Palladium(II) and platinum(II) complexes of 2-hydroxy acetophenone N(4)-ethylthiosemicarbazone – crystal structure and description of bonding properties

Abstract

Reaction of H 2PtCl 4 and K 2PdCl 4 with 2-hydroxyacetophenone N(4)-ethylthiosemicarbazone, H 2Ap4Et, afforded [Pt(Ap4Et)(H 2Ap4Et)] and [Pd(Ap4Et)(H 2Ap4Et)]. Their crystal and molecular structures are reported and represent the first 1:2 thiosemicarbazone complexes with ligands having both different formal charge and denticity. The dianion, Ap4Et 2−, coordinates in a planar conformation to palladium(II) or platinum(II) via the phenolato O, imine N and thiolato S atoms, while the neutral molecule exhibits monodentate coordination by the thione S atom. Intra-, intermolecular hydrogen bonds and C–H⋯π contacts lead to aggregation and a supramolecular assembly. Electronic, IR, and NMR spectral data, as well as electrochemical measurements, are included. The p K a values of the poorly water soluble H 2Ap4Et were obtained spectrophotometrically in aqueous solutions of constant ionic strength.