Unusual Four-Membered Metallocycles in Complexes of Main Group III Metals


The most important chemical and physical properties of Al, Ga, In, and Tl, as well as the basic aspects of their inorganic chemistry are summarized in this review. Special attention is given to the formation of stable and unusual 4-membered chelate rings in compounds of these metals. The current status of structural coordination and organometallic chemistry of main group III metals in oxidation states +1, +2 and +3, in respect of the formation of those uncommon metallocycles with variety of O, N, S, Se, and Te donor atoms, is reviewed. It turns out that thallium is the least represented metal in the group for this type of binding with conventionally used organic ligands. However, Tl+ readily forms Werner-type complexes with cyanoximes, which are a new subclass of ampolidentate organic ligands with the general formula NC–C(=N–OH)–R (where R is an electron-withdrawing group), capable of binding numerous metal ions. These Tl(I) cyanoximates possess unusual structures with dimeric Tl2O2 core, which can adopt either symmetrical or unsymmetrical planar/non-planar geometry. Structural chemistry, binding modes, thermal and spectroscopic properties of these ‘TlL’ composition complexes are discussed.


Chemistry and Biochemistry

Document Type





Al, chelate rings, crystal structures, Ga, In, Raman spectra, thermal analysis, Tl

Publication Date


Journal Title

Russian Journal of Inorganic Chemistry