oxygendonor

An oxygen donor, in coordination chemistry, refers to a ligand that donates electron density to a metal center through one or more oxygen atoms. Oxygen donors can be neutral or anionic and may coordinate as a monodentate ligand via a single oxygen or as a multidentate chelate through two or more oxygen atoms. They are commonly classified by their donor atom as O-donor ligands and are often considered hard bases in the hard-soft acid-base framework, preferring bonding to harder metal centers.

Common examples of oxygen-donor ligands include water (H2O), alcohols (ROH), and ethers (ROR′), which typically bind in a one-to-one fashion, though their binding can be labile and influenced by solvent and pH. Anionic oxygen donors include carboxylates (RCO2−), alkoxides (RO−), phenoxides (ArO−), and oxide ligands. Ligands containing multiple oxygen donor sites, such as β-diketonates (for example acetylacetonate, acac−) and polycarboxylates, can chelate a metal via two or more oxygens, often providing increased complex stability. Multidentate oxygen donors are important in spanning metal centers and shaping coordination geometry.

Applications and relevance of oxygen donors span catalysis, inorganic synthesis, and bioinorganic chemistry. They influence the electronic structure, geometry, and reactivity of metal complexes. The bond strength and lability of M–O interactions depend on the metal, the oxidation state, and the specific oxygen donor type; carboxylates and oxido/alkoxide donors typically form robust, often bridging, connections, while neutral donors like water can be more easily displaced or protonated.