Reaction of the simple alane adduct [Me3Al · HN(CH2Ph)2] (2) with the lithium amide [(PhCH2)2NLi] leads to the formation of the mixed adduct [Me3Al · (PhCH2)2NLi · HN(CH2Ph)2] (1). The crystal structures of 1 and 2 are reported. Exhibiting a four-membered, mixed-metal, mixedanion ring-core, the structure of 1 is unusual in containing a monomeric lithium dibenzylamide fragment. Such fragments generally convert to aza-allyl derivatives, so its existence here can be attributed to the stabilising effect of the attached Me3Al ligand. Crystalline 2 adopts the classical, distorted-tetrahedral arrangement of simple monomeric alane adducts. Ab initio MO calculations on model systems show that mixed adduct formation from Me3Al and Me2NLi is exothermic, while further reaction to give Me2AlNMe2 and MeLi (i.e., complete transmetallation) is endothermic.
- alane adduct
- monomeric lithium dibenzylamide fragment
- aza-allyl derivatives