Synthesis and oxidation of hexafluoroisopropoxyborylferrocenes

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(ORF)4]– by oxidation of 1,1'-(BOhfip2)2Fc with Ag+[Al(ORF)4]– (RF = 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(ORF)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.