Redox-Active Phosphorus Ligands Bearing a [4Fe−4C] Core Substituent

Reaction of [(η5-C5H4Me)4Fe4(HCCH)(HCCBr)](PF6) (1) with HPPh2 in the presence of NEt3, followed by treatment of [Cp2Co], afforded [(η5-C5H4Me)4Fe4(HCCH)(HCC−PPh2)] (2). The electron-rich [4Fe−4C] core substituent leads to the extremely electron-releasing character of the phosphine part, estimated by the JPSe coupling constant of the corresponding selenide [(η5-C5H4Me)4Fe4(HCCH)(HCC−P(Se)Ph2)] (3). Reaction of 2 with [AuCl(SMe2)] gave [(η5-C5H4Me)4Fe4(HCCH)(HCC−P(AuCl)Ph2)] (4). The cyclic voltammogram of 4 shows two reversible one-electron oxidation waves, indicating the existence of one- and two-electron oxidized forms.