Can a Wanzlick-like equilibrium exist between dicoordinate borylenes and diborenes?

Area of Science:

• Inorganic Chemistry
• Organoboron Chemistry
• Computational Chemistry

Background:

• Recent advances in boron chemistry have yielded compounds with unique electronic structures, including Lewis-base-stabilized borylenes and diborenes.
• A Wanzlick-type equilibrium between borylenes and diborenes, a potential route to diborenes, has not been experimentally observed.

Purpose of the Study:

• To investigate the electronic, structural, and kinetic factors governing the reactivity of CAAC-stabilized cyanoborylene.
• To understand why this borylene undergoes cyclotetramerization instead of dimerization.
• To compare the behavior of CAAC- vs. NHC-stabilized borylenes.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Coupled-cluster and multireference methods.
• Natural Bond Orbital (NBO) and Natural Resonance Theory (NRT) analyses.

Main Results:

• Borylene ground state multiplicity determines the preference for cyclooligomerization over boron-boron dimerization.
• CAAC-stabilized cyanoborylene cyclotetramerizes into a (BCN)4 ring, with dimerization being kinetically hindered.
• NHC-stabilized borylenes consistently yield diborenes upon reduction, unlike CAAC-stabilized counterparts.

Conclusions:

• The ground state multiplicity is the key factor controlling borylene self-assembly pathways.
• This study provides a theoretical basis for designing base-stabilized borylenes.
• Findings could enable new synthetic routes to diborenes or non-dimerizing systems for small-molecule activation.