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

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)](infinity) (1), [dioxane . Na(HMDS)(2-F-C10H6)Fe(HMDS)](infinity) (2), [dioxane . {Na(HMDS)(2,5-F-2-C6H3)Fe(HMDS)}(2)](infinity) (3), [dioxane . {Na(HMDS)(2,3,6-F-3-C6H2)Fe(HMDS)}(2)](infinity) (4), [(dioxane)(1.5) . Na(HMDS)(2,4,6-F-3-C6H2)Fe(HMDS)](2) (5), [(dioxane)(1.5) . {Na(HMDS)(4-Br-2,6-F-2-C6H2)Fe(HMDS)(2)] (6), [{(dioxane)(2) . Na2Fe(HMDS)(2)(2-methoxy-6-F-C6H3)}(+){Fe(HMDS)(3)}(-)](infinity) (7) and [dioxane . {Na(HMDS)(4-methoxy-2,6-F-2-C6H2)Fe(HMDS)}(2)](infinity) (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.