Showing papers by "Guillermo Mínguez Espallargas published in 2006"

Reversible extrusion and uptake of HCl molecules by crystalline solids involving coordination bond cleavage and formation.

Abstract: Yellow crystalline salts (3-XpyH)2[CuCl4] (3-XpyH = 3-halopyridinium, X = Cl, Br) lose HCl upon exposure to air in an open vessel, yielding quantitatively blue crystalline coordination compounds [CuCl2(3-Xpy)2]. The reaction is prevented if the vessel is sealed, but can be driven forward under such conditions by providing a trapping agent for HCl, such as an aqueous solution of AgNO3. The reaction requires cleavage of Cu-Cl and N-H bonds and formation of Cu-N bonds. The metal coordination geometry also changes from distorted tetrahedral to square planar. Remarkably, the reaction is fully reversible upon exposure of the blue coordination compound to vapor from a concentrated aqueous solution of HCl, and the initial yellow crystalline salt results. The structural changes occurring in these reactions have been followed by X-ray powder diffraction, including Rietveld refinement, of the crystal structures.

Unexpected structural homologies involving hydrogen-bonded and halogen-bonded networks in halopyridinium halometallate salts

Abstract: The synthesis and crystal structures of three halopyridinium halometallate salts are reported. (4-ClpyH)2[PdCl4] (1) and (4-ClpyH)2[Cu3Cl8] (2) adopt tape structures closely resembling a series of hydrogen-bonded structures that contain either dications such as 4,4-bipyridinium or their supramolecular analogues. This requires a short interaction between cations via a symmetric C–Cl⋯Cl–C arrangement that is most probably repulsive. The third compound, (4-BrpyH)2[PtCl6] (3), forms a 3-D network structure that involves not only bifurcated N–H⋯[Cl(Pt)]2 hydrogen bonds but also uncommon bifurcated C–Br⋯[Cl(Pt)]2 halogen bonds. This set of structures provides unanticipated extensions to established homologous series of hydrogen-bonded halometallate salts.