The potassium pentafluorophenylfluoroborates were prepared by hydroxy-fluoride-substitution of fluoroorganoalkoxyboranes and -borates with potassium bifluoride. Those intermediate boranes and borates were obtained by the reaction of fluoroorganomagnesium reagents and alkoxyboranes. The introduction of one or two pentafluorophenylgroups into various alkoxyboranes is investigated to optimize the yield of potassium pentafluorophenyltrifluoroborate and bis(pentafluorophenyl)difluoroborate. Reactions of pentafluorophenylfluoroborates with the Lewis acids borontrifluoride and tris(pentafluorophenyl)borane show the Lewis acidity of pentafluorophenyldifluoroborane compared with borontrifluoride and tris(pentafluorophenyl)borane. Pentalfuorophenylfluoroborate salts reacted with iodinepentafluoride by transfer of a pentafluorophenylgroup to iodinepentafluoride. To develop an alternative method to fluorooganofluoroborates systematic investigations on the reactivity of fluoroorganoboranes to fluorides were undertaken. Potassium-1H,1H,2H,2H-perfluorooctyltrifluoroborate is prepared by the reaction of an organogrignard reagent with chlorodimethoxyborane and hydrolysis and hydoxy-fluoride-substitution of the product. Treatment of the borate wit borontrifluoride provides the corresponding difluoroborane with ponytailgroup.