How common are true aminopyridinato complexes?

An overview over the binding situation in transition metal and lanthanide aminopyridinato complexes is given. True aminopyridinato complexes in which we observe a significant longer N-amido than N-pyridine bond length are rare and for instance observed for ruthenium. Additional examples of ruthenium aminopyridinato complexes were synthesized and characterized by X-ray crystal structure analysis.