Organosilicon Hydrides Research Articles

Mechanism of carbene insertion into hydrides of Group 4 via chromium carbene complexes. Part I. Organosilicon hydrides

Measurements of the kinetics of reaction between chromium carbene complexes, [Cr(CO)5{C(X)C6H4Y}](X = OMe or NC4H8; Y =p-OMe, H, or p-Cl), and organosilicon hydrides, SiR3H (R = Et, Pri, Bun, or Ph), in hexane solution in the presence of pyridine, to give [Cr(CO)5(py)] and SiR3[CH(X)(C6H4Y)] as the primary products, have been made. The reactions have been studied by i.r. spectrophotometry under pseudo-first-order conditions as a function of reagent concentration and temperature. In general, a three-term rate equation is obeyed in which the kinetically significant contributions to the insertion process comprise a first-order dissociative path, which involves a major internal rearrangement of the carbene complex, and a second-order associative path in which the organosilicon hydride acts as a nucleophile. The pattern of substituent effects at the silicon atom and at the carbene-carbon atom support this picture. The reaction between [Cr(CO)5(py)] and pyridine to give cis-[Cr(CO)4(py)2] is first order in [Cr(CO)5(py)] and a predominantly dissociative mechanism is indicated.

Preparation of silylplatinum complexes by interaction of organosilicon hydrides and carbonatobis(phosphine)platinum(II) complexes

The carbonatoplatinum complexes [Pt(CO3)L2](L = PMe2Ph, PEt2Ph, PMePh2, and PPh3) react in benzene with the silicon hydrides SiHR3(R3= MePh2) or SiH2R2(R2= Ph2 or MePh) to give the bis(silyl) complexes [Pt-(SiR3)2L2] or [Pt(SiHR2)2L2]. With R3=(p-FC6H4)3 and L = PMe2Ph, the product, formed in low yield, is [PtH(SiR3)L2]. All the products have been shown to have cis configurations by 31P{1H} n.m.r. spectroscopy. The dihydrides (Me2HSi)2O, (Ph2HSi)2O, (Ph2HSiCH2)2, O-(Me2HSi)2C6H4, and O-Me2HSi·C6H4·CH2SiHMe2 give chelated complexes such as [Pt(Me2SiOSiMe2)L2].

Hydrosilylation of 1,3-butadiene catalysed by palladium(II) complexes

The addition of organosilicon hydrides (C 2 H 5 0) n (n-C 3 H 7 )3 _ n SiH (« = 0—3), (t-C 4 H 9 0) n . . (CH 3 )3 _ n SiH (n = 1 — 3), and (CH 3 )n (neo-C 5 H u ) 3 _ n SiH (n = 0—2) to 1,3-butadiene catalysed by PdCl 2 L2 (L = C 6 H 5 CN, (C 6 H 5 ) 3 P) and [PdCl(7r-C3H5)]2 was studied. It was found that the reaction proceeds under mild conditions to give corresponding 1-silylsubstituted 2,6-octadienes (1/2 adducts), in addition to silylsubstitu ted butenes (1/1 adducts). The structure of 1/1 adducts depended on the structure of the silicon hydride. While the reaction of triethoxysila ne gave a mixture of 1-silylsubsti tuted cis- and /r<ms-2-butenes, the additions of diethoxypropy l- and ethoxydipropylsilane produced unexpectedly 4-silylsubstituted 1-butenes, along with 1-silylsubstituted 1,3-butadienes. Formation of these products as well as the effects of reaction conditions, silicon hydrides and catalysts are discussed in relation to the earlier proposed mechanism of the reaction.

The reaction of organosilicon hydrides with carbomethoxycarbene generated from methyl diazoacetate

The reaction of various organosilicon hydrides including hydropolysilanes with methyl diazoacetate in the preence of copper catalyst gave α-silyl- and polysilyl- esters in 44 – 90% yields. The relative reactivities of a series of m- and p-substituted phenyldimethylsilane towards the active species generatedfrom the diazoacetate correlate well with the Hammett σ constants for the ring substituents, with a ϱ value of −0.26 and a correlation coefficient of 0.984. Based on the consideration of the observed ϱ value, it is concluded that the reaction involves the insertion of the free carbomethoxycarbene into the siliconhydrogen bond via an only slighty ionic transition state.

The interaction of organosilicon hydrides and dimethyl-bis(phosphine)platinum(II) complexes

The silicon hydrides Ph 3SiH and ( p-FC 6H 4) 3SiH react with cis-[PtMe 2(PMe 2Ph) 2] to give the hydridosilyl complexes cis-[PtH(SiR 3)(PMe 2Ph) 2], where R = Ph or p-FC 6H 4, while an excess of methyldiphenylsilane reacts to give the bis(silyl) complex, cis-[Pt(SiMePh 2) 2(PMe 2Ph) 2]. The silicon dihydride Ph 2SiH 2 reacts more readily, to give cis-[Pt(SiPh 2H) 2(PMe 2Ph) 2] and some methyldiphenylsilane. With [PtMe 2(PMePh 2) 2], diphenylsilane gives the bis(silyl) compound only on heating.

The preparation of hydrido(silyl)bis(triphenylphosphine)platinum(II) complexes from bis(triphenylphosphine)platinum-ethylene and silicon hydrides

The reaction between [PtL 2(C 2H 4)] (L = PPh 3) and a variety of organosilicon hydrides, R 3SiH, has given the complexes [PtH(SiR 3)L 2], (I), where R 3Si = Ph 3Si, Ph 2MeSi, Ph 2HSi, PhMe(CH 2CH)Si, Et 3Si, (EtO) 3Si, and (Me 3SiO) 2MeSi; the hydride Me 2ClSiH, however, gives the bis(silyl) complex [Pt(SiMe 2Cl) 2L 2]. The acetylene complexes [PtL 2(PhCCX)] (X = H or Ph) also react, though less readily, with Ph 2MeSiH to give [PtH(SiMePh 2 )L 2]; this complex reacts with an excess of PhCCX to regenerate the [PtL 2 (PhCCX)]. The complexes of type (I), which are thought to have cis configurations, are stable in the air as solids, but unstable in benzene solution. The hydrides Cl 3SiH and MeCl 2SiH react with [Pt(PPh 2Me) 4] to give [Pt(SiCl 3) 2(PPh 2Me) 2] and [Pt(SiMeCl 2) 2(PPh 2Me) 2], respectively.

HYDROSILANE-RHODIUM(I) COMPLEX COMBINATIONS AS SILYLATING AGENTS OF ALCOHOLS

Abstract The dehydrogenative condensation of organosilicon hydrides with alcoholic substances catalyzed by rhodium (I) complex was found to furnish a convenient route for the preparation of silylated alcohols.

The photochemical reaction of benzoyltrimethylsilane with organosilicon hydrides

Photolysis of benzoyltrimethylsilane in various hydrosilanes was investigated. It was found that the benzoylsilane was subjected to photoisomerization under neutral conditions to give an open-chain siloxycarbene intermediate which was inserted into the siliconhydrogen bond of hydrosilanes, yielding a new type of compounds (III). The verification of the nature of the new reaction by means of a series of competition photolyses in hydrosilanes showed that the attacking species toward hydrosilanes has nucleophilic and almost ionic character.

Organosilicon compounds. LXXXIII. Structure effects in bromination of some organosilicon hydrides in dimethylformamide

Organosilicon compounds. LXXXIII. Structure effects in bromination of some organosilicon hydrides in dimethylformamide

Reductions with organosilicon hydrides. III. Reduction of acyl fluorides to esters

Reductions with organosilicon hydrides. III. Reduction of acyl fluorides to esters

The reaction of organosilicon and organotin hydrides with zinc carbenoids generated fromd iethylzinc and geminal diiodoalkanes

The reaction of organosilicon hydrides with diethylzinc and methylene iodide or ethylidene iodide gave methyl- or ethylsilicon compounds in 61–83% yield, respectively. It is concluded that the reaction is an insertion of the methylene or ethylidene group into the siliconhydrogen bond. The relative reactivities of substituted phenyldimethylsilanes in this homogeneous reaction were investigated. The Hammett ϱ-values for the methylene and ethylidene insertions were −1.11 against σ 0-values and −1.19 against σ-values, respectively. The mechanism of the reaction is discussed and compared with CCl 2 and CH 2 insertion into the siliconhydrogen bond via halomethylmercury compounds. On the other hand, the reaction of triethyltin hydride with diethylzinc and methylene iodide gave tetraethyltin as the major product and methyltriethyltin as a minor product. In the latter case, the reduction of organic iodide by the organotin hydride predominated over the insertion of the methylene group into the tinhydrogen bond.

A New Synthesis of Organofluorosilicon Hydrides

Abstract The synthesis of the new organofluorosilicon hydrides, C2H5Sill2F, C2H5SiHF2, CH2[dbnd]CHSiH2F, CH2[dbnd]CHCH2SiH2F and CH2[dbnd]CHCH2SiHF2 has been achieved by the interaction of the corresponding organosilicon hydride with PF5. Each of the compounds has been purified by vapor phase chromatography and characterized.

Reaction of phenyl azide with organosilicon hydrides

Reaction of phenyl azide with organosilicon hydrides

The interaction of acyl halides and organosilicon hydrides catalysed by platinum and rhodium complexes. A new route to ketones

Acyl halides react with triethylsilane in presence of certain platinum complexes to give aldhydes, but in the presence of rhodium catalysts (e.g. mer-[RhCl3(PBun2-Ph)3]) formation of ketones can predominate.

Thermal and photochemical addition reactions of organosilicon hydrides

Thermal and photochemical addition reactions of organosilicon hydrides

Halomethyl—metal compounds XXIX. Reactions of monohalomethyl—mercury compounds with organosilicon hydrides: A new preparation of methylsilicon compounds

The reactions of the halomethyl—mercury reagents Hg(CH 2Br) 2, ICH 2HgI/ Ph 2Hg and Hg(CH 2Br) 2/Ph 2Hg with a number of organosilicon hydrides [Et 3SiH, Ph 3SiH, Ph 2SiH 2, ViPh 2SiH, Me 2PhSiH, Me 2(ZC 6H 4)SiH (Z = p-Cl, p-F, m-CF 3 and p-CH 3)] resulted in CH 2 insertion into the SiH bonds to give methylsilanes. A similar reaction with triethylgermane gave triethylmethylgermane. Although the mechanism of this new methylenation reaction is not known, a free methylene process seems to be excluded and it is likely that a direct reaction between the halomethyl— mercury reagent and the hydride is involved. A Hammett study of the reaction of Hg(CH 2Br) 2 with substituted phenyldimethylsilanes showed a good correlation between log k rel and σ°, giving a ϱ value of −1.31 ± 0.04. A competition study established that triethylsilane is ca. 12 times more reactive toward bis(bromomethyl)mercury than is 3-ethyl-2-pentene.

Reductions with organosilicon hydrides. II. Preparation of aldehydes from acyl chlorides

Reductions with organosilicon hydrides. II. Preparation of aldehydes from acyl chlorides

Halomethyl-metal compounds XXVII. The Reaction of Phenyl(Dihalomethyl)Mercury Compounds with Organosilicon Hydrides: A Preparation of Halomethyl-Silicon Compounds

Phenyl(dihalomethyl)mercury compounds, PhHgCBr 2H and PhHgCClBrH, have been found to transfer CHBr and CHCl, respectively, to organosilicon hydrides forming (bromomethyl)- and (chloromethyl)silanes. Such reactions appear to be of preparative utility only in the case of alkylsilicon hydrides. (Bromomethyl)triethylgermane also was prepared in moderate yield by this procedure. (Dibromomethyl)mercuric bromide by itself was not a CHBr transfer agent, but did become effective in this application when an equivalent of diphenylmercury was added to it. It was found that diphenylmercury “activates” (dibromomethyl)mercuric bromide by reacting with it to form phenylmercuric bromide and phenyl(dibromomethyl)mercury.

Mechanism of Chloroplatinic acid Catalyzed Reduction of Alkyl Halides by Hydrosilanes

The chloroplatinic acid catalyzed reduction of alkylhalides by organosilicon hydrides has been assumed to proceed through a quasi-free-radical mechanism. This paper presents evidence to support such assumption. Namely, (1) selectivity found in this reduction is comparable with that effected in peroxide catalyzed reductions ; (2) some benzylic halides give the corresponding reductive coupling products (3) the characteristic color of diphenylpicrylhydrazyl in triethylsilane fades rapidly in the presence of chloroplatinic acid; and (4) the Hammett correlation for the relative rates of substituted chloroform (X-CC13) toward triethylsilane in the presence of chloroplatinic acid gives a ρ* value of +0.28, which essentially agrees with the value of +0. 29 previously found for the reaction of triethylsilyl radicals.

Reactions of dimethyl sulfoxide with organosilicon hydrides

Reactions of dimethyl sulfoxide with organosilicon hydrides