ja991147x_si_002.pdf (1.05 MB)
The First Kinetically Stabilized Germanethiones and Germaneselones: Syntheses, Structures, and Reactivities
journal contribution
posted on 1999-09-08, 00:00 authored by Tsuyoshi Matsumoto, Norihiro Tokitoh, Renji OkazakiThe first kinetically stabilized germanethiones (germanium−sulfur double-bond species) and
germaneselones (germanium−selenium double-bond species) were synthesized. Dechalcogenation of the novel
1,2,3,4,5-tetrachalcogenagermolane Tbt(Tip)GeX4 (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Tip =
2,4,6-triisopropylphenyl, X = S or Se) with 3 molar equiv of triphenylphosphine gave diaryl-substituted
germanethione Tbt(Tip)GeS 1a and germaneselone Tbt(Tip)GeSe 2a as orange−yellow crystals and red
crystals, respectively, which were unstable in air but thermally quite stable. Chalcogenation of germylene
Tbt(Dis)Ge: resulted in the isolation of the corresponding germanethione Tbt(Dis)GeS 1b and germaneselone
Tbt(Dis)GeSe 2b (Dis = bis(trimethylsilyl)methyl). The molecular structures of germanethione 1a and
germaneselones 2a,b determined by X-ray crystallographic analysis indicate that they have trigonal planar
geometies around the germanium atom and a remarkably shorter Ge−S (2.049(3) Å for 1a) or Ge−Se bond
lengths (2.180(2) Å for 2a and 2.173(3) Å for 2b), compared with that of typical single bonds. The double-bond characters are also reflected in their spectral data such as UV/vis (1a, 450 nm; 1b, 432 nm; 2a, 519 nm;
2b, 492 nm), Raman (1a, 521 cm-1; 1b, 512 cm-1; 2a, 381 cm-1; 2b, 386 cm-1), and 77Se NMR (2a, 941
ppm; 2b, 872 ppm). The germanethiones and germaneselones underwent [2 + 2] (with phenyl isothiocyanate),
[3 + 2] (with mesitonitrile oxide), and [4 + 2] cycloadditions (with 1,3-dienes) to give the corresponding
adducts in high yields. The regioselectivities of the [4 + 2] cycloadditions were examined using unsymmetrical
dienes such as isoprene and interpreted in terms of the interaction between LUMO of the GeX unit and
HOMO of the diene part.