The relatively thermally stable adduct Cl3AsO . AsF5 1 is prepared in
high yield from AsCl4+AsF6- and Me(3)SiOSiMe(3) in liquid SO2 at -40 d
egrees C, and originally surprisingly isolated from the reaction of Pr
Cl3 and AgAsF6 in liquid SO2; the X-ray crystal structure of 1 is comp
ared with that of Cl3PO . AsF5.