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

Reduction of the FeII complex [((PP2Cy)-P-Ph)FeCl2] (2) generated an electron-rich and unsaturated Fe-0 species, which was reacted with white phosphorus. The resulting new complex, [((PP2Cy)-P-Ph)Fe(eta(4)-P-4)] (3), is the first iron cyclo-P-4 complex and the only known stable end-deck cyclo-P-4 complex outside Group V. Complex 3 features an Fe-II center, as shown by Mossbauer spectroscopy, associated to a P-4(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 [((PP2Cy)-P-Ph)Fe(eta(4)-P-4)(H)](+) (4), whereas with CuCl and BCF, the complexes [((PP2Cy)-P-Ph)Fe(eta(4):eta(1)-P-4)(mu-CuCl)](2) (5) and [((PP2Cy)-P-Ph)Fe(eta(4):eta(1)-P-4)B(C6F5)(3)] (6) were formed.