Boron-based stepwise dioxygen activation with 1,4,2,5-diazadiborinine

Area of Science:

• Organoboron Chemistry
• Inorganic Chemistry
• Catalysis

Background:

• Activation of small molecules like dioxygen (O2) is crucial in chemistry.
• Diazadiborinine compounds are emerging as novel reagents in synthesis.
• Understanding reaction mechanisms involving boron centers and O2 is of significant interest.

Purpose of the Study:

• To investigate the reactivity of 1,4,2,5-diazadiborinine (1) with dioxygen (O2).
• To elucidate the mechanism of O2 activation and subsequent transformations.
• To synthesize and characterize novel boron-containing compounds.

Main Methods:

• Reaction of 1,4,2,5-diazadiborinine (1) with dioxygen (O2) at room temperature.
• Characterization of reaction intermediates and products using spectroscopic techniques.
• Stepwise addition of the diazaborinine reagent to control the reaction pathway.

Main Results:

• A formal [4 + 2] cycloaddition between diazaborinine 1 and O2 was observed, yielding bicyclo[2.2.2] molecule 2 with a B-O-O-B unit.
• Treatment of intermediate 2 with another equivalent of 1 led to O-O bond cleavage and formation of two B-O bonds.
• The reaction produced extremely rare B4C2N2O2 ten-membered rings (4), demonstrating stepwise scission of O2's π- and σ-bonds.

Conclusions:

• 1,4,2,5-diazadiborinine (1) is an effective reagent for activating dioxygen (O2).
• The study reveals a novel pathway for O2 activation and functionalization.
• The formation of B4C2N2O2 rings highlights the synthetic utility of diazaborinines in constructing complex boron-containing structures.