57Fe-NMR spectroscopy revisited: ferrocene derivatives containing heterosubstituents

57Fe-NMR spectra (16.1 MHz; natural abundance) of mono- and 1,1′-disubstituted ferrocene derivatives (1–15), including two ferrocenophanes (14, 15), could be measured in a much shorter time than expected according to previous reports (500 MHz spectrometer, standard equipment; solutions in 5-mm tubes). Substituents were tBu, alkynyl, silyl, germyl, stannyl and boryl groups, and the bridges in the ferrocenophanes were SiMe2 (14) and Me2SiSiMe2 units (15). The δ57Fe values cover a fairly large range of >450 ppm. There is a large difference (365 ppm) in 57Fe nuclear shielding for the two ferrocenophanes, with the higher 57Fe shielding in the [1]ferrocenophane 14. Parallel trends were observed between δ57Fe of ferrocene derivatives and δ55Mn of comparable sandwich complexes derived from [(η5-C5H5)Mn(η6-C6H6)].