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Synthesis and Electrochemical Investigations of [Ru(η 5 ‐Ferrocenyl‐Thiophene)(η 5 ‐C 5 R 5 )] + Sandwich Compounds
Author(s) -
Speck J. Matthäus,
Korb Marcus,
Hildebrandt Alexander,
Lang Heinrich
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201900121
Subject(s) - chemistry , thiophene , redox , moiety , electrochemistry , cyclopentadienyl complex , transition metal , electron transfer , medicinal chemistry , crystallography , stereochemistry , inorganic chemistry , electrode , catalysis , organic chemistry
The synthesis of [Ru(η 5 ‐2‐Fc‐3‐R 3 ‐4‐R 2 ‐5‐R 1 ‐ c C 4 S)(η 5 ‐C 5 R 5 )] + [PF 6 ] – (R = H, Me; R 1 –R 3 = H; R 1 = Me, R 2 = R 3 = H; R 1 –R 3 = Me; R 1 = Fc, R 2 = R 3 = OCH 2 CH 2 O; Fc = Fe(η 5 ‐C 5 H 4 )(η 5 ‐C 5 H 5 )) is reported with the aim of a better understanding of the influence of π ‐thiophene‐bonded transition metal units on the thermodynamic stabilities and charge transfer interactions of the resulting compounds and their oxidized intermediates. Within the electrochemical studies, reversible one‐electron Fe‐based redox events were found for the mono‐Fc Ru species, whereby the Fc/Fc + redox potential increases as the degree of methylation of the thiophene and the Ru‐cyclopentadienyl moiety decreases. For [Ru(η 5 ‐2,5‐Fc 2 ‐ c C 4 H 2 S)(η 5 ‐C 5 R 5 )] + [PF 6 ] – a hindered 2 nd Fc‐based electrode reaction was observed under “weak‐coordinating” conditions. Two separated Fc/Fc + redox events were detected by the use of stronger solvating solvents or (smaller) anions. With regard to the non complexed 2,5‐Fc 2 thiophenes, the thermodynamic stabilities of the appropriate mixed‐valent species decrease, when the thiophene is η 5 ‐coordinated to [Ru(η 5 ‐C 5 R 5 )] + . Contrary to the redox potential, the substitution of the [Ru(η 5 ‐C 5 R 5 )] + moiety does not have a major impact on the thermodynamic stabilities of the mixed‐valent species. The related decrease of electronic coupling between the Fc unit(s) via the thiophene in the corresponding oxidized states, could be verified during UV/Vis/NIR spectroelectrochemical studies.