Solvent-free synthesis of metal complexes

Abstract

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.

Mortar-Pestle and Microwave Assisted Regioselective Nitration of Aromatic Compounds in Presence of Certain Group V and VI Metal Salts under Solvent Free Conditions

“…Rate accelerations could be explained due to the conversion of mechanical energy (kinetic energy exerted due to grinding) into heat energy, which becomes driving force for better activation of molecules. The kinetic energy supplied during grinding can have several effects on a crystalline solid [28][29][30][31][32][33][34] including: heating, reduction of particle size (with concomitant increase in surface area and the generation of fresh surfaces), formation of defects and dislocations in crystal lattices, local melting and even phase changes to alternative polymorphs. Collisions between crystals during grinding can also lead to local deformations and potentially melting.…”

“…Solvent free organic reactions make synthesis simpler, save energy and prevent solvent wastes, hazards and toxicity. In this part of our work we aimed at to explore solvent free nitration methods such as (a) grinding the solvent free reactants in a mortar with a pestle [28][29][30][31][32][33][34] and (b) conducting micro wave assisted nitration reactions [35][36][37][38][39][40][41][42][43].…”

Organic-Inorganic Hybrid Compounds Based on Lead Halide Units: Preparation from Melts and through Grinding Effects

“…This compound could be prepared by using PbCl 2 and PbBr 2 , instead of PbBr 2 only, and organic ammonium bromides, instead of chlorides. During the mixing of the starting materials, a solvent-free reaction [18] or the intercalation of PbX 2 into the organic crystals [11a] takes place and changes in the color are observed (e. g. from colorless to pale-orange). Then, the mixture of the powders was transferred to a glass tube and heated to a temperature close to the melting points of the organic components.…”

Mechanochemical synthesis andin vitroanti-Helicobacter pyloriand uresase inhibitory activities of novel zinc(II)–famotidine complex

“…It is therefore desirable that the drug substances be made solvent free. Recently, methods have been developed for solvent-free synthesis of metal complexes 10 which have promise in pharmaceutical manufacture. In this study we report the preparation of the title compound by use of a solvent-free mechanochemical method.…”