Two Push-Pull Channels Enhance the Dinitrogen Activation by Borylene Compounds.

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• Nitrogen (N₂) is a crucial element but notoriously difficult to activate due to its strong triple bond.
• Borylenes, compounds containing a boron-ligand bond with a divalent boron, have emerged as potential activators for small molecules.
• Understanding the electronic interactions between borylenes and N₂ is key to designing efficient nitrogen fixation catalysts.

Purpose of the Study:

• To elucidate the electronic structure and bonding interactions in end-on bridging borylene-N₂ complexes.
• To identify the key factors governing the activation of dinitrogen (N₂) by borylenes.
• To explain the origin of the observed bent BNNB geometry in these complexes.

Main Methods:

• Theoretical calculations were employed to analyze the electronic properties of borylene-N₂ complexes.
• Focus on the analysis of frontier molecular orbitals (π and π*) of N₂ and their interactions with borylene orbitals.
• Investigation of charge transfer pathways and their influence on molecular geometry.

Main Results:

• Nitrogen (N₂) activation is facilitated by two distinct, perpendicular push-pull electronic channels involving borylenes.
• The π orbitals of N₂ donate electron density to one borylene, while the π* orbitals accept back-donations from another borylene.
• These electronic interactions are responsible for the characteristic bent BNNB geometry observed in the complexes.

Conclusions:

• The push-pull mechanism involving borylene π and N₂ π/π* orbitals is critical for N₂ activation.
• This electronic interplay dictates the molecular geometry, leading to the bent BNNB structure.
• The findings provide fundamental insights into the activation of inert small molecules by main group element compounds.