Molecules with all triple bonds: OCBBCO, N2BBN2, and [OBBBBO](2-)

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• Boron-boron bonding is a complex area of inorganic chemistry.
• Understanding the nature of multiple bonds in heavier elements is crucial.

Purpose of the Study:

• To investigate the bonding characteristics of the central B-B bonds in OCBBCO, N(2)BBN(2), and [OBBBBO](2-).
• To determine the extent of triple bond character and the role of pi-bonding and backdonation.

Main Methods:

• Density Functional Theory (DFT) calculations at the BP86/TZ2P level.
• Energy Decomposition Analysis (EDA) to probe bonding interactions.

Main Results:

• DFT calculations predict very short B-B distances and high bond dissociation energies.
• Energy Decomposition Analysis confirms genuine triple bonds for the central B-B moieties.
• Pi-bonding contributes significantly (38-40%) to the B[triple bond]B interactions.
• Ligand backdonation (CO, N(2)) strengthens the B-B bonds, supporting triple bond character.
• [OBBBBO](2-) exhibits weaker pi-bonding, making its B-B bonds borderline triple bonds.

Conclusions:

• The central B-B bonds in the studied compounds possess significant triple bond character.
• Strong pi-backdonation from ligands like CO and N(2) is key to stabilizing these triple bonds.
• The findings provide insights into the unique bonding capabilities of boron compounds.