Trichlorosilane HSiCl

Homer and Balzer had earlier reported 32) that reduction of optically active phosphine oxides with either trichlorosilane (HSiCls), HSiClj/pyridine, or HSiCls/N, N-diethylaniline affords phosphines with overall retention of configuration, whereas reduction with HSiCls/triethylamine affords phosphine with inversion of configuration at phosphorus. In summary, it was suggested 32) that this difference in overall stereochemistry of reduction reflected a difference in the mode of hydride transfer from silicon to phosphorus intra- and intermolecular hydride transfer led to retention and inversion, respectively. The essential features of these mechanistic rationalizations are represented by Eq. (3). The intramolecular hydride transfer mechanism ), which may include pseudorotation (see Sect. 3) if intermediate phospho-HSiClj + O=PR3 - 0 PRj PRj + [ClsSiOH]... 

An additional approach toward the preparation of tertiary phosphines is by the reduction of more highly coordinated phosphorus species, particularly phosphine oxides [0=PR3] and phosphine sulfides [S=PR3] (see Section 5.2), but also phosphonium salts [R4P+X ] and quasiphosphonium salts [R3P-YR +X ] (see Sections 4.2 and 4.4). Numerous reducing agents have been used to accomplish these conversions, including hexachlorodisilane [ClsSi-SiCls], trichlorosilane [HSiCls], phenylsilane [PhSiHs], and lithium aluminum hydride [LiAlH4]. 

At atmospheric pressure, the conversion to trichlorosilane is limited to about 16%. The conversion of SiCl to HSiCl was found to be at equiUbrium. If contact time was greater than 45 s and the mole ratio of hydrogen to siUcon tetrachloride 1 1, then at 14 kPa (2 psi) and 550°C, the HSiCl mole fraction reached 0.7 but substantial formation of H2SiCl2 occurred (62). Enhancements in yield have been reported through preactivating the siUcon mass by removal of oxides (73) and the rapid thermal quench of the effluent gas stream (74). The reduction of siUcon tetrachloride in a plasma has also been reported (75). 

The study of silicon halides began in the eady 1800s (1). Since then, essentially all of the monomeric silicon halides have been extensively studied and reported in the literature. These include mixed silicon halides and halohydrides. A large number of halogenated polysilanes have also been reported (1). Despite the extensive research in silicon halides, only two of these chemicals are produced on alaige industrial scale (excluding oiganohalosilanes). These are tetrachlorosilane [10026-04-7], SiCl and trichlorosilane [1025-78-2], HSiCl. ... 

Hydrometalation. The hydrosilylation of alkenes, 1,3-dienes, and 1,4-diene may be realized by Pd(PhCN)2Cl2 with PPhs as the ligand (eqs 118-122). For terminal alkenes, only 2-alkylsilanes were afforded (eq 118). For 2-methyl or 2,3-dimethyl buta-1,3-dienes, a mixture of 1,2- or 1,4-addition products were formed (eq 119). For 2-substituted or 1,2-disubstituted buta-1,3-dienes, 1,4-additon products were generated highly selectively (eq 120). The reaction of cyclopentadiene with HSiCls afforded 2-cyclopentyl trichlorosilane (eq 121), while those of eye lohexa-1,3-diene or cyclohexa-1,4-diene afforded a mixture of trichloro(cyclohex-2-enyl)silane and trichloro(cyclohex-3-enyl)silane (eq 122). 

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