SYNTHESES AND CHARACTERIZATION OF THE 1ST THALLIUM POLYSULFIDE ANIONS

The reaction of potassium tetrasulfide with thallium chloride in dimethylformamide (DMF) was investigated. The addition of the cations Ph4P+, Et4N+, and Me4N+ to this reaction afforded six new soluble thallium(I) polysulfide complexes, alpha-(Ph4P)2[Tl2(S4)2] (I), beta-(Ph4P)2[Tl2(S4)2].2DMF (II), beta'-(Ph4P)2[Tl2(S4)2].2DMF (III) gamma-(Ph4P)2-Tl2(S4)2].DMF (IV), (Et4N)2[Tl2(S4)2] (V), and (Me4N)2[Tl2(S4)2] (VI). Compound I (pale yellow platelets) crystallizes in the triclinic space group P1BAR (No. 2) with unit cell dimensions a = 9.907(3) angstrom, b = 11.014(3) angstrom, c = 12.794(4) angstrom, alpha = 71.05(3)degrees, beta = 87.33(3)degrees, gamma = 68.79(2)degrees, V = 1227(1) angstrom3 (at 23-degrees-C), and Z = 1. Single-crystal X-ray diffraction studies show that compounds II and III are isostructural and crystallize in the monoclinic space group P2(1)/c (No. 14). The unit cell dimensions of the pale orange crystals of II are a = 10.815(3) angstrom, b = 14.486(5) angstrom, c = 18.281(5) angstrom, beta = 97.29(3)degrees, V = 2841 (1)angstrom3 (at 23 OC), and Z = 2, and the unit cell dimensions of the deep red crystals of III are a = 10.810(5) angstrom, b = 14.480(8) angstrom, c = 18.294(7) angstrom, beta = 97.37(3)degrees, V = 2839(2) angstrom3 (at 23-degrees-C), and Z = 2. Compound IV (orange crystals) crystallizes in the monoclinic space group C2/c (No. 15) with unit cell dimensions a = 26.324(6) angstrom, b = 9.269(10) angstrom, c = 24.062(5) angstrom, beta = 117.36(1)degrees, V = 5213(4) angstrom3 (at -120-degrees-C), and Z = 4. Compound V (orange crystals) crystallizes in the monoclinic space group P2(1)/n (No. 14) with unit cell dimensions a = 11.880(10) angstrom, b = 17.202(6) angstrom, c = 7.200(6) angstrom, beta = 97.29(3)degrees, V = 1457(2) angstrom3 (at -100-degrees-C), and Z = 2. Compound VI (pale orange platelets) crystallizes in the triclinic space group P1BAR (No. 2) with unit cell dimensions a = 6.160(3) angstrom, b = 9.683(6) angstrom, c = 10.160(5) angstrom, alpha = 66.05(4)degrees, beta = 84.88(4)degrees, gamma - 80.64(4)degrees, V = 546(1) angstrom3 (at -100-degrees-C), and Z = 1. Surprisingly, all the complexes (I-VI) stabilize the same [Tl2(S4)2]2-anions. Despite their different colors II and III are structurally identical. The anion features two trigonal pyramidal Tl+ centers each chelated by a tetrasulfide ligand and the third coordination site is satisfied by bonding a terminal sulfur atom of another TlS4 unit, forming a dimer. This bonding mode of the S4(2-) ligands results in a new condensed inorganic ring system with a central, strictly planar, four-membered Tl2S2 rhombic unit and two five-membered TlS4 rings in an envelope configuration. The envelope configuration of the five membered TlS4 ring in the [Tl2(S4)2]2- anions results in either the boat-boat or the chair-chair conformation. The reaction of potassium tetrasulfide with thallium chloride in acetonitrile afforded orange red crystals of K0.68Tl1.32S5 (VII). Compound (VII) crystallizes in the orthorhombic space group P2(1)2(1)2(1) (No. 19) with unit cell dimensions of a = 6.630(4) angstrom, b = 16.989(6) angstrom, c = 6.499(2) angstrom, V = 727(1) angstrom3, and Z = 4. Compound VII is isostructural to the known K2S5 and Tl2S5 and consists of a S5(2-) chain with Tl+ and K+ as charge-compensating cations. VII can be considered as a solid solution of the two known compounds. All complexes show similar UV/vis spectra in DMF with two absorptions at approximately 432 and approximately 617 nm. The solid-state far-IR spectra of all compounds exhibit strong absorptions in the 500-100-cm-1 region due to the S-S and M-S stretching frequencies; tentative assignments are reported.