Four-membered C^N chelation in main-group organometallic chemistry.

Main-group organometallic compounds containing four-membered C^N chelating rings are being studied because of the interest in harnessing the enhanced reactivity of such compounds which arises as a result of the release of steric strain. In this article, we have reviewed the literature on these systems. This review is organised in terms of the types of ligand systems that allow the assembly of such compounds, ., compounds containing aliphatic amine motifs, pyridine motifs and aniline motifs. In addition to a discussion on the synthesis and structure, we also examine the reactivity and applications of the main-group element compounds involved. In particular, applications involving H activation, carbonyl activation, olefin reduction, C-H activation, hydroalumination, cyanamide oligomerisation, borylation of olefins and heteroarenes, isocyanate activation and C-C bond activation are discussed.