Amidines: a deeper look at the archetypal pro-ligand

Area of Science:

• Inorganic Chemistry
• Main Group Chemistry
• Ligand Synthesis

Background:

• Amidinates are versatile, anionic, bidentate ligands crucial in inorganic and main group chemistry.
• Their tunability allows for modification of steric and electronic properties.

Purpose of the Study:

• To synthesize 23 bulky N-aryl substituted amidinate ligands.
• To compare three distinct synthetic methodologies for ligand preparation.
• To investigate the impact of ligand steric bulk on aluminium complexation.

Main Methods:

• Synthesis of amidinate ligands via condensation reactions with PPSE.
• Ligand synthesis through carbodiimide treatment with lithium salts.
• Sequential addition of anilines to acyl and imidoyl chlorides.
• Complexation studies with aluminium (AlH3·NMe3).
• Computational analysis of ligand steric and electronic properties.

Main Results:

• Successfully synthesized 23 N-aryl substituted amidinate ligands.
• Demonstrated that ligand steric bulk dictates the stoichiometry of aluminium complexes formed.
• Bulkier ligands yielded aluminium dihydride complexes.
• Less bulky ligands resulted in bis-ligated aluminium monohydride complexes.

Conclusions:

• Established efficient synthetic routes for bulky N-aryl amidinate ligands.
• Correlated ligand structure with aluminium complexation behavior.
• Computational methods elucidated the steric and electronic influences of substitution patterns.