The new highly electron deficient ferrocenyldiphosphines [Fe{η5-C5H4P(CF3)2}2] (dfmpf) and [Fe{η5-C5H4P(C2F5)2}2] (dfepf) were synthesized by reaction of [Fe{η5-C5H4P(OPh)2}2] with CnF2n+1SiMe3/CsF (n = 1, 2), and the structure of dfmpf was determined. The structures of the complexes (dfmpf)PtCl2 and (dfepf)PtCl2 indicate that both ligands offer significantly wider bite angles than (C2F5)2PCH2CH2P(C2F5)2 (dfepe) and that dfepf is the bulkiest chelating (perfluoroalkyl)diphosphine yet made.