Iron-Catalyzed Selective Hydrogenation and Hydroboration/Hydrosilylation of CO_(2)

Carbon dioxide(CO_(2))serves as a sustainable carbon source for building biomass,fossil fuels,and organic chemicals.Converting CO_(2) into value-added chemicals or fuels is an ideal approach to achieve carbon cycling.The reduction and conversion of CO_(2),a pivotal aspect of C1 chemistry,have long been a subject of intense research interest.Previous studies have demonstrated that through transition metal catalysis,hydrogen,boranes,and silanes(E-H,E=H,B or Si)act as effective reducing agents to transform CO_(2) into a range of C1 chemicals,such as formate,formaldehyde,and methanol.Over the past decade,research focus in this field has shifted towards utilizing cost-effective metals as catalysts for selective CO_(2) reduction.A comprehensive review of homogeneous iron-catalyzed CO_(2)reduction using E-H is presented,emphasizing reaction mechanisms and selectivity.

Kinetics of Hydrosilylation of Polyhydrosiloxane and Polyether

The hydrosilylation of polyhydrosiloxane and unsaturated allylic polyether terminated with ester group is processed with chloroplatinic acid as catalyst and ethyl acetate as solvent to exclude the mass transfer resistance in the system. The kinetic study is performed by means of Gel Permeation Chromatography. Within the experimental range （mass ratio of the whole reactants to solvent is 1：4, the tool ratio of Si-H bond to carbon-carbon double bond is 1： 1.3, the catalyst concentration from 1.0×10^-4mol·L^-1 （Pt） to 3.1×10^-4mol·L^-1 （Pt）, temperature between 338.15K and 350.35K）, a kinetic model of zero-th order reaction is built up and the evaluated model parameters are found to change linearly with the catalyst concentration.

Hydrosilylation of olefins over rhodium complex anchored over thioether-functionalized MCM-41

The hydrosilylation of alkenes with triethoxysilane has been achieved at 120 C in the presence of 0.01 mol%of thioetherfunctionalized MCM-41 anchored rhodium complex,affording the corresponding addition products in 68-91%yields.This supported rhodium complex can be reused several times without noticeable loss of activity.Our system not only solves the basic problems of catalyst separation and recovery,but also avoids the use of phosphine ligands.

Tri(t-butyl)phosphine-assisted selective hydrosilylation of terminal alkynes

A highly efficient and regio-/stereoselective method of hydrosilylating terminal alkynes was developed using Pt(DVDS)-tri(t-butyl) phosphine catalyst system at room temperature.Trans-products or alpha-products were obtained almost exclusively depending on the alkynes and silanes employed.

Functional Polyethylene Glycol with Carboxyl-supported Platinum as an Efficient Catalysis System for the Hydrosilylation of Alkenes

A series of carboxylated long chain polyethylene glycols(abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid.These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes.The factors affecting their catalytic properties,e.g.relative molecular mass of polyethylene glycol,reaction temperature,platinum content,and type of alkenes,have been studied.It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain,and increased with reaction temperature.Moreover,these catalysts could be reused several times without a noticeable decrease in activity or selectivity.The reaction pathway leading to excellent selectivity for the β-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed.

Effect of Aminoaromatic Acids as Additives on the Activity and Selectivity of the Platinum-catalyzed Hydrosilylation of Alkenes

A series of aromatic acids has been tested as additives for the platinum-catalyzed hydrosilylation of styrene with triethoxysilane. Both excellent conversion of styrene and selectivity in favor of the ,β-adduct were achieved using aminobenzoic acids as additive. Moreover, the use of 4-aminobenzoic acid led to significantly superior enhancement in both catalytic activity and selectivity among the tested aminobenzoic acids. Indeed, 100% conversion of styrene and 98.4% selectivity in favor of the β-adduct were obtained. Additionally, hydrosilylations of various alkenes with a variety of platinum catalysts have also been tested, and in each case the conversion of substrate and the selectivity of the β-adduct were promoted by using 4-aminobenzoic acid as additive.

SYNTHESIS OF POLYSILOXANE-SUPPORTED SELENAETHER PLATINUM COMPLEX AND ITS CATALYTIC PROPERTY FOR HYDROSILYLATION OF OLEFINS

A new type of selenious polymer, silica-bound polybispropoxyethyl-selenidesilsesquinoxane, and its platinum complex were synthesized from bis-allyloxyethyl selenide via hydrosilylation with triethoxysilane, followed by immobilized on fumed silica, and then reacting with potassium chloroplatinite under nitrogen atmosphere in acetone. It was found that the platinum complex can catalyze the hydrosilylation of olefins with triethoxysilane effectively. The effects of the nature of the substrate, the amount of complex used, and the reaction temperature on the catalytic activity were investigated.

THE HYDROSILYLATION REACTION OF LADDERLIKE POLYVINYLSILSESQUIOXANE WITH 1, 1, 3, 3-TETRAMETHYLDISILOXANE

The hydrosilylation reaction of ladderlike polyvinylsilsesquioxane (Vi-T) with 1, 1, 3, 3-tetramethyldisiloxane (H-MM) catalyzed by dicyclopentadienyl-dichloroplatinium (Cp2PtCl2) was carried out well in tetrahydrofuran (THF) to produce a soluble white solid. This product was characterized by IR, H-1-NMR, C-13-NMR, Si-29-NMR, DSC, X-ray diffraction method, gel permeation chromatography (GPC), vapour pressure osmometry (VPO), atomic force microscopy (AFM) and molecular simulation. These results prove that the product contains nanoscale tubular structure.

Synthesis of Calix[4] dithiacrown PlatinumComplexes and Their Catalytic Behavior in the Hydrosilylation of Olefins with Triethoxysilane

5,11,17,23-Tetrakis-1′, 1′-dimethylethyl-25,27-dihydroxy-26,28-1″, 7″, 13″-trioxa-4″, 10″-dithiatridecylcene-calix[4]arene (calix[4]dithiacrown-5) and its O-methylated derivate (dimethylcalix[4]dithiacrown-5) were synthesized fromp-tert-butylcalix[4] arene via 1, 3-lower rim functionalization with chloroethyltosylate, followed by ring-closing condensation with β,β/t'-dimercaptoethyl ether in the presence of sodium ethoxide as a base in reflux ethanol under nitrogen atmosphere, followed by methylation with methyltosylate in the presence of NaH as a base in dioxane. It was found that they can coordinate with platinous chloride and the platinous complexes are efficient catalysts for the hydrosilylation of olefins with triethoxysilane.

SYNTHESIS AND CATALYTIC HYDROSILYLATION PROPERTY OF POLYSILOXANE-SUPPORTED MERCAPTOSELENAETHER PLATINUM OR RHODIUM COMPLEX

Silica-bound mercaptoselenaether-containing silsesquioxane and its platinum or rhodium complex were synthesized from gamma-(2,3-epithiopropyl) propyltrimethoxysilane via ring-opening reaction with bis(2-hydroxyethyl) selenide, followed by hydrolysis and immobilization on fumed silica, and then reacting with potassium chloroplatinite or rhodium chloride in acetone under nitrogen atmosphere. It was found that two noble metal complexes can catalyze the hydrosilylation of olefins with triethoxysilane effectively. The influences of temperature, the amount of complex used, the nature of olefin on catalytic activity were investigated.

Chemo- and regioselective hydroboration of Δ^(14,15) in certain cephalostatin analogue

The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study aiming at the synthesis of multihydroxylated cephalostatin analogues, as for example cephalostatin 1Ⅰ, a potent anti-tumor natural product. Compound Ⅵ underwent chemo- and regioselective hydroboration reaction at only one of △14.15 double bonds furnishing compound Ⅸ as a major product in a fair yield.

CROWN FUNCTIONALIZED LINEAR POLYSILOXANE PLATINUM COMPLEX AS HYDROSILYLATION CATALYST

A modified method of preparing crown functionalized linear polysiloxane has been described.4'-allylbenzo-15-crown-5 was subjected to hydrosilylation with methyldichlorosilane,followed bypolycondensation with silanol-terminated polydimethylsiloxane to give the title crownfunctionalized linear polysiloxane. It was found that the polysiloxane could be coordinated withplatinum salt to form platinum complex, which could catalyze the hydrosilylation of olefins withtriethoxysilane efficiently.

Synthesis,Characterization and Catalytic Hydrosilylation Activity of [60] Fullerene n-Propylamine Platinum,Rhodium Complex

Fullerene n propylamine platinum,rhodium complex have been prepared from C 60 via amination with n propylamine, then reacting respectively with potassium chloroplatinite or rhodium chloride. The two noble metal complexes can effectively catalyze hydrosilylation of olefins with triethoxysilane. The Pt complex exhibits high regioselectivty for styrene, nearly 100% branched product is obtained.

SILICA-BOUND CROWN ETHERS PLATINUM COMPLEX AS HYDROSILYLATION CATALYST

Silica-bound 15-Crown-5, 18-Crown-6 with a spacer of propyloxymethyl and their platinum complexes have been synthesized. It was found that they were efficient catalysts for the hydrosilylation of olefms with triethoxysilane in the temperature range of 60 to 130 ℃.

Studies On A Selena-aza-crown Ether: Synthesis and Catalytic Behavior In Hydrosilylation

The synthesis of a new type of selena aza crown ether 6 (4 nitrobenzyl) 1,4,7,10 selenatriazacyclododecane (L) derivated from phenylalanine , and its platinum(Ⅱ) complex was described. The catalytic activity of this complex for the hydrosilylation of olefins by triethoxysilane was investigated.

4-Selena-7-thiaoctyl Polystyrene-supported Platinum Complex as Hydrosilylation Catalyst

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(η^(2)C_(60))Pt (PPh_3)_2 as the Catalystfor the Hydrosilylation of Olefins

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ATR-FTIR and XPS Evaluation of Alkyl Immobilization by Hydrosilylation on n-Si(111) for Photoelectrochemical Cell Electrode

An electrode development was needed with high efficiency and low costs as next generation solar cells. We attempted the electrode fabrication for a photoelectrochemical cell by immobilizing functional groups on a n-Si(111) surface. The immobilization was applied by hydrosilylation terminated with ester (hydrophobic) or carbonyl (hydrophilic) group. Results confirmed the immobilization on the Si surface by measuring ATR-FTIR and XPS.

Zirconium-hydride-catalyzed site-selective hydroboration of amides for the synthesis of amines:Mechanism,scope,and application

Developing mild and efficient catalytic methods for the selective synthesis of amines is a longstanding research objective.In this respect,catalytic deoxygenative amide reduction has proven to be promising but challenging,as this approach necessitates selective C-O bond cleavage.Herein,we report the selective hydroboration of primary,secondary,and tertiary amides at room temperature catalyzed by an earth-abundant-metal catalyst,Zr-H,for accessing diverse amines.Various readily reducible functional groups,such as esters,alkynes,and alkenes,were well tolerated.Furthermore,the methodology was extended to the synthesis of bio-and drug-derived amines.Detailed mechanistic studies revealed a reaction pathway entailing aldehyde and amido complex formation via an unusual C-N bond cleavage-reformation process,followed by C-O bond cleavage.