The Chemistry of Gold–Metal Bonds

This chapter summarizes the preparation, structural characterization and properties of heterometallic gold compounds built through metal–metal interactions or bonds. They are mainly synthesized following four different strategies. Two of them use the acid-base process with gold precursors acting as acids or organoaurates acting as bases, the third one consists of the use of bidentate bridging ligands, and the fourth uses the isolobal relationship between the [(R3P)Au]+ cations and the proton in carbonyl clusters. The structural behavior of these complexes has been studied by different methods, mainly Mossbauer spectroscopy, nuclear magnetic resonance spectroscopy, and single-crystal X-ray diffraction. Their structures show discrete molecules, extended linear chains or even two- or three-dimensional networks. Many of these complexes display luminescence and the emissions are strongly dependent on their structures. Some theoretical calculations are able to show that the formation of metal–metal interactions or bonds, as well as the gold environments, are the main aspects that affect the energy of the emissions. Other very promising areas of research such as the potential applications in electrochemistry, in biology (antiproliferative and antitumoral activity) or as homogeneous and heterogeneous catalysts are also discussed. Keywords: biological properties; catalysis; heterometallic gold complexes; luminescence; metal–gold bonds; metal–gold clusters; metal–gold interactions; silver complexes; thallium complexes