The systematic nucleophilic functionalisation of the cationic pentaphosphole ligand complex [Cp*Fe(eta 4-P5Me)][OTf] ([OTf]- = [SO3CF3]-) (A) with sterically demanding CpR derivatives is reported. This newly developed protocol turned out to be a highly reliable method for the synthesis of end-deck cyclo-P5 ligand complexes bearing bulky CpR substituents. By the reaction of A with anionic CpR salts, complexes of the type [Cp*Fe(eta 4-P5MeCpR)] (Cp* = eta 5-C5Me5; CpR = Cp ' (1), Cp '' (2), Cp & tprime; (3), CpMe (4); Cp ' = eta 5-C5H4tBu, Cp '' = eta 5-1,3-tBu2C5H3, Cp & tprime; = eta 5-1,3,4-tBu3C5H2, CpMe = eta 5-C5Me4H) are obtained. All products feature a selective 1,1 '-disubstitution at the cyclo-P5 ligand. Further reactivity studies of these complexes with FeBr2 enabled the formation of novel, sterically demanding ferrocene derivatives [{Cp*Fe(eta 4-P5Me(eta 5-Cp ''))}2Fe] (5) and [Cp*Fe(eta 4-P5Me(eta 5-Cp ''))FeCp ''] (6), featuring three different Fe atoms in a ferrocene-like environment. Oxidation of 5 yielded the dicationic complex [{Cp*Fe(eta 4-P5Me(eta 5-Cp ''))}2Fe][FAl]2 (7). EPR, zero-field 57Fe M & ouml;ssbauer, as well as DFT investigations on 7 showed a symmetric distribution of the positive charges on the outer Fe atoms.