Ethyl-Zinc(II)-Cation Equivalents: Synthesis and Hydroamination Catalysis

Area of Science:

• Organometallic Chemistry
• Catalysis

Background:

• Weakly coordinating anions are crucial for stabilizing reactive cationic species in catalysis.
• Ethylzinc(II) compounds are versatile precursors for various chemical transformations.

Purpose of the Study:

• To synthesize and characterize novel ion-like ethylzinc(II) compounds with weakly coordinating aluminate anions.
• To investigate the catalytic activity of these novel compounds in hydroamination reactions.

Main Methods:

• One-pot synthesis of ethylzinc(II) aluminate complexes.
• Characterization using single-crystal X-ray diffraction, NMR, and vibrational spectroscopy.
• Quantum chemical calculations to understand electronic structure.
• Catalytic evaluation in intermolecular and double hydroamination reactions.

Main Results:

• Successful synthesis and full characterization of ion-like ethylzinc(II) compounds with [Al(OR(F))4](-) and [(R(F)O)3Al-F-Al(OR(F))3](-) anions.
• Demonstrated catalytic activity in intermolecular hydroamination of anilines and alkynes.
• Observed efficient double hydroamination of anilines and alkynes with the Et-Zn[Al(OR(F))4] catalyst.
• Achieved favorable performance compared to a known system (Et2Zn/[PhNMe2H](+)[B(C6F5)4](-)) at lower catalyst loadings (2.5 mol%).

Conclusions:

• The synthesized ethylzinc(II) aluminate complexes are effective catalysts for hydroamination reactions.
• These catalysts offer an efficient alternative for challenging hydroamination processes, including double hydroamination.
• The study highlights the potential of ion-like ethylzinc(II) compounds in catalysis, particularly with the use of bulky, weakly coordinating aluminate anions.