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 monoand 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, azaand oxaphilicity, mechanisms and rates of ligand substitution, and the “macrocyclic effect.”