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

Reduction of the FeII complex [(Ph PP2Cy )FeCl2 ] (2) generated an electron-rich and unsaturated Fe0 species, which was reacted with white phosphorus. The resulting new complex, [(Ph PP2Cy )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 FeII center, as shown by Mössbauer spectroscopy, associated to a P42- 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 PP2Cy )Fe(η4 -P4 )(H)]+ (4), whereas with CuCl and BCF, the complexes [(Ph PP2Cy )Fe(η4 :η1 -P4 )(μ-CuCl)]2 (5) and [(Ph PP2Cy )Fe(η4 :η1 -P4 )B(C6 F5 )3 ] (6) were formed.