Hydrosilylation Processes Research Articles

Synthesis of Alkynylsilanes: A Review of the State of the Art

AbstractThis contribution offers a comprehensive overview of methods for forging sp C−Si bonds. Over time, alkynylsilanes (silylacetylenes), once considered mere byproducts of hydrosilylation processes, have become essential building blocks in organic synthesis. This literature review traces the evolution of their synthesis, from traditional methodologies relying on organolithium and organomagnesium compounds to more advanced cross‐coupling reactions involving hydro‐ and carbosilanes. Focused primarily on the past 25 years (2000–2024), it also extensively references significant historical breakthroughs. By analyzing synthetic methodologies, the review not only offers a comprehensive survey of the current state of knowledge but also identifies areas for improvement. Furthermore, to emphasize the importance of 1‐alkynylsilanes (1‐silyl‐1‐alkynes), selected applications of these compounds are highlighted, confirming their significant potential in organic synthesis.

Cobalt‐Catalyzed Hydrosilylation across Carbon‐Carbon, Carbon‐Oxygen, and Carbon‐Nitrogen Multiple Bonds – A Comprehensive Review

AbstractThe selective conversion of unsaturated compounds has emerged as a crucial method in chemical synthesis, enabling the synthesis of functional organic molecules. In recent decades, transition metal‐catalyzed hydrosilylation has emerged as a highly successful exemplar of industrialization within the realm of organic chemistry for the production of organosilanes, which have a pivotal role in organic chemistry and materials science. Precious metal complexes are typically employed as catalysts in most industrial hydrosilylation processes. The exploration of Earth‐abundant alternatives has emerged as a focal point of considerable research attention due to the high cost, poor selectivity, and many side reactions reported for precious metal catalysts. Ligand skeleton construction, selectivity, and mechanism research are areas where cobalt catalysts have more potential than iron and nickel. This review discusses the recent advances in cobalt‐catalyzed hydrosilylation across carbon‐carbon, carbon‐oxygen, and carbon‐nitrogen multiple bonds from 2019 to 2023.

Enantioselective Cobalt-Catalyzed Cascade Hydrosilylation and Hydroboration of Alkynes to Access Enantioenriched 1,1-Silylboryl Alkanes

Enantioenriched 1,1-silylboryl alkanes possess silyl and boryl groups that are both connected to the same stereogenic carbon center at well-defined orientations. As these chiral multifunctionalized compounds potentially offer two synthetic handles, they are highly valued building blocks in asymmetric synthesis as well as medicinal chemistry. Despite the potential usefulness, efficient synthetic approaches for their preparation are scarce. Seeking to address this deficiency, an enantioselective cobalt-catalyzed hydrosilylation/hydroboration cascade of terminal alkynes has been realized. This protocol constitutes an impressive case of chemo-, regio-, and stereoselectivity wherein the two different hydrofunctionalization events are exquisitely controlled by a single set of metal catalyst and ligand, an operation which would usually require two separate catalytic systems. Downstream transformations of enantioenriched 1,1-silyboryl alkanes led to various valuable chiral compounds. Mechanistic studies suggest that the present reaction undergoes highly regioselective and stereocontrolled sequential hydrosilylation and hydroboration processes.

Cobalt bis(2‐ethylhexanoate) and terpyridine derivatives as catalysts for the hydrosilylation of olefins

A simple method for the hydrosilylation of olefins by using air‐stable cobalt catalysts is developed. The catalyst system is composed of simple, cheap, and readily available cobalt(II) salts and well‐defined terpyridine derivatives as cocatalysts or ligands, and the hydrosilylation processes can be processed smoothly under mild conditions without either Grignard reagents or NaHBEt3 as activator.

Piperidinium and Pyrrolidinium Ionic Liquids as Precursors in the Synthesis of New Platinum Catalysts for Hydrosilylation

Six new air-stable anionic platinum complexes were synthesized in simple reactions of piperidinium [BMPip]Cl or pyrrolidinium [BMPyrr]Cl ionic liquids with platinum compounds ([Pt(cod)Cl2] or K2[PtCl6]). All these compounds were subjected to isolation and spectrometric characterization using NMR and ESI-MS techniques. Furthermore, the determination of melting points and thermal stability of the above derivatives was performed with the use of thermogravimetric analysis. The catalytic performance of the synthesized complexes was tested in hydrosilylation of 1-octene and allyl glycidyl ether with 1,1,1,3,5,5,5-heptamethyltrisiloxane. The study has shown that they have high catalytic activity and are insoluble in the reaction medium which enabled them to isolate and reuse them in consecutive catalytic cycles. The most active complex [BMPip]2[PtCl6] makes it possible to conduct at least 10 catalytic runs without losing activity which makes it an attractive alternative not only to commonly used homogeneous catalysts, but also to heterogeneous catalysts for hydrosilylation processes. The activity of the studied catalysts is also affected by the kind of anion and, to some extent, the kind of cation.

Diverse Catalytic Systems and Mechanistic Pathways for Hydrosilylative Reduction of CO2.

Catalytic hydrosilylation of carbon dioxide has emerged as a promising approach for carbon dioxide utilization. It allows the reductive transformation of carbon dioxide into value-added products at the levels of formate, formaldehyde, methanol, and methane. Tremendous progress has been made in the area of carbon dioxide hydrosilylation since the first reports in 1981. This focus review describes recent advances in the design and catalytic performance of leading catalyst systems, including transition-metal, main-group, and transition-metal/main-group and main-group/main-group tandem catalysts. Emphasis is placed on discussions of key mechanistic features of these systems and efforts towards the development of more selective, efficient, and sustainable carbon dioxide hydrosilylation processes.

The effect of the morpholinium ionic liquid anion on the catalytic activity of Rh (or Pt) complex-ionic liquid systems in hydrosilylation processes.

Studies were performed on the catalytic activity for olefin hydrosilylation shown by three rhodium complexes, [{Rh(μ-OSiMe3)(cod)}2] (I), [{Rh(μ-Cl)(cod)}2] (II) and [RhCl(PPh3)3] (III), and three platinum complexes, [Pt(PPh3)4] (IV), [Pt(PPh3)2Cl2] (V) and PtCl4 (VI), immobilized in a series of different anion-containing morpholinium ionic liquids. The effect of the kind of anion (its nucleophilic character) on the activity, stability and possibility of a catalytic system with multiple uses in the hydrosilylation process has been established. In the case of the best systems it was possible to reuse the same catalyst sample 10 times almost without any decrease in the activity and a TON value over 99 000 was obtained.

Synthesis and characterization of new (dimethylsilyl)phenoxy and (dimethyl(vinyl)silyl)phenoxy substituted cyclotriphosphazenes

The routes of synthesis, as well as, spectroscopic and X-ray diffraction characterization of a new group of bis- or hexakis-4-(dimethyl(vinyl)silyl)phenoxy and 4-(dimethylsilyl)phenoxy-substituted cyclotriphosphazenes as a versatile starting substrates for the synthesis of a variety of organic cyclophosphazene derivatives, via catalytic hydrosilylation or silylative coupling processes, is presented.

Iron N‐Heterocyclic Carbenes in Reduction Reactions

AbstractIron N‐heterocyclic carbene research has witnessed a spectacular growth in the last decade. A wide number of catalytic applications have been recently disclosed, demonstrating the enormous potential of Fe‐NHCs in organic synthesis. Catalytic reductions of multiple bonds through hydrogenation, transfer hydrogenation, hydrosilylation and hydroboration processes constitute important transformations. To date, this field of research is still in its infancy. Over the past few years our group has contributed to this area by developing new efficient and selective iron‐NHC complexes for the reduction of unsaturated organic groups. This review provides a concise overview of Fe‐NHC catalysed reduction reactions to push for further progress in this exciting area of research.

Tuning the activity and selectivity of iridium-NSiN catalyzed CO2 hydrosilylation processes

Catalyst design for iridium-catalyzed CO2 hydrosilylation processes: improvement of the selectivity and reduction of the reaction time.

Functionalization of spherosilicates via hydrosilylation catalyzed by well-defined rhodium siloxide complexes immobilized on silica

Well-defined rhodium siloxide complexes immobilized on silica ([(SiO)(SiOX)Rh(cod)](Aerosil 200) 1 and [(SiO)Rh(cod)(PCy3)](Aerosil 200) 2) synthesized via direct condensation of respective molecular precursors appeared to be very effective catalysts for quantitative synthesis of functionalized spherosilicates via direct hydrosilylation of olefins with octahydridospherosilicate. Catalyst 1 was also very active in subsequent hydrosilylation of two different olefins, which permitted efficient syntheses of spherosilicates with mixed functional groups of desired stoichiometric ratios. The catalysts were recycled at least 10 times without loss of efficiency in all the hydrosilylation processes performed.

Theoretical study on copper-catalyzed reaction of hydrosilane, alkyne and carbon dioxide: A hydrocarboxylation or a hydrosilylation process ?

The hydrocarboxylation and hydrosilylation processes proposed in the copper-catalyzed reaction among carbon dioxide, diphenylacetylene and HSi(OEt)3 were comparatively studied with the aid of density functional theory calculations. Our study is to explore why the reaction preferred a hydrocarboxylation rather than a hydrosilylation process. It was found that the σ bond metathesis between Cu–C and H–Si involved in the hydrosilylation process had a significantly high reaction barrier in the presence of CO2 (47.4 kcal/mol). Instead, CO2 insertion and the subsequent σ bond metathesis between Cu–O and H–Si involved in the hydrocarboxylation process were confirmed kinetically feasible, consistent with the experimental facts.

Synthetic Strategies to Combine High Performance Benzoxazine Thermosets with Polymers

AbstractSummary: Polybenzoxazines are newly developed thermosetting polymers exhibiting versatility in a wide range of applications including electronics and aerospace industries. They exhibit highly competitive combination of properties compare to the conventional thermosets. In this paper we present synthetic strategies to incorporate thermally curable benzoxazine functions into polymers as main and side chain groups in order to further improve various properties. The strategies successfully employed include monomer synthesis, macromonomer method, polycondensation, oxidative polymerization, photo‐polymerization, click chemistry and hydrosilylation processes. In the case of macromononomer method functional initiators were used in various controlled/living polymerizations to give polymers with benzoxazine end groups. The thermal curing behaviors of the obtained polymers were also demonstrated.

Hydrosilylation of functionalised olefins catalysed by rhodium siloxide complexes in ionic liquids

The use of ionic liquids for the immobilization of rhodium siloxide complexes has permitted development of highly effective catalysts for the hydrosilylation processes. Herein, we report the synthesis of organosilicon compounds in a biphasic reaction setup, allowing separation of the product, recovery and reuse of the catalyst, which is fundamental from the point of view of “green chemistry”.

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.

Application of Chiral Mixed Phosphorus/Sulfur Ligands to Enantioselective Rhodium‐Catalyzed Dehydroamino Acid Hydrogenation and Ketone Hydrosilylation Processes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Application of chiral mixed phosphorus/sulfur ligands to enantioselective rhodium-catalyzed dehydroamino acid hydrogenation and ketone hydrosilylation processes.

Chiral mixed phosphorus/sulfur ligands 1-3 have been shown to be effective in enantioselective Rh-catalyzed dehydroamino acid hydrogenation and ketone hydrosilylation reactions (eqs 1, 2). After assaying the influence of the substituents at sulfur, the substituents on the ligand backbone, the relative stereochemistry within the ligand backbone, and the substituents at phosphorus, ligands 2c (R = 3,5-dimethylphenyl) and 3 were found to be optimal in the Rh-catalyzed hydrogenation of a variety of alpha-acylaminoacrylates in high enantioselectivity (89-97% ee). A similar optimization of the catalyst for the Rh-catalyzed hydrosilylation of ketones showed that ligand 3 afforded the highest enantioselectivities for a wide variety of aryl alkyl and dialkyl ketones (up to 99% ee). A model for asymmetric induction in the hydrogenation reaction is discussed in the context of existing models, based on the absolute stereochemistry of the products and the X-ray crystal structures of catalyst precursors and intermediates.

Hyperbranched polymers from propargyloxysilanes: New types of acetylenic resins

AbstractNew hyperbranched polymers (1P–3P) from propargyloxysilanes (1–3) are described. The propargyloxysilanes were prepared from readily available reagents in 53–61% yields. The polymerizations were clean, one‐pot hydrosilylation processes catalyzed by Pt/C that were typically complete within 3 h. The polymers contained pendant acetylenic groups that underwent thermally induced crosslinking reactions. Heating the polymers to 1300 °C in flowing nitrogen resulted in weight losses ranging from 33 to 66%. Methyl substitution resulted in lower thermal stability. Further modification of the polymers was demonstrated by the reaction of 1P and 2P with phenylethynyldimethylsilane in the presence of a Pt catalyst. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3383–3391, 2001

ChemInform Abstract: Synthesis of Organo‐Silicon Monomers by Radiative Hydrosilylation and Condensation Processes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.