Imidazolium dithiocarboxylates

Adducts of CS₂ to imidazol-2-ylidenes, N,N^′-dialkyl-4,5-dimethylimidazolium-2-dithio-carboxylates (alkyl = CH₃, C₂H₅, i-C₃H₇) are reduced to dianions (1,1-dithiolates) in a two-step process. The size of the alkyl ligands modulates the relative formal redox potentials of the two steps, leading to an inverted potential situation for the i-C₃H₇-derivative. In the latter case, the second reduction occurs at less negative potentials as the first one. The steric effect is explained by the structural changes occuring during reduction (arrangement of heterocyclic ring and CS₂ fragment changes from orthogonal to planar).

Coworkers in this project:

Stefan Dümmling

This project relied on a cooperation with Norbert Kuhn (Institut für Anorganische Chemie).

Oral presentations:

Bernd Speiser at the 59th ISE Annual Meeting, Sevilla/Spain, Sept. 7-12, 2008, keynote lecture

Publications from this project:

S. Dümmling, B. Speiser, N. Kuhn und G. Weyers, Acta Chem. Scand., 53, 876 - 886 (1999); Two-Electron-Transfer Redox Systems. Part 3. Electrochemical Reduction of N,N^′-Dialkyl-4,5-dimethylimidazolium-2-dithiocarboxylates to 1,1-Dithiolate Anions in THF. Steric Modulation of Potential Ordering by Substituents.

N. Kuhn, G. Weyers, S. Dümmling, und B. Speiser, Phosphorus, Sulfur, and Silicon 128, 45 - 62 (1997); Derivate des Imidazols. 25. Reduktion von Carben-Addukten des Kohlenstoffdisulfids: ein neuer Weg zu elektronenreichen 1,1-Dithiolaten.