An orbitally adapted push-pull template for N₂ activation and reduction to diazene-diide

Area of Science:

• Organometallic Chemistry
• Boron Chemistry
• Nitrogen Fixation

Background:

• Tungsten-nitrogen complexes are key intermediates in nitrogen fixation research.
• Lewis acid-mediated activation of small molecules is a growing area in chemistry.
• Bis(borane) compounds offer unique reactivity due to their Lewis acidity.

Purpose of the Study:

• To synthesize and characterize novel tungsten-nitrogen-boron complexes.
• To investigate the reactivity of bis(borane) Lewis acids with tungsten dinitrogen complexes.
• To explore the activation of dinitrogen (N2) through Lewis acid coordination.

Main Methods:

• Reaction of tungsten dinitrogen complexes with a Lewis superacidic bis(borane).
• Characterization of resulting zwitterionic boryldiazenido tungsten(II) complexes.
• Investigation of hydrogen splitting and subsequent boron transfer using spectroscopic and DFT methods.

Main Results:

• Synthesis of zwitterionic boryldiazenido W(II) complexes via intramolecular boron-to-boron transfer.
• Complex 5 exhibited H2 splitting, forming a seven-coordinate complex with reversed boron transfer.
• Two-fold Lewis acid coordination to N2 induced strong activation to the diazene-diide (N2^2-) state.

Conclusions:

• This study presents the first example of neutral Lewis acid coordination inducing N2 reduction.
• The reversible boron transfer mechanism highlights a new pathway for N2 activation.
• The findings open avenues for developing new catalysts for nitrogen fixation and related transformations.