Theoretical Design of Stable Pentacoordinate Boron Compounds

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Boron compounds are typically trivalent and electron-deficient.
• Understanding hypercoordination in main group elements is crucial for novel compound design.
• Previous studies have explored hypercoordinate boron, but stable pentacoordinate forms remain elusive.

Purpose of the Study:

• To investigate the theoretical possibility of forming stable pentacoordinate boron (penta-B) compounds.
• To elucidate the bonding characteristics and stability criteria for penta-B species.
• To design novel, synthesizable penta-B compounds.

Main Methods:

• Utilized theoretical computations to explore boron's coordination chemistry.
• Analyzed bonding in proposed penta-B structures, focusing on multicenter bonds and electronegativity.
• Systematically investigated model compounds like HnB(CH3)(XH3) and BR5.

Main Results:

• Confirmed that boron can form thermodynamically stable pentacoordinate compounds.
• Established that penta-B is hypercoordinate but not hypervalent, forming four covalent bonds, including multicenter bonds.
• Identified specific structural motifs and substituent requirements (low electronegativity atoms) for penta-B stability.
• Designed three novel penta-B compounds with potential for synthesis.

Conclusions:

• Pentacoordinate boron compounds are theoretically feasible and can be thermodynamically stable.
• The design principles derived from model compounds enable the prediction of stable penta-B structures.
• These findings open possibilities for synthesizing new boron-based materials under mild conditions.