Undecafluorodiarsenate Anion: Synthesis and Crystal Structure of (MeS)(2)CSH(+)As(2)F(11)(-)

Dimethyltrithiocarbonate reacts with the superacidic systems HF/MF(5) and DF/MF(5) (M = As, Sb) to form (MeS)(2)CSX(+)MF(6)(-) (X = H, D). With an excess of AsF(5) the reaction leads to (MeS)(2)CSX(+)As(2)F(11)(-) (X = H, D). The latter salt crystallizes in the monoclinic space group P2(1)/c (No. 14 with a = 7.687(1) Å, b = 21.327(6) Å, c = 8.704(1) Å, and beta = 91.99(1) degrees ) with four formula units per cell. The undecafluorodiarsenate anion contains an As-F-As bridge with two As-F bonds significantly longer than the nonbridging bonds and an As-F-As angle of 159.1(6) degrees. The Raman, IR, and (1)H, (75)As, (19)F, and (13)C NMR spectra of (MeS)(2)CSX(+)SbF(6)(-) and (MeS)(2)CSX(+)As(2)F(11)(-) (X = H, D) are reported.