Mechanochemical interconversion between discrete complexes and coordination networks formal hydration/dehydration by LAGElectronic supplementary information (ESI) available: TGA and PXRD patterns of products. See DOI: 10.1039/c2ce06469c

Using a small planetary ball mill, liquid-assisted grinding (LAG) of metal salts or oxides (ZnO, CdO, CdCO 3 , Cu(OAc) 2 H 2 O, Co(OAc) 2 4H 2 O, Mn(OAc) 2 4H 2 O, Ni(OAc) 2 4H 2 O, FeSO 4 7H 2 O) with two equivalents of isonicotinic acid (HINA) and small amounts of water (up to 5.6 molar equivalents) gave discrete aquo complexes trans -[M(INA) 2 (OH 2 ) 4 ] (M = Zn, Cd, Cu, Fe, Co, Ni, Mn) efficiently within 30 min. For M = Zn, Cd and Cu these complexes readily undergo reversible formal dehydration to the extended network structures [M(INA) 2 ] (M = Zn, Cu) or [Cd(INA) 2 (OH 2 )]DMF by further LAG with non-aqueous liquids such as methanol or DMF. Overall, the mechanochemical dehydrations are more effective than heating or immersion in bulk solvents. The work demonstrates a two-step mechanochemical synthesis of coordination networks via discrete aquo complexes which may be preferable to single step reactions or grinding-annealing procedures in some cases. For example, the two step method was the only way to prepare [Cd(INA) 2 (OH 2 )]DMF mechanochemically and the porous network Cu(INA) 2 could not be obtained from the aquo complex by heating. Extending ball-milling approaches: from discrete complexes to polymers and back again by grinding-induced hydrations and dehydrations.