Document Type

Article

Journal/Book Title

The Journal of Physical Chemistry

Publication Date

2-21-2018

Publisher

American Chemical Society

Volume

122

Issue

9

First Page

2550

Last Page

2562

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.

Available for download on Thursday, February 21, 2019

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