Mechanochemical preparation of molecular and supramolecular organometallic materials and coordination networks

This Dalton Perspective deals with solvent-free reactions taking place within solids or between solids or involving a solid and a vapor. The focus is on reactions involving organometallic and coordination compds. and occurring via reassembling of non-covalent bonding, e.g. hydrogen bonds, and/or formation of ligand-metal coordination bonds. It is argued that reactions activated by mech. mixing of solid reactants as well as those obtained by exposing a cryst. solid to a vapor can be exploited to "make crystals", which is the quintessence of crystal engineering. It is demonstrated through a no. of examples that solvent-free methods, such as co-grinding, kneading, milling of mol. solids, or reactions of solid with vapors represent viable alternative, when not unique, routes for the prepn. of novel mol. and supramol. solids as well as for the prepn. of polymorphic or solvate modifications of a same species. The structural characterization of the products requires the prepn. of single crystals suitable for X-ray diffraction, a goal often achieved by seeding.