Some further studies of estertin compounds. Crystal structures of [NEt4][MeO2CCH2CH2Sn(dmio) 2] (dmio = 1,3-dithiole-2-one-4,5-dithiolato) and (MeO2CCH2CH2)2SnX2[X 2 = I2, (NCS)2 or Cl, Br]

Article abstract of DOI:10.1016/S0277-5387(97)00226-X

Estertin compounds, (MeO₂CCH₂CH₂)₂SnX₂ [X₂ = I₂ (2); X₂ = Br₂ (9); X₂ = Cl,Br (4); or X² = (NCS)₂ (3)] have been obtained by halide exchange reactions of (MeO₂CCH₂CH₂)₂SnCl₂. Crystal structure determinations of 2-4 revealed chelating MeO₂CCH₂CH₂ units with distorted octahedral geometries at tin. The Sn-O bond lengths in the isothiocyanato complex, 3, are shorter [2.390(11) to 2.498(12), mean 2.439 A], with the chelate bite angles, C-Sn-O, larger [74.3(7) to 78.2(6), mean 76.0°] than those in the halide analogues 2 and 4 [Sn-O = 2.519(2) to 2.541(8), mean 2.530 A; C-Sn-O 72.8(3) to 73.9(4), mean 73.3°]. ¹H, ¹³C and ¹¹⁹Sn NMR and IR spectra of 2-4 and 9 were determined in CDCl₃ solution: the NMR spectra of (MeO₂CCH₂CH₂)₂SnX₂ show the following trends: (i) both δ¹H_α and δ¹³C_α, increase and (ii) both ²J(Sn-H) and ¹J(Sn-C) decrease in the sequence X₂ = (NCS)₂, Cl₂, ClBr, Br₂ and I₂. The MeO₂CCH₂CH₂ and dmio groups (dmio = 1,3-dithiole-2-one-4,5-dithiolato) are all chelating groups in (MeO₂CCH₂CH₂)₂Sn(dmio) (5). As shown by X-ray crystallography, the tin atom in the anion of solid [Q][MeO₂CCH₂CH₂Sn(dmio)₂] 6 (Q = NEt₄) forms 5 strong bonds [to C and the 4 thiolato S atoms, Sn-S 2.459(2) to 2.559(2) A], arranged in a near trigonal bipyramidal array. There is an additional intramolecular, but weaker, interaction with the carbonyl oxygen atom [Sn-O = 3.111(5) A]; v(C=O) = 1714 cm^-1 in solid 6 (Q = NEt₄). NMR spectra of 5 and 6 are also reported.