Synthesis and characterization of dithiolene complexes of bismuth as green redox active catalysts

Abstract

Catalysts are essential in the majority of chemical reactions, allowing industrial processes to progress with increased efficiency, environmental sustainability and synthetic precision. Conventional catalysts employ transition metals that often have adverse effects on humans, terrestrial and aquatic organisms and ecosystems. Thus, the objective of this study is to develop an effective and environmentally sustainable catalytic complex that is capable of facilitating a two-electron transfer in complex reactions. Bismuth is a viable alternative and candidate for catalysis research as it is less toxic, environmentally benign, and relatively inexpensive. Bismuth, however, is predominantly stable in only the +3- oxidation state, indicative of its limited redox activity. As a remedy, redox active dithiolene ligands may be employed. This allows the metal complex to undergo electron transfer reactions without requiring a change in the oxidation state of the metal center. The goal of this project is to synthesize two molecular arylbismuth dithiolene complexes [ArBi(dithiolene)], electrochemically characterize their redox potential through cyclic voltammetry, and subsequently test their oxidative potential using diphenyl disulfide. Progress has been made towards the synthesis of the two target compounds [MesBi(L)] (1) and [(4-tBuC6H4)Bi(L)] (2) (L = cis-1,2-dicyano-1,2-ethylenedithiolate). By using a “onepot” synthesis, it is possible to avoid decomposition of the photo- and thermally sensitive RBiCl2 intermediates. Although the formation of both compounds has been suggested via NMR spectroscopy and FT-IR spectroscopy, further purification and characterization of both materials is required.