Synthetic Chemistry of Cluster Compounds

Clusters are viewed as solids at the nano-scale. A cluster is a group of the same or similar elements gathered or occurring closely together. In chemistry, a "cluster" is an ensemble of bound atoms intermediate in size between a molecule and a bulk solid. The clusters exist in diverse stoichiometries and nuclearities. Carbon and boron atoms form fullerene and borane or mixed carborane clusters, respectively. Transition metals, lanthanides, and main group elements form especially robust clusters. The concept of clusters has been greatly extended in modern chemistry. According to the attribute of the central atoms, the clusters in chemistry can generally be divided into metal clusters and nonmetal clusters. Both clusters contain two main types in the light of coordination environments of the central atoms: one type is the clusters by reduction of heavy main group metals and semimetals with alkali metals under a solid-state reaction in anhydrous and vacuum conditions or a solution in anhydrous and anaerobic liquid ethylenediamine or ammonia. Some unstable naked clusters such as certain aluminum clusters and gold clusters as well as fullerenes are often produced by laser-induced evaporation and observed in gas-phase by means of the mass spectrometry.