Synthesis and characterisation of new arsonium salts and crystal structures of trimethylarsonium undecafluorodiarsenate (CH3)(3)AsH+As2F11- and trimethylarsonium hexafluoroantimonate (CH3)(3)AsH+SbF6-

The reaction of trimethylarsane in the superacidic systems hydrogen/fluorid e antimony pentafluoride and hydrogen fluoride/arsenic pentafluoride leads to trimethylarsonium fluorometallates. These salts are stable up to 60 degr ees C and 5 degrees C, respectively. Structures were successfully elucidate d in the cases of trimethylarsonium undecafluorodiarsenate and trimethylars onium hexafluoroantimonate. (CH3)(3)AsH+As2F11- crystallizes in the monocli nic space group P2(1)/n with four formula units per unit cell with the dime nsions a = 7.362(1), b = 12.589(1), c = 13.598(1) Angstrom and beta = 95.37 (1)degrees. (CH3)(3)AsH+SbF6- crystallizes in the monoclinic space group P2 (1)/m with four formula units per unit cell with the dimensions a! = 8.313( 1), b = 8.855(1), c = 13.285(1) Angstrom and beta = 94.358(1)degrees.