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

A route to directly access mixed Al-Fe polyphosphide complexes was developed. The reactivity of pentaphosphaferrocene, [CpFe(η -P )] (Cp=C Me ), with two different low-valent aluminum compounds was investigated. The steric and electronic environment around the [Al ] centre are found to be crucial for the formation of the resulting Al-Fe polyphosphides. Reaction with the sterically demanding [Dipp-BDIAl ] (Dipp-BDI={[2,6- Pr C H NCMe] CH} ) resulted in the first Al-based neutral triple-decker type polyphosphide complex. For [(CpAl ) ], an unprecedented regioselective insertion of three [CpAl ] moieties into two adjacent P-P bonds of the cyclo-P ring of [Cp*Fe(η -P )] 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.