Investigating the Coordination Chemistry of Tetrathiooxalate
Dr. William Polik and Dr. Amanda Eckermann
Transition metal complexes with bridging ligands containing sulfur and carbon are commonplace in molecular electronics. Tetrathiooxalate (C2S42-; tto) has redox properties which allow it to store electrons, which could provide useful functionality in molecular circuitry. To date, there are only a handful of molecular complexes with tto due to difficulties in synthesizing and utilizing this ligand. Our research investigates tto as a bridging ligand and alkylated derivatives of tto as terminal ligands. The reaction of tto with dichloro(p-cymene) ruthenium(II) dimer at low temperature gives insoluble green microcrystals which have been characterized by IR spectroscopy, SEM/EDS, and XRD. We believe that the insolubility may arise from the lability of the p-cymene ligands giving rise to polymers of ruthenium metal centers bridged by tto ligands. To find a solution to this issue, we have been investigating the trispyrazolylborate (Tp) ligand since it is negatively charged and might prove to be less labile. We have made attempts to coordinate the Tp ligand to Co(II), and future work will involve trying to bridge two Co(II) centers with tto. Alkylation of tto with hexyl bromide and benzyl bromide results in a mixture of products. The NMR spectra of the purified products revealed unexpected anisotropies, which were hypothesized to be due to the formation of cis/trans conformers. Coordinate scans for dimethyltetrathiooxalate using the Gaussian computational engine do not support this hypothesis. A competing alternative hypothesis is that a hetero Diels-Alder dimerization reaction produces multiple constitutional isomers.
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