Dimethyldisilane

A ceramic fiber with Si-C-N-0 composition can be prepared by melt-spinning, cure and pyrolysis of a polymethyldisilylazane polymer precursor (14, 15), which is the reaction product of a mixture of 50 mol % 1,1,2,2- tetrachloro-1,2-dimethyldisilane (la), 40 mol % 1,1,2-trichloro- 1,2,2-trimethyldisilane (lb) and 10 mol %... 

Copolymerisation is also possible (Fig. 4). Dimethyldisilane reacts with diphenylsilane with formation of a copolymer with the composition H[(MeSiHx)(PhSiHy)]nH. This copolymer is a viscous liquid and is spinnable. By heating to 180° C the polymerization continues and a solid results [23]. The presence of branched structures, which were not found with the polymerization of monosilanes, the very rapid polymerization rate achievable, and the observable SiSi cleavage points to another mechanism, as was postulated for monosilanes. 

When tetraethoxy-l,2-dimethyldisilane is treated with tetramethylene-dimagnesium dibromide in tetrahydrofuran, bis(l-methyl-1-silacyclo-pentyl) (XV), and not its isomeric bicyclodisilane (XVI), is formed in 62% yield (110). Analogously, the reaction with 2,2 -dilithiodiphenyl produces 5,5 -dimethyl-5,5 -bis(dibenzosilole) (127). 

Some new aspects in the chemistry of dimethyldisilanes recently reported by Atwell and Weyenburg include the pyrolysis of dimethyldimethoxy-silanes 18 2°) to polysilanes and tetramethyldimethoxydisilane ... 

As the bulk of the substituents on silicon increases, the shorter become the chains in the coupled product, to the limit of disilane. This limit occurs for both primary and secondary silanes. One difference between the metallocene (Group 4) promoted dehydrocoupling reactions and that of metals such as Rh or Pt, is the difficulty in the condensation of dialkylsilanes from the former grouping. Dialkylsilanes condense in the presence of metallocene catalysts only if a hydrogen acceptor (such as an olefin) is present. An interesting exception to the condensation of a secondary silane center comes from the reactions of hydrogen terminated disilanes such as 1,2-dimethyldisilane which forms polymers from both metallocene promoted reactions as well as with Rh and Pd complexes. 

Likewise, tetrachloro-l,2-dimethyldisilane reacts with bis(trimethylsilyl)carbodiimide to give Si/C/N gels. In the reaction of methyltrichlorosilane with bis(trimethylsilyl)carbodi-imide in the presence of pyridine, a highly crosslinked ceramic precursor is also obtained." ... 

The C NMR spectra confirm these conclusions. It is interesting to note that the corresponding inethoxy compound was isolated by Atwell et al. [3] after disproportionation of tetramethoxy-dimethyldisilane. The formation of the branched silane was considered as a proof for a silylene reaction mechanism which is also discussed for our system. 

Summary Copyrolytic gas-phase reactions of l,l,2,2-tetra(alkoxy)- and tetrakis-(dimethylamino)dimethyldisilanes with dienes, heterodienes, and heterotrienes in a flow-system furnish a number of unsaturated silicon heterocycles via silylene-intermediates with the exception of 1,4-diaza- and 1,4-oxazadienes, yielding 40-65 % of 1,3,2-diaza- and l,3,2-oxazasilacyclopent-4-enes, respectively, mixtures of diastereoisomeric 1-oxa- or 1-aza-2-silacyclopent-4-enes and -3-enes are formed. Conjugated oxatrienes were found to undergo additionally [6+l]-cycloadditions giving l-oxa-2-silacyclohepta-4,6-dienes. 

The energy profiles for rotation around the central M-M bond (M = Si, P) in steps of 10° for the title structures, l,l,2,2-tetrakis(trimethylsilyl)dimethyldisilane (1), l,l,2,2-tetrakis(trimethylsilyl)-disilane (2) and tetrakis(trimethylsilyl)diphosphine (3) were investigated by ab initio calculations at... 

Craig, A. D., MacDiarmid, A. G. Application of the Wurtz reaction to the synthesis of disilane and 1,2-dimethyldisilane. Journal of Inorganic and Nuclear Chemistry i062, 24,161-164. 

Using this route, Harrod et al. prepared a poly(meth)dsilane) fi-om methylsilane, which gives after pyrolysis at 1000 °C in Ar atmosphere a ceramic yield of 77% [75]. The exchange of the gaseous methylsilane against the liquid 1,2-dimethyldisilane leads to a similar polymer which forms after pyrolysis SiC in 88% ceramic yield [68] ... 

An enlargement of the silicon skeleton is possible by coupling reactions with lithium metal or silyllithium reagents [4-6]. The homocoupling of tris(diethylamino)-l-chloro-l,2-dimethyldisilane results in the linear hexakis(diethylamino)-l,2,3,4-tetramethyltetrasilane [7]. After treatment with HCl the hexachloro compound could be obtained. By the reaction of aminochlorophenylsilanes with... 

Summary A 9 1 molar ratio mixture of 1,1,2,2-tetrachloromethyldisilane 2 plus pentamethyldisilane 4 reacted with tetrakis(dimethylamino)ethylene (TDAE) to yield, in dimethoxyethane (DME), a crystal mixture of [SiaMesClel ETDAE] (5a) plus [Si3Me2Cl7]"-[TDAE] (5b). The molecular structure of 5b was determined. Conversely, from donor-substituted disilanes such as l,l,2-tris(diethylamino)-2-chloro-dimethyldisilane 6 or the lV,Af -diphenylethylenediamino-substituted dimethyidisilane 7, electron transfer occurs toward tetracyanoethylene (TCNE). 

According to Scheme 1 the disilane 2 was reacted with the corresponding amine plus triethylamine, yielding l,l,2-tris(diethylamino)-2-chlorodimethyldisilane (6) and Ai,lV -diphenylethylenediamino -substituted dimethyldisilane (7) respectively. The results of the GC/MS analysis point to the formation of five-membered rings (see Scheme 1). 

The reaction of A-methylaniline with 1,1,2,2-tetrachlorodimethyldisilane in presence of NEts gives the mono-, di- and triaminodisilanes depending on the reactant ratio. The tetraamide 3 is only formed in the reaction with lithium A-methylanilide. The compounds possess very different reactivity. l-Chloro-l,2,2-tris(lV-methylanilino)dimethyldisilane (2) is rather inert towards nucleophilic reagents. 1,2-Dichloro-l,2-bis(iV-methylanilino)dimethyldisilane (1) reacts with nucleophiles with substitution of both chlorine atoms (see Scheme 1). The products formed during... 

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