Donor properties of triphenylantimony dihalides : preparation and crystal structures of Ph3SbCl2·SbCl3 and [Ph3SbCl][SbCl6]

Abstract

Triphenylantimony dichloride reacts with both antimony(III) and antimony(V) chloride to give addition compounds with the stoicheiometry Ph₃SbCl₂·SbCl₃ and Ph₃SbCl₂·SbCl₅, respectively. X-Ray analysis of the former shows the presence of only weak interactions between the axial chlorine atoms of Ph₃SbCl₂ and adjacent SbCl₃ molecules to give polymeric chains parallel to the a axis. The trigonal bipyramidal geometry of Ph₃SbCl₂ is little changed; co-ordination about Sb^III is square pyramidal with three short (mean 2.337 Å) and two long (mean 3.262 Å) distances. In the SbCl₅ compound there is a chloride ion transfer to SbCl₅ giving a structure best described in terms of the ionic formulation [Ph₃SbCl]⁺[SbCl₆]^–. Residual anion–cation interaction is shown by a Cl ⋯ Sb contact of 3.231 Å, and the cation geometry is intermediate between the trigonal pyramidal and tetrahedral extremes. Reactions between Ph₃SbX₂(X = F, Br, or I) and SbCl₃, SbBr₃, or SbCl₅ are also described.