Partner effect in accelerating pincer-co catalyzed nitrile hydroboration reactions

Area of Science:

• Organometallic Chemistry
• Catalysis
• Computational Chemistry

Background:

• Pincer-Co catalysts enable nitrile hydroboration for amine synthesis.
• Ligand engineering is typically required to tune catalyst performance.
• Alternative strategies for catalyst tuning are needed.

Purpose of the Study:

• Investigate the effect of external partners on pincer-Co catalyzed nitrile hydroboration.
• Understand how additives influence catalyst reactivity and selectivity.
• Explore a new method for tuning catalyst behavior without modifying the ligand.

Main Methods:

• Computational investigations using density functional theory (DFT).
• Analysis of π-coordination of partners to the pincer ligand's aromatic ring.
• Evaluation of electronic effects and reaction barriers.

Main Results:

• Additives like (18-crown-6)K+, W(CO)3, and W(PMe3)3 bind to the pincer ligand's phenyl ring.
• Catalyst electron-richness is modulated by partners in the order: (18-crown-6)K+ > W(PMe3)3 > no partner > W(CO)3.
• The overall reaction barrier is reduced by 4.9 kcal mol-1 with (18-crown-6)K+, demonstrating a significant partner effect.

Conclusions:

• External partners can effectively tune pincer-Co catalyst reactivity for nitrile hydroboration.
• The non-covalent (18-crown-6)K+ partner enhances catalyst performance through polarization.
• This work presents a novel approach to catalyst optimization without ligand modification, valuable for experimental chemists.