1,3-diarylated-1 H-1,2,3-triazolium salts. Both synthetic routes can be carried out in multigram scales, making these MICS readily available. Importantly, MICs do not dimerize which contrasts with NHCs that can give the corresponding Wanzlick-type olefin. This property leads to relaxed steric requirements for their isolation; even C-unsubstituted MICs can be stored for months in the solid state at room temperature. The practicality and easily scalable syntheses of MICs allow for the preparation of polycarbenes, such as bis(1,2,3-triazol-5-ylidenes) (i-bitz), the analogues of the well-known 2,2'-bipyridines (bpy). MIC-transition metal complexes are excellent precatalysts for variety of chemical transformations, which include hydrohydrazination of alkynes, olefin metathesis, reductive formylation of amines with carbon dioxide and diphenylsilane, hydrogenation and dehydrogenation of N-heteroarenes in water, cycloisomerization of enynes, asymmetric Suzuki-Miyaura cross-coupling, and water oxidation (WO) reactions. Besides their catalytic applications, MIC-transition metal complexes have found applications in material sciences as exemplified by the preparation of the first iron(III) complex that is luminescent at room temperature. The peculiar properties of mesoionic triazolylidenes, combined with their enhanced stability, position them as excellent candidates to address some current challenges such as access to high-oxidation-state 3d metal complexes, the stabilization of highly reactive main group elements, the stabilization of nanoparticles, the preparation of efficient catalysts and photosensitizers based on earth-abundant transition metals, and the functionalization of self-assembled monolayers (SAMs) on gold.
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Affiliation(s)
- Gregorio Guisado-Barrios
- Institute of Advance Materials (INAM), Universitat Jaume I, Avenida Vicente Sos Baynat s/n, 12071 Castellon, Spain
| | - Michèle Soleilhavoup
- UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0343, United states
| | - Guy Bertrand
- UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0343, United states
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316
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Xu X, Li L, Zhang Z, Yan X. Nucleophilic substitution of 4-bromomethyltriazolium with different nucleophiles. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.10.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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317
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Antoni PW, Hansmann MM. Pyrylenes: A New Class of Tunable, Redox-Switchable, Photoexcitable Pyrylium–Carbene Hybrids with Three Stable Redox-States. J Am Chem Soc 2018; 140:14823-14835. [DOI: 10.1021/jacs.8b08545] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Patrick W. Antoni
- Georg-August Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
| | - Max M. Hansmann
- Georg-August Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
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318
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Wang G, Freeman LA, Dickie DA, Mokrai R, Benkő Z, Gilliard RJ. Highly Reactive Cyclic(alkyl)(amino) Carbene- and N-Heterocyclic Carbene-Bismuth(III) Complexes: Synthesis, Structure, and Computations. Inorg Chem 2018; 57:11687-11695. [PMID: 30160485 DOI: 10.1021/acs.inorgchem.8b01813] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cyclic(alkyl)(amino) carbene (CAAC)-stabilized complexes of phosphorus, one of the lightest group 15 elements, are well-established and can often be obtained in high yields. In contrast, analogous CAAC compounds of bismuth, the heaviest nonradioactive member of group 15, are unknown. Indeed, reactivity increases as you descend the group, and as a result there are only a few examples of N-heterocyclic carbene (NHC)-bismuth complexes. Moreover, activated bismuth compounds often readily extrude bismuth metal, making isolation of stable complexes highly challenging. We report that CAACs react with phenylbismuth dichloride (PhBiCl2) to afford Et2CAAC-Bi(Ph)Cl2 and CyCAAC-Bi(Ph)Cl2. Significantly, these complexes represent the first structurally characterized examples of CAAC-coordination to bismuth. The CAAC-stabilized bismuth compounds can also be obtained from air-stable salts, [Et2CAAC-H]22+ [Cl2(Ph)Bi(μ-Cl2)Bi(Ph)Cl2]2- and [CyCAAC-H]22+ [Cl2(Ph)Bi(μ-Cl2)Bi(Ph)Cl2]2-, by deprotonation with potassium bis(trimethylsilyl)amide, K[N(SiMe3)2]. The electronic effects of the ligand on the bismuth center were investigated by comparing the CAAC-Bi(Ph)Cl2 complexes to the NHC analogues, SIPr-Bi(Ph)Cl2(THF) and IPr-Bi(Ph)Cl2 (SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazole-2-ylidene; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene). Interestingly, the "normal" IPr-Bi(Ph)Cl2 slowly isomerizes to the "abnormal" carbene complex, Cl2(Ph)Bi-IPr-H, at -37 °C. In the solid-state, the CAAC-, NHC-, and abnormal NHC-bismuth compounds exhibit Bi atomic centers in unique coordination environments. The complexes were fully characterized by NMR, elemental analysis, and single crystal X-ray diffraction studies. In addition, the bonding was probed by natural bond orbital (NBO) calculations.
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Affiliation(s)
- Guocang Wang
- Department of Chemistry , University of Virginia , 409 McCormick Road , P.O. Box 400319, Charlottesville , Virginia 22904-4319 , United States
| | - Lucas A Freeman
- Department of Chemistry , University of Virginia , 409 McCormick Road , P.O. Box 400319, Charlottesville , Virginia 22904-4319 , United States
| | - Diane A Dickie
- Department of Chemistry , University of Virginia , 409 McCormick Road , P.O. Box 400319, Charlottesville , Virginia 22904-4319 , United States
| | - Réka Mokrai
- Department of Inorganic and Analytical Chemistry , Budapest University of Technology and Economics , Szent Gellért tér 4 , Budapest , 1111 , Hungary
| | - Zoltán Benkő
- Department of Inorganic and Analytical Chemistry , Budapest University of Technology and Economics , Szent Gellért tér 4 , Budapest , 1111 , Hungary
| | - Robert J Gilliard
- Department of Chemistry , University of Virginia , 409 McCormick Road , P.O. Box 400319, Charlottesville , Virginia 22904-4319 , United States
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