Stable [M2F11 ] - (M = Nb, Ta) Salts of Protonated 1,3-Dimethoxybenzene

TitleStable [M2F11 ] - (M = Nb, Ta) Salts of Protonated 1,3-Dimethoxybenzene
Publication TypeJournal Article
Year of Publication2013
AuthorsMarchetti, F, Pampaloni, G, Pinzino, C, Zacchini, S
JournalEuropean Journal of Inorganic Chemistry
Date Publishednov
KeywordsArene protonation, Fluorides, Niobium, Reduction, Tantalum

The 3:1 molar reactions of MF5 (M = Nb, 1a; M = Ta, 1b) with 1,3-dimethoxybenzene in CHCl3 led to the formation of the arenium salts [2,4-(OMe)2C6H5][M2F 11] (M = Nb, 3a; M = Ta, 3b) in good yields. The reactions took place with the intermediate formation of (MF5)2[$ąppa$ 2-1,3-(OMe)2C6H4] (M = Nb, 2a; M = Ta, 2b), followed by single-electron oxidation of the arene and production of MF4 (identified by means of EPR spectroscopy as the acetonitrile adduct). Compounds 3a and b were fully characterised both in solution (NMR) and in the solid-state (X-ray, IR and elemental analysis), while 2a and b were identified by NMR spectroscopy in CD2Cl2 solution. The reactions of 1,3-dimethoxybenzene with Ag[NbF6] or Ag[Sb 2F11] in CD2Cl2/CHCl3 afforded [2,4-(OMe)2C6H5]+. It was found that 1,3-dimethoxybenzene was inert towards the addition of aqueous H[SbF6] under comparable experimental conditions. The unusual characteristics of MF5 (M = Nb, Ta), i.e. oxidising behaviour and capability of generating inert anion derivatives, have been exploited for the preparation of [M2F11]- salts of protonated 1,3-dimethoxybenzene. The salts are stable at room temperature under an inert atmosphere both in the solid-state and in chlorinated solvents. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.