Special Issue "N-Heterocyclic Carbene Metal Complexes: From Design to Applications"

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Organometallic Chemistry".

Deadline for manuscript submissions: closed (31 December 2017)

Special Issue Editor

Guest Editor
Dr. Hani Amouri

CNRS Research Director, Sorbonne Universités, UPMC Universités Paris 06, and CNRS, IPCM, UMR 8232, 4 place Jussieu, 75252 Paris Cedex 05, France
Website | E-Mail
Interests: N-heterocyclic carbene metal complexes; coordination chemistry; luminescent properties; organometallics and catalysis; structural aspects in N-heterocyclic carbene metal complexes; metallodrugs

Special Issue Information

Dear Colleagues,

N-Heterocyclic Carbenes (NHCs) have witnessed tremendous growth over the last quarter century, since the report by Arduengo and coworkers, in 1991, on the isolation of the first stable free carbene. However, the synthesis of the first (NHC)-metal complexes was reported back in 1968 by Ofele and Wanzlick. The ubiquitous nature of these carbene ligands allowed them to become privileged ligands in the area of organometallics and catalysis. More recently, the chemistry of metallo-carbenes has started gain interest from other fields by acting as metallodrugs, in metallosupramolecular chemistry and also in the area of photoluminescence. Indeed, due to their strong σ-donor, a novel class of stable luminescent materials with useful properties was obtained. This Special Issue aims to highlight the structural and chemical diversity of N-heterocyclic carbene metal complexes, as well as their broad fields of application.

Dr. Hani Amouri
Guest Editor

Manuscript Submission Information

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Keywords

  • N-heterocyclic carbene metal complexes
  • coordination chemistry
  • luminescent properties
  • organometallics and catalysis
  • structural aspects in N-heterocyclic carbene metal complexes
  • metallodrugs

Published Papers (6 papers)

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Research

Open AccessArticle Probing the Effect of Six-Membered N-Heterocyclic Carbene—6-Mes—on the Synthesis, Structure and Reactivity of Me2MOR(NHC) (M = Ga, In) Complexes
Received: 3 January 2018 / Revised: 31 January 2018 / Accepted: 12 February 2018 / Published: 16 February 2018
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Abstract
The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure
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The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure and reactivity of Me2MOR(6-Mes) (M = Ga, In) complexes. While the reactions of simple dimethylgallium alkoxides with 6-Mes lead to the formation of stable monomeric Me2Ga(OCH2CH2OMe)(6-Mes) (1) and Me2GaOMe(6-Mes) complexes, the analogous Me2InOR(6-Mes) are unstable and disproportionate to methylindium alkoxides and Me3In(6-Mes) (2). The use of bulky alkoxide ligand—OCPh2Me or aryloxide ligand—OC6H4OMe allowed for the synthesis of stable Me2M(OCPh2Me)(6-Mes) (M = Ga (3) and In (4)) as well as Me2M(OC6H4OMe)(6-Mes) (M = Ga (5) and In (6)). The structures of 16 have been determined using both spectroscopic methods in solution and X-ray diffraction studies, which confirmed the effect of both steric hindrances and donor properties of 6-Mes on their structure and catalytic properties in the ring-opening polymerization (ROP) of rac-lactide. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle Cationic Protic Imidazolylidene NHC Complexes of Cp*IrCl+ and Cp*RhCl+ with a Pyridyl Tether Formed at Ambient Temperature
Received: 16 January 2018 / Revised: 6 February 2018 / Accepted: 7 February 2018 / Published: 14 February 2018
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Abstract
Protic NHC (PNHC) complexes with N1H, N2-alkyl/aryl imidazolylidene ligands are relatively rare, and routes for their synthesis differ from what is used to make non-protic analogs. Prior work from our group and others showed that in the presence of
[...] Read more.
Protic NHC (PNHC) complexes with N1H, N2-alkyl/aryl imidazolylidene ligands are relatively rare, and routes for their synthesis differ from what is used to make non-protic analogs. Prior work from our group and others showed that in the presence of a tethering ligand (phosphine or in one case, pyridine), CpM and Cp*M (M = Ir, Ru) PNHC complexes could be made by heating. Here, we find that the use of ionizing agents to activate [Cp*MIIICl(μ-Cl)]2 (M = Ir, Rh) allows for what we believe is unprecedented ambient temperature formation of PNHC complexes from neutral imidazoles; the product complexes are able to perform transfer hydrogenation. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle Sterically Bulky NHC Adducts of GaMe3 and InMe3 for H2 Activation and Lactide Polymerization
Received: 22 December 2017 / Revised: 20 January 2018 / Accepted: 23 January 2018 / Published: 25 January 2018
Cited by 1 | PDF Full-text (2066 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The sterically bulky Ga(III) and In(III) (IPr*)MMe3 adducts (1 and 2) and (SItBu)MMe3 adducts (3 and 4) (M = Ga, In; IPr* = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}-1,3-dihydro- imidazol-2-ylidene; SItBu = 1,3-bis(1,1-dimethylethyl)-imidazolidin-2-ylidene) were prepared and structurally characterized,
[...] Read more.
The sterically bulky Ga(III) and In(III) (IPr*)MMe3 adducts (1 and 2) and (SItBu)MMe3 adducts (3 and 4) (M = Ga, In; IPr* = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}-1,3-dihydro- imidazol-2-ylidene; SItBu = 1,3-bis(1,1-dimethylethyl)-imidazolidin-2-ylidene) were prepared and structurally characterized, allowing an estimation of the steric hindrance of such Lewis pairs (yields in 14: 92%, 90%, 73%, and 42%, respectively). While the IPr* adducts 1 and 2 are robust species, the more severely congested SItBu adducts 3 and 4 are more reactive and exhibit a limited stability in solution. Adduct (SItBu)GaMe3 (3) reacts quickly with H2 at room temperature to afford the corresponding aminal product, 1,3-di-tert-butylimidazolidine (5), along with free GaMe3. Such Frustrated Lewis Pair (FLP) reactivity constitutes the first instance of a H2 activation involving a simple trialkyl GaR3 species. Adduct 3 also mediates the ring-opening polymerization (ROP) of rac-lactide at room temperature to afford cyclic polylactide (PLA). Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle A Robust Pyridyl-NHC-Ligated Rhenium Photocatalyst for CO2 Reduction in the Presence of Water and Oxygen
Received: 2 January 2018 / Revised: 19 January 2018 / Accepted: 22 January 2018 / Published: 25 January 2018
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Abstract
Re(pyNHC-PhCF3)(CO)3Br is a highly active photocatalyst for CO2 reduction. The PhCF3 derivative was previously empirically shown to be a robust catalyst. Here, the role of the PhCF3 group is probed computationally and the robust nature of
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Re(pyNHC-PhCF3)(CO)3Br is a highly active photocatalyst for CO2 reduction. The PhCF3 derivative was previously empirically shown to be a robust catalyst. Here, the role of the PhCF3 group is probed computationally and the robust nature of this catalyst is analyzed with regard to the presence of water and oxygen introduced in controlled amounts during the photocatalytic reduction of CO2 to CO with visible light. This complex was found to work well from 0–1% water concentration reproducibly; however, trace amounts of water were required for benchmark Re(bpy)(CO)3Cl to give reproducible reactivity. When ambient air is added to the reaction mixture, the NHC complex was found to retain substantial performance (~50% of optimized reactivity) at up to 40% ambient atmosphere and 60% CO2 while the Re(bpy)(CO)3Cl complex was found to give a dramatically reduced CO2 reduction reactivity upon introduction of ambient atmosphere. Through the use of time-correlated single photon counting studies and prior electrochemical results, we reasoned that this enhanced catalyst resilience is due to a mechanistic difference between the NHC- and bpy-based catalysts. These results highlight an important feature of this NHC-ligated catalyst: substantially enhanced stability toward common reaction contaminates. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle N-Heterocyclic Carbene Coinage Metal Complexes Containing Naphthalimide Chromophore: Design, Structure, and Photophysical Properties
Received: 10 July 2017 / Revised: 21 July 2017 / Accepted: 25 July 2017 / Published: 24 August 2017
Cited by 2 | PDF Full-text (3318 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of novel N-heterocyclic carbene coinage metal complexes containing a naphthalimide (NI) chromophore has been prepared and fully characterized. Two types of molecules are described those where the NI unit is directly attached to the carbene unit with the general formulae
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A series of novel N-heterocyclic carbene coinage metal complexes containing a naphthalimide (NI) chromophore has been prepared and fully characterized. Two types of molecules are described those where the NI unit is directly attached to the carbene unit with the general formulae [(L1)–M–X], M = Cu, X = Cl (1a); M = Ag, X = I (1b) and M = Au, X = Cl, (1c). While in the second family, a π-extended carbene ligand precursor L2–H+I (3) was prepared where the NI unit is distant from the imidazole unit via a phenyl-alkyne bridge. Only two N-heterocyclic carbene metal complexes were prepared [(L2)–M–Cl], M = Cu (2a) and M = Au (2c). The related silver carbene compound could not be isolated. The molecular structure of the carbene complex 1c was determined and confirmed the formation of the target compound. Interestingly, the structure shows the presence of an aurophilic interaction Au···Au at 3.407 Å between two individual molecules. The photophysical properties of the compounds were investigated in solution at room temperature. Preliminary results suggested that all compounds are luminescent and act as blue emitters (420–451 nm). These transition emissions can be attributed to the intraligand origin of the NI chromphore. Moreover, the carbene complexes featuring L2 ligand with π-extended system were found to be more luminescent. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle Computational Studies on the Selective Polymerization of Lactide Catalyzed by Bifunctional Yttrium NHC Catalyst
Received: 20 June 2017 / Revised: 13 July 2017 / Accepted: 13 July 2017 / Published: 20 July 2017
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Abstract
A theoretical investigation of the ring-opening polymerization (ROP) mechanism of rac-lactide (LA) with an yttrium complex featuring a N-heterocyclic carbine (NHC) tethered moiety is reported. It was found that the carbonyl of lactide is attacked by N(SiMe3)2 group
[...] Read more.
A theoretical investigation of the ring-opening polymerization (ROP) mechanism of rac-lactide (LA) with an yttrium complex featuring a N-heterocyclic carbine (NHC) tethered moiety is reported. It was found that the carbonyl of lactide is attacked by N(SiMe3)2 group rather than NHC species at the chain initiation step. The polymerization selectivity was further investigated via two consecutive insertions of lactide monomer molecules. The insertion of the second monomer in different assembly modes indicated that the steric interactions between the last enchained monomer unit and the incoming monomer together with the repulsion between the incoming monomer and the ligand framework are the primary factors determining the stereoselectivity. The interaction energy between the monomer and the metal center could also play an important role in the stereocontrol. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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