The Reaction of Bunsen's Cacodyl Disulfide, Me2As(S)-S-AsMe2, with Iodine: Preparation and Properties of Dimethylarsinosulfenyl Iodide, Me2As-S-I†

Bunsen's cacodyl disulfide, Me2As(S)-S-AsMe2 (1), reacted with iodine giving the novel dimethylarsinosulfenyl iodide, Me2As-S-I (3) although theoretical calculations indicated that the AsV compound Me2As(S)-I (4) was more stable in the gas phase. The oily product was stable neat and as a solution in CDCl3 at +4 °C and –20 °C for at least 15 d. Light, H2O, H2O2, and Zn dust, but not NaI or Ag, decomposed it. Compound 3 did not interact with Ph3N, with Ph2NH and PhNH2 it interacted but not reacted. 3 was decomposed by piperidine, with pyridine and 4-dimethylaminopyridine it interacted and produced Me2As-SS-AsMe2 (2) and I2 that formed charge transfer complexes Base·I2, whereas Et3N decomposed 3, and 3Et3N·2I2 was isolated. 3 was desulfurized by Ph3P and (Me2N)3P completely, and by (PhO)3P and (PhS)3P partially. The reactions of 3 with (Me2N)3P, (PhS)3P, and (EtO)3P were complicated. From the AsIII nucleophiles, only Ph3As was bound, while (PhS)3As reacted slowly in a complicated manner with 3. No interaction of 3 with MeOH or PhOH was observed but NaOH, Ag2O, and PhONa decomposed it. Thiophenol produced traces of Me2As-SPh (10) and sodium thiophenolate attacked mainly at AsIII of 3. Thus, externally stabilized sulfenium ions of the type Me2As-S-Nu+I– were not obtained.