Structure Elucidation of Lithium Compounds Using ⁷ Li Residual Quadrupolar Couplings

Area of Science:

• * Inorganic Chemistry
• * Analytical Chemistry
• * Structural Chemistry

Background:

• * Elucidating lithium compound structures in solution is challenging.
• * Traditional methods may not accurately reflect solution-state behavior.
• * Nuclear Magnetic Resonance (NMR) spectroscopy offers potential for structural analysis.

Purpose of the Study:

• * To introduce a new NMR method for lithium compound structure elucidation.
• * To enable structure determination under solution-like conditions.
• * To investigate the coordination environment of lithium ions in model complexes.

Main Methods:

• * Measurement of ⁷Li residual quadrupolar couplings (RQCs) in stretched polystyrene (PS) gel.
• * Calculation of RQCs from crystal or DFT-derived structures.
• * Determination of alignment tensors from ¹H,¹³C residual dipolar couplings (RDCs).

Main Results:

• * The method was successfully applied to five lithium model complexes.
• * Four complexes were identified as monomeric with fourfold Li coordination (two THF molecules).
• * One complex showed monomeric structure with one THF molecule due to bulky tBu groups.

Conclusions:

• * The developed NMR method effectively determines lithium compound structures in solution-like conditions.
• * The findings provide insights into the coordination chemistry of lithium ions with various ligands.
• * Structural variations in lithium complexes are influenced by ligand steric bulk and coordination number.