Polydentate Amine and Ether Solvates of Lithium Hexamethyldisilazide (LiHMDS):  Relationship of Ligand Structure, Relative Solvation Energy, and Aggregation State

6Li, 15N, and 13C NMR spectroscopic investigations of [6Li,15N]lithium hexamethyldisilazide ([6Li,15N]LiHMDS) coordinated by 29 polyamines, polyethers, and aminoethers reveal a range of structural types including η1-coordinated mono- and disolvated dimers, η2-coordinated (3-coordinate) monomers, η1,η2-coordinated (4-coordinate) monomers, η2,η2-coordinated (5-coordinate) monomers, polymers (linked dimers), triple ions, and solvent-separated ion pairs. Ligand binding constants on the LiHMDS monomers shed light on chelate ring size and steric effects, aza- and oxaphilicity, mechanisms and rates of ligand substitution, and the “macrocyclic effect.”