From Phosphidic to Phosphonium? Umpolung of the P4‐Bonding Situation in [CpFe(CO)(L)(η1‐P4)]+ Cations (L=CO or PPh3).

Upon coordinating P4 to electron poor cyclopentadienyl‐iron cations, the average P−P bond distances shrink and the respective P4 breathing mode in the Raman spectra (600 cm−1, P4, free) is blueshifted by >40 cm−1 in [CpFe(CO)(L)(η1‐P4)]+ cations (L=CO or PPh3). Analysis suggests that this corresponds to an umpolung of the bonding from more phosphidic in the known, electron‐rich systems to more phosphonium‐like in the reported electron‐poor versions. This may open new functionalization pathways for white phosphorus P4. [ABSTRACT FROM AUTHOR]