Thermally robust metal coordination polymers: The cobalt, nickel, and zinc pyrimidin-2-olate derivatives

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 N-2 Only at T > 550 degreesC), with the metal atoms, linked by mu (2)-eta (1)-eta (1) (N;N') (Co, Zn) or mu (2)-eta (2)-eta (1) (N,O;N') bridges, about 5.4-5.7 Angstrom 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 degreesC. In contrast, one dimensional chains are found in the three hydrazine adducts, M(pymo)(2)(N2H4)(2), which show unique bis(mu (2)-hydrazine) bridges (M...M ca. 4.0 Angstrom) and terminally O-bonded pymo ligands.