Structural and Synthetic Insights into Sodium‐Mediated‐Ferration of Fluoroarenes

• Published in: Helvetica chimica acta Vol. 104; no. 12
• Main Authors: Maddock, Lewis C. H., Kennedy, Alan R., Hevia, Eva
• Format: Journal Article
• Language: English
• Published: Zürich Wiley Subscription Services, Inc 01-12-2021
• Subjects: Bimetals; cooperative effects; Crystallography; Ferrates; fluoroarenes; Iron; metallation; Selectivity; Sodium; Thermal stability
• ISSN: 0018-019X; 1522-2675
• DOI: 10.1002/hlca.202100206

Exploiting chemical cooperation between Na and Fe(II) within the bimetallic base [dioxane ⋅ NaFe(HMDS)3] (I), (dioxane=1,4‐dioxane, HMDS=N(SiMe3)2) the selective ferration of fluorobenzene, 1‐fluoronaphthalene, 1,4‐difluorobenzene, 1,2,4‐trifluorobenzene, 1,3,5‐trifluorobenzene, 1‐bromo‐3,5‐difluorobenzene, 3‐fluoroanisole and 3,5‐difluoroanisole has been realized, affording sodium ferrates [dioxane ⋅ Na(HMDS)(2‐F‐C6H4)Fe(HMDS)]∞ (1), [dioxane ⋅ Na(HMDS)(2‐F‐C10H6)Fe(HMDS)]∞ (2), [dioxane ⋅ {Na(HMDS)(2,5‐F2‐C6H3)Fe(HMDS)}2]∞ (3), [dioxane ⋅ {Na(HMDS)(2,3,6‐F3‐C6H2)Fe(HMDS)}2]∞ (4), [(dioxane)1.5 ⋅ Na(HMDS)(2,4,6‐F3‐C6H2)Fe(HMDS)]2 (5), [(dioxane)1.5 ⋅ {Na(HMDS)(4‐Br‐2,6‐F2‐C6H2)Fe(HMDS)2] (6), [{(dioxane)2 ⋅ Na2Fe(HMDS)2(2‐methoxy‐6‐F‐C6H3)}+{Fe(HMDS)3}−]∞ (7) and [dioxane ⋅ {Na(HMDS)(4‐methoxy‐2,6‐F2‐C6H2)Fe(HMDS)}2]∞ (8), respectively. Reactions take place under mild reaction conditions, with excellent control of the selectivity and no competing C−F bond activation is observed. Showcasing complex polymeric arrangements in some cases, the structures of compounds 1–8 have been determined by X‐ray crystallographic studies. In all cases, the Fe(II) centers occupy the position in the relevant fluoroarene that was previously filled by a proton, confirming that these metallations are actually ferration processes whereas the Na atoms prefer to form Na⋅⋅⋅F dative interactions. Compounds 1–8 are thermally stable and do not undergo benzyne formation (through NaF elimination) and their formation contrasts with the inertness of Fe(HMDS)2 which fails to act as a base to metallate fluoroarenes.