The Journal of Physical Chemistry A· 2018Q2
Steric Crowding in Tetrel Bonds
- 68citations
- Q2SCImago
- 2018year
Short summary
Tetrel bond strength increases up to 54 kcal/mol with larger central atoms (Si, Ge, Sn, Pb), electron-withdrawing groups (-CF3), and anionic bases, despite steric crowding from bulky R groups (H, CH3, isopropyl, tert-butyl).
AI-generated from the title and abstract; the full text is not read.
Key points
- Tetrel bond strength is influenced by the size of the central tetrel atom (T) and the steric bulk of surrounding R groups.
- Steric crowding from larger R groups (isopropyl, tert-butyl) can be offset by using larger T atoms (Si, Ge, Sn, Pb) or electron-withdrawing substituents (-CF3).
- Anionic bases significantly strengthen tetrel bonds compared to neutral bases.
- Maximum tetrel bond energies observed are 10 kcal/mol (neutral, no EWG), 35 kcal/mol (-CF3 substituted), and 54 kcal/mol (anionic base, -CF3 substituted).
AI-generated from the title and abstract; the full text is not read.
Abstract
The tetravalent character of tetrel atoms leaves only limited room for an incoming nucleophile to approach and engage in a noncovalent bond with a tetrel atom. Any such approach can only occur at the expense of internal geometric distortions. The balance between attractive forces and repulsive steric crowding was studied for a series of Lewis acids of the type FTR3 (T = Si, Ge, Sn, Pb) which were allowed to interact with various bases. The strength and other properties of the tetrel bond are examined as the R groups are made progressively larger, varying from H and CH3 to isopropyl and tert-butyl, which induce steric crowding with the incoming base. The effects of crowding which impede the bond can be offset by enlarging the T atom, by adding electron-withdrawing substituents to the Lewis acid, or by considering stronger bases such as anions. The tetrel bond energies reach up to 10 kcal/mol for a pair of neutral molecules with no electron-withdrawing substituents on the Lewis acid. Adding −CF3 substituents grows the interaction energy to as high as 35 kcal/mol, and a further increment occurs for an anionic base, taking the maximum up to 54 kcal/mol.
The authors' abstract, as published at the source. The Journal of Physical Chemistry A, 2018 · DOI ↗
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Field: Archeology (Social Sciences)
ArcheologySocial Sciences