Low valent palladium benzoquinone complexes bearing different spectator ligands. The versatile coordinative capability of benzoquinone

The synthesis of some benzoquinone palladium complexes bearing different spectator ligands was carried out and the hapticity of the coordinated olefin was inferred from the features of their 1H and 13C NMR spectra. It was shown that benzoquinone coordinates either η2 and η4 and that its coordinative choice is not easily predictable, although the η2 coordination seems to be predominant in the presence of rigid ancillary ligands. The coordinative capability of benzoquinone was tested by means of thermodynamic and kinetic reference reactions and its slightly enhanced inertness with respect to the isofunctional naphthoquinone was assessed. Finally, the re-crystallization by slow diffusion at low temperature of diethylether in a dichloromethane solution of the complex [Pd(η2-bq)(TTbQ-Me)] (bq = benzoquinone, TTbQMe = 8-t-Butylsulfanyl-2-methyl-quinoline) allows the separation of the dimer [Pd2(η2-bq)(TTbQ-Me)2] whose solid state structure was resolved.