Synthesis, characterization and crystal structure of the tridentate metalloligand formed from mono-condensation of ferrocenoylacetone and 1,2-phenylenediamine

Reaction of the ferrocenoylacetone 1 with o-phenylenediamine in refluxing dry toluene affords the new air and thermally stable organometallic tridentate compound (“half unit”) 2, which was isolated and characterized by elemental analysis, IR, UV–visible, 1H and 13C NMR spectroscopy and, in addition, authenticated by a single crystal X-ray diffraction analysis. In solution, the metalloligand 2 exists as a mixture of two tautomeric isomers: a keto-amine or enaminone form (60%), CpFe(η5-C5H4)–C(O)CHC(CH3)N(H)-o-C6H4NH2 (Cp = η5-C5H5), and a keto-imine or iminone form (40%), CpFe(η5-C5H4)–C(O)CH2C(CH3)N-o-C6H4NH2, whereas only the enaminone form is found in the solid state. The structure of 2 is stabilized by a network of intra- and intermolecular hydrogen bonds involving N–H, NH2 and CO groups.