From ferrocenyl selenoesters to diferrocenyl methanols

The reaction of FcSeSiMe(3) (Fc = Fe(eta(5)-C5H5)(eta(5)-C5H4)) (1) with equimolar amounts of the acid chlorides Cl(O) C-2-(C4H3X)-C-c (2a, X = O; 2b, X = NMe) gave the ferrocenyl selenoesters FcSe(C(O)-2-(C4H3X)-C-c) (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 Fc(2)C(OH)(2-(C4H3X)-C-c) (4a, X = O; 4b, X = NMe). Compounds 3a, 3b, 4a and 4b have been characterized by elemental analysis, IR and NMR (H-1, C-13{H-1}, Se-77{H-1}) 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 Xray diffraction studies. The electrochemical studies exhibit for 3a and 3b reversible one-electron Fc/Fcthorn redox processes. During the electrochemical investigations of 4a and 4b two well-separated one-electron redox events could be determined (4a, Delta E0' = 330mV; 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] thorn and [4b] thorn according to Robin and Day classification. (c) 2018 Elsevier B.V. All rights reserved.