Collect. Czech. Chem. Commun. 1993, 58, 1534-1547

Unique Dialkylsulfonio-Methylation of the 7,8-C2B9H12(-) Ion to the 9-R2S-CH2-7,8-C2B9H11 Zwitterions by Formaldehyde and Dialkyl Sulfides. General Synthesis of the Compounds 10-R2E-7,8-C2B9H11 (E = O, S)

Jaromír Plešek, Tomáš Jelínek, František Mareš and Stanislav Heřmánek

Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 250 68 Řež near Prague, Czech Republic


Dialkylsulfonio-methylation has been observed on the treatment of the 7,8-C2B9H12(-) ion with formaldehyde and dialkyl sulfides in aqueous acidic medium. Four zwitterions of the type 9-R2S-CH2-7,8-C2B9H11 were formed with dimethyl and diethyl sulfide, tetrahydrothiophene and thioxane. In contrast, dialkyl ethers (diethyl ether, tetrahydrofuran, dioxane) afforded low amounts of the 10-R2O-7,8-C2B9H11 zwitterions, with the carborane 4,5- C2B7H13 being the principal product. Using acetaldehyde instead of formaldehyde, moderate yields of the 10-R2O- and high yields of the 10-R2S-7,8-C2B9H11 derivatives were obtained. With tertiary amines, only corresponding ammonium salts precipitated. Possible reaction pathways for these transformations are discussed and compared with the specific degradation of the 7,8-C2B9H12(-) ion to the arachno-4,5- C2B7H13 carborane.