Kinetic studies on the hydrosilylation of phenylacetylene with R3SiH (R3 = PhMe2, Ph2Me,Ph3, Et3) using bis(1,2‐diphenylphosphinoethane)norbornadiene rhodium(I) hexafluorophosphate as catalyst

Product distribution and kinetic studies on the hydrosilylation of phenylacetylene by Ph₃SiH, Ph₂MeSiH, PhMe₂SiH and Et₃SiH were performed using bis‐[1,2‐diphenylphosphinoethane]norbornadienerhodium(I) hexafluorophosphate, 1, as catalyst. Pre‐equilibration of the catalyst with the acetylene produced hydrosilylations, pre‐equilibration with the silane did not. The catalyst showed a pronounced selectivity for cis‐addition to form β‐products, t‐PhCH­CHSiR₃, unlike most hydrosilylation catalysts. The kinetic studies showed a hydrosilylation reaction that is zero order with respect to both acetylene and the silane, with a dependency upon catalyst concentration. The k_obs value is directly influenced by the substituents on the silane: k(PhMe₂SiH) > k (Et₃SiH > k (Ph₂MeSiH) > k (Ph₃SiH). Intercalation of the catalyst in hectorite was not useful, since either no reaction occurred in non‐polar solvents, or extraction of the catalyst occurred in polar solvents to produce the same product distributions. Copyright © 2000 John Wiley & Sons, Ltd.     

Hydrogenolysis of the C-Cl bond of the dichloromethylene group in polychloroalkanes initiated by Fe(CO)5, Mn2(CO)10, or tert-butyl peroxide in combination with triethylsilase

Conclusions The dichloromethylene group in polychloroalkanes is selectively reduced by the action of Fe(CO)₅, Mn₂(CO)₁₀ or (Me₃CO)₂O in combination with Et₃SiH to a chloromethylene group. The Mn₂(CO)₁₀-Et₃SiH system is the most efficient in this reaction.Translated from Izvestiya Akademii Nauk SSSK, Seriya Khimicheskaya, No. 5, pp. 1136–1138, May, 1986.     

Facile hydrosilylation of norbornadiene by silanes R3SiH and R2SiH2 with molybdenum catalysts

Photochemically activated [Mo(CO)₆] and [Mo(CO)₄(η⁴-nbd)] have been demonstrated to be very effective catalysts for hydrosilylation of norbornadiene (nbd) by tertiary (Et₃SiH, Cl₃SiH) and secondary (Et₂SiH₂ and Ph₂SiH₂) silanes to give 5-silyl-2-norbornene, which under the same reaction conditions transform in ring-opening metathesis polymerization (ROMP) to unsaturated polymers and to a double hydrosilylation product, 2,6-bis(silyl)norbornane. The yield of a particular reaction depends very strongly on the kind of silane involved. The reaction products were identified by means of chromatography (GC–MS) and ¹H and ¹³C NMR spectroscopy. In photochemical reaction of [Mo(CO)₄(η⁴-nbd)] and Ph₂SiH₂ in cyclohexane-d₁₂, η²-coordination of the SiH bond to the molybdenum atom is supported by ¹H NMR spectroscopy due to the detection of two equal-intensity doublets with ²J_HH = 5.4 Hz at δ 6.12 and −5.86 ppm.     

Photochemical reactions of [W(CO)4(η-nbd)] with hydrosilanes: Generation of new hydrido complexes of tungsten and their reactivity

Photolysis of the norbornadiene (nbd) complex [W(CO)₄(η⁴-nbd)] (1) creates a coordinatively unsaturated d⁶ species which interacts with the Si-H bond of tertiary and secondary silanes (Cl₃SiH, Et₃SiH, Et₂SiH₂, Ph₂SiH₂) to yield hydride complexes of varying stability. In reaction of complex 1 with Cl₃SiH, oxidative addition of the Si-H bond to the tungsten(0) center gives the seven-coordinate tungsten(II) complex [WH(SiCl₃)(CO)₃(η⁴-nbd)], which has been fully characterized by NMR spectroscopic methods (¹H, ¹³C{¹H}, 2D ¹H-¹H COSY, 2D ¹³C-¹H HMQC and ²⁹Si{¹H}). Reaction of 1 with Et₃SiH leads to the hydrosilylation of the η⁴-nbd ligand to selectively yield endo-2-triethylsilylnorbornene (nbeSiEt₃). The latter silicon-substituted norbornene gives the unstable pentacarbonyl complex [W(CO)₅(η²-nbeSiEt₃)], whose conversion leads to the initiation of ring-opening metathesis polymerization (ROMP). Reaction of secondary silanes (Et₂SiH₂ and Ph₂SiH₂) with 1 leads to the hydrosilylation and hydrogenation of nbd and the formation of bis(silyl)norbornane and silylnorbornane as the major products. In reaction of 1 and Et₂SiH₂, the intermediate dihydride complex [WH(μ-H-SiEt₂)(CO)_x(η⁴-nbd)] was detected by ¹H and ¹³C NMR spectroscopy. As one of the products formed in photochemical reaction of W(CO)₆ with Ph₂SiH₂, the dinuclear complex [{W(μ-η²-H-SiPh₂)(CO)₄}₂] was identified by NMR spectroscopic methods.     

Transition metal reactions of silanes II. The reaction of cycloalkenes with various hydrosilanes and carbon monoxide catalyzed by Co2(CO)8

The reaction of cycloalkenes(cyclopentene, cyclohexene, cycloheptene, cyclooctene, 1-methylcyclohexene, and norbornene) with Et₂MeSiH and carbon monoxide in the presence of Co₂(CO)₈ gave the corresponding diethylmethylsiloxymethylenecycloalkenes. In such reactions of cyclohexene, the following hydrosilanes gave the corresponding siloxymethylenecyclohexanes: Me₃SiH, EtMe₂SiH, Et₂MeSiH, Et₃SiH, PhMe₂SiH, Ph₂MeSiH. Effects of the reaction conditions(the pressure of carbon monoxide, the temperature, and the molar ratio of cyclohexene to Et₂MeSiH) were examined. The yield of diethylmethylsiloxymethylenecyclohexane increased remarkably with increasing molar ratio of cyclohexene to Et₂MeSiH. At higher temperature, the yield of the isomerization product, 1-(diethylmethylsiloxymethyl)-cyclohex-1-ene, increased.     

Efficient carbonyl hydrosilylation reaction: Toward EVA copolymer crosslinking

In this article, the hydrosilylation reaction of carbonyl groups of acetate derivatives and SiH groups of hydride‐terminated polydimethylsiloxane at high temperature (100–130 °C) are described. Triruthenium dodecacarbonyl, Ru₃(CO)₁₂, was used as effective catalyst for hydrosilylation reaction. The hydrosilylation reactions with octyl acetate and 4‐heptyl acetate were investigated by multinuclear NMR spectroscopy (¹H, ¹³C, and ²⁹Si). This work provides evidence of the addition reaction of SiH groups onto carbonyl groups. The influence of the nature of the acetate structure on the reaction kinetics was shown and the slight contribution of side reactions at high temperature highlighted. Hydrosilylation reaction was extent to the crosslinking of ethylene‐vinyl acetate (EVA) copolymer in the same range of temperature. The formation of EVA chemical network was demonstrated by HR‐MAS NMR spectroscopy and by measuring the gel fraction of EVA chains in hot toluene. From Flory theory, the crosslinking density of elastic strand was calculated to be 80 mol m^?3 in agreement with the measurements from swelling ratio (VA/SiH molar ratio: 11.8). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Catalytic Hydrosilylation of Imines by Aluminum Hydride Cations

In this work, the catalytic activity of electronically unsaturated three coordinated aluminum hydride cations [ L AlH]⁺[HB(C₆F₅)₃]⁻ ( 1 ) and [ L AlH]⁺[B(C₆F₅)₄]⁻ ( 2 ) in hydrosilylation of imines has been disclosed ( L ={(2,6-ⁱPr₂C₆H₃N)P(Ph₂)}₂N). A variety of organo-silanes such as Et₃SiH, MePhSiH₂, PhSiH₃, TMDSO, and PHMS are screened in this endeavour. The amines as products of catalysis were obtained in good to excellent yields after the hydrolysis of silylamine intermediates. Further, a series of controlled experiments systematically designed to investigate the underlying mechanistic pathway through multinuclear NMR analysis showed Lewis adduct formation between cationic aluminum centre and the imine nitrogen, which subsequently undergoes reaction with silane to afford the product. The hydrosilylation of imine performed with Et₃SiH using catalyst 1 with a loading of 2 mol % at 60 °C occurs smoothly. Whereas 2 led to the product formation with Et₃SiH only when used in stoichiometric quantity. Further, to investigate this unique behaviour of 1 NMR investigations were performed and revealed that the anion in 1 competes for hydride delivery and in-situ generates B(C₆F₅)₃ that cooperatively reinforces the catalytic activity of 1 .     

Homogeneous catalysis of O-silylation reactions using octacarbonyldicobalt(O)

Octacarbonyldicobalt(O) has been used to catalyze the reaction of R₃SiH (R = Et and EtO) with R′OH (R′ = Me, Et, n-Pr, i-Pr, and t-Bu). The reaction of MeOH with (EtO)₃SiH, in toluene at 27 °C, was first-order with respect to the catalyst, to the silane, and to the alcohol. The order of reactivity of the alcohols was MeOH > EtOH > n-PrOH > i-PrOH > t-BuOH, reflecting the steric effect associated with the size of the organic group. Addition of triphenyl phosphine (Ph₃P) to the reaction mixture slowed down the reaction. The reaction proceeds faster if nonpolar solvents are used, and the rate of the reaction is very sensitive to temperature.     

Organocobalt cluster complexes XXIX. Novel silicon compounds containing the nonacarbonyl tricobaltcarbon substituent

The reaction of bromomethylidynetricobalt nonacarbonyl or, more effectively, of methylidynetricobalt nonacarbonyl with diverse silicon hydrides (R₃SiH, Ph₃SiH, Me₂(EtO)SiH, R_nCl_3-nSiH (n = 02), etc. results in formation of silylmethylidynetricobalt nonacarbonyl complexes. Silicon-functional interconversions such as SiCl → SiOH, SiCl → SiOMe, SiOH → SiF, and SiOH → SiOSiMe₃, have provided still other substituted silylmethylidynetricobalt nonacarbonyl complexes, generally in high yield. The compounds Me(HO)₂SiCCO₃(CO)₉ and (HO)₃SiCCo₃(CO)₉ have been incorporated into methylsilicone polymers by H₂SO₄-induced reactions with cyclo-(Me₂SiO)₃.     

Synthesis, characterization and study of the chromogenic properties of the hybrid polyoxometalates [PW11O39(SiR)2O] (R = Et, (CH2)nCHCH2 (n = 0, 1, 4), CH2CH2SiEt3, CH2CH2SiMe2Ph)

Reaction of Cl₃SiR or (EtO)₃SiR with [PW₁₁O₃₉]⁷⁻ affords the disubstituted hybrid anions [PW₁₁O₃₉(SiR)₂O]³⁻. These species have been characterized by IR spectroscopy in the solid state and by multinuclear NMR (¹H, ²⁹Si, ³¹P and ¹⁸³W) and cyclic voltammetry in solution. The hydrosilylation of [PW₁₁O₃₉(Si-CHCH₂)₂O]³⁻ has been achieved with Et₃SiH and PhSiMe₂H. These are the first examples of hydrosilylation on a hybrid tungstophosphate core. The chromogenic behaviour of hybrid species has been demonstrated in solution.     

Highly Regio‐ and Stereoselective Hydrosilylation of Internal Thioalkynes under Mild Conditions

A general and mild hydrosilylation of thioalkynes is described. With the cationic catalyst [Cp*Ru(MeCN)₃]⁺ and the bulky silane (TMSO)₃SiH, a range of thioalkynes underwent smooth hydrosilylation at room temperature with excellent α regioselectivity and syn stereoselectivity. DFT calculations provided important insight into the mechanism, particularly the unusual syn selectivity with the [Cp*Ru(MeCN)₃]⁺ catalyst. The sulfenyl group in the substrates was found to provide important chelation stabilization to direct the reaction through a new mechanistic pathway.     

Die darstellung von [(CH3)3PRu(CO)2Cl2]2 und [(Ch3)3P]2Ru(CO)2Cl2; Eine berichtigung zu: Die alkoholyse des triethylsilans katalysiert von [(Ch3)3P]2Ru(CO)2Cl2

The ruthenium(II) complex used as a catalyst in reactions of alcohols and Et₃SiH proved to be the dimer [(CH₃)₃PRu(CO)₂Cl₂]₂ and not the complex [(CH₃)₃P]₂ Ru(CO)₂Cl₂. Both complexes were prepared, characterized and their catalytic properties were compared.     

Use of carboxylated polyethylene glycol as promoter for platinum‐catalyzed hydrosilylation of alkenes

Several carboxylated polyethylene glycols as promoters were applied in the platinum‐catalyzed hydrosilylation of alkenes, and polyethylene glycol maleic acid monoester as a promoter for hydrosilylation was investigated. It was found that an improvement of the selectivity was achieved in the presence of carboxylated polyethylene glycol, and the β‐adduct as major product was obtained. Additionally, the effect of alkenes and silanes employed on the selectivity was investigated; better selectivity could be achieved when (EtO)₃SiH was used as the hydride than ClMe₂SiH. Copyright © 2011 John Wiley & Sons, Ltd.     

Palladium- and platinum-catalyzed coupling reactions of allyloxy aromatics with hydridosilanes and hydridosiloxanes: Novel liquid crystalline/organosilane materials

Pt-and Pd-catalyzed reactions of a set of allyloxyaromatic mono-and diesters with selected silanes were examined to develop simple, mild methods of forming liquid crystal (LC)/ siloxane and LC/silsesquioxane polymers. Pt complexes catalyze hydrosilylation to give primarily (≤ 80% selectivity at 100% conversion) terminal silylation of the allyloxys. The catalyst, platinum-1,3-divinyltetramethyldisiloxane [Pt (dvs), gives the cleanest reactions, fewest side products, under the mildest conditions. Model studies of Pt(dvs) catalyzed hydrosilylation of 4-allyloxy methylbenzoate gave relative reactivities (HSiO_1.5)₈ ? Et₃SiH > HMe₂Si? O? SiMe₂H > Ph₂SiH2. The cubic silsesquioxane, (HSiO_1.5)₈, is so reactive hydrosilylation is over in 1–3 h at 0°C. All other reactions required > 40°C and longer reaction times. Initial efforts to form high polymers by Pt-catalyzed reactions of bis-allyloxy aromatics with Ph₂SiH₂ provide polymers with bimodal MW distributions (polystyrene), M_ws ≈ 30 kDa, and PDIs ≈ 5. Pd catalysis gives quite different products resulting from loss of propene with coincident formation of Si? O bonds, “oxysilylation.” The same products appear (10–15%) in some Pt catalyzed reactions. Palladium dibenzylideneacetone/ Ph₃P[Pd(dba)₂/Ph₃P], gives the cleanest oxysilylation reactions. Relative oxysilylation activities are: Ph₂SiH₂ > HMe₂SiOSiMe₂H > Et₃SiH. Polymerization with Pd catalysts provides polymers with M_ws ≈ 11 kDa, and PDIs ≈ 2. Reaction of 1 equiv. of (HSiO_1.5)₈ with 4 equiv. of 4-(4-allyloxy-benzoyloxy) biphenyl gives relatively pure tetrasubstituted LC/silsesquioxane [M_n ≈ 1860 Da, PDI ≈ 1.09 (styrene equiv.) vs. 1746 Da caled.] A detailed analysis of the products formed, the catalytic reactivity patterns of the his (allyloxy) aromatic diesters and their LC transitions is presented. © 1994 John Wiley & Sons, Inc.     

Silylium dual catalysis in living polymerization of methacrylates via In situ hydrosilylation of monomer

Silylium ions (“R₃Si⁺”) are found to catalyze both 1,4‐hydrosilylation of methyl methacrylate (MMA) with R₃SiH to generate the silyl ketene acetal initiator in situ and subsequent living polymerization of MMA. The living characteristics of the MMA polymerization initiated by R₃SiH (Et₃SiH or Me₂PhSiH) and catalyzed by [Et₃Si(L)]⁺[B(C₆F₅)₄]^– (L = toluene), which have been revealed by four sets of experiments, enabled the synthesis of the polymers with well‐controlled M_n values (identical or nearly identical to the calculated ones), narrow molecular weight distributions (? = 1.05–1.09), and well defined chain structures {H? [MMA]_n? H}. The polymerization is highly efficient too, with quantitative or near quantitative initiation efficiencies (I* = 96–100%). Monitoring of the reaction of MMA + Me₂PhSiH + [Et₃Si(L)]⁺[B(C₆F₅)₄]^– (0.5 mol%) by ¹H NMR provided clear evidence for in situ generation of the corresponding SKA, Me₂C?C(OMe)OSiMe₂Ph, via the proposed “Et₃Si^+”‐catalyzed 1,4‐hydrosilylation of monomer through “frustrated Lewis pair” type activation of the hydrosilane in the form of the isolable silylium‐silane complex, [Et₃Si? H? SiR₃]⁺[B(C₆F₅)₄]^–. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1895–1903     

Enantioselective Synthesis of α‐Hydroxy Amides and β‐Amino Alcohols from α‐Keto Amides

Synthesis of enantiomerically enriched α‐hydroxy amides and β‐amino alcohols has been accomplished by enantioselective reduction of α‐keto amides with hydrosilanes. A series of α‐keto amides were reduced in the presence of chiral Cu^II/(S)‐DTBM‐SEGPHOS catalyst to give the corresponding optically active α‐hydroxy amides with excellent enantioselectivities by using (EtO)₃SiH as a reducing agent. Furthermore, a one‐pot complete reduction of both ketone and amide groups of α‐keto amides has been achieved using the same chiral copper catalyst followed by tetra‐n‐butylammonium fluoride (TBAF) catalyst in presence of (EtO)₃SiH to afford the corresponding chiral β‐amino alcohol derivatives.     

Cobalt Nanoparticles Formed upon Reaction of Cp*Co(III) Metallacycles with Na[BHEt3] Show Catalytic Activity in the Hydrosilylation of Aryl Ketones,Aldehydes and Nitriles

The reactivity of the 2-phenylpyridine-derived [Cp*CoI(phpy-κ^C,N)] metallacycle towards Et₃SiH and hydrides was evaluated. The treatment of the same Co(III) complex with Na[BHEt₃] resulted in its decomposition into cobalt nanoparticles. The hydride-promoted decomposition of the metallacycle involves the transient formation of an elusive hydrido-cobalt(III) intermediate, the traces of which were detected by ¹H NMR spectroscopy at sub-ambient temperature. The Co nanoparticles produced from a 5 mol% and 10 mol% load of cobaltacycle and Na[BHEt₃] respectively contain Co(0) that is responsible for the hydrosilylation by Et₃SiH of arylketones into silylalkyl ethers. To minimize the residual side reduction of carbonyls by Na[BHEt₃], a mixture of 5 mol% of the latter with 5 mol% of BEt₃ was found to produce optimal hydrosilylation yields at 40 °C in 2 h. Under similar conditions, several arylnitriles were mono-hydrosilylated into N-silyl-imines in yields ranging from 68 to 100 %.     

A Cationic Zinc Hydride Cluster Stabilized by an N‐Heterocyclic Carbene: Synthesis,Reactivity, and Hydrosilylation Catalysis

The trinuclear cationic zinc hydride cluster [(IMes)₃Zn₃H₄(THF)](BPh₄)₂ ( 1 ) was obtained either by protonation of the neutral zinc dihydride [(IMes)ZnH₂]₂ with a Brønsted acid or by addition of the putative zinc dication [(IMes)Zn(THF)]²⁺. A triply bridged thiophenolato complex 2 was formed upon oxidation of 1 with PhS? SPh. Protonolysis of 1 by methanol or water gave the corresponding trinuclear dicationic derivatives. At ambient temperature, 1 catalyzed the hydrosilylation of aldehydes, ketones, and nitriles. Carbon dioxide was also hydrosilylated under forcing conditions when using (EtO)₃SiH, giving silylformate as the main product.     

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.     

Iron‐Complex‐Catalyzed C?C Bond Cleavage of Organonitriles: Catalytic Metathesis Reaction between H?Si and R?CN Bonds to Afford R?H and Si?CN Bonds

The first example of the catalytic C? CN bond cleavage of acetonitrile as well as Si? CN bond formation have been achieved in the photoreaction of MeCN with Et₃SiH promoted by [Cp(CO)₂FeMe]. This catalytic system is applicable to other organonitriles. Several iron complexes [(η⁵‐C₅R₅)(CO)₂FeR′] (R₅=H₅, H₄Me, Me₅, H₄SiMe₃, H₄I, H₄P(O)(OMe)₂; R′=SiMe₃, CH₂Ph, Me, Cl, I) were examined as catalyst, and [Cp(CO)₂FeMe] was found to be the best precursor. A catalytic reaction cycle was proposed, which involves oxidative addition of Et₃SiH to [Cp(CO)FeMe], reductive elimination of CH₄ from [Cp(CO)FeMe(H)(SiEt₃)], coordination of RCN to [Cp(CO)Fe(SiEt₃)], silyl migration from Fe to N in the coordinated RCN, and dissociation of Et₃SiNC from Fe. The reaction with MeCN of [Cp(CO)Fe(py)(SiEt₃)], which was newly prepared and determined by X‐ray analysis, and the reaction of Et₃SiH with MeCN in the presence of a catalytic amount of [Cp(CO)Fe(py)(SiEt₃)] showed that the 16‐electron species [Cp(CO)Fe(SiEt₃)] is the active species in the catalytic cycle (TON up to 251).