Modification of a Common β-diketiminate NacNac Framework via Sequential Lithiation and Small Molecule Insertion

Area of Science:

• Coordination Chemistry
• Organic Synthesis
• Catalysis

Background:

• β-diketiminate (BDI) or NacNac ligands are widely used in synthesis and catalysis.
• Previously, the γ-C-H unit of the NacNac backbone was considered unreactive.
• Recent findings revealed reactivity of the γ-C-H unit with electrophiles.

Purpose of the Study:

• To leverage the reactivity of the NacNac backbone for creating novel ligand architectures.
• To synthesize tripodal modifications of the common NacNac ligand.
• To explore the coordination chemistry of these new ligand variants.

Main Methods:

• Deprotonation of the γ-C-H unit of NacNacH (Me, Dipp) to form NacNacLi.
• Reaction of NacNacLi with electrophiles: isocyanates, isothiocyanates, and carbodiimides.
• Crystallographic characterization of the synthesized tripodal NacNac variants and their lithiated derivatives.

Main Results:

• A series of tripodal NacNac ligands with N,N,N,O; N,N,N,S; or N,N,N,N potential dentation sites were successfully synthesized.
• Multiple new ligand structures were confirmed through X-ray crystallography.
• Distinct ligating modes of the novel tripodal ligands were elucidated via crystal structures of their lithiated intermediates.

Conclusions:

• The γ-C-H unit of NacNac ligands can be advantageously functionalized to create versatile tripodal ligands.
• These new ligands offer tunable coordination environments for catalytic applications.
• The study expands the scope of NacNac ligand design and application in coordination chemistry.