Syntheses and electrical resistivities of TTF and TSF salts with tris(oxalato)silicate, -germanate, and -stannate

Abstract

Several tetrathiafulvalene (TTF) and tetraselenafulvalene (TSF) salts of tris(oxalato)silicate, -germanate, and -stannate, (TTF) x[X(C 2O 4) 3]·nCH 3CN (x = 2 and n = 0.5 for M = Si and Ge, and x = 2.8 and n = 0 for M = Sn) and (TSF) 2[M(C 2O 4) 3· nCH 3CN (n 0 for M = Si, Sn and n = 0.5 for M = Ge), have been prepared by the reaction of (TTF) 3(BF 4) 2 or (TSF) 3(BF 4) 2 with [R 4N] 2[M(C 2O 4) 3] (R = Et or n-Bu) in acetornitrile. Electrocrystallization for the TTF[Et 4N] 2[Sn(C 2O 4) 3] and TSF[Et 4N] 2[Ge(C 2O 4) 3] systems in acetonitrile afforded (TTF) 2.8[Sn(C 2O 4) 3]·0.5SH 3CN and (TSF) 2[Ge(C 2O 4) 3], respectively. Electrical resistivities of the TTF salts as compacted samples at 25°C fall in the range 10 4–10 5 Ω cm and those of the TSF salts in the range 10 3–10 4 Ω cm. Electronic reflectance spectra of the TTF and TSF salts show bands at 13 30013 600 cm −1 and 11 40012 500 cm −1 due respectively to the (TTF ???) 2 and (TSF ???) 2 dimers. In addition, (TTF) 2.8[Sn(C 2O 4) 3 exhibited a band at 8900 cm −1, ascribed to a charge transfer transition between neutral TTF and the TTF ??? radical cation. All the salts display weakly diamegnetic properties, consistent with the appearance of anisotropic weak ESR signals attributable to the TTF ??? and TSF ??? radical cations.