Chalcogen‐Bridged Copper Clusters

The investigation of coinage metal molecular clusters bridged by chalcogen atoms represents an area of ever increasing activity in recent chemical and material science research. This is largely due to the relatively high ionic and even higher electric conductivity of binary coinage metal chalcogenides, which leads to properties intermediate between those of semiconducting and metallic phases. In addition, the size‐dependency of the chemical, physical, and structural properties of substances on going from small molecules to bulk materials is of general interest. Approaches towards the synthesis and investigation of such clusters have included the study of colloidal nanoparticles with a narrow size distribution, as well as the formation and isolation of crystalline cluster compounds amenable to structural determination by single‐crystal X‐ray diffraction analysis. Irrespective of the chosen synthesis route, the molecules have to be kinetically protected from decomposition to the thermodynamically favored binary phases by a suitable ligand sphere, often consisting of tertiary phosphane molecules, or a combination of phosphanes and organic groups. In this report, we concentrate on the syntheses and structural as well as physical properties of ligand‐stabilized, chalcogen‐bridged copper clusters, which have been comprehensively studied by means of experimental and quantum chemical investigations.