Insight into the Bonding and Aggregation of Alkyllithiums by Experimental Charge Density Studies and Energy Decomposition Analyses

In this Article, the organolithiums [((−)-sparteine)­Li^tBu] (1), [(ABCO)­Li^tBu]₂ (2), and [(ABCO)₂(LiⁱPr)₄] (3) are investigated by means of experimental and theoretical charge density determination to elucidate the nature of the Li–C and Li–N bonds. Furthermore, the valence shell charge concentrations (VSCCs) in the nonbonding region of the deprotonated C_α-atom will provide some insight on the localization of the carbanionic lone pair. Analysis of the electron density (ρ­(r_BCP)), Laplacian (∇²ρ­(r_BCP)), and the energy decomposition (EDA) confirmed that the Li–C/N bond exhibits astonishingly similar characteristics, to reveal an increasingly polar contact with decreasing aggregate size. This explains former observations on the incorporation of halide salts in organolithium reagents. Furthermore, it could be shown that the bonding properties of the ⁱPr group are similar to those of the ^tBu substituent. The accuracy of fit to all previously determined properties in organolithiums is remarkable.