Bidentate aryldichalcogenide complexes of [(diphosphino)ferrocene]palladium(II) and [(diphosphino)ferrocene]platinum(II). Synthesis, molecular structures and electrochemistry

A series of homochalcogenide and mixed-chalcogenide ligand complexes of palladium and platinum have been prepared from the reactions of Pd(dppf)Cl₂, (dppf = 1,1′-bis(diphenylphosphino)ferrocene), Pd(dippf)Cl₂ (1,1′-bis(diisopropylphosphino)ferrocene), and Pt(dppf)Cl₂ with 1,2-benzenedithiol (HSC₆H₄SH) (a), 3,4-toluenedithiol (HSC₆H₃MeSH) (b), 3,6-dichloro-1,2-benzenedithiol (HSC₆H₂Cl₂SH) (c), 2-mercaptophenol (HSC₆H₄OH) (d), thiosalicylic acid (HSC₆H₄CO₂H) (e) and thionicotinic acid (HSC₆H₃NCO₂H) (f). Single-crystal X-ray diffraction studies show that all complexes have distorted square-planar geometry. The complexes undergo two quasi-reversible or irreversible one-electron redox processes that involve the chalcogen ligands and diphosphinoferrocene ligands. The oxidation potentials of the chalcogen ligands increase when they bear electron-withdrawing substituents.