The first 4d/4f polyphosphides were obtained from reactions of the divalent metallocenes [Cp* ₂ Ln(thf) ₂ ] (Ln = Sm, Yb) with [{CpMo(CO) ₂ } ₂ (μ,η ^2:2 -P ₂ )] or [Cp*Mo(CO) ₂ (η ³ -P ₃ )]. New aggregation of the central phosphorus scaffold in combination with P–P bond formation within the coordination sphere of the transition metal was observed.