Crystal structure of bis-(1-methyl-2-quinolone) hydrogen hexafluoroarsenate(V): a structure of pseudo-A-type involving a very short hydrogen bond

Abstract

This compound crystallises in space group P2₁/c with four molecules in the unit cell with a= 11·650, b= 16·036, c= 14·114 Å, β= 128·95°. Its structure has been determined and refined to R 11% for nearly 2000 observed, and non-zero, reflexions. It proves to contain the cation [QHQ]⁺ and the anion [AsF₆]^–, where Q is 1-methyl-2-quinolone. Though the cation is not crystallographically symmetrical, it deviates only slightly from strict symmetry, and the hydrogen bond between the two Q molecules has O ⋯ H ⋯ O 2·439 (±12)Å. The i.r. spectrum resembles those of acid salts, and some other similar crystals, whose hydrogen bonds are crystallographically symmetrical and which have been classified as of type A. The [AsF₆]^– ion is significantly distorted from a regularly octahedral shape; and this may be due to a fairly close approach of one fluorine atom to the centre of the [QHQ]⁺ ion.