Direct one step preparation and C-13-NMR spectroscopic characterization ofalpha-ferrocenyl carbocations derived from ferrocene and carbonyl compounds in trifluoroacetic acid medium

Reaction of aldehydes and ketones with ferrocene, in the presence of triflu oroacetic acid, afforded a series of stable long lived alpha-ferrocenylalky l carbocations which were characterized by C-13-NMR spectroscopy. When this reaction was attempted using tetraphenylcyclopentadienone, quite unexpecte dly the corresponding dihydro derivative 3 was isolated, in very good yield . Formation of this compound may require ferrocene acting as a reducing age nt.