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, H-1 and C-13 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(eta(5)-C5H4)-C(O)CH=C(CH3)N(H)-o-C6H4NH2 (Cp = eta(5)-C5H5), and a keto-imine or iminone form (40%), CpFe(eta(5)-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 C=O groups. (C) 2007 Elsevier B.V. All rights reserved.