Nonahalogenodiantimon(III)ates; their preparation and the crystal structures of [Hpy]3[Sb2Cl9], [NMe4]3[Sb2Br9], and [NMe4]3[Sb2Br3Cl6]

Abstract

Compounds of the type Y₃[Sb₂Br_nCl_9–n]{Y = Hpy [pyridinium(1+)], n= 0–9; Y = NMe₄⁺, n= 0,3,6, and 9; and Y = Cs⁺, n= 0,3,6, and 9} have been prepared by a variety of methods and investigated by i.r. and Raman spectroscopy, mass spectrometry, and X-ray single crystal and powder diffraction. Two further mixed halides [Hpy][SbCl₂X₂](X = Br or I) have also been isolated. Crystals of [Hpy]₃[Sb₂Cl₉] are monoclinic, space group C2/c, with a= 29.168(8), b= 10.178(5), c= 9.425(5), β= 106.70(1)°, and Z= 4. Crystals of [NMe₄]₃[Sb₂Br₉] and [NMe₄]₃[Sb₂Br₃Cl₆] are hexagonal, space group P6₃/mmc, Z= 2, with a= 9.499(4), c= 22.225(8)Å, and a= 9.341 (4), c= 22.038(9)Å respectively. The structure of [Hpy]₃[Sb₂Cl₉] has been refined to R= 0.037 for 1 975 observed reflections and shows a polymeric structure with three terminal and three bridging chlorine atoms similar to that of β-Cs₃[Sb₂Cl₉]. Refinement for the two tetramethylammonium salts (R= 0.140 for 385 and R= 0.115 for 408 observed reflections for the nona- and tri-bromides respectively) was very poor, probably as a consequence of disorder in the necessarily high symmetry of the space group but both show clearly confacial bioctahedral structures. In the mixed halide, the bridging positions are occupied by the bromine atoms.