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

Abstract

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.