Auf dem Wege zu einem stabilen germaethen > ge=c < 1: Sterisch überladene digermylsilylmethane tbu2six-cy(geme3) 2 und struktur der germaethenquelle tbu2sif-cli(geme3) 2 · 2thf

Nils Wiberg, Hae Sook Hwang-Park, Patrizia Mikulcik, Gerhard Müller

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Abstract

Sterically overloaded digermylsilylmethanes tBu2SiX-CY(GeMe3)2 (X = H, Me, F, Br; Y = H, Br, Li) 7-16 are accessible via tBu2SiH-CH(GeMe3)2 7 (from tBu2SiHF and LiCH(GeMe3)2). The compounds are distinguished by hindered rotation about the SiC single bond shown. 7-16 enter into many reactions: (i) electrophilic substitution of Y = H by Li started with MeLi/THF, or of Y = Li by Br, EMe3, R started with Br2, Me3SnCl, Me3GeCl, Me3SiO(CH2)4Cl, or of X - H by Br started with Br2; (ii) homophilic substitution of Y = Br by H started with tBu3SiNa; (iii) nucleophilic substitution of X = F, Br by R started with MeLi, nBuLi. The latter reactions are possible only when Y = Li, and probably proceed over the silaethen tBu2Si=C(GeMe3)2 as reaction intermediate. tBu2SiF-CLi(GeMe3)2, a potential precursor of the hitherto unknown germaethene Me2Ge=C(GeMe3)(SiMetBu2), forms an adduct Li(THF)+4 [tBu2SiF-C(GeMe3)2] in THF and an adduct tBu2SiF-CLi(GeMe3)2·2THF after evaporation of THF. The structure of the latter compound shows a distorted tetrahedral geometry of the central Si and C atom with the Li atom being bonded to the latter. In addition, Li is coordinated by two molecules of THF in a slightly distorted trigonal-planar geometry. A short F ··· Li contact is not observed. (Crystals of tBu2SiF-CLi(GeMe3)2·2THF are orthorhombic, space group Pca21, with a = 20.739(3), b = 16.185(5), c = 17.642(4) Å, V = 5921.4 Å3, Z= 8, Dcalc = 1.256 g cm-3. R = 0.057 for 527 refined parameters and 4144 observed data.) tBu2SiF-CLi(GeMe3)2·TMEDA is supposed to have a similar structure. tBu2SiH-CLi(GeMe3)2·OP(NMe2)3 and tBu2SiMe-CLi(GeMe3)2·OEt2 have different strutures.

Original languageGerman
Pages (from-to)239-253
Number of pages15
JournalJournal of Organometallic Chemistry
Volume511
Issue number1-2
DOIs
StatePublished - 5 Apr 1996
Externally publishedYes

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