Be(CO)₃ as a Nontraditional Lewis Base Engaging in Halogen Bonding

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Supramolecular Chemistry

Background:

• The highest occupied molecular orbital (HOMO) of beryllium tricarbonyl (Be(CO)3) exhibits lone pair characteristics.
• This lone pair can act as an electron donor in the formation of halogen bonds.

Purpose of the Study:

• To investigate the nature and strength of halogen bonds formed between Be(CO)3 and various halogenated compounds.
• To explore the influence of molecular structure and halogen type on halogen bond characteristics.

Main Methods:

• Quantum chemical calculations were employed to model interactions.
• Be(CO)3 was paired with halogenated molecules: XF, XCl, XCN, and XCF3 (where X = I, Br, Cl).

Main Results:

• Noncovalent halogen bonds formed with XCN and XCF3 (2.2–9.7 kcal/mol), showing increased strength with larger halogens.
• Stronger interactions (≥40 kcal/mol) with XF and XCl exhibited covalent character, termed halogen sharing.
• Halogen sharing resulted in X-C bond stretching and red-shifted vibrational frequencies.

Conclusions:

• Be(CO)3 can participate in both noncovalent and partially covalent halogen bonds.
• The strength and nature of the interaction are dependent on the halogenated partner, with XF and XCl forming stronger, more covalent bonds.
• Trends in interaction strength differ between noncovalent and halogen-shared complexes.