Modeling lithium dialkylamides in ethereal solvents: A test of the microsolvation model

The dimerization energies of lithium diisopropylamide (LDA), lithium tetramethylpiperidide (LiTMP), and lithium hexamethyldisilazide (LiHMDS) were calculated with the hybrid B3LYP DFT method. The effects of ethereal solvents were modeled using explicit dimethyl ether or THF ligands. The trends in calculated dimerization free energies were in good agreement with the observed aggregation states of these compounds in THF. Substitution of the THF ligands by the computationally less demanding dimethyl ether introduced significant error in the calculated dimerization free energies. This solvent model also generated structures and energies of lithium diethylamide (LiEDA) aggregates that were in good agreement with published experimental data.