Polysilane Dendrimers

Krempner, Clemens

doi:10.3390/polym4010408

Cited by 34 publications

(25 citation statements)

References 118 publications

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“…The NMR spectroscopic properties observed, and in particular the 29 Si and 119 Sn chemical shifts of 1 [37] and 2 (Table 1), are quite similar and completely within the range of what to expect [38,39]. …”

Section: Resultssupporting

confidence: 72%

Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

2017

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Molecules containing catenated heavy group 14 atoms are known to exhibit the interesting property of σ-bond electron delocalization. While this is well studied for oligo- and polysilanes the current paper addresses the UV-absorption properties of small tin containing oligosilanes in order to evaluate the effects of Sn–Si and Sn–Sn bonds as well as the results of substituent exchange from methyl to phenyl groups. The new stannasilanes were compared to previously investigated oligosilanes of equal chain lengths and substituent pattern. Replacing the central SiMe2 group in a pentasilane by a SnMe2 unit caused a bathochromic shift of the low-energy band (λmax = 260 nm) of 14 nm in the UV spectrum. If, instead of a SnMe2, a SnPh2 unit is incorporated, the bathochromic shift of 33 nm is substantially larger. Keeping the SnMe2 unit and replacing the two central silicon with tin atoms causes shift of the respective band (λ = 286 nm) some 26 nm to the red. A similar approach for hexasilanes where the model oligosilane [(Me3Si)3Si]2(SiMe2)2 (λmax = 253 nm) was modified in a way that the central tetramethyldisilanylene unit was exchanged for a tetraphenyldistannanylene caused a 50 nm bathochromic shift to a low-energy band with λmax = 303 nm.

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Section: Resultssupporting

confidence: 72%

Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

2017

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“…While 4-fold silylated silicon atoms typically resonate around −130 ppm, the incorporation of such units into cyclotetrasilanes is accompanied by a downfield shift of some 40 ppm. 998,999 The presence of strongly branched substituents 26 causes further downfield shift behavior, so that we assign the Si (SiMe 3 ) group in the central ring to the resonance at −69.7 ppm, whereas the Si (SiMe 3 ) 2 unit is associated with the resonance at −94.1 ppm.…”

Section: Resultsmentioning

confidence: 96%

Cyclic Disilylated and Digermylated Germylenes

et al. 2013

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The preparation of triethylphosphine adducts of cyclic disilylated or digermylated germylenes was achieved by reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with GeBr2·(dioxane) and PEt3. Phosphine abstraction with B(C6F5)3 allowed formation of the base-free germylenes, which undergo 1,2-trimethylsilyl shifts to the germylene atom to form the respective silagermene or digermene, which further dimerize in [2 + 2] cycloadditions to tricyclic compounds. The reasons responsible for the germylenes’ completely different reactivities in comparison to the previously studied analogous stannylenes and plumbylenes were elucidated in a theoretical study.

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“…The deshielded 29 Si NMR resonance and the size of the Si−H coupling constant ( J ) are characteristic of Si−H−Si linkages in silicon cations . In addition, the high‐field signal at δ ( 29 Si)=−127.7 ppm indicates the presence of tetrasilyl‐substituted silicon atoms . These distinctive 29 Si NMR spectroscopic features clearly rule out the targeted formation of the hydrogen‐substituted silyl cation 6 .…”

Section: Resultsmentioning

confidence: 98%

Cationic Si−H−Si Bridges in Polysilanes: Their Detection and Targeted Formation in Stable Ion Studies

Albers

Baumgartner

Marschner

et al. 2016

Chemistry A European J

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The ionization of 1,1‐dihydridocyclopentasilane 7 has been found to yield the cyclic polysilanylsilyl cation 8 instead of the expected hydrogen‐substituted silylium ion 6. The silyl cation 8 is stabilized by the formation of an intramolecular Si−H−Si bridge, which also provides the thermodynamic driving force for its formation. In general, the preference for the formation of Si−H−Si bridges can be used to scavenge and identify transient intermediates in the Lewis acid induced rearrangement of polysilanes. The validity of this concept has been demonstrated for one central step in this chemistry, the ring‐contraction reaction of cyclohexasilanes to form silylcyclopentasilanes.

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Polysilane Dendrimers

Cited by 34 publications

References 118 publications

Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

Cyclic Disilylated and Digermylated Germylenes

Cationic Si−H−Si Bridges in Polysilanes: Their Detection and Targeted Formation in Stable Ion Studies

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