Preparation, characterization, electrochemical studies and crystal structure determination of salicylaldehyde–aroylhydrazone, ferrocenyl–aroylhydrazone and salicylaldehyde–ferrocenoylhydrazone complexes of indium

The reaction of triethylindium with salicylaldehyde–aroylhydrazone, C6H4(o-OH)CHNNHC(O)C6H4X (X=p-H, p-OCH3, p-NO2, m-NO2, o-OH), yields the tetrahydrofuran (THF) adduct of (C14H9N2O2X)2InC2H5. With formylferrocenyl–aroylhydrazones C5H5FeC5H4CHNNHC(O)C6H4X (X=p-H, p-OCH3, p-NO2, m-NO2, p-Cl, o-Cl), the diethylindium–hydrazone complex, (C18H14N2OFeX)In(C2H5)2, was formed. With salicylaldehyde–ferrocenoylhydrazone, C6H4(o-OH)CHNNHC(O)C5H4FeC5H5, the monohydrazone complex (C18H15N2O2Fe)In(C2H5)2 tetrahydrofuran solvate was obtained. The crystal structures of the p-OCH3 derivatives of the first two series of complexes and of the ferrocenoylhydrazone derivative were determined. In the solid state, the three complexes are dimers, containing a set of seven, three and five fused rings, respectively. In every case, it was observed a symmetric anti arrangement of fused rings in relation to a central In2O2 four-membered ring, resulting in a configuration that resembles a chair. Cyclic voltammetric studies on the ferrocenylaroylhydrazone complexes revealed electron transference from the ferrocene group towards the indium atom, while for the salicilaldehyde–ferrocenoyl complex this was not observed.