The degree of disorder of [Cp″Fe­(η5-P5)] [Cp″ = η5-1,3-(tBu)2C5H3] molecules with respect to their mirrored positions in the orthorhombic Pca21 space group varies from ∼1 to 24% depending on the single crystal chosen from the same sample for the X-ray structural determination. This unusual behavior is caused by stacking faults in adjacent layers parallel to the (001) direction giving rise to two polytypes. A comprehensive search in the Cambridge Structural Database revealed only a few similar examples of the crystal-dependent disorder caused by stacking faults. Moreover, crystals of [Cp″Fe­(η5-P5)] possessing a low amount of stacking faults demonstrate slight temperature-induced superstructural ordering (modulation) between 20 and 80 K, accompanied by a doubling of the b parameter (b′ → 2 × b).

The heterobimetallic triple‐decker complex [(Cp*Fe)(Cp’’’Co)(μ,η5 : η4‐P5)] (1) was functionalized by main group nucleophiles and subsequently electrophilically quenched or oxidized. Reacting 1 with group 14 nucleophiles revealed different organo‐substituted P5R middle‐decks depending on the steric and electronic effects of the used alkali metal organyls (2: R=tBu; 3: R=Me). Further, with group 15 nucleophiles, the first structural characterized monosubstituted complexes with phosphanides could be obtained as P5 ligands containing exocyclic {PR2} units (4: R=Cy, H; 5: R=Ph). These monoanionic complexes 2–5 were isolated and subsequent electrophilic quenching revealed novel types of neutral functionalized polyphosphorus complexes. These complexes bear formal chains of P5R'R’’ (6: R’=tBu, R’=Me) in a 1,3‐disubstitution pattern or P6R'R’’R’’’ units (7: R’=Cy, R’’=H, R’’’=Me; 8: R’=Me, R’’=Ph, R’’’=Me) in a 1,1,3‐substitution as middle‐decks stabilized by one {Cp’’’Co} and one {Cp*Fe} fragment. One‐electron oxidation of 2, 3 or 5 by AgBF4 gave access to paramagnetic triple‐decker complexes bearing P5R middle‐decks in various coordination fashions (R=tBu (10), R=PPh2 (12)). Interestingly, for R=Me (11), a dimerization is observed revealing a diamagnetic tetranuclear cluster containing a unique dihydrofulvalene‐type P10R2 ligand. All complexes were characterized by crystallographic and spectroscopic methods (EPR, multinuclear NMR and mass spectrometry) and their electronic structures were elucidated by DFT calculations.