Hexameric chiral α-amino lithium alkoxides:: a solid-state and theoretical structural investigation

The nucleophilic reagents lithium N-methylpiperazide, 1-Li, and lithium N,N,N'-trimethylethylenediamide, 2-Li, react with 1 equiv. of 4-methoxybenzaldehyde and 2-methylbenzaldehyde respectively to afford the corresponding chiral alpha-amino lithium alkoxides, (3)(6) . 2PhMe . THF and (4)(6) . 2PhMe, which are hexamers in the solid state. Stabilisation of the metal centres is assisted by dative coordination of the dialkylamine alpha-N-centres. While for (3), 2PhMe THF this is rationalised in terms of steric constraints imposed by the employment of a heterocyclic dialkylamine, for (4), 2PhMe it contrasts starkly with previously observed structural analogues. Ab initio MO calculations are employed to investigate the relationship between structure and ligand chirality.