Molecular self-assembly controlled by gallium–gallium single bonds—facile syntheses of macrocyclic octagallium compounds

Abstract

Treatment of the digallane(4) derivative R 2GaGaR 2 ( 1) [R=CH(SiMe 3) 2] with the dicarboxylic acid muconic acid or with squaric acid yielded macrocyclic compounds ( 4 and 5, respectively) by retention of the GaGa single bonds and release of 2 equiv. of bis(trimethylsilyl)methane per formula unit of 1. Both products contain four GaGa single bonds connected by four dicarboxylato or diolato ligands. Large heterocycles resulted which contain 36 ( 4) and 20 atoms ( 5), respectively. The cavity of the macrocycle of 5 is filled by two n-pentane molecules. In contrast, two pentane molecules are located in hollows on the surface of the macrocycle of 4 in a supramolecular arrangement. They influence the molecular conformation significantly. The reaction with squaric acid gave a by-product ( 6) which also has eight gallium atoms in a heterocycle, but one GaGa bond was cleaved by oxidation and probably by the release of elemental hydrogen.