Pseudotetrahedral Organocobalt(III) Compounds Containing Specific Coordination Sites for Brønsted Acids

Meneghetti, Mário R.; Grellier, Mary; Pfeffer, Michel; Cian, André De; Fischer, Jean

doi:10.1002/1099-0682(200007)2000:7<1539::aid-ejic1539>3.0.co;2-1

Cited by 14 publications

(2 citation statements)

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“…Unfortunately, the mechanisms of these reactions are still relatively poorly understood, although organometallic Co(III) intermediates are generally implicated . Stable organometallic aryl-Co(III) compounds have been prepared via transmetalation reactions in the past, , although examples of the preparation of stable organometallic Co(III) compounds through direct C–H activation are still extremely rare, which has limited the understanding of this field. Organometallic aryl-Co(III) compounds derived from N-confused porphyrins and m -benziphthalocyanines have been metalated using Co(II) salts furnishing the Co(III) C–H activated products, although further reactivity studies were somewhat limited as a result of their stability …”

Section: Introductionmentioning

confidence: 99%

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

et al. 2016

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The selective annulation reaction of alkynes with substrates containing inert C-H bonds using cobalt as catalyst is currently a topic attracting significant interest. Unfortunately, the mechanism of this transformation is still relatively poorly understood, with little experimental evidence for intermediates, although an organometallic Co(III) species is generally implicated. Herein, we describe a rare example of the preparation and characterization of benchtop-stable organometallic aryl-Co(III) compounds (NMR, HRMS, XAS, and XRD) prepared through a C(sp)-H activation, using a model macrocyclic arene substrate. Furthermore, we provide crystallographic evidence of an organometallic aryl-Co(III) intermediate proposed in 8-aminoquinoline-directed Co-catalyzed C-H activation processes. Subsequent insights obtained from the application of our new organometallic aryl-Co(III) compounds in alkyne annulation reactions are also disclosed. Evidence obtained from the resulting regioselectivity of the annulation reactions and DFT studies indicates that a mechanism involving an organometallic aryl-Co(III)-alkynyl intermediate species is preferred for terminal alkynes, in contrast to the generally accepted migratory insertion pathway.

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Section: Introductionmentioning

confidence: 99%

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

et al. 2016

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“…Higher pH water molecule coordinates, through a hydrogen bond to the dimethylamine unit by the host and the water molecule, inhibits the anion binding. Selectivity towards the acetate and phosphate anions (pK = 3.1) was observed compared to chloride (pK = 1.8) [ 21 , 22 ]. The crystal structure showed that the substrates are bound through a seven-member cycle (the carboxyl group binds directly to the cobalt center and a hydrogen bond is displayed with the dimethylammonium unit of the ligand ( Figure 5 ).…”

Section: Recognition Of Carboxylic Anions By Metal Based Receptorsmentioning

confidence: 99%

Recognition of Chiral Carboxylic Anions by Artificial Receptors

Dieng

Sirlin

2010

IJMS

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Many carboxylic molecules, ranging from drugs to flavors and fragrances, contain chiral centers. As a consequence, research has been carried out in order to design and synthesize artificial receptors for carboxylic anions. Many problems have to be solved for binding anions. The results obtained in the binding of carboxylic anions by guanidine, secondary ammonium and metal-center have been selected. The last part of this review focuses on chiral recognition of carboxylic anions by organic and metal-based chiral receptors.

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Molecular Recognition of Anions by a Novel Organocobalt Receptor: Oxyanion versus Halide Selectivity in Water

Robitzer

Sirlin

Kyritsakas³

et al. 2002

Eur. J. Inorg. Chem.

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The dissolution of [Co{2,6‐(Me2NCH2)2C6H3}(η5‐C5H5)(H2O)]PF6 (1a) in dry methanol or dry acetonitrile affords compounds 1b and 1c, respectively, in which the water ligand of 1a has been substituted by MeOH or by CH3CN. The crystal structure analysis of 1b established that a strong intramolecular interaction exists between the methanolic proton and the NMe2 group that was interacting with H2O in 1a. For 1c no interaction could be found between the Co‐bound acetonitrile ligand and this NMe2 as it has changed its position in order to be as far away from the cobalt atom as possible. Whereas no reaction takes place between 1a and an excess of sodium iodide in water or in methanol, in acetone I− easily substitutes the water ligand of 1a to afford high yields of the neutral compound 3. Here also 1H NMR spectroscopic data are in favour of a structure with no interaction between the NMe2 and the iodide ligand as in 1c. Protonation of the free NMe2 unit of 1a by adding increasing amounts of HPF6 in water leads to the synthesis of 4a. The pKa of 1a in D2O was found to be 6.1. Treating 1a with acidic buffered water solutions (pH = 5.5) leads to the in situ formation of 4a. From these solutions, association constants were determined for Cl−, Br−, I−, AcO−, H2PO4− and NO3−. Significant selectivity in water for AcO− and H2PO4− vs. halide anions has been established. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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Pseudotetrahedral Organocobalt(III) Compounds Containing Specific Coordination Sites for Brønsted Acids

Cited by 14 publications

References 9 publications

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

Recognition of Chiral Carboxylic Anions by Artificial Receptors

Molecular Recognition of Anions by a Novel Organocobalt Receptor: Oxyanion versus Halide Selectivity in Water

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Pseudotetrahedral Organocobalt(III) Compounds Containing Specific Coordination Sites for Brønsted Acids

Cited by 14 publications

References 9 publications

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp2)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp2)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

Recognition of Chiral Carboxylic Anions by Artificial Receptors

Molecular Recognition of Anions by a Novel Organocobalt Receptor: Oxyanion versus Halide Selectivity in Water

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Product

Resources

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Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms