Synthesis and Reactivity of an End‐Deck cyclo ‐P 4 Iron Complex

Reduction of the Fe II complex [( Ph PP 2 Cy )FeCl 2 ] ( 2 ) generated an electron‐rich and unsaturated Fe 0 species, which was reacted with white phosphorus. The resulting new complex, [( Ph PP 2 Cy )Fe(η 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 Mössbauer 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 [( Ph PP 2 Cy )Fe(η 4 ‐P 4 )(H)] + ( 4 ), whereas with CuCl and BCF, the complexes [( Ph PP 2 Cy )Fe(η 4 :η 1 ‐P 4 )(μ‐CuCl)] 2 ( 5 ) and [( Ph PP 2 Cy )Fe(η 4 :η 1 ‐P 4 )B(C 6 F 5 ) 3 ] ( 6 ) were formed.