Pure and Applied Chemistry

Abstract: The ferrocenylboranes (BOhfip₂)Fc and 1,1'-(BOhfip₂)₂Fc were prepared (Fc = ferrocenyl, Ohfip = (CF₃)₂CH-O); 1,1'-(BOhfip₂)₂Fc was further oxidized giving [1,1'‑(BOhfip₂)₂Fc]⁺[Al(OR^F)₄]^– by oxidation of 1,1'-(BOhfip₂)₂Fc with Ag⁺[Al(OR^F)₄]^– (R^F = C(CF₃)₃). Their X-ray crystal structures were determined and give further information on the Fe–B interaction through the dip angles α*. In [1,1'-(BOhfip₂)₂Fc]⁺[Al(OR^F)₄]^–, this Fe–B interaction is enfeebled: the dip angles α* (0.3º and 5.4º) are significantly smaller than in (BOhfip₂)Fc (7.8º) and 1,1'-(BOhfip₂)₂Fc (8.0º), and the hexafluoroisopropoxy moieties are twisted out of the Cp plane by up to 66.1º. NMR and vibrational spectra support the crystal structure assignments.