The binding mode of 3-hydroxypyridine in complexes with zinc and nickel was investigated using data from the Cambridge Structural Database and Mercury programmes. In nickel complexes, 3-hydroxypyridine and pyridin-3-olate ions are terminal ligands coordinating only through one nitrogen atom. The central ions in polynuclear nickel complexes with 3-hydroxypyridine are connected by oxalate or azide ions. In mononuclear zinc complexes, 3-hydroxypyridine is also a terminal ligand coordinating through a nitrogen atom. Pyridin-3-one and pyridin-3-olate, the tautomeric and deprotonated forms of 3-hydroxypyridine, are bridging ligands in the polynuclear zinc complexes. Pyridin-3-one coordinates to two adjacent zinc ions via the oxygen atom only, while pyridin-3-olate coordinates to two zinc ions via the oxygen atom and to a third zinc ion via the nitrogen atom.
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