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(HOPO3)2] (2) (M(II) = Co; azolate = 5-(4-pyridyl)tetrazole or 4-Hpt; and anion = PO43− (1) and HPO42− (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 {HOPO3}2− tetrahedra to generate cobalt(II)-hydrogen phosphate layers, which are linked through the 4-pt ligands into the overall framework.

Graphical abstractHydrothermal reactions of a Co(II) salt, 5-(4-pyridyl)tetrazole and a phosphate source provided the three-dimensional materials [Co3(4-pt)3(PO4)] (1) and [Co3(H2O)4(4-pt)2(HOPO3)2] (2). A view in the ab-plane of the structure of 1 is shown.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Hydrothermal synthesis of Co(II)/pyridyltetrazolate/phosphate materials. ► Structural study of Co(II) phases with trinuclear secondary building units. ► Coordination modes of the 4-pyridyltetrazolate ligand. ► A novel variant of the {M3(μ3-O)(azolate)3} secondary building unit.