Syntheses of THF solutions of SeX2 (X = Cl, Br) and a new route to selenium sulfides SenS8-n (n=1-5): X-ray crystal structures of SeCl2(tht)(2) and SeCl2 center dot tmtu

A simple and efficient synthesis of solutions of pure SeCl2 in THF or dioxa ne (ca. 0.4 M) at 23 degrees C was achieved by treatment of elemental selen ium with an equimolar amount of SO2Cl2. SeCl2 was characterized by Se-77 NM R and Raman spectra. SeCl2 forms 1:1 or 1:2 adducts with tetramethylthioure a (tmtu) or tetrahydrothiophene(tht), respectively. The crystal structure o f SeCl2 tmtu (1) reveals a T-shaped geometry [d(Se-Cl) = 2.443(4) Angstrom] with weak intramolecular Se ... Cl interactions [d(Se-Cl) = 3.276(4) Angst rom]. Crystals of 1 are triclinic, space group P (1) over bar, with a = 8.4 73(3) Angstrom, b = 9.236(3) Angstrom, c = 7.709(4) Angstrom, alpha = 109.9 0(3)degrees, beta = 92.26(4)degrees, gamma = 107.89(3)degrees, V = 532.9(4) Angstrom(3), and Z = 2. The complex SeCl2(tht)(2) (2) adopts a square plan ar geometry with d(Se-Cl) = 2.4149(8) Angstrom. Crystals of 2 are monoclini c, space group C2/c, with a 15.6784(8) Angstrom, b = 9.1678(4) Angstrom, c = 9.1246(4) Angstrom, beta = 110.892(2)degrees, V = 1225.3(1) Angstrom,(3) and Z = 4. The reaction of Ph3PS with SeCl2 gives Ph3PCl2 and a complex mix ture of selenium sulfides SenS8-n, (n = 1-5), which were identified by 77Se NMR. Halogen exchange between SeCl2 and Me3SiBr in THF yields thermally un stable SeBr2 (ca. 0.4 M) characterized by Se-77 NMR and Raman spectra.