The coordination chemistry of pyridyl oximes

The coordination chemistry of pyridyl oximes is reviewed. Simple pyridyl oximes have the general formula (py)C(R)NOH, where py is a pyridyl group (2-, 3- or 4-) attached to the oxime carbon atom and R can be a donor or a non-donor group. There are also ligands containing more pyridyl and/or oxime groups. The coordination chemistry of twenty-three such ligands is described, including 2-acetylpyridine N-oxide oxime (which strictly speaking is not a pyridyl oxime) and of four polydentate ligands containing pyridyl groups that are not directly attached to the oxime carbon. References are given to methods for the synthesis of the ligands that are not available in the market. The coordination chemistry of each ligand with all metals is detailed, with emphasis being placed on structural features and physical properties (mainly magnetic) of the resulting metal complexes. This report shows that the anions of pyridyl oximes are versatile ligands for a variety of objectives/advantages, including μ2 and μ3 behavior, preparation of polynuclear complexes (clusters) and coordination polymers, mixed-metal chemistry and interesting magnetic characteristics. The activation of 2-pyridyl oximes by 3d-metal centers towards further reactions seems to be an emergent area of synthetic chemistry.

Graphical abstractThis paper reviews the coordination chemistry of pyridyl oximes. The immense structural diversity of the pyridyloximate complexes stems from the ability of these ligands to exhibit a great variety of coordination modes. The products range from simple mononuclear metal complexes to heterometallic clusters and polymeric metallosupramolecular arrays. Aspects of the activation of 2-pyridyl oximes by 3d-metal centers are also detailed.Figure optionsDownload full-size imageDownload as PowerPoint slide