Arene complexes of gallium: An effective tool for the synthesis of transition metal clusters and complexes

In this review, the interactions between gallium(III) halides or gallium(I) subvalent halides and aromatic hydrocarbons in solution and solid state are discussed. Such unique properties of gallium halides–arene mixtures as the ability to reduce metallic centers and accept halide atoms make them very efficient tool for the preparation of low-valent clusters and complexes of transition metals. Diverse mono- and polynuclear arene complexes of d- and f-elements, including coordination polymers, may be achieved by the reactions between transition metal halides and gallium(III) halides in arene media. The role of Lewis acidity of gallium halides, the nature of the substituents on the arene ring and the nature of transition metals are discussed in terms of coordination mode of arenes and resulting structure of the transition metal–arene complexes.