Utilising Sodium‐Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C−H and C−F Bond Activations

Maddock, Lewis C. H.; Nixon, Tracy D.; Kennedy, Alan R.; Probert, Michael R.; Clegg, William; Hevia, Eva

doi:10.1002/anie.201709750

Cited by 46 publications

(44 citation statements)

References 33 publications

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“…[5] By expanding the scope of AMMM beyond main‐group chemistry, we recently reported that pairing the iron(II) amide Fe(HMDS) 2 (HMDS=N{SiMe 3 } 2 ) with NaHMDS in the same coordination compound allows regioselective ferration (Fe‐H exchange) of a wide range of fluoroarenes. [6] Since sodium is mandatory for the metallation to occur, these reactions can be described as examples of alkali‐metal‐mediated ferration (AMMFe) processes. This reactivity is surprising considering the lower polarity of Fe−N vs. Na−N bonds, which is why applications of iron amides in metallation are rare.…”

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confidence: 99%

Facilitating the Ferration of Aromatic Substrates through Intramolecular Sodium Mediation

Maddock

Kennedy

et al. 2021

Angew Chem Int Ed

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Exploiting cooperative effects between Na and Fe II centres present in tris(amide) ferrate complexes has led to the chemoselective ferration of pentafluorobenzene, benzene, toluene, anisole, and pyridine being realised at room temperature. The importance of this bimetallic partnership is demonstrated by neither the relevant sodium amide (NaHMDS or NaTMP) nor the Fe II amide Fe(HMDS) 2 efficiently metallating these substrates under the conditions of this study. By combining NMR studies with the isolation of key intermediates and DFT calculations, we offer a possible mechanism for how these reactions take place, uncovering a surprising reaction pathway in which the metals cooperate in a synchronised manner. Although the isolated products are formally the result of Fe-H exchange, theoretical calculations indicate that the aromatic substrates undergo Na-H exchange followed by fast intramolecular transmetallation to Fe, thus stabilizing the newly generated aryl fragment.Heterobimetallic amide bases containing a complementary combination of an alkali metal with a less electropositive metal, such as Mg or Zn, have emerged as a powerful class of reagents for selectively deprotonating functionalised arenes. [1] Profiting from the cooperation between the two metals, these bimetallic strategies can offer greater functional group tolerance and special regioselectivities that conventional single-metal bases cannot match. [2] Through the isolation

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confidence: 99%

Facilitating the Ferration of Aromatic Substrates through Intramolecular Sodium Mediation

Maddock

Kennedy

et al. 2021

Angew Chem Int Ed

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“…poorly modelled toluene solvent molecule, for which a significant distortion is not likely to be real. Compared with genuine cases of in-plane angular distortions in this way, our own results (Maddock et al, 2018) are indeed extreme, the smallest C-C-Fe angle in these ferrated benzene derivatives being 97 with others not much larger. Clearly the cause here is a significant secondary FeÁ Á ÁN interaction that may be regarded as incipient covalent bonding leading to angular distortions also at the Fe and N atoms.…”

Section: Angular Distortions In and Around Benzene Ringsmentioning

confidence: 44%

Distortions, deviations and alternative facts: reliability in crystallography

Clegg

2021

Int Union Crystallogr J

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This feature article is derived from the author's presentation of the Lonsdale lecture at the BCA Spring Meeting in 2018. One of the research results for which Kathleen Lonsdale is best known was her 1929 demonstration that the benzene ring in crystalline hexamethylbenzene is planar and has essentially hexagonal symmetry, resolving decades of dispute among organic chemists. More recent crystallographic studies of hexamethylbenzene have shown that there are actually small deviations from planarity. Such deviations for aromatic compounds may be due to electronic, steric, and/or intermolecular factors. Some substituted benzene molecules display remarkably large deviations, both from a planar ring structure and from regular hexagonal angular geometry around the ring. Starting from this specific connection with Kathleen Lonsdale's research, a number of stories are recounted of structural distortions and deviations from expected results and explanations that have been suggested for them, across a wide range of chemical topics including macrocycles, metal clusters, unusual coordination geometry and isomerism. On the way we find genuine surprises and results that have led to new understanding, but also examples of poor experiments, misinterpretation of data, scientific bias and preconceived ideas, incompetence and even deliberate fraud. Some aspects of structure validation are discussed. While showcasing some interesting research in its own right, this account also serves an educational purpose.

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“…Compound 2 is then the first example of a sodium aluminate of stoichiometry [NaAlMe 3 (L)] n with phenoxo-imino ligands and one of the very few reported. The influence of Na···F interactions has been acknowledged not only in the structure but also in the reactivity of heterometallic sodium species as it has been reported for metallated reactions [55].…”

Section: Resultsmentioning

confidence: 99%

Aluminates with Fluorinated Schiff Bases: Influence of the Alkali Metal–Fluorine Interactions in Structure Stabilization

et al. 2018

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New heterometallic aluminium-alkali metal compounds have been prepared using Schiff bases with electron withdrawing substituents as ligands. The synthesis of these new species was achieved via the reaction of AlMe3 with the freshly prepared alkali-metallated ligand. The derivatives formed were characterized by NMR in solution and by single crystal X-ray diffraction in the solid state. Aluminate derivatives with lithium and sodium were prepared and a clear influence of the alkali metal in the final outcome is observed. The presence of a Na···F interaction in the solid state has a stabilization effect and the species [NaAlMe3L]2 can de isolated for the first time, which was not possible when using Schiff bases without electron withdrawing substituents as ligands.

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Utilising Sodium‐Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C−H and C−F Bond Activations

Cited by 46 publications

References 33 publications

Facilitating the Ferration of Aromatic Substrates through Intramolecular Sodium Mediation

Facilitating the Ferration of Aromatic Substrates through Intramolecular Sodium Mediation

Distortions, deviations and alternative facts: reliability in crystallography

Aluminates with Fluorinated Schiff Bases: Influence of the Alkali Metal–Fluorine Interactions in Structure Stabilization

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