Hydrosilylation Of Alkenes Research Articles

Contra-thermodynamic Olefin Isomerization by Chain-Walking Hydrofunctionalization and Formal Retro-hydrofunctionalization.

We report a contra-thermodynamic isomerization of internal olefins to terminal olefins driven by redox reactions and formation of Si-F bonds. This process involves chain-walking hydrosilylation of internal olefins and subsequent formal retro-hydrosilylation. The process rests upon the high activities of platinum hydrosilylation catalysts for isomerization of metal alkyl intermediates and a new, metal-free process for the conversion of alkylsilanes to alkenes. By this approach, 1,2-disubstituted and trisubstituted olefins are converted to terminal olefins.

Hydrosilylation of Ketones Catalyzed by Iron Iminobipyridine Complexes and Accelerated by Lewis Bases.

Fe-iminobipyridine complexes ((R BPIAr,R' )FeBr2 , R BPIAr,R' =iminobipyridine derivatives) were found to exhibit good catalytic activity for hydrosilylation of ketones. The highest TOF (turnover frequency) was obtained for the hydrosilylation of 2-octanone with phenylsilane (4190 min-1 ). The reactions of various 4-substituted acetophenone derivatives revealed that the introduction of an electron-withdrawing group at the 4-position retarded the reaction. The TOF of the hydrosilylation of 4-chloroacetophenone with diphenylsilane was quite low (30 min-1 ), however the addition of a catalytic amount of Lewis base, especially pyridine, dramatically accelerated this hydrosilylation (980 min-1 ). Comparison of this additive effect for several N-donor ligands revealed that the coordination ability of the N-donor ligand was responsible for the acceleration. The rate determining step in the hydrosilylation of ketones appeared to be the reductive elimination of alkoxy and silyl groups from the iron center, which was facilitated by the coordination of N-donor ligand to the iron. This coordination ability of the N-donor ligand, however, inhibited olefin hydrosilylation. Addition of KOt Bu instead of N-donor also showed the same acceleration and inhibition effects on ketone and olefin hydrosilylations, respectively.

A Dicationic Bismuth(III) Lewis Acid: Catalytic Hydrosilylation of Olefins

AbstractInvited for the cover of this issue is Ajay Venugopal from the Indian Institute of Science Education and Research Thiruvananthapuram. The cover image shows dication [TpMe2Bi]2+ catalyzing olefin hydrosilylation under mild conditions.

Theoretical Study on the Rhodium-Catalyzed Hydrosilylation of C═C and C═O Double Bonds with Tertiary Silane

Reaction mechanisms of hydrosilylation of ketone and alkene with tertiary silane using the Wilkinson-type catalyst were theoretically investigated on the basis of density functional calculations using ωB97XD functional. Previously proposed three mechanisms, the Chalk-Harrod (CH) mechanism, the modified Chalk-Harrod (mCH) mechanism, and the outer-sphere mechanism were examined. Besides, we also found two mechanisms, the alternative CH (aCH) mechanism and the double hydride (DH) mechanism. In the aCH mechanism, a four-coordinate rhodium hydride complex formed through the elimination of R3Si-Cl is a catalytically active species. In the DH mechanism, the active species is a six-coordinate complex with two Rh-H bonds. For the C═O double bond hydrosilylation, the rate-determining steps of the aCH and DH mechanisms are both acetone insertion into the Rh-H bond, and the order of the activation barrier is DH < aCH ≈ CH < mCH. For the C═C double bond hydrosilylation, except for the mCH pathway whose rate-determining step is the hydrosilane addition reaction, the rate-determining steps of the CH, aCH, and DH pathways are Si-C reductive elimination reactions. The order of the energy barrier is DH ≈ mCH < aCH ≈ CH. In the outer-sphere mechanism, no stable intermediate or transition state was found. Consequently, we concluded that the DH mechanism is adopted as the mechanism for the Rh-catalyzed hydrosilylation of the carbonyl group while the mCH or DH mechanism is adopted as the mechanism for alkenes under conditions where their active intermediates are formed. The present result revises a hypothesis that the hydrosilylation of the carbonyl group is in general accomplished by the mCH mechanism. The active species in the DH mechanism has one more extra Rh-H bond compared to that of the other pathways, and its interaction with a silyl group, trans-influence, and small steric effect are the origin of the highly efficient catalytic activity, which was not reported before.

Xile Hu

ChemCatChemVolume 11, Issue 14 p. 3127-3127 InterviewFree Access Xile Hu First published: 30 May 2019 https://doi.org/10.1002/cctc.201900931AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Xile Hu was interviewed in celebration of his Royal Society of Chemistry Homogeneous Catalysis Award. Xile Hu Professor Hu was interviewed in celebration of his Royal Society of Chemistry Homogeneous Catalysis Award. Date of birth: August 7, 1978 Position: Professor of Chemistry, Ecole Polytechnique Fédérale de Lausanne (Switzerland) E-mail: [email protected] Homepage: http://lsci.epfl.ch ORCID: 0000-0001-8335-1196 Education: 2000 B.Sc. Peking University (P. R. China). 2004 PhD under the supervision of Prof. Karsten Meyer, University of California at San Diego (USA). 2005–2007 Postdoctoral scholar under the supervision of Prof. Jonas C. Peters, California Institute of Technology (USA). Awards: 2019 Royal Society of Chemistry Homogeneous Catalysis Award 2018 Resonate Award, Caltech 2017 National Latsis Prize of Switzerland Hobbies: Napping; travel (for pleasure); complaining Figure 1Open in figure viewerPowerPoint Xile Hu I admire people who engage themselves to make the world a better place. The thing I like most about my work is the substantial freedom in research. I would have liked to have discovered a reaction that matters. Guaranteed to make me laugh is seeing memes of reviewer 3 (hint: there is a site called shitmyreviewersays). What prompted you to investigate the topics you are interested in? Often I am problem-inspired. But sometimes I enter a new field impulsively, after wandering around intellectually or reading a paper in that field. What aspects of your research do you find most exciting? Our research is broad and encompasses homogeneous, heterogeneous, and biocatalysis. We can both make and measure. Now we try to connect these three traditionally distinct domains in catalysis. Do you have any tips you would like to share with early-career scientists? Originality is probably the best ticket to peer recognition. My 3 top papers: 1“Nickamine and Analogous Nickel Pincer Catalysts for Cross-Coupling of Alkyl Halides and Hydrosilylation of Alkenes”: R. Shi, Z. Zhang, X. Hu, Acc. Chem. Res. 2019, DOI 10.1021/acs.accounts.9b00118. (This account summarizes our work on Nickamine and related nickel pincer compounds, which had lifted my independent career.) 2“An Unconventional Iron Nickel Catalyst for the Oxygen Evolution Reaction”: F. Song, M. M. Busch, B. Lassalle-Kaiser, C.-S. Hsu, E. Petkucheva, M. Bensimon, H. M. Chen, C. Corminboeuf, X. Hu, ACS Cent. Sci. 2019, 5, 558. (Along the development of an OER catalyst with off-scale activity, we proposed a bifunctional mechanism which might overcome the limitation of scaling relationship in OER.) 3“Amorphous Molybdenum Sulfide Films as Catalysts for Electrochemical Hydrogen Production in Water”: D. Merki, S. Fierro, H. Vrubela, X. Hu, Chem. Sci. 2011, 2, 1262. (The discovery of a novel class of HER catalyst. It took almost 2 years to settle the referees, but time has proven the value of the paper, which is cited 100 times a year for the last 8 years.) Volume11, Issue14July 18, 2019Pages 3127-3127 This article also appears in:Catalysis Awards FiguresReferencesRelatedInformation

Alkene Hydrosilylation on Oxide‐Supported Pt‐Ligand Single‐Site Catalysts

AbstractHeterogeneous single‐site catalysts (SSCs), widely regarded as promising next‐generation catalysts, blend the easy recovery of traditional heterogeneous catalysts with desired features of homogeneous catalysts: high fraction of active sites and uniform metal centers. We previously reported the synthesis of Pt‐ligand SSCs through a novel metal‐ligand self‐assembly method on MgO, CeO2, and Al2O3 supports (J. Catal. 2018, 365, 303–312). Here, we present their applications in the industrially‐relevant alkene hydrosilylation reaction, with 95 % yield achieved under mild conditions. As expected, they exhibit better metal utilization efficiency than traditional heterogeneous Pt catalysts. The comparison with commercial catalysts (Karstedt and Speier) reveals several advantages of these SSCs: higher selectivity, less colloidal Pt formation, less alkene isomerization/hydrogenation, and better tolerance towards functional groups in substrates. Despite some leaching, our catalysts exhibit satisfactory recyclability and the single‐site structure remains intact on oxide supports after reaction. Pt single‐sites were proved to be the main active sites rather than colloidal Pt formed during the reaction. An induction period is observed in which Pt sites are activated by Cl detachment and replacement by reactant alkenes. The most active species likely involves temporary detachment of Pt from ligand or support. Catalytic performance of Pt SSCs is sensitive to the ligand and support choices, enabling fine tuning of Pt sites. This work highlights the application of heterogeneous SSCs created by the novel metal‐ligand self‐assembly strategy in an industrially‐relevant reaction. It also offers a potential catalyst for future industrial hydrosilylation applications with several improvements over current commercial catalysts.

Hydrosilylation of Alkenes Catalyzed by Nickel Carboxylate Metal–Organic Frameworks

Hydrosilylation of Alkenes Catalyzed by Nickel Carboxylate Metal–Organic Frameworks

Highly efficient hydrosilylation catalysts based on chloroplatinate “ionic liquids”

The reaction between ionic liquid [Cat]+Cl− (where Cat stands for 1-butyl-3-methylimidazolium, 1-butyl-2,3-dimethylimidazolium or 1-butyl-4-methylpyridinium) and the metal precursor ([PtCl2(cod)], PtCl4, K2[PtCl4] or K2[PtCl6]) yielded two groups of derivatives: [Cat]+[PtCl4]− and [Cat]+[PtCl6]−, which formally are counted among halometallate ionic liquids, however, due to their high melting points they should be classified into anionic platinum complexes rather than into ionic liquids. All the derivatives were isolated and characterized spectroscopically (NMR, ESI-MS) and crystallographic structures were determined for three derivatives: ([BMPy]2[PtCl4], [BMIM]2[PtCl6] and [BMMIM]2[PtCl6]. Moreover, their melting points were measured and thermal stability was assessed. The above derivatives were employed as catalysts for hydrosilylation of olefins with diverse properties. All the studied catalysts showed high activity and their insolubility in the reaction medium made easy their isolation and multiple use in subsequent catalytic runs. The most effective catalysts did not lose their activity even after ten runs, thereby they make a very good alternative to commonly used homogeneous catalysts. Their simple synthesis and stability make them interesting both for economic and ecological reasons.

Cyclic(Alkyl)(Amino)Carbene (CAAC)-Supported Zn Alkyls: Synthesis, Structure and Reactivity in Hydrosilylation Catalysis.

The reactivity of ZnII dialkyl species ZnMe2 with a cyclic(alkyl)(amino)carbene, 1-[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2-pyrrolidinylidene (CAAC, 1), was studied and extended to the preparation of robust CAAC-supported ZnII Lewis acidic organocations. CAAC adduct of ZnMe2 (2), formed from a 1:1 mixture of 1 and ZnMe2 , is unstable at room temperature and readily undergoes a CAAC carbene insertion into the Zn-Me bond to produce the ZnX2 -type species (CAAC-Me)ZnMe (3), a reactivity further supported by DFT calculations. Despite its limited stability, adduct 2 was cleanly ionized to robust two-coordinate (CAAC)ZnMe+ cation (5+ ) and derived into (CAAC)ZnC6 F5 + (7+ ), both isolated as B(C6 F5 )4 - salts, showing the ability of CAAC for the stabilization of reactive [ZnMe]+ and [ZnC6 F5 ]+ moieties. Due to the lability of the CAAC-ZnMe2 bond, the formation of bis(CAAC) adduct (CAAC)2 ZnMe+ cation (6+ ) was also observed and the corresponding salt [6][B(C6 F5 )4 ] was structurally characterized. As estimated from experimental and calculations data, cations 5+ and 7+ are highly Lewis acidic species and the stronger Lewis acid 7+ effectively mediates alkene, alkyne and CO2 hydrosilylation catalysis. All supporting data hints at Lewis acid type activation-functionalization processes. Despite a lower energy LUMO in 5+ and 7+ , their observed reactivity is comparable to those of N-heterocyclic carbene (NHC) analogues, in line with charge-controlled reactions for carbene-stabilized ZnII organocations.

Nickamine and Analogous Nickel Pincer Catalysts for Cross-Coupling of Alkyl Halides and Hydrosilylation of Alkenes.

Ligand development plays an essential role in the advance of homogeneous catalysis. Tridentate, meridionally coordinating ligands, commonly termed pincer ligands, have been established as a privileged class of ligands in catalysis because they confer high stability while maintaining electronic tenability to the resulting metal complexes. Pincer ligands containing "soft" donors such as phosphines are typically used for late transition-metal ions, which are considered "soft" acids. Driven by our interest to develop base-metal catalysis and in view of the "hard" character of base-metal ions, our group explored a pincer ligand containing only "hard" nitrogen donors. A prototypical nickel complex of this ligand, "Nickamine", turned out to be an efficient catalyst in a wide range of organic reactions. Because of its propensity to mediate single-electron redox chemistry, Nickamine is particularly suited to catalyze cross-coupling of nonactivated alkyl halides through radical pathways. These coupling partners have been challenging substrates for traditional, palladium-based catalysts because of difficult oxidative addition and nonproductive β-H elimination. The high activity of Nickamine for cross-coupling leads to high chemoselectivity and functional group tolerance, even when reactive Grignard reagents are employed as nucleophiles. The scope of the catalysis is broad and encompasses sp3-sp3, sp3-sp2, and sp3-sp cross-coupling. The defined nature of Nickamine facilitated the mechanistic study of cross-coupling reactions. Experiments involving radical-probe substrates, presumed intermediates and dormant species, kinetics, and density functional theory computations revealed a bimetallic oxidative addition pathway. In this pathway, two Ni centers each provide one electron to support the two-electron activation of an alkyl halide substrate. The success of Nickamine motivated our systematic structure-activity studies aiming at improved activity in certain reactions through ligand modification. Indeed, better catalysts have been developed for cross-coupling of secondary alkyl halides as well as direct alkynylation of alkyl halides. The improvement is attributed to a more accessible Ni center in the new catalysts than in Nickamine. Surprisingly, the improvement could be obtained simply by replacing a dimethyl amino group in Nickamine with a pyrrolidino group. During the study of the catalytic cycle of Nickamine in cross-coupling reactions, we synthesized the corresponding Ni-H species. Consequently, we explored the catalytic application of Nickamine in Ni-H mediated reactions, such as hydrosilylation. To our delight, Nickamine is a chemoselective catalyst for hydrosilylation of alkenes while tolerating a reactive C=O group. An analogous Ni pincer complex was found to catalyze unusual hydrosilylation reactions using alkoxy hydrosilanes as surrogates of gaseous silanes.

Platinum(II) complexes bearing bulky Schiff base ligands anchored onto mesoporous SBA‐15 supports as efficient catalysts for hydrosilylation

Reported herein is an easy‐to‐prepare novel heterogeneous catalyst of platinum complexes bearing binary ligands of bidentate naphthalenolimine and cyclo‐1,5‐octadiene that are anchored onto mesoporous silica SBA‐15. The presence of the binary ligands not only stabilized the platinum, but also enabled the platinum atoms to form nanoclusters with diameters of ca 1 nm, and led to high platinum loading (8.69 wt%). Moreover, the platinum catalyst exhibited high catalytic activity towards hydrosilylation of terminal alkenes and styrene with silanes under mild and solvent‐free conditions, with excellent regioselectivity.

Preparation and evaluation of a novel and high efficient boronic acid-substituted silica supported Pt catalyst

A smart design of transition metal nanocatalyst can efficiently improve its catalytic activity and use value. In this work, platinum (Pt) was successfully anchored to silica gel with phenylboronic acid group first time and formed nanoparticles (0.5–5 nm) which afforded a highly active supported catalyst for the hydrosilylation of olefins. The turnover number and regioselectivity in the reaction of methyldichlorosilane and 1-octene using 0.00000004 mol of the immobilized Pt catalyst approached 1,321,317 and 99% over 12 h. The corresponding hydrosilylation products in excellent yields and regioselectivities were obtained when we employed a broad range of terminal aliphatic olefins and methyldichlorosilane as substrates. The fully immobilized Pt nanoparticles could be recycled at least 10 runs without any obvious loss in catalytic activity.

Silole Amino Acids with Aggregation‐Induced Emission Features Synthesized by Hydrosilylation

The synthesis of silole amino acids was achieved through hydrosilylation of alkene or alkyne‐containing amino acids with 1‐methyl‐2,3,4,5‐tetraphenyl‐1H‐silole, using Karstedt's catalyst with yield up to 95 % and without epimerization. After selective deprotection of carboxylic acid or amine functions respectively, C‐ or N‐peptide coupling with an alanine moiety proved their possible incorporation into peptides. A model tripeptide was synthesized by solid phase synthesis with the N‐Fmoc protected silole amino acid version. The silole moiety can be also grafted on a precursor peptide directly on the solid support. These amino acids and peptides exhibit AIE properties with λem ca. 500 nm and Δλ ca. 100 nm. This approach constitutes an alternative and promising strategy for incorporation of such AIE fluorogens to peptides.

Genesis of electron deficient Pt1(0) in PDMS-PEG aggregates

While numerous single atoms stabilized by support surfaces have been reported, the synthesis of in-situ reduced discrete metal atoms weakly coordinated and stabilized in liquid media is a more challenging goal. We report the genesis of mononuclear electron deficient Pt1(0) by reducing H2PtCl6 in liquid polydimethylsiloxane-polyethylene glycol (PDMS-PEG) (Pt1@PDMS-PEG). UV–Vis, far-IR, and X-ray photoelectron spectroscopies evidence the reduction of H2PtCl6. CO infrared, and 195Pt and 13C NMR spectroscopies provide strong evidence of Pt1(0), existing as a pseudo-octahedral structure of (R1OR2)2Pt(0)Cl2H2 (R1 and R2 are H, C, or Si groups accordingly). The weakly coordinated (R1OR2)2Pt(0)Cl2H2 structure and electron deficient Pt1(0) have been validated by comparing experimental and DFT calculated 195Pt NMR spectra. The H+ in protic state and the Cl− together resemble HCl as the weak coordination. Neutralization by a base causes the formation of Pt nanoparticles. The Pt1@PDMS-PEG shows ultrahigh activity in olefin hydrosilylation with excellent terminal adducts selectivity.

Rare-earth metal catalysts for alkene hydrosilylation

Rare-earth metal catalyzed hydrosilylation of alkenes has emerged as a powerful and selective strategy for the synthesis of organosilanes. This transformation can offer distinctive catalytic sequences and reaction patterns from other catalysts because of the high electropositivity and lack of oxidative-addition process of rare-earth metal. This review summarizes the rare-earth metal catalysts for hydrosilylation of alkene according to the type of ligands. The synthesis and structure of rare-earth metal catalysts, the substrate scope as well as some preliminary structure-activity relationship and mechanism are discussed.

Publisher Correction: Bridging homogeneous and heterogeneous catalysis by heterogeneous single-metal-site catalysts

In the version of this Review originally published, the titles of Table 1 and Table 3 were mistakenly swapped. The title for Table 1 should be “Single Pt site catalysed selective hydrosilylation of various olefins”, and the title for Table 3 should be “Synthesis and applications of single-metal-site catalysts”. These errors have now been amended.

Hydrosilylation of alkenes catalyzed by Fe powder

A novel iron-catalyzed hydrosilylation of alkenes process under solvent-free conditions has been reported. The influence of the amount of Fe catalyst, reaction temperature and various alkenes and silanes on the hydrosilylation were investigated. High yields of adduct were obtained in the hydrosilylation of octene with MeCl2H, Me2ClSiH and Ph2SiH2 by using 10 mol% iron powder as a signal catalyst.

The catalytic activity of alkali metal alkoxides and titanium alkoxides in the hydrosilylation of unfunctionalized olefins

The catalytic activities of titanium alkoxides and alkali metal alkoxides for hydrosilylation of unfunctionalized olefins have been studied. Titanium(IV) alkoxides showed excellent catalytic activity, while alkali metal alkoxides have low catalytic activity for the hydrosilylation of olefins. However, by using titanocene dichloride as an additive, alkali metal alkoxides showed also excellent catalytic property for hydrosilylation. In comparison with titanium alkoxides, no α-adduct was obtained by using alkali metal alkoxides/Cp2TiCl2 as catalysts.

Hydrosilylation of Alkenes Catalyzed by Platinum on N-Doped Graphene

Key words N-doped graphene - platinum catalysis - hydrosilylation - alkenes - nanostructures

A magnetically recyclable superparamagnetic silica supported Pt nanocatalyst through a multi-carboxyl linker: synthesis, characterization, and applications in alkene hydrosilylation.

To simplify separation procedures, improve the reusability and decrease the loss of Pt, two Pt catalysts anchored on superparamagnetic silica (Fe3O4@SiO2-EDTA@Pt and Fe3O4@SiO2-DTPA@Pt) were prepared for the first time. The stable magnetic properties made them easily recyclable using a magnet rather than filtration, decantation or centrifugation. After 12 catalytic runs for both 30–50 nm Pt catalysts, the yield of 1-heptylmethyldichlorosilane was still up to 90%. The average loss of Pt in each reaction was only 0.87% for Fe3O4@SiO2-EDTA@Pt and 0.66% for Fe3O4@SiO2-DTPA@Pt owing to the strong interaction between Pt and carboxyl. The unprecedented activity and selectivity of the two Pt nanoparticle catalysts were observed in the hydrosilylation of alkenes. The turnover number in the reaction between 1-hexene and methyldichlorosilane using 5 × 10−8 mol of the Pt approached 662 733 for Fe3O4@SiO2-EDTA@Pt and 579 947 for Fe3O4@SiO2-DTPA@Pt over 12 h. The corresponding hydrosilylation products in excellent yields were obtained when we employed a broad range of alkenes as substrates, including 5 isomerous hexenes and 14 important industry raw materials. Fe3O4@SiO2-DTPA@Pt showed a better activity. They have potential for catalyzing more reactions and replacing the current homogeneous Pt catalysts in industry.