Frustrated Lewis Acid-Base-Pair-Catalyzed Amine-Borane Dehydrogenation

Area of Science:

• * Inorganic Chemistry
• * Catalysis
• * Green Chemistry

Background:

• * Metal-free catalysis using frustrated Lewis pairs (FLPs) is an emerging green alternative to transition-metal catalysis.
• * Catalyst deactivation by reaction products hinders amine-borane dehydrogenation.
• * Dimethylamine-borane (DMAB) is a key substrate in this field.

Purpose of the Study:

• * To theoretically investigate the catalytic dehydrogenation of DMAB using a B,P-FLP.
• * To elucidate a mechanism that circumvents catalyst inhibition by reaction products.
• * To understand the factors influencing FLP catalysis with amine-boranes.

Main Methods:

• * Theoretical investigation using computational chemistry.
• * Analysis of reaction pathways and intermediate species.
• * Mechanistic study of B,P-FLP catalyzed DMAB dehydrogenation.

Main Results:

• * A novel catalytic cycle for DMAB dehydrogenation by a B,P-FLP was elucidated.
• * The mechanism involves ion pair formation and indirect B-H activation.
• * The FLP's unfavorable binding to the reaction product prevents catalyst inhibition.
• * Ammonia-borane dehydrogenation is inhibited due to hydrogen bonding, causing partial catalyst deactivation.

Conclusions:

• * The investigated B,P-FLP enables efficient, metal-free dehydrogenation of DMAB without product inhibition.
• * The mechanism highlights the importance of weak product binding for catalytic cycle propagation.
• * Hydrogen bonding interactions can lead to catalyst deactivation with other amine-boranes, like ammonia-borane.