Hydrosilylation Products Research Articles

Platinum-catalyzed double silylations of alkynes with bis(dichlorosilyl)methanes

Bis(dichlorosilyl)methanes 1 undergo the two kind reactions of a double hydrosilylation and a dehydrogenative double silylation with alkynes 2 such as acetylene and activated phenyl-substituted acetylenes in the presence of Speier’s catalyst to give 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 and 1,1,3,3-tetrachloro-1,3-disilacyclopent-4-enes 4 as cyclic products, respectively, depending upon the molecular structures of both bis(dichlorosilyl)methanes ( 1) and alkynes ( 2). Simple bis(dichlorosilyl)methane ( 1a) reacted with alkynes [R 1–C C–R 2: R 1 = H, R 2 = H ( 2a), Ph ( 2b); R 1 = R 2 = Ph ( 2c)] at 80 °C to afford 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 as the double hydrosilylation products in fair to good yields (33–84%). Among these reactions, the reaction with 2c gave a trans-4,5-diphenyl-1,1,3,3-tetrachloro-1,3-disilacyclopentane 3ac in the highest yield (84%). When a variety of bis(dichlorosilyl)(silyl)methanes [(Me n Cl 3 − n Si)CH(SiHCl 2) 2: n = 0 ( 1b), 1 ( 1c), 2 ( 1d), 3 ( 1e)] were applied in the reaction with alkyne ( 2c) under the same reaction conditions. The double hydrosilylation products, 2-silyl-1,1,3,3-tetrachloro-1,3-disilacyclopentanes ( 3), were obtained in fair to excellent yields (38–98%). The yields of compound 3 deceased as follows: n = 1 > 2 > 3 > 0. The reaction of alkynes ( 2a– c) with 1c under the same conditions gave one of two type products of 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 and 1,1,3,3-tetrachloro-1,3-disilacyclopent-4-enes ( 4): simple alkyne 2a and terminal 2b gave the latter products 4ca and 4cb in 91% and 57% yields, respectively, while internal alkyne 2c afforded the former cyclic products 3cc with trans form between two phenyl groups at the 3- and 4-carbon atoms in 98% yield, respectively. Among platinum compounds such as Speier’s catalyst, PtCl 2(PEt 3) 2, Pt(PPh 3) 2(C 2H 4), Pt(PPh 3) 4, Pt[ViMeSiO] 4, and Pt/C, Speier’s catalyst was the best catalyst for such silylation reactions.

Highly (Z)-Selective Hydrosilylation of Terminal Alkynes Catalyzed by a Diphosphinidenecyclobutene-Coordinated Ruthenium Complex: Application to the Synthesis of (Z,Z)-Bis(2-bromoethenyl)arenes

[reaction: see text] Complex 1 bearing a diphosphinidenecyclobutene ligand (DPCB-OMe) catalyzes highly stereoselective hydrosilylation of diethynylarenes with HSiMe2Ph to afford (Z,Z)-bis(2-silylethenyl)arenes. Treatment of the hydrosilylation products with N-bromosuccinimide causes bromodesilylation in a stereospecific manner, giving (Z,Z)-bis(2-bromoethenyl)arenes in high geometrical purity (>98%).

Synthesis, hydrosilylation reactivity and catalytic properties of group 4 ansa-metallocene complexes

The following ansa-ligand precursors, Et(H)Si(C 5H 5) 2 ( 1), Et(H)Si(C 5HMe 4)Cl ( 2), Et(H)Si(C 5HMe 4)(C 5H 5) ( 3), Ph(H)Si(C 5HMe 4)Cl ( 4), Ph(H)Si(C 5HMe 4)(C 5H 5) ( 5), Ph(H)Si(C 5HMe 4) 2 ( 6), CH 2 CHCH 2(H)Si(C 5HMe 4)Cl ( 7), CH 2 CHCH 2(H)Si(C 5HMe 4)(C 5H 5) ( 8), CH 2 CHCH 2(H)Si(C 5HMe 4) 2 ( 9), and their lithium derivatives, Li 2{Et(H)Si(C 5H 4) 2} ( 10), Li 2{Et(H)Si(C 5Me 4)(C 5H 4)} ( 11), Li 2{Ph(H)Si(C 5Me 4)(C 5H 4)} ( 12), Li 2{Ph(H)Si(C 5Me 4) 2} ( 13), Li 2{CH 2 CHCH 2(H)Si(C 5Me 4)(C 5H 4)} ( 14) and Li 2{CH 2 CHCH 2(H)Si(C 5Me 4) 2} ( 15) have been prepared. The group 4 metal complexes, [M{Et(H)Si(η 5-C 5H 4) 2}Cl 2] (M = Ti ( 16a), Zr ( 16b), Hf ( 16c)), [M{Et(H)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 17a), Zr ( 17b), Hf ( 17c)), [M{Ph(H)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 18a), Zr ( 18b), Hf ( 18c)), [M{Ph(H)Si(η 5-C 5Me 4) 2}Cl 2] (M = Ti( 19a), Zr ( 19b), Hf ( 19c)), M{CH 2 CHCH 2(H)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 20a), Zr ( 20b)) and [M{CH 2 CHCH 2(H)Si(η 5-C 5Me 4) 2}Cl 2] (M = Ti ( 21a), Zr ( 21b), Hf ( 21c)) were synthesized from the reaction of the lithium ansa-derivatives and the tetrachloride salts of the transition metal. The reactivity of the group 4 metal complexes in hydrosilylation processes has been studied. The reaction of 16b, 17a and 17b with tetravinylsilane gave [Zr{(CH 2 CH) 3SiCH 2CH 2(Et)Si(η 5-C 5H 4) 2}Cl 2] ( 22b) and [M{(CH 2 CH) 3SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 23a), Zr ( 23b)), respectively. The reaction of 17a and 17b with dimethyldivinylsilane yielded the hydrosilylation products [M{(CH 2 CH)Me 2SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 24a), Zr ( 24b)), respectively. 23b and 24b reacted with the silane reagent HSiEt 3 to form, via hydrosilylation, [Zr{(Et 3SiCH 2CH 2) 3SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] ( 25b) and [Zr{(Et 3SiCH 2CH 2)Me 2SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] ( 26b), respectively. The previously synthesized compounds, [M{CH 2 CH(Me)Si(η 5-C 5Me 4) 2}Cl 2] (M = Ti ( 27a), Zr ( 27b)) and [Zr{CH 2 CHCH 2(Me)Si(η 5-C 5Me 4) 2}Cl 2] ( 28b), have also been tested in reactions of hydrosilylation with SiHMeCl 2 to give [M{Cl 2MeSiCH 2CH 2(Me)Si(η 5- C 5Me 4) 2}Cl 2] (M = Ti ( 29a), Zr ( 29b)) and [Zr{Cl 2MeSiCH 2CH 2CH 2(Me)Si(η 5-C 5Me 4) 2}Cl 2] ( 30b). All the zirconocene compounds are active to varying degrees as catalysts in the polymerization of ethylene. The molecular structures of 21b and 21c have been determined by single crystal X-ray diffraction studies.

Grafted Self-Assembled Monolayers Derived from Naturally Occurring Phenolic Lipids

Self-assembled monolayers grafted onto silicon surfaces were obtained from the hydrosilylation products by trialcoxysilanes of naturally occurring phenolic lipid allyl ethers. The as-obtained materials were characterized by various physical and physicochemical methods. Thus, contact angles of water drops showed that they possess very high hydrophobicity. Their excellent regularity was corroborated by AFM microscopy. The frequencies of the stretching CH2 infrared modes indicate the presence of alkyl chains mainly in the trans/trans conformation. Additionally, optical ellipsometry and quartz microbalance measurements enabled us to estimate the thickness of the films. The results, as a whole, are in good agreement with the formation of densely packed monolayers.

Hydrosilylation of cyclohexene, 1-methylcyclohexene, and isopropylidenecyclohexane

Hydrosilylation of cyclohexene and isopropylidenecyclohexane with chloro(methyl)silanes Me3−nSiHCln (n = 1–3) gives rise to cyclohexyl- and chloro(2-cyclohexylpropyl)methylsilanes. Hydrosilylation of 1-methylcyclohexene with chlorodimethylsilane (n = 1) occurs anomalously and involves double-bond migration to form a mixture of seven compounds: the cis and trans isomers of 2-, 3-, 4-chlorodimethyl(methylcyclohexyl)silanes and chlorodimethyl(cyclohexylmethyl)silane. Chlorodimethylsilane (n = 2) adds to 1-methylcyclohexene to form a mixture of the cis and trans isomers of dichloro(methyl)(2-methylcyclohexyl)silane and dichloro(cyclohexylmethyl)methylsilane. With trichlorosilane (n = 3), no other products than trichloro(cyclohexylmethyl)silane are formed. The hydrosilylation products were reacted with ethynylmagnesium bromide to synthesize the corresponding ethynyl derivatives.

Highly Efficient Hydrosilylation of Diyne and Triyne π-Electron Bridges: Its Application to Fluorescent Dyes and Silylene-Spaced Vinylarene Compounds

A variety of diyne and triyne π-electron bridges were hydrosilylated to afford the bis- and tris(silylvinyl) π-electron bridges. The hydrosilylation products underwent substitution reactions with a variety of compounds containing chromophore units to give fluorescent dye substituted products. The easy access of the silyl hydrides may be applied to construct a large number of copolymers.

Hydrosilylation in the Design and Functionalization of ansa-Metallocene Complexes

The ansa-ligand precursors Me(H)Si(C5HMe4)(C5H5) (2) and Me(H)Si(C5HMe4)2 (3) and their dilithium derivatives [Me(H)Si(C5Me4)(C5H4)]Li2 (4) and [Me(H)Si(C5Me4)2]Li2 (5) have been prepared. The group 4 metal complexes [Me(H)Si(η5-C5Me4)(η5-C5H4)]MCl2 (M = Ti (6), Zr (7), Hf (8)) and [Me(H)Si(η5-C5Me4)2]MCl2, (M = Ti (9), Zr (10), Hf (11)) were synthesized from the reaction of the lithium ansa derivative and the tetrachloride salts of the transition metal. 6−8 reacted with Si(CHCH2)4 and Me2Si(CHCH2)2 to give the hydrosilylation products [Me{(CH2CH)3SiCH2CH2}Si(η5-C5Me4)(η5-C5H4)]MCl2, (M = Ti (12), Zr (13), Hf (14)) and [Me{(CH2CH)Me2SiCH2CH2}Si(η5-C5Me4)(η5-C5H4)]MCl2 (M = Ti (15), Zr (16), Hf (17)). 12, 13, 15, and 16 reacted with the silane reagent HSiEt3 to give [Me{(Et3SiCH2CH2)3SiCH2CH2}Si(η5-C5Me4)(η5-C5H4)]MCl2 (M = Ti (18), Zr (19)) and [Me{(Et3SiCH2CH2)Me2SiCH2CH2}Si(η5-C5Me4)(η5-C5H4)]MCl2 (M = Ti (20), Zr (21)). The molecular structure of 10 has been determined by single-crystal X-ray diffracti...

Hydrosilylation of Aromatic Azomethines

The reactions of aromatic azomethines with methyldichlorosilane, phenyldichlorosilane, and dimethylchlorosilane, performed in the presence of Speier's, Wilkinson's, and Karstedt's catalysts and a series of Pt(II) complexes LL'PtCl2, give hydrosilylation and reduction products whose ratio depends on the catalyst used. The highest yield of hydrosilylation products is attained with Pt(II) complexes as catalysts.

Chiral organochlorosilanes derived from terpenes: diastereoselective hydrosilylation of methylene bicyclo[2.2.1]heptanes with HSiMe nCl n − 2 ( n=0–2)

The H 2PtCl 6 catalysed hydrosilylation of the terpenes (+)-α-fenchene ( XI), (−)-2-methylene bornane ( XII), (+)-camphene ( XIII) and (−)-3-methylene fenchane ( XIV) using HSiMe 2Cl or HSiMeCl 2 proceeds with high regioselectively and in some cases, with high diastereoselectivity. KF-assisted oxidation of the hydrosilylation products gives predominately endo-terpene alcohols. The alcohols have inverted endo/exo ratios to those formed by oxidative hydroboration. Reaction of XIV with HSiMe 2Cl or HSiMeCl 2 is accompanied by a clean rearrangement of the isocamphane skeleton into (+)-2-methylene bornane ( XII) prior to hydrosilylation.

HYDROSILYLATION OF AROMATIC AZOMETHINS

The interaction of aromatic azomethins with methyldichlorosilane, phenyldichlorosilane, and dimethylchlorosilane has been investigated in the presence of a Speier catalyst, a Wilkinson catalyst, a Karsted catalyst, and a range of LL'PtCl 2 complexes. The reaction yielded the products of hydrosilylation and reduction as identified by 1 H NMR. The ratio of hydrosilylation/reduction products depends of the catalyst used. The higher yield of hydrosilylation products was observed with using Pt(II) complexes as a catalyst.

Catalytic Hydrosilylation of Acetylenes Mediated by Phosphine Complexes of Cobalt(I), Rhodium(I), and Iridium(I).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic hydrosilylation of acetylenes mediated by phosphine complexes of cobalt(I), rhodium(I), and iridium(I)

The complexes [Co(PPh 3) 3Cl] ( 1), [Co(PPh 3) 2(CO) 2Cl] ( 2), [Co(PMe 3) 3Cl] ( 3), [Co(PMe 3) 2(CO) 2Cl] ( 4), [Rh(dppe)(CO)Cl] ( 5), [Rh(PPh 2Me) 2(CO)Cl] ( 6), [Ir(dppe)(CO)Br] ( 7), and [Ir(PPh 2Me) 2(CO)Cl] ( 8) catalyse the hydrosilylation of a range of acetylenes including 1-hexyne, phenylacetylene, and 1-phenyl-1-propyne with triethylsilane. In the case of 1-hexyne and 1-phenyl-1-propyne, only the expected hydrosilylation products were observed; however, when the substrate was phenylacetylene, cyclotrimerisation and dimerisation products were observed in addition to the expected vinylsilanes. No hydrosilation was observed with alkene substrates; however, in the presence of some metal complexes, there was double bond migration and cis/ trans-isomerisation probably mediated by the formation of metal hydrides in the reaction mixture.

Selective hydrosilylation of styrene using an in situ formed platinum(1,3-dimesityl-dihydroimidazol-2-ylidene) catalyst

A highly active and selective in situ formed platinum( N-heterocyclic carbene) catalyst for the hydrosilylation of styrene with triethylsilane is described, which unlike all other known hydrosilylation catalysts, selectively yields hydrosilylation products, but (almost) no dehydrogenative silylation products.

Analysis of the enantioselectivities and initial rates of the hydrosilylation of acetophenone catalyzed by [Rh(cod)Cl] 2/(chiral diphosphine). The quantitative analysis of ligand effects

Through the application of the quantitative analysis of ligand effects (QALE) method to the study of the hydrosilylation of acetophenone, we have shown, for the first time, that the initial rate and enantioselectivity of a complicated catalytic system responds in a rational manner to the variations in the stereoelectronic properties of the silane. The reactions (in benzene- d 6 at 63 °C) were catalyzed by [Rh(cod)Cl] 2/(chiral diphosphine) (chiral diphosphine=( R)-BINAP [( R)-(+)-2,2′-bis(diphenylphosphino)-1,1′binaphthyl], ( R, R)-tolyl-BINAP [( R)-(+)-2,2′-bis(di- p-tolylphosphino)-1,1′-binaphthyl], ( R, R)-Me-DUPHOS [( R, R)-(–)-1,2-Bis-2,5-dimethylphospholano)benzene], ( R, R)-DIOP [( R, R)-(−)-2,3- O-isopropylidine-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane], and ( R)-QUINAP [( R)-(+)-1-(2-diphenylphosphino-1-naphthyl)isoquinoline]. The ee's ( R) of the hydrosilylation products (CH 3CH(OSiR 3)Ph) range between −9 and 53% with the ( R)-QUINAP giving the poorest enantioselectivity. The QALE analyses of log( R/ S) for ( R)-BINAP, ( R)-tolyl-BINAP, ( R, R)-Me-DUPHOS, and ( R, R)-DIOP reveal that the steric effects associated with the silanes are not monotonic.

Metal‐Catalyzed Hydrosilylation of Alkenes and Alkynes Using Dimethyl(pyridyl)silane.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane.

Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane is described. The hydrosilylation of alkenes using dimethyl(2-pyridyl)silane (2-PyMe(2)SiH) proceeded well in the presence of a catalytic amount of RhCl(PPh(3))(3) with virtually complete regioselectivity. By taking advantage of the phase tag property of the 2-PyMe(2)Si group, hydrosilylation products were isolated in greater than 95% purity by simple acid-base extraction. Strategic catalyst recovery was also demonstrated. The hydrosilylation of alkynes using 2-PyMe(2)SiH proceeded with a Pt(CH(2)=CHSiMe(2))(2)O/P(t-Bu)(3) catalyst to give alkenyldimethyl(2-pyridyl)silanes in good yield with high regioselectivity. A reactivity comparison of 2-PyMe(2)SiH with other related hydrosilanes (3-PyMe(2)SiH, 4-PyMe(2)SiH, and PhMe(2)SiH) was also performed. In the rhodium-catalyzed reaction, the reactivity order of hydrosilane was 2-PyMe(2)SiH >> 3-PyMe(2)SiH, 4-PyMe(2)SiH, PhMe(2)SiH, indicating a huge rate acceleration with 2-PyMe(2)SiH. In the platinum-catalyzed reaction, the reactivity order of hydrosilane was PhMe(2)SiH, 3-PyMe(2)SiH >> 4-PyMe(2)SiH > 2-PyMe(2)SiH, indicating a rate deceleration with 2-PyMe(2)SiH and 4-PyMe(2)SiH. It seems that these reactivity differences stem primarily from the governance of two different mechanisms (Chalk-Harrod and modified Chalk-Harrod mechanisms). From the observed reactivity order, coordination and electronic effects of dimethyl(pyridyl)silanes have been implicated.

Unexpected Silicon Group Transfer in Difunctional Alkoxy Silanes

During the hydrosilylation reaction of a difunctional silane with allyl glycidyl ether (AGE), two scrambled hydrosilylation products were produced in significant amounts. This scrambling is reaction condition dependent and has been observed in a few other examples. It appears to be the first such alkoxysilane transformation to occur under these conditions, although similar siloxane transformations have been documented. This also introduces a method of preparing certain organofunctional alkyldialkoxysilanes in high purities via hydrosilylation, where the close boiling rearrangement by-products are minimized.

Asymmetric hydrosilylation of styrenes catalyzed by palladium-MOP complexes: ligand modification and mechanistic studies.

In the palladium-catalyzed asymmetric hydrosilylation of styrene (3a) with trichlorosilane, several chiral monophosphine ligands, (R)-2-diarylphosphino-1,1'-binaphthyls (2a-g), were examined for their enantioselectivity. The highest enantioselectivity was observed in the reaction with (R)-2-bis[3,5-bis(trifluoromethyl)phenyl]phosphino-1,1'-binaphthyl (2g), which gave (S)-1-phenylethanol (5a) of 98% ee after oxidation of the hydrosilylation product, 1-phenyl-1-(trichlorosilyl)ethane (4a). The palladium complex of 2g also efficiently catalyzed the asymmetric hydrosilylation of substituted styrenes on the phenyl ring or at the beta position to give the corresponding chiral benzylic alcohols of over 96% ee. Deuterium-labeling studies on the hydrosilylation of regiospecifically deuterated styrene revealed that beta-hydrogen elimination from 1-phenylethyl(silyl)palladium intermediate is very fast compared with reductive elimination giving hydrosilylation product when ligand 2g is used. The reaction of o-allylstyrene (9) with trichlorosilane catalyzed by (R)-2g/Pd gave (1S,2R)-1-methyl-2-(trichlorosilylmethyl)indan (10) (91% ee) and (S)-1-(2-(propenyl)phenyl)-1-trichlorosilylethanes (11a and 11b) (95% ee). On the basis of their opposite configurations at the benzylic position, a rationale for the high enantioselectivity of ligand 2g is proposed.

Modification of Chiral Monodentate Phosphine (MOP) Ligands for Palladium-Catalyzed Asymmetric Hydrosilylation of Styrenes

Abstract In the palladium-catalyzed asymmetric hydrosilylation of styrene with trichlorosilane, several chiral monophosphine ligands, (R)-2-diarylphosphino-1,1′-binaphthyls (2), were examined for their enantioselectivity. The highest enantioselectivity was observed in the reaction with (R)-2-bis[3,5-bis(trifluoromethyl)phenyl]phosphino-1,1′-binaphthyl (2g), which gave (S)-1-phenylethanol of 98% ee after oxidation of the hydrosilylation product.

Photolysis of tris(trimethylsilyl)silane: trapping of sisyl radicals

The photolysis of tris(trimethylsilyl)silane (TTMSS) was studied in the absence and in the presence of added trapping agents such as alkenes and alcohols. It was found that, unlike the case with pyrolysis, silyl radicals rather than silylenes are produced. They may be efficiently trapped with alkenes, to give the hydrosilylation products, but not with alcohols. The major product from the photolysis of TTMSS in the absence of added trapping agent (or with alcohols as trapping agents) was tetrakis(trimethylsilyl)silane. Possible mechanisms to account for the photoproducts are presented.Key words: hydrosilane, photolysis, silylenes, silyl radical, sisyl hydride.