Supersilylsilane R*SiX3: Darstellung, Charakterisierung und Strukturen; sterische und van-der-Waals Effekte der Substituenten X [1] / Supersilylsilanes R*SiX3: Syntheses, Characterization and Structures; Steric and van-der-Waals Effects of Substituents X [1]
-
Nils Wiberg
,
Wolfgang Niedermayer
Supersilylsilanes R*SiX3 (R* = supersilyl = SitBu3; X = H, Me, tBu, Ph, SiMe3, F, Cl, Br, I, OMe, OSO2CF3) are prepared (i) by reactions of supersilylhalosilanes with supersilyl sodium NaR* (Hal/R* exchange), (ii) by reactions of supersilylhalosilanes with hydride H- (Hal/H exchange), (iii) by reactions of supersilylsilanes with halogens Hal2 (H/Hal exchange, R*/Hal exchange), (iv) by reactions of supersilylhalosilanes with nucleophiles like F- , MeO- (Hal/F or Hal/OMe exchange) and (v) by reactions of supersilylsilanes with strong acids (H/OSO2CF3 exchange). NMR chemical shifts δ (29Si) of the SiX3 groups of R*SiX3 strongly depends on the nature of X. The supersilylsilanes R*SiX3 are in part moisture sensitive (especially compounds with SiX3≡SiHHal2 and SiH2Hal), in part sensitive against oxygen (compounds with SiX≡SiBr or SiI), and some of them react with supersilyl sodium by supersilanidation (for example R*SiF3, R*SiH2Cl, R*SiMeHCl) or by reduction (for example R*SiCl3, R*SiMeBr2, R*SiPhBrCl). X-ray structure analyses of disilanes tBu3Si-SiX3 with SiX3≡SitBu3, SiPh3, Sil3, SiPhCl2 show a staggered conformation. Due to steric repulsion of the tBu3Si and SiX3 groups as well as van-der-Waals attraction of the substituents tBu and X in tBu3Si-SiX3 the SiSi bonds are longer than 2.34 Å (the normal SiSi single bond length) and the torsion angles are smaller/larger than 60° (the ideal staggered conformation). From the extent of SiSi bond elongation and CSiSiX angle compression it is concluded that the bulkiness of X increases in direction Cl < I < Ph < SiMe3 < CMe3 (tBu3Si-SitBu3 has to date the longest SiSi bond of all disilanes) and the van-der-Waals forces between tBu/X increase in direction tBu/I < tBu/tBu < tBu/Ph.
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Articles in the same Issue
- Crystal and Molecular Structures of the Sulfurization and Selenation Products of Bis[bis(trimethylsilyl)amino]germanium(II). Crystal Structure of (Triphenylphosphine)gold(I) Bis(trimethylsilyl)amide
- New Diazasilaphosphetidines and their Precursors
- The Solid State Conformation of Diaryl Ditellurides and Diselenides: The Crystal and Molecular Structures of (C4H3E2)2E'2 (E = O, S; E' = Te, Se)
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- Synthesis and Characterization of Bromo- and Bromochloroplumbates(II). Crystal Structures of [Ph4E]2[Pb3Br8] (E = P, As) and [Ph4P][PbBrCl2] • CH3CN
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- Chemistry of Seven-Membered Heterocycles, VI. Synthesis of Novel Bicyclic Heterocyclic Compounds as Potential Anticancer and Anti-HIV Agents
- Crystal Structure and Properties of the Titanium Stannide Ti2Sn3
- Regeneration of Carbonyl Compounds from Oximes under Microwave Irradiation in Solventless System
- Umsetzung von N-Alkylpyridinium-Salzen mit Hydroxylamin / Reaction of N-Alkylpyridinium Salts with Hydroxylamine
- Enaminouraciles as Precursors for Synthesis of Pyrimido[4,5-a]pyrimidine- 2,4-diones
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