Crystal Structure of a Representative Mixed Adduct of Trimethylaluminium and a Lithium Amide and a Theoretical MO Study on Model Systems

Reaction of the simple alane adduct [Me 3 Al · HN(CH 2 Ph) 2 ] ( 2 ) with the lithium amide [(PhCH 2 ) 2 NLi] leads to the formation of the mixed adduct [Me 3 Al · (PhCH 2 ) 2 NLi · HN(CH 2 Ph) 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 Me 3 Al 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 Me 3 Al and Me 2 NLi is exothermic, while further reaction to give Me 2 AlNMe 2 and MeLi (i.e., complete transmetallation) is endothermic.