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  • Synthesis, structure and ca...
    Karmakar, Anirban; Hazra, Susanta; Guedes da Silva, M Fátima C; Pombeiro, Armando J L

    Dalton transactions : an international journal of inorganic chemistry, 01/2015, Letnik: 44, Številka: 1
    Journal Article

    Hydrothermal reactions of a lead(II) salt with 3-aminopyrazine-2-carboxylic acid (HL1) gave rise to a series of lead(II) coordination compounds (1–6) having zero, one, two and three dimensional structures. X-ray diffraction structural analyses reveal that complexes Pb(L1)22 (1) and Pb(L1)(OCHNH2)(η-OCHO)2 (2) possess dinuclear structures, containing a centre of symmetry. Complexes Pb2(L1)4(NHMeCHO)2n (3) and Pb2(L1)4n·(H2O)n·(2.5DMF)n (4) have 1D chain like structures, and Pb5(L1)7(η-NO3)(μ-HCOO)(η-HCOO)n·(DMF)n·(MeOH)n (5) shows a 2D sheet like structure constructed by the Pb5O5(HCOO) cluster and 3-aminopyrazine-2-carboxylate anions. The hydrothermal reaction of lead(II) nitrate with HL1 in DMF led to in situ formation of 3,3′-(methylenebis(azanediyl))bis(pyrazine-2-carboxylic acid) H2L2 which produces the 3D framework Pb2(L2)2n·(2DMF)n·(H2O)n (6). The L1(−) and L2(2−) ligands bind the metal cations by means of a pyrazine N-atom and one, or both, carboxylate O-atoms. The carboxylate group of L1(−) presents a diversity of coordination modes, viz., monodentate (1 and 3), bridging μ2 (3) and bridging μ3 (4), monodentate bridging μ2 (1, 2, 4, 5 and 6) and bridging chelate μ2 (5). The carboxylate moiety of L2(2−) in 6 binds the metal in a bridging μ2 fashion. The Pb(II) ions display coordination numbers from 5 to 8 with hemi- or holodirected coordination environments. The Pb(II) complexes act as heterogeneous catalysts for the cyanosilylation reaction, at 15 °C, of different aldehydes with trimethylsilyl cyanide (TMSCN) and can be recycled at least three times without losing activity.