Die Herstellung von Reinstsiliciumscheiben: Mehr Chemie als man glaubt

The synthesis, structure, and reactivity of the first silylene-functionalized N-heterocyclic carbene (Si-NHC), {(L )Si}(L ), (3) (L =PhC(NtBu) , L =CCH(CNAr) C:, Ar=2,6-diisopropylphenyl) are reported. The ditopic carbanionic-NHC (dc-NHC), [Li(L )] (1) reacts with the monochlorosilylene (L )SiCl (2) to afford 3. The HOMO of 3 is the silylene lone-pair orbital, whereas the HOMO-1 is located at the carbene carbon atom. Both Si and C functionalities of 3 undergo reactions with chalcogens to give heavier ketone derivatives {(L )Si(E)}L (E) (E=S, 4; Se, 5; and Te, 6). Compounds 4-6 feature a highly polarized Si -E bond with a formal charge of -0.72 (4), -0.64 (5), and -0.50 e (6) on the E atom. The Wiberg bond indices of 1.64 (4), 1.66 (5), and 1.63 (6) for the Si-E bond however indicate a moderate p -p interaction between Si and E atoms. Compound 3 functions as a reducing agent and induces disproportionation of Si Cl to yield the silyl-functionalized NHC, {(L )SiCl }(L ) (7). Treatment of 3 with HSiCl leads to the formation of the silyl-functionalized imidazolium salt [{(L )SiCl }(L H)]Cl (8). The silylene moiety of 3 readily forms the iridium-silylene complex [{(L )(L )Si}Ir(cod)Cl] (9) featuring a free NHC ligand on treatment with [Ir(cod)(μ-Cl)] .

Section: Resultsmentioning

confidence: 99%

Silylene‐Functionalized N‐Heterocyclic Carbene (Si−NHC)

Rottschäfer

Blomeyer

Neumann

et al. 2017

“…While trichlorosilane and monosilane are produced on a large scale and are relatively cheap, higher silanes need to be synthesized beforehand, sometimes at great expense. Some disilanes, such as hexachlorodisilane, pentachlorodisilane or various organochlorodisilanes, are by‐products of the Siemens [92] or Müller‐Rochow processes [93] . However, there are several methods for the direct preparation of higher silanes or the targeted construction and modification of silicon frameworks [94,70,41] .…”

Section: Synthesis Of Hydrogenated and Chlorinated Oligosilanesmentioning

confidence: 99%

Challenges in the Synthesis and Processing of Hydrosilanes as Precursors for Silicon Deposition

Gerwig,

Böhme,

Friebel

2024

Liquid hydrosilanes are required for the production of silicon films. The silicon layers can be processed for electronic devices like transistors or thin‐film solar cells. Hydrosilanes are highly reactive and pyrophoric. Therefore, the synthesis of these compounds is challenging and dangerous. The available synthesis methods for hydrosilanes are reviewed and compared.Hydrosilanes are highly attractive compounds, which can be processed as liquids with printing technology to amorphous silicon films on nearly any solid substrate. The silicon layers can be processed for electronic devices like transistors or thin‐film solar cells. The endothermic character of hydrosilanes with their positive enthalpies of formation results in favorable properties for processing. The larger the molecules, the lower their decomposition temperature and the higher their photoactivity. Cyclic hydrosilanes such as cyclopentasilane and cyclohexasilane can be easily deposited. The branched neopentasilane is more difficult to deposit but yields better‐quality films after processing.The key challenge is the complex synthesis of the precursors and the hydrosilanes. The available preparative methods are presented in this review and their advantages and disadvantages are evaluated. The following synthesis methods are presented and discussed in this article: Wurtz coupling and other reductive coupling processes, dehydrogenative coupling of silanes, plasma synthesis of chlorinated polysilanes, amine‐ or chloride‐induced disproportionations, and transformation of monosilane to higher silanes.Plasma synthesis is already carried out today as a continuous industrial process. The most effective synthesis methods in the laboratory are currently amine‐ and chloride‐induced disproportionations. There is a great need to further optimize the syntheses of hydrosilanes and to develop new simple synthesis variants.

Thermal Synthesis of Perchlorinated Oligosilanes: A Fresh Look at an Old Reaction

Neumeyer

Schweizer

Meyer

et al. 2017

DedicatedtoProf. Nino Russo on theoccasiono fhis 70th birthday.Abstract: Ac ombined experimentala nd theoretical study of the high-temperature reactiono fS iCl 4 and elemental silicon is presented. The nature and reactivity of the product formed upon rapid coolingo ft he gaseous reactionm ixture is investigated by comparison with the defined model compounds cyclo-Si 5 Cl 10 , n-Si 5 Cl 12 and n-Si 4 Cl 10 .ADFT assessment provides mechanistic insight into the oligosilane formation. Experimental 29Si NMR investigations, supported by quantum-chemical 29 Si NMR calculations, consistently show that the reactionp roduct is composed of discrete molecular perchlorinated oligosilanes. Low-temperature chlorination is an unexpectedly selective means for the transformation of cyclosilanes to acyclic speciesb ye ndocyclic SiÀSi bond cleavage, and we provide am echanistic rationalization for this observation. In contrast to the raw material, the product obtained after low-temperature chlorination represents an efficient source of neo-Si 5 Cl 12 or the amine-stabilizedd isilene EtMe 2 N·SiCl 2 Si(SiCl 3 ) 2 through reactionwith aliphatic amines.