Crystal structure of dicaesium octa-µ3-chloro-hexachloro-octahedro-hexa-tungstate(II) and -molybdate(II) complexes

Abstract

The crystal structures of the title compounds have been determined from single-crystal photographic X-ray diffraction data by Patterson and Fourier techniques, and refined by block-diagonal least-squares methods. Cs₂[(W₆Cl₈)Br₆] : trigonal, P31c, a= 10·07 ± 0·03, c= 14·75 ± 0·01 Å; Z= 2; R= 0·11 for 665 observed reflections. Cs₂[(Mo₆Cl₈)Br₆] : trigonal, P31c, a= 10·06 ± 0·02, c= 14·70 ± 0·01 Å, Z= 2; R 0·12 for 598 observed reflections. The anion consists of an octahedral cluster of metal atoms with the chlorine atoms bridging the octahedral faces and the bromine atoms axially co-ordinated to the M₆ core. The mean metal–metal distances are W–W 2·620 ± 0·007 and Mo^–Mo 2·615 ± 0·006 Å. Other bonding distances are as expected. Implications of the structure concerning the vibrational spectrum are discussed. Cell dimensions are given for the range of isomorphous complexes Cs₂[(M₆Cl₈)Y₆], M = Mo or W; Y = Cl, Br, or I.