Diphenylarsenic (V) Oxide Chloride and the Crystal Structure of Dihydroxodiphenylarsonium Chloride

Diphenylarsenic (III) chloride can be oxidized with t-butyl hydroperoxide to a compound with the stoichiometry AsPh2OCl, which, on the basis of mass and IR spectroscopy, is thought to be a cyclic oligomer (AsPh2OCl)n where n = 3 or 4 although an AsPh2Cl2O (AsPh2O)2 OasPh2Cl2 tetramer containing a central As2O2 ring cannot be ruled out. Crystallization in the presence of traces of water yields a monohydrate, which x-ray diffraction shows is the salt [AsPh2(OH)2]Cl. (Space group P21/c, a = 8.617 (3), b = 13.890 (5), c = 11.146(3) Å, β = 107.69 (2)°; Z = 4, Dc = 1.56 g cm−3, 1842 observed reflections, final R = 0.033). The cation has slightly distorted tetrahedral geometry, and strong hydrogen bonds are formed between the chloride anion and hydroxo groups from two symmetry-related cations.