Sulfonium Ions with Other Heteroligands

Hydroxy- and Alkoxysulfonium Ions. In addition to the well-documented formation of the S02-SbFs complex in a mixture of the two components,227 Minkwitz and co-workers228 have recently detected the formation of the fluorodihydroxysulfonium cation 83 [Eq. (4.61)]. Crystal structure analysis of the isolated salt showed bond distances typical of S—O single bonds (1.537 and 1.522 A) and S—F single bonds (1.547 A). The steric demand of the lone electron pair of sulfur results in the compression of bond angles from the ideal tetrahedral arrangement 

Dimethoxyfluorosulfonium ion 84 has been generated from methylfluorosulfite by methylation with CH3F under superacidic conditions236 [Eq. (4.63)]. A similar 

Minkwitz and Molsbeck23 8 have performed (3-methylation of various sulfoxides to obtain the corresponding methoxysulfonium ions [Eq. (4.64)] and also reported their spectroscopic characterization (Raman and H, 13C, and 19F NMR). 

Shine and co-workers239,240 have reported the synthesis and full NMR characterization of a series of alkoxysulfonium ion perchlorates including ions 85 derived from cis- and fraws-substituted cyclohexanols. The X-ray structural study of four salts showed that the orientation of the S O bond is always pseudoaxial. The optically active (—)-86 ion and similar systems have been synthesized.241 1H and 13C NMR measurements indicate that sulfur has a trigonal bipyramidal geometry due to the S—O intramolecular interaction in the axial position. 

Sulfonium Ions with Nitrogen Ligands. Long-lived aminofluorosulfonium ions have been prepared by ionization under superacidic conditions242 243 [Eq. (4.65)]. The stereochemistry of ion Me2NSF2+ was studied by dynamic 1H NMR spectroscopy 

---