Insights into the Factors Controlling the Origin of Activation Barriers in the [2 + 2] Cycloaddition Reactions of Heavy Imine-like Molecules Featuring a Ge=Group 15 Double Bond with Heterocumulenes

Insights into the Factors Controlling the Origin of Activation Barriers in the [2 + 2] Cycloaddition Reactions of Heavy Imine-like Molecules Featuring a Ge=Group 15 Double Bond with Heterocumulenes

The [2 + 2] cycloaddition reactions of the heterocumulene (<b>N=C=N</b>) with the heavy imine-like molecule <b>Ge=G15-Rea</b> (G15 = Group 15 element) were examined using density functional theory (M06-2X-D3/def2-TZVP). The theoretical findings indicate that the doubly bonded...

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Bibliographic Details
Main Authors: Zheng-Feng Zhang, Ming-Der Su
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Molecules
Subjects:
[2 + 2] cycloaddition
heterocumulene
heavy imine
donor–acceptor interaction
electron-sharing
Online Access:https://www.mdpi.com/1420-3049/30/9/1905
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Summary:The [2 + 2] cycloaddition reactions of the heterocumulene (<b>N=C=N</b>) with the heavy imine-like molecule <b>Ge=G15-Rea</b> (G15 = Group 15 element) were examined using density functional theory (M06-2X-D3/def2-TZVP). The theoretical findings indicate that the doubly bonded Ge=G15 moiety in <b>Ge=G15-Rea</b> (L<sub>1</sub>L<sub>2</sub>Ge=G15L<sub>3</sub>) is characterized by electron-sharing bonding between the triplet L<sub>1</sub>L<sub>2</sub>Ge and triplet G15–L<sub>3</sub> fragments. All five Ge=G15-based heavy imine analogues readily undergo [2 + 2] cycloaddition reactions with <b>N=C=N</b>. Energy decomposition analysis (EDA–NOCV) suggests that the [2 + 2] cycloaddition reaction between <b>Ge=G15-Rea</b> and <b>N=C=N</b> involves a donor–acceptor (singlet–singlet) interaction instead of an electron-sharing (triplet–triplet) interaction. Frontier molecular orbital (FMO) theory and the energy decomposition analysis–natural orbitals for chemical valence (EDA–NOCV) findings emphasize that the key bonding interaction involves the occupied p-π orbital of <b>Ge=G15-Rea</b> and the vacant p-π* orbital of <b>C=N=C</b>. Based on the activation strain model results, the activation barrier of the [2 + 2] cycloaddition reaction is predominantly controlled by the deformation energies of <b>Ge=G15-Rea</b> and <b>N=C=N</b>.
ISSN:1420-3049

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