Cover Picture: Assembly of Hybrid Organic–Organometallic Materials through Mechanochemical Acid–Base Reactions (Chem. Eur. J. 18/2003)

Abstract

The cover picture shows schematically the preparation of a crystalline material by grinding (top) of the solid reagents or by crystallization by seeding (bottom) of a solution of the powder obtained from the mechanochemical process. Manual grinding of the organometallic complex [Fe(η5-C5H4COOH)2] with a number of solid bases, namely 1,4-diazabicyclo[2.2.2]octane, 1,4-phenylenediamine, piperazine, trans-1,4-cyclohexanediamine and guanidinium carbonate generates quantitatively the corresponding adducts, [HC6H12N2][Fe(η5-C5H4COOH)(η5-C5H4COO)], [HC6H8N2][Fe(η5-C5H4COOH)(η5-C5H4COO)], [H2C4H10N2][Fe(η5-C5H4COO)2], [H2C6H14N2][Fe(η5-C5H4COO)2] ⋅ 2 H2O and [C(NH2)3]2[Fe(η5-C5H4COO)2]⋅2 H2O, respectively. Crystallization from methanol in the presence of seeds of the ground sample allows to grow single crystals of the adducts, hence determination of the adduct structures by single crystal X-ray diffraction. This, in turn, allows identification and characterization of the polycrystalline materials obtained by the grinding process. These solid-solid processes imply molecular diffusion through the lattice and breaking and reassembling of hydrogen bonded networks and proton transfer from acid to base. For more details see the article by D. Braga, F. Grepioni et al. on p. 4362 ff.