Triel Bonds with Methyl Groups as Electron Donors. A Pentacoordinate Carbon Atom

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Supramolecular Chemistry

Background:

• Triel bonds (TrB) are a class of non-covalent interactions involving elements from Group 13 (Boron, Aluminum, Gallium).
• Understanding these interactions is crucial for designing novel materials and chemical processes.

Purpose of the Study:

• To investigate the formation and characteristics of triel bonds between M(CH3)2 (M=Be, Mg) and TrX3 (Tr=B, Al, Ga; X=H, F, Cl, Br, I).
• To explore the electronic and structural properties of these complexes, including potential pentacoordinate carbon intermediates.

Main Methods:

• Utilized the MP2/aug-cc-pVTZ(PP) quantum chemical protocol for theoretical calculations.
• Analyzed electrostatic potentials and interaction energies to characterize the triel bond.

Main Results:

• Identified triel bonds where methyl group carbons act as electron donors to the π-hole of planar trihalides.
• Interaction energies ranged from -2 to -69 kcal/mol, with Mg(CH3)2 forming stronger bonds than Be(CH3)2.
• Observed significant methyl group transfer and pyramidalization in some Mg-containing complexes, suggesting pentacoordinate carbon characteristics.

Conclusions:

• The study elucidates the nature of triel bonds involving organometallic compounds.
• The findings provide insights into the elusive pentacoordinate carbon species, potentially opening new avenues in chemical synthesis and bonding theory.