Preparation and properties of tetrathiafulvalene (ttf) and tetramethyltetraselenafulvalene salts of tin(IV) halide anions and X-ray crystal structure of [ttf]3[SnCl6]

Abstract

Tetrathiafulvalene (ttf) reacts with SnX₄(X = Cl or Br) in MeCN to give [ttf]₂[SnX₆]. The corresponding tetramethyltetraselenafulvalene (tmtsf) salt also is obtained as an acetonitrile solvate, [tmtsf]₂[SnCl₆]·MeCN, by the reaction of tmtsf with SnCl₄ in MeCN. On the other hand, electrocrystallization of ttf and tmtsf in the presence of SnX₆^2–(X = Cl or Br) or [SnMe₂Cl₃]^– in MeCN or in CHCl₂CH₂Cl affords [ttf]₃[SnX₆], [ttf]₃[SnMe₂Cl₄], or [tmtsf][SnMe₂Cl₃]. Electrical resistivities of these salts as compacted samples fall in the range 1.6 × 10¹–9.9 × 10₄Ω cm at 25 °C. The stacking of the ttf and tmtsf moieties is discussed on the basis of electronic reflectance spectra. A single-crystal X-ray analysis of the salt [ttf]₃[SnCl₆] has revealed a layer structure consisting of ttf trimers. The tetragonal crystal, space group P4/mbm, has cell dimensions a= 11.807(1), c= 11.861(2)Å;, and Z= 2. Block-diagonal least-squares refinement, based on 876 independent reflections with |F_o| > 3σ(F), yielded an R factor of 0.040.