Phenoxo

Phenoxo refers to the phenoxide oxygen ligand derived from phenol, typically represented as the deprotonated phenol anion bound through the oxygen atom (for example, C6H5O−). In coordination chemistry, the term is used to describe the phenoxo group when it acts as a ligand to a metal center.

As a monoanionic, O-donor ligand, the phenoxo group commonly serves as a bridging connector that links two or more metal centers, forming dinuclear or polynuclear complexes. Phenoxo ligands can arise by deprotonation of phenol in the presence of a metal salt or by reaction of a metal-bound phenol with a base. The primary coordination mode is through the phenoxide oxygen, though the aromatic ring can participate in secondary interactions such as π-donor contacts in some structures.

The geometry and connectivity of phenoxo-containing complexes depend on the metal and substituents, and phenoxo ligands can support a range of coordination environments, including square planar and octahedral geometries, as well as more complex multinuclear arrangements. Phenoxo ligands are widely used in coordination chemistry research to model biological metal centers, study redox properties, and build metal-organic frameworks and various dinuclear or multinuclear assemblies.

Related terms include phenolate and phenoxide, which describe the deprotonated phenol form, and aryl oxido ligands when discussing oxygen-based ligand systems. In the literature, phenoxo is a common descriptor in reports of metal-phenolate chemistry and bridges within coordination polymers and supramolecular clusters.