Structure and reactivity of an Al/P-based frustrated Lewis pair bearing relatively small substituents at aluminium

Reaction of Mes2 P─C≡C─Ph (Mes = mesityl) with dineopentylaluminium hydride afforded by hydroalumination a geminal Al/P-based frustrated Lewis pair (FLP;4 ). Its steric shielding is relatively low, and its reactivity in various secondary reactions is less hindered by steric repulsion than observed for related compounds having bulkier groups attached to aluminium. FLP4 yielded adducts with Me3 C─NCO or benzaldehyde via the formation of Al–O and P–C bonds. Trimethylsilyl azide reacted with4 under surprisingly mild conditions to afford a nitrene complex by spontaneous N2 elimination below room temperature. A carbodiimide molecule was coordinated via one of the C=N bonds to form a five-membered AlCPNC heterocycle with an intact C=N bond in an exocyclic position. A very large molecule was obtained by the reaction of two equivalents of4 with a bifunctional methylene-bridged phenylene isocyanate precursor.This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.