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Thermally Robust Metal Coordination Polymers: The Cobalt, Nickel, and Zinc Pyrimidin-2-olate Derivatives

2000; Wiley; Volume: 2000; Issue: 12 Linguagem: Inglês

10.1002/1099-0682(200012)2000

1099-0682

Norberto Masciocchi, G. Attilio Ardizzoia, G. LaMonica, Angelo Maspero, Angelo Sironi,

Metal complexes synthesis and properties

A number of coordination polymers of the pymo ligand (Hpymo = 2-hydroxypyrimidine) have been prepared and fully characterized by chemical, spectroscopic, and thermal analyses. Their complete crystal structures have been solved ab initio from laboratory X-ray powder diffraction data and ultimately refined by the Rietveld method. The M(pymo)2 species (M = Co, Ni, Zn) consist of structurally related three-dimensional frameworks of very high thermal stability (decomposing under N2 only at T > 550 °C), with the metal atoms, linked by μ2-η1-η1 (N;N′) (Co, Zn) or μ2-η2-η1 (N,O;N′) bridges, about 5.4−5.7 Å apart. The hydrated species Ni(pymo)2(H2O)2.5 is based on a two-dimensional array of Ni(pymo)2 stoichiometry, containing both coordinated and clathrated water molecules, and can be selectively transformed into Ni(pymo)2 by thermal treatment, through an amorphous intermediate, recrystallizing at T > 315 °C. In contrast, one dimensional chains are found in the three hydrazine adducts, M(pymo)2(N2H4)2, which show unique bis(μ2-hydrazine) bridges (M···M ca. 4.0 Å) and terminally O-bonded pymo ligands.