Synthesis and characterization of phosphonium and phosphine oxide linked to a tetrairon cluster

► Fe4 cluster-bonded phosphonium and phosphine oxide are prepared. ► Reaction of Cp3Fe4(CO)4(C5H4PPh2) with Me+ produces [Cp3Fe4(CO)4(C5H4PPh2Me)]+. ► Treatment of Cp3Fe4(CO)4(C5H4PPh2) with H2O2 leads to Cp3Fe4(CO)4(C5H4PPh2(O)). ► The redox potentials of the product are shifted anodically.