Regioselective Insertion of Aluminum(I) in the cyclo-P5 Ring of Pentaphosphaferrocene.

A route to directly access mixed Al-Fe polyphosphide complexes was developed. The reactivity of pentaphosphaferrocene, [Cp*Fe(η5 -P5 )] (Cp*=C5 Me5 ), with two different low-valent aluminum compounds was investigated. The steric and electronic environment around the [AlI ] centre are found to be crucial for the formation of the resulting Al-Fe polyphosphides. Reaction with the sterically demanding [Dipp-BDIAlI ] (Dipp-BDI={[2,6-i Pr2 C6 H3 NCMe]2 CH}- ) resulted in the first Al-based neutral triple-decker type polyphosphide complex. For [(Cp*AlI )4 ], an unprecedented regioselective insertion of three [Cp*AlIII ]2+ moieties into two adjacent P-P bonds of the cyclo-P5 ring of [Cp*Fe(η5 -P5 )] was observed. The regioselectivity of the insertion reaction could be rationalized by isolating an analogue of the reaction intermediate stabilized by a strong σ-donor carbene.