Far-infrared and Raman spectra of tetrahalogeno-complexes of arsenic(III), antimony(III), and bismuth(III)

Abstract

Tetra-alkylammonium salts of [MX₄]^– anions (M = As; X = Cl or Br; M = Sb or Bi; X = Cl, Br, or I) have been prepared and their low-frequency (<400 cm.^–1) i.r. and Raman spectra studied in the solid state (i.r. and Raman) and in solution (Raman). Excepting for solid [Et₄N][AsCl₄] and [Buⁿ₄N][SbI₄], the results point to distorted tetrahedral structures (C_2v symmetry) for the anions in both phases, arising from trigonal bipyramidal arrangements of electron pairs with a lone pair occupying an equatorial position.