Issue 22, 2016

Applications of N-heterocyclic imines in main group chemistry


The imidazolin-2-imino group is an N-heterocyclic imino functionality that derives from the class of compounds known as guanidines. The exocyclic nitrogen atom preferably bonds to electrophiles and its electron-donating character is markedly enhanced by efficient delocalization of cationic charge density into the five-membered imidazoline ring. Thus, this imino group is an excellent choice for thermodynamic stabilization of electron-deficient species. Due to the variety of available imidazoline-based precursors to this ligand, its steric demand can be tailored to meet the requirements for kinetic stabilization of otherwise highly reactive species. Consequently, it does not come as a surprise that the imidazolin-2-iminato ligand has found widespread applications in transition-metal chemistry to furnish pincer complexes or “pogo stick” type compounds. In comparison, the field of main-group metal compounds of this ligand is still in its infancy; however, it has received growing attention in recent years. A considerable number of electron-poor main-group element species have been described today which are stabilized by N-heterocyclic iminato ligands. These include low-valent metal cations and species that are marked by formerly unknown bonding modes. In this article we provide an overview on the present chemistry of main-group element compounds of the imidazolin-2-iminato ligand, as well as selected examples for the related imidazolidin- and benzimidazolin-2-imino system.

Graphical abstract: Applications of N-heterocyclic imines in main group chemistry

Article information

Article type
Review Article
29 Feb 2016
First published
08 Aug 2016
This article is Open Access
Creative Commons BY license

Chem. Soc. Rev., 2016,45, 6327-6344

Author version available

Applications of N-heterocyclic imines in main group chemistry

T. Ochiai, D. Franz and S. Inoue, Chem. Soc. Rev., 2016, 45, 6327 DOI: 10.1039/C6CS00163G

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