BIS(HALODIPHENYLSTANNYL)ALKANES AS BIDENTATE LEWIS-ACIDS TOWARD HALIDE-IONS

Sn-119 and F-19 NMR spectroscopies were used to study reaction of bis( halodiphenylstannyl)alkanes (Ph(2)XSn)(2)(CH2)(n) (X = F, Cl, Br, I; n = 1, 2, 3) with various halide ions in dichloromethane solution. Ah t hree series of bis(halodiphenylstannyl)alkanes, (Ph(2)XSn)(2)-(CH2)(n) (X = F, Cl, Br, I; n = 1, 2, 3), exhibit chelate ability toward halid e, forming anionic 1:1 adducts [(Ph(2)XSn)(2)(CH2)(n)X](-) which are s tatic at -100 degrees C on the NMR time scale. The bis(halodiphenystan nyl) alkanes always preferentially chelate fluoride ion over chloride or bromide. Endocyclic Sn-CH2 rotation brings about intramolecular exc hange between bridging and terminal fluorine atoms at higher temperatu re. For n = 1, and 1:1 adducts [(Ph(2)XSn)(2)(CH2)X](-) react with add itional fluoride (but not chloride or bromide) eventually to give [(Ph (2)F(2)Sn)(2)(CH2)(2)](2-) in which both tin atoms are five-coordinate d. For n = 2, the 1:1 adducts [(Ph(2)XSn)(2)(CH2)(2)X](-) appear parti cularly stable and there is no evidence for formation of 1:2 adducts [ (Ph(2)X(2)Sn)(2)(CH2)(2)](2-). Propylene-bridged 1:1 adducts, [(Ph(2)X Sn)(2)(CH2)(3)X](-), react with both fluoride and chloride to give 1:2 adducts, [(Ph(2)F(2)Sn)(2)(CH2)(3)](2-) and [(Ph(2)Cl(2)Sn)(2)(CH2)(3 )](2-), respectively, in which the tin atoms remain five-coordinated. The crystal structures of [(Ph(2)FSn)(2)CH2F](-) (1), [(Ph(2)BrSn)(2)C H2F](-) (4), [(Ph(2)ISn)(2)CH2F](-) (8), and [(Ph(2)ClSnCH(2))(2)F](-) (11), as their tetraethylammonium salts (la, 4a, 8a, and 11a, respect ively), are described. Colorless crystals of la are monoclinic, space group P2(1)/n, with a = 11.695(4) Angstrom, b = 14.667(2) Angstrom, c = 18.956(2) Angstrom, beta = 103.33(1)degrees, V = 3164(1) Angstrom(3) and Z = 4. Colorless crystals of 4a are monoclinic, space group Cc wi th a = 11.758(1) Angstrom, b = 14.880(2) Angstrom, c = 19.316(2) Angst rom, beta = 93.981(9)degrees, V = 3371.3(6) Angstrom(3), and Z = 4. Co lorless crystals of 8a are monoclinic, space group P2(1)/n, with a = 1 0.032(1) Angstrom, b = 16.993(3) Angstrom, c = 20.523(3) Angstrom, bet a = 99.65(1)degrees, V = 3434.9(8) Angstrom(3), and Z = 4, Colorless c rystals of 11a are monoclinic, space group P2(1), with a = 9.562(2) An gstrom, b = 15.529(4) Angstrom, c = 11.359(4) Angstrom, beta = 95.51(2 )degrees, V = 1678.9(9) Angstrom(3), and Z = 2. The structures were re fined to final R = 0.027, 0.029, 0.033, and 0.029 for 4661, 2647, 3843 , and 3457 reflections with I greater than or equal to 3.0 sigma(I), r espectively.