Synthesis and characterisation of novel multidentate ferrocene ligands and their Re(I) and Pt(II) complexes

Two new multiply methylthio-substituted ferrocene ligands 1,1′,2-tris- and 1,1′,2,2′-tetrakis-(methylthio)ferrocene (TriMSF and TMSF, respectively), have been prepared by a simple, single-step procedure. Adjacent substitution of the cyclopentadienyl rings leads to potentially versatile multidentate ligands. The coordination chemistry of these ligands has been explored by reaction with labile Re(I) and Pt(II) metal centres to give complexes 1–4, featuring binding of one or two metal centres. The complexes have been characterised by 1H-NMR and infrared spectroscopies, mass spectrometry and microanalysis. The solid state structures of 1 and 3 have been determined, and show distorted octahedral environments about rhenium and out-of-plane folds of the five-membered chelate rings within the structures. The ligands TriMSF and TMSF exhibit the expected reversible one-electron oxidation of ferrocene molecules. The coordination of thioether substituents to the rhenium or to the platinum centres has a strong electronic impact on the redox ability of the respective complexes, resulting in ferrocene oxidation being more difficult by about 0.3–0.5 V, but it does not compromise the chemical reversibility of the respective ferrocene/ferrocenium redox changes.