Solvent-free synthesis of metal complexes

Avoiding the use of solvents in synthesis can reduce environmental contamination and even be more convenient than using solvent-based synthesis. In this tutorial review we focus on recent research into the use of mechanochemistry ( grinding) to synthesise metal complexes in the absence of solvent. We include synthesis of mononuclear complexes, coordination clusters, spacious coordination cages, and 1-, 2- and 3-dimensional coordination polymers ( metal organic frameworks) which can even exhibit microporosity. Remarkably, in many cases, mechanochemical synthesis is actually faster and more convenient than the original solvent-based methods. Examples of solvent-free methods other than grinding are also briefly discussed, and the positive outlook for this growing topic is emphasised.