Hypervalent iodine(III) difluoride reagent used to transfer of fluorine to organic substrates. Prepn: R. F. Weinland, W. Stille, Ann. 328, 132 (1903); W. Bockemüller, Ber. 64, 522 (1931); and spectral studies: D. Naumann, G. Rüther, J. Fluorine Chem. 15, 213 (1980). Improved prepn: M. Sawaguchi et al., Synthesis 2002, 1802. Synthetic applications in fluorination reactions: W. B. Motherwell et al., J. Chem. Soc. Perkin Trans. 1 2002, 2809; M. A. Arrica, T. Wirth, Eur. J. Org. Chem. 2005, 395.