Search results for "hydrosilylation"

Cyclic metal(oid) clusters control platinum-catalysed hydrosilylation reactions : from soluble to zeolite and MOF catalysts

2020

The Pt-catalysed addition of silanes to functional groups such as alkenes, alkynes, carbonyls and alcohols, i.e. the hydrosilylation reaction, is a fundamental transformation in industrial and academic chemistry, often claimed as the most important application of Pt catalysts in solution. However, the exact nature of the Pt active species and its mechanism of action is not well understood yet, particularly regarding regioselectivity. Here, experimental and computational studies together with an ad hoc graphical method show that the hydroaddition of alkynes proceeds through Pt-Si-H clusters of 3-5 atoms (metal(oid) association) in parts per million amounts (ppm), which decrease the energy of…

Alkoxysilyl substituted oligo(phenylenevinylene)s: chromophores with reactive side chains

2003

The synthesis and properties of highly luminescent oligo(phenylenevinylene)s (OPV) with curable alkoxysilyl groups are described. Two diethoxymethylsilane moieties are connected directly or through flexible spacers to monodisperse alkoxy-substituted OPVs via hydrosilylation of alkinyl and allyloxy groups, Heck reaction with silylstyrene or condensation of aldehydes with aminopropyl silanes. Hydrolysis of the alkoxysilanes yields silanols condensing to curable three-dimensional networks, thus allowing the transformation of small molecules to transparent and fluorescent films with well-defined chromophores.

Palladium on Charcoal as a Catalyst for Stoichiometric Chemo- and Stereoselective Hydrosilylations and Hydrogenations with Triethylsilane

2014

Stoichiometric quantities of triethylsilane in the presence of activated Pd/C as the catalyst can be used to effect chemo-, regio-, and stereoselective hydrosilylation and transfer hydrogenation reactions. α,β-Unsaturated aldehydes and ketones are selectively hydrosilylated to give the corresponding enol silanes or transfer hydrogenated to give the saturated carbonyl compounds in the presence of other reducible functional groups.

Synthesis and Reactivity of New Complexes of Rhodium and Iridium with Bis(dichloroimidazolylidene) Ligands. Electronic and Catalytic Implications of …

2006

The preparation of a new bis(dichloroimidazolylidene) ligand has provided chelate-N-heterocyclic complexes of Rh(I) and Ir(I), which have been fully characterized. The crystal structures of three of the new complexes are described. The study of the electronic properties of the new ligands was made on the basis of the ν(CO) stretching frequencies of the carbonyl derivatives, showing that the chloroimidazolylidene ligand is significantly less σ-donating than the related nonchlorinated analogue. This electronic modification of the ligand has important implications for the catalytic properties of the compounds obtained, as observed from enhanced activity shown in catalytic hydrosilylation of te…

Bis-organosilane applications and synthesis

2017

Tutkielman kirjallisuusosuudessa perehdytään organofunktionaalisiin silaaneihin. Näitä yhdisteitä käytetään kytkentäaineina komposiittien valmistuksessa sekä monessa muussa sovelluksessa, kuten hydrofobisten ja hydrofiilisten pintojen muodostamiseen, kuivausaineina, ulkoisena elektroniluovuttajana polymeroinnissa, sekä kosteuskovettuvien silaanimodifioitujenpolymeeriliimojen (SMP) kovettumisreaktiossa. Silaanien kosteuskovettuminen johtuu pii-atomiin (Si) sitoutuneiden ryhmien hydrolysoitumisesta kosteuden vaikutuksesta, jolloin syntyy silanoli-ryhmiä (Si-OH), jotka voivat edelleen kondensoitua keskenään muodostaen siloksaanisidoksia (Si-O-Si) tai sidoksia pintojen hydroksyyliryhmien kanssa…

1994

The synthesis of linear carbohydrate modified polysiloxanes has been successfully performed by hydrosilation of functionalized and protected carbohydrate derivates. The functionalization (allyl glycosilation) may be applied to a wide variety of reducing carbohydrates. In this study, mono-, di- and oligosaccharides were converted by a simple two-step reaction (β-acetylation and allyl glycosilation) into active compounds, allowing the polymer analogous addition to random poly[dimethyl-co-hydromethyl]siloxanes (hydrosilation). By variation of the Si–H amount in the starting polymers, polysiloxanes with 1.5% to 56% (by weight) carbohydrate content were prepared. At small degrees of substitution…

Direct observation of a borane-silane complex involved in frustrated Lewis-pair-mediated hydrosilylations.

2014

Perfluorarylborane Lewis acids catalyse the addition of silicon-hydrogen bonds across C=C, C=N and C=O double bonds. This 'metal-free' hydrosilylation has been proposed to occur via borane activation of the silane Si-H bond, rather than through classical Lewis acid/base adducts with the substrate. However, the key borane/silane adduct had not been observed experimentally. Here it is shown that the strongly Lewis acidic, antiaromatic 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene forms an observable, isolable adduct with triethylsilane. The equilibrium for adduct formation was studied quantitatively through variable-temperature NMR spectroscopic investigations. The interactio…

Electrocatalytic Properties of Carbosilane‐Based Hyperbranched Polymers Functionalized with Interacting Ferrocenyl Units

2012

Two types of hyperbranched ferrocene-containing polycarbosilanes were obtained by hydrosilylation of polydiallylmethylsilane (hb-PDAMS) and polymethyldiundecenylsilane (hb-PMDUS) with diferrocenylmethylsilane. The redox properties of both polymers have been investigated both in solution and confined onto platinum electrodes. The electrocatalytic activity of polymer-modified electrodes toward the reduction of oxygen as well as the electrochemical reduction and oxidation of hydrogen peroxide has been examined.

Electroactive linear-hyperbranched block copolymers based on linear poly(ferrocenylsilane)s and hyperbranched poly(carbosilane)s.

2009

A convenient two-step protocol is presented for synthesis of linear-hyperbranched diblock copolymers consisting of a linear, organometallic poly(ferrocenylsilane) (PFS) block and hyperbranched poly(carbosilane) (hbPCS) segments. Linear PFS diblock copolymers were synthesized through photolytic ring-opening polymerization of dimethyl[1]silaferrocenophane as the first block and methylvinyl[1]sila-ferrocenophane as the second. These block copolymers served as polyfunctional cores in a subsequent hydrosilylation polyaddition of different silane-based AB 2 monomers. Three AB 2 monomers (methyldiallylsilane; methyldiundecenylsilane, and ferrocenyldiallylsilane) were investigated; they introduced …

Coordination versatility of pyridine-functionalized N-heterocyclic carbenes: a detailed study of the different activation procedures. Characterizatio…

2005

Three different reaction procedures for the coordination of N-n-butyl-N'-(2-pyridylmethyl)imidazolium salt have produced new N-heterocyclic complexes of Rh and Ir. The direct reaction of the imidazolium salt with [IrCl(cod)](2) provides a NHC-Ir(III)-H complex, while transmetalation from a silver-NHC complex and deprotonation with NEt(3) give new NHC complexes of M(I) and M(III) when reacting with [MCl(cod)](2) or [MCl(coe)(2)](2) (M = Rh, Ir). The crystal structures of the biscarbene Rh(III) and Ir(III) complexes are described. The catalytic properties of the compounds obtained have been tested in the hydrosilylation of acetylenes, the cyclization of acetylenic carboxylic acids, and hydrog…