By cothermolysis of [CpRFe(CO)2]2 [CpR = η5-C5(CH2Ph)5 (Cpbn) (1) and η5-C5Me4C2H4SMe (CpS) (2)] with P4 phosphorus two novel pentaphosphaferrocenes of the formula [CpRFe(η5-P5)] [CpR = CpS (3), Cpbn (4)] have been synthesised and comprehensively characterised. These two products represent the first derivatives of this class of compounds with a functionalised as well as a sterically bulky adjacent cyclopentadienyl ligand. The pentabenzylcyclopentadienyl derivative 4 as well as both of the starting materials [CpRFe(CO)2]2 1 and 2 have been additionally characterised by X-ray diffraction structure determinations. The pentaphosphaferrocene 4 represents in the crystal lattice highly aggregated units via intra- and intermolecular π-stacking interactions of the phenyl rings of the Cpbn ligand.