Synthesis and Reactivity of an End-Deck cyclo-P4 Iron Complex

Abstract

Reduction of the Fe^II complex [(^Ph PP₂^Cy )FeCl₂ ] (2) generated an electron-rich and unsaturated Fe⁰ species, which was reacted with white phosphorus. The resulting new complex, [(^Ph PP₂^Cy )Fe(η⁴ -P₄ )] (3), is the first iron cyclo-P₄ complex and the only known stable end-deck cyclo-P₄ complex outside Group V. Complex 3 features an Fe^II center, as shown by Mössbauer spectroscopy, associated to a P₄^2- fragment. The distinct reactivity of complex 3 was rationalized by analysis of the molecular orbitals. Reaction of complex 3 with H⁺ afforded the unstable complex [(^Ph PP₂^Cy )Fe(η⁴ -P₄ )(H)]⁺ (4), whereas with CuCl and BCF, the complexes [(^Ph PP₂^Cy )Fe(η⁴ :η¹ -P₄ )(μ-CuCl)]₂ (5) and [(^Ph PP₂^Cy )Fe(η⁴ :η¹ -P₄ )B(C₆ F₅ )₃ ] (6) were formed.

Keywords: electron transfer; end-deck complexes; iron; main group chemistry; phosphorus.