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 , P_{4, 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 .

Keywords: cations; clusters; iron; weakly coordinating anion (WCA); white phosphorus (P4).