Chiral-at-Metal Complexes as Asymmetric Catalysts

Fontecave, Marc; Hamelin, Olivier; Ménage, Stéphane

doi:10.1007/b136353

Cited by 100 publications

(42 citation statements)

References 47 publications

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“…Thus, the two rhodiumchlorine bond distances observed in 11a, 2.4314 (13) On the other hand, the distances between the metal and the centroid of the h 5 -bonded C 5 Although in the crystal both diastereomers are present in a 1:1 molar ratio, at room temperature, proton NMR data of CDCl 3 solutions of the crystals showed, in both cases, a 95:5 molar ratio which remained unchanged for hours. Thus, an epimerisation process at the metal should occur when going from solid to solution and vice versa.…”

Section: Chloride Complexesmentioning

confidence: 80%

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Half-sandwich organometallic complexes with stereogenic metal centres: Synthesis and characterization of diastereomeric [(ηn-ring)M(Aa)X] (Aa = α-amino carboxylate) compounds

Carmona

Lamata

Viguri

et al. 2012

Journal of Organometallic Chemistry

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Section: Chloride Complexesmentioning

confidence: 80%

“…The diastereoselectivity encountered is mostly governed by the nature of the amino acid employed. Solution 1 H NMR and X-ray crystallographic data for the prolinates [(h 5 …”

Section: Resultsmentioning

confidence: 99%

Half-sandwich organometallic complexes with stereogenic metal centres: Synthesis and characterization of diastereomeric [(ηn-ring)M(Aa)X] (Aa = α-amino carboxylate) compounds

Carmona

Lamata

Viguri

et al. 2012

Journal of Organometallic Chemistry

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“…Typically, a chiral environment is generated around the metal by coordination of enantiopure organic ligands and centered axial or planar chirality, residing in the ligands, is transferred to the substrates . Taking into account that metal coordination is the most common manner through which substrates are activated toward chemical transformations, it seems reasonable to assume that catalysts based on stereogenic metal centers would offer the most promising approach for achieving efficient transfer of chirality during an asymmetric process …”

Section: Introductionmentioning

confidence: 99%

The Stepwise Reaction of Rhodium and Iridium Complexes of Formula [MCl₂(κ⁴C,N,N′,P−L)] with Silver Cations: A Case of trans‐Influence and Chiral Self‐Recognition

Carmona

Tejedor

Rodrı́guez

et al. 2017

Chemistry A European J

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Acetonitrile suspensions of the dichlorido complexes [MCl (κ C,N,N',P-L)] [M=Rh (1), Ir (2)] react with AgSbF in a 1:2 molar ratio affording the bis-acetonitrile complexes [M(κ C,N,N',P-L)(NCMe) ][SbF ] (3 and 4). The reaction takes place in a sequential manner and the intermediates can be isolated varying the M:Ag molar ratio. In a 2:1 molar ratio, it affords the dimetallic monochlorido-bridged compounds [{MCl(κ C,N,N',P-L)} (μ-Cl)][SbF ] (5 and 6). In a 1:1 molar ratio, the monosubstituted solvato-complexes [MCl(κ C,N,N',P-L)(Solv)][SbF ] (Solv=H O, MeCN, 7-10) were obtained. Finally, in a 2:3 molar ratio, it gives complexes 11 and 12 of formula [{M(κ C,N,N',P-L)(NCMe)(μ-Cl)} Ag][SbF ] in which a silver cation joints two cationic monosubstituted acetonitrile-complexes [MCl(κ C,N,N',P-L)(NCMe)] through the remaining chlorido ligands and two Ag⋅⋅⋅C interactions with one of the phenyl rings of each PPh group. In all the complexes, the aminic nitrogen and the central metal atom are stereogenic centers. In the trimetallic complexes 11 and 12, the silver atom is also a stereogenic center. The formation of the cation of the dimetallic complexes 5 and 6, as well as that of the trimetallic complexes 11 and 12, takes place with chiral molecular self-recognition. Experimental data and DFT calculations provide plausible explanations for the observed molecular recognition. The new complexes have been characterized by analytical, spectroscopic means and by X-ray diffraction methods.

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“…1). In both complexes, the octahedral iridium centre is coordinated by two achiral bidentate ligands in a left (L)-or right (D)-handed propeller-type fashion, thereby establishing metal-centred chirality 24,25 , and coordinated by two additional labile acetonitriles which give access to a Lewis acid metal centre upon ligand exchange (see Supplementary Fig. 1 for a crystal structure of L-Ir2).…”

mentioning

confidence: 98%

Asymmetric photoredox transition-metal catalysis activated by visible light

Huo

Shen

Wang

et al. 2014

Nature

560

265

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Asymmetric catalysis is seen as one of the most economical strategies to satisfy the growing demand for enantiomerically pure small molecules in the fine chemical and pharmaceutical industries. And visible light has been recognized as an environmentally friendly and sustainable form of energy for triggering chemical transformations and catalytic chemical processes. For these reasons, visible-light-driven catalytic asymmetric chemistry is a subject of enormous current interest. Photoredox catalysis provides the opportunity to generate highly reactive radical ion intermediates with often unusual or unconventional reactivities under surprisingly mild reaction conditions. In such systems, photoactivated sensitizers initiate a single electron transfer from (or to) a closed-shell organic molecule to produce radical cations or radical anions whose reactivities are then exploited for interesting or unusual chemical transformations. However, the high reactivity of photoexcited substrates, intermediate radical ions or radicals, and the low activation barriers for follow-up reactions provide significant hurdles for the development of efficient catalytic photochemical processes that work under stereochemical control and provide chiral molecules in an asymmetric fashion. Here we report a highly efficient asymmetric catalyst that uses visible light for the necessary molecular activation, thereby combining asymmetric catalysis and photocatalysis. We show that a chiral iridium complex can serve as a sensitizer for photoredox catalysis and at the same time provide very effective asymmetric induction for the enantioselective alkylation of 2-acyl imidazoles. This new asymmetric photoredox catalyst, in which the metal centre simultaneously serves as the exclusive source of chirality, the catalytically active Lewis acid centre, and the photoredox centre, offers new opportunities for the 'green' synthesis of non-racemic chiral molecules.

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Chiral-at-Metal Complexes as Asymmetric Catalysts

Cited by 100 publications

References 47 publications

Half-sandwich organometallic complexes with stereogenic metal centres: Synthesis and characterization of diastereomeric [(ηn-ring)M(Aa)X] (Aa = α-amino carboxylate) compounds

Half-sandwich organometallic complexes with stereogenic metal centres: Synthesis and characterization of diastereomeric [(ηn-ring)M(Aa)X] (Aa = α-amino carboxylate) compounds

The Stepwise Reaction of Rhodium and Iridium Complexes of Formula [MCl₂(κ⁴C,N,N′,P−L)] with Silver Cations: A Case of trans‐Influence and Chiral Self‐Recognition

Asymmetric photoredox transition-metal catalysis activated by visible light

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Chiral-at-Metal Complexes as Asymmetric Catalysts

Cited by 100 publications

References 47 publications

Half-sandwich organometallic complexes with stereogenic metal centres: Synthesis and characterization of diastereomeric [(ηn-ring)M(Aa)X] (Aa = α-amino carboxylate) compounds

Half-sandwich organometallic complexes with stereogenic metal centres: Synthesis and characterization of diastereomeric [(ηn-ring)M(Aa)X] (Aa = α-amino carboxylate) compounds

The Stepwise Reaction of Rhodium and Iridium Complexes of Formula [MCl2(κ4C,N,N′,P−L)] with Silver Cations: A Case of trans‐Influence and Chiral Self‐Recognition

Asymmetric photoredox transition-metal catalysis activated by visible light

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The Stepwise Reaction of Rhodium and Iridium Complexes of Formula [MCl₂(κ⁴C,N,N′,P−L)] with Silver Cations: A Case of trans‐Influence and Chiral Self‐Recognition