From ferrocenyl selenoesters to diferrocenyl methanols

Abstract

The reaction of FcSeSiMe3 (Fc = Fe(η5-C5H5)(η5-C5H4)) (1) with equimolar amounts of the acid chlorides Cl(O)C-2-cC4H3X (2a, X = O; 2b, X = NMe) gave the ferrocenyl selenoesters FcSe(C(O)-2-cC4H3X) (3a, X = O; 3b, X = NMe). Upon exposure to silica gel compounds both 3a and 3b underwent an intermolecular conversion followed by transesterification with the silica surface to afford diferrocenyl methanols Fc2C(OH)(2-cC4H3X) (4a, X = O; 4b, X = NMe). Compounds 3a, 3b, 4a and 4b have been characterized by elemental analysis, IR and NMR (1H, 13C{1H}, 77Se{1H}) spectroscopy and ESI-TOF mass spectrometry (4a and 4b). The molecular structures of 3a, 4a and 4b in the solid state were determined by single crystal X-ray diffraction studies. The electrochemical studies exhibit for 3a and 3b reversible one-electron Fc/Fc+ redox processes. During the electrochemical investigations of 4a and 4b two well-separated one-electron redox events could be determined (4a, ΔE0’ = 330 mV; 4b, 367 mV). UV-Vis/NIR spectroelectrochemical studies on 4a and 4b reveal a weak electronic coupling between the iron centers in the corresponding mixed-valent species of [4a]+ and [4b]+ according to Robin and Day classification.