Primary organosilanes

Further studies quickly revealed that the rapid dehydrogenative coupling of primary organosilanes to oligomers and the slower coupling of secondary silanes to dimers can be effected under ambient conditions with compounds of the type CP2MR2 (M = Ti, R = alkyl M = Zr, R = alkyl or H)(11,12,13). None of the other metallocenes, metallocene alkyls, or metallocene hydrides of groups 4, 5 or 6 have shown any measurable activity for polymerization... 

The polymerization of primary organosilanes proceeds according to Equation 2. The rate of polymerization is strongly dependent on the... 

The only homogeneous catalyst that has been systematically studied for the reaction of silanes with ammonia is Cp2TiMe2.147 This catalyst is effective for tertiary, secondary, and primary organosilanes, but the products from secondary and primary organosilanes are quite complex and strongly dependent on the reaction conditions. Reasonable rates were achieved at temperatures of 70 to 100°C, at partial pressures of 1 to 2 atm NH3, and at a catalyst concentration of ca. 1 mol % relative to silane. Some typical results are shown in Table V. 

Polyorganosilylenes have attracted a lot of attention recently, in particular as precursors to SiC via pyrolytic decomposition [1][2], Theoretically, the ideal precursor to SiC is poly(methylsilylene) [MeSiH]n. The maximum theoretical SiC yields for some polyorganosilylenes are listed in table 1. However, this polymer is not readily available by the commonly used sodium condensation of the appropriate dichlorosilane [3], since the SiH function is not completely inert under the conditions of the condensation. We have recently reported an alternative synthesis of Si-Si bonds via catalyzed dehydrocoupling of primary organosilanes [4], according to (1). 

Direct Process. The preparation of organosilanes by the direct process, first reported in 1945, is the primary method used commercially (142,143). Organosilanes in the United States, France, Germany, Japan, and the CIS are prepared by this method, including CH SiHCl, (CH2)2SiHCl, and C2H SiHCl2. Those materials are utilized as polymers and reactive intermediates. The synthesis involves the reaction of alkyl haUdes, eg, methyl and ethyl chloride, with siUcon metal or siUcon alloys in a fluidized bed at 250—450°C ... 

Reductive Amidation of Aldehydes. The reductive amidation of aldehydes using an organosilane as the reducing agent has been realized. Benzaldehyde reacts over a 74-hour period with triethylsilane and acetonitrile in 75% aqueous sulfuric acid at room temperature to produce an 80% isolated yield of N-benzylacetamide (Eq. 169).313 Octanal fails to react under the same conditions.313 Reductive amidation of aldehydes also occurs with the reagent combination Et3SiH/TFA/primary amide (Eq. 170).326... 

In Table 1 the reactivities of some organosilanes toward primary alkyl radicals are reported. The rate constants cover a range of several orders of magnitude and, therefore, the hydrogen donating abilities in organosilanes can be modulated by the substituents. 

Keduction of alkyl halides. Alkyl halides are reduced readily to hydrocarbons by organosilanes under catalysis with aluminum chloride. This hydrocarbon synthesis is limited to alkyl halides that are not rearranged by the catalyst. Primary, secondary, and tertiary halides are reduced. Reduction with triethyl-... 

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