C(sp³)-H Amination with an Ammonia-Derived Copper(III) Amide

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Catalysis

Background:

• Metal-ammine and metal-amide species are key intermediates in ammonia oxidation.
• Weak N-H bonds in these complexes typically facilitate sequential bond breakage.
• High N-H bond dissociation free energy (BDFE) in metal-ammine complexes is rare but desirable for specific synthetic applications.

Purpose of the Study:

• To synthesize and characterize novel copper(II) and copper(III) complexes with ammonia (NH3) and amide (NH2) ligands.
• To investigate the N-H bond strength in a copper(II) ammine complex.
• To explore the reactivity of a copper(III) amide complex in C(sp3)-H functionalization.

Main Methods:

• Synthesis and characterization of copper-ammine and copper-amide complexes.
• Measurement of N-H bond dissociation free energy (BDFE) using experimental techniques.
• Evaluation of catalytic activity in C(sp3)-H functionalization reactions.

Main Results:

• The copper(II) ammine complex (LCuII NH3) exhibited the highest reported N-H BDFE for an M-NH3 species at 92.8(1.5) kcal/mol.
• The formal copper(III) amide congener (LCuIII NH2) demonstrated reactivity towards C(sp3)-H bonds.
• Efficient mediation of C(sp3)-H activation and C(sp3)-N bond formation was achieved, yielding nitriles, ketones, and primary amines.

Conclusions:

• The study reports unprecedentedly strong N-H bonds in a copper-ammine complex.
• The copper(III) amide complex serves as an effective catalyst for C(sp3)-H functionalization.
• These findings open new avenues for synthesizing functionalized hydrocarbons via C-N bond formation.