Polarographic reduction of some mesoionic 2,3-diaryl-2 H-tetrazolium-5-thiolate compounds

The polarographic behaviour at the DME of 2,3-diphenyl-, 2,3-di(4-methylphenyl)- 2,3-di(3-chlorophenyl- and 2,3-di(2-chlorophenyl)-2 H-tetrazolium-5-thiolate compounds was investigated in 10% (v/v) aqueous methanol over a wide range of pH. The reduction proceeded through one four-electron irreversible wave to give the corresponding thiocarbazide. A mechanism for this reduction was proposed and subsequently substantiated by a controlled potential electrolysis of a mesoionic compound whereby the identify of the final reduction product has been proved spectrophotometrically to be the thiocarbazide.