Synthesis of Exceptionally Stable Iron and Ruthenium η¹ -tetrahedro-Tetraphosphorus Complexes: Evidence for a Strong Temperature Dependence of M-P₄ π Back Donation

At variance with white phosphorus, the most reactive allotrope of the element, which is unstable and ignites spontaneously in air, the new η¹ -tetrahedro-tetraphosphorus complexes [Cp*M(PR₃ )₂ (η¹ -P₄ )]Y (M=Fe, Ru; Y=Cl, PF₆ , BPh₄ , BAr$\rm{^{\prime }_{4}}$; Cp*=C₅ Me₃ the structure of the [Cp*Fe(Ph₂ PCH₂ CH₂ PPh₂ )(η¹ -P₄ )]⁺ ion is depicted) exhibit a surprising and unprecedented thermal stability and an astonishing reluctance to react with oxygen and other oxidants.