Solid state coordination chemistry of metal-azolate compounds: Structural consequences of incorporation of phosphate components in the Co(II)/4-pyridyltetrazolate/phosphate system

The hydrothermal reactions of a cobalt(II) salt and 5-(4-pyridyl)tetrazole in the presence of phosphate provided two three-dimensional materials of the M(II)/azolate/anion family [Co₃(4-pt)₃(PO₄)] (1) and [Co₃(H₂O)₄(4-pt)₂(HOPO ₃)₂] (2) (M(II) = Co; azolate = 5-(4-pyridyl)tetrazole or 4-Hpt; and anion = PO₄^3- (1) and HPO₄ ^2- (2)). The structures are characterized by the incorporation of metal cluster secondary building units (SBU). The structure of 1 features a variant of the common {M₃(μ₃-O)} sbu with the central bridging ligand provided by a phosphate oxygen rather than the more common oxo- or hydroxy-ligand. These trinuclear units are bridged through the remaining phosphate oxygen donors into chains which are in turn linked through the pyridyltetrazolate ligands into the framework structure. In the case of compound 2, {Co₃(H₂O)₄}⁶⁺ linear trinuclear secondary building units are linked to four adjacent clusters through {HOPO ₃}^2- tetrahedra to generate cobalt(II)-hydrogen phosphate layers, which are linked through the 4-pt ligands into the overall framework.