Chalcogen bonding in coordination chemistry

The chalcogen bond (ChB) is defined as a noncovalent interaction between the electron density deficient region (so-called as σ or π hole) of a covalently bonded chalcogen atom and a nucleophilic (Nu) site in the same (intramolecular) or another (intermolecular) molecular entity: R–Ch⋯Nu [Ch = O, S, Se or Te; R = C, Pn (pnictogen), Ch, metal, etc.; Nu = lone pair possessing Ha, Ch, Pn or metal atom, π-system, anion, radical, etc.]. Like in halogen (Ha) and pnictogen (Pn) bonds, the bond parameters (strength, high directionality and tunability) make ChB a relevant supramolecular tool in the design of the secondary coordination sphere of metal complexes, which concerns an important synthetic strategy in the improvement of functional properties of materials. In this review we discuss/illustrate several relevant examples, taken from the Cambridge Structural Database, in which ChB plays a crucial role in the decoration of the secondary coordination sphere of coordination compounds, controlling molecular conformation, packing and aggregation of tectons, as well as formation of supramolecular 0D aggregates, 1D chains, 2D layers, 3D frameworks, etc.