Structure and properties of polycoordinate planar boron compounds.

Area of Science:

• Computational Chemistry
• Materials Science
• Inorganic Chemistry

Background:

• Boron compounds exhibit diverse coordination chemistries.
• Understanding polycoordinate boron structures is crucial for novel material design.
• Planar boron structures with high coordination numbers present unique bonding challenges.

Purpose of the Study:

• To computationally investigate the structural, electronic, and aromatic properties of polycoordinate planar boron compounds (BXn).
• To determine the coordination limits of central boron atoms with various substituents (X=B, Al, C, N, Si).
• To elucidate the factors contributing to the stability and planarity of these novel boron systems.

Main Methods:

• Density Functional Theory (DFT) calculations using the B3LYP/6-311++G (3df,p) level of theory.
• Natural Bond Orbital (NBO) analysis to assess electronic structure and octet rule compliance.
• Molecular Orbital (MO) analysis and Nucleus Independent Chemical Shift (NICS) calculations to evaluate aromaticity.

Main Results:

• Optimized structures for polycoordinate planar BXn (n=3-8) compounds were obtained.
• Central boron atoms can coordinate up to eight atoms (for X=B) or five atoms (for X=Al, C, Si, N) without violating the octet rule.
• Both alpha and pi aromaticity were identified in these compounds, correlating with their stability and planarity.

Conclusions:

• Polycoordinate planar boron compounds (BXn) exhibit remarkable stability due to dual aromaticity.
• The coordination number of the central boron atom is influenced by the nature of the substituent X.
• These findings provide insights into the design principles for stable, planar boron-based materials.