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Rhodocenium Monocarboxylic Acid Hexafluoridophosphate and Its Derivatives: Synthesis, Spectroscopy, Structure, and Electrochemistry
Author(s) -
Jochriem Markus,
Casper Larissa A.,
Vanicek Stefan,
Petersen Dirk,
Kopacka Holger,
Wurst Klaus,
Müller Thomas,
Winter Rainer F.,
Bildstein Benno
Publication year - 2020
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.202000071
Subject(s) - chemistry , carboxylate , substituent , cyclopentadienyl complex , electrochemistry , amide , trimethylsilyl , metal , carboxylic acid , inorganic chemistry , combinatorial chemistry , medicinal chemistry , polymer chemistry , organic chemistry , electrode , catalysis
As an extension of our continuing work in metallocenium chemistry, we report here on new functionalized rhodocenium salts. In contrast to isoelectronic cobaltocenium compounds, rhodium as a 4d metal allows synthetic routes via prefunctionalized cyclopentadienyl half‐sandwich precursors, thereby facilitating access to monofunctionalized rhodocenium salts containing substituents comprising methyl, trimethylsilyl, carboxylate and carboxylate ester as well as amide derivatives. Synthetic aspects, scope and limitations, as well as spectroscopic ( 1 H/ 13 C‐NMR, IR, HR‐MS), and structural (XRD) properties are reported. Like the parent rhodocenium ion, all new derivatives undergo two chemically consecutive reductions at potentials that depend on the respective ring substituent. The second reduction competes with a rapid reaction of the corresponding rhodocenes to their 18 VE dimers. Rate constants for this process range from 2 × 10 3 s –1 to 2.5 × 10 5 s –1 as estimated from digital simulations of experimental voltammograms. Rhodocenium carboxylic acid ( 8 ) constitutes a special case in that proton instead of metal reduction is observed at Pt or Au electrodes.