Herstellung oberflächenmodifizierter Adsorbentien

Unger, Klaus K.; Thomas, W. Walsh; Adrian, P.

doi:10.1007/bf01501419

Cited by 39 publications

(8 citation statements)

References 14 publications

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“…A vast majority of commercially available bonded phases belong to this category, n-octyl-and n-octadecyldimethylsilyls being the preferred modifying groups. In another approach, direct Si-R linkages have been formed by sequentially reacting silica with thionyl chloride (SOCl2) and a proper Grignard (3,4) or organolithium reagent (5,6). Based upon steric considerations as well as relative bond strengths in silicon chemistry (7)(8)(9), the latter method should provide not only a closer attachment and a denser coverage of organic functionalities onto the silica surface but also a more hydrolytically stable bonded phase than that obtained by the corresponding organosiloxane-type structure.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and characterization of a hydride-modified porous silica material as an intermediate in the preparation of chemically bonded chromatographic stationary phases

Sandoval¹,

Pesek²

1989

Anal. Chem.

113

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A novel synthetic approach to produce chemically bonded slllca-based chromatographic stationary phases Is presented and discussed. The procedure Involves the preparation of a silica Intermediate containing stable silicon hydride (silane) surface species followed by the catalytic addition of these to organic compounds bearing a terminal vinyl group. This paper deals with the preparation of the hydride Intermediate via chlorination of silica followed by reduction with lithium tetrahydridoalumlnate. Several spectroscopic and thermoanalyt-Ical techniques were used to obtain information regarding the structural characteristics of the surface-reduced silica material. It was found that the surface SIH species formed were hydrolytically stable at low pH and thermally stable in the presence of oxygen at temperatures up to about 450 °C. Postreaction treatment of the hydrlde-derivatized solid with aqueous hydrochloric acid was also found to be essential to remove aluminum byproducts from the silica surface while presumably increasing the extent of silane formation.

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Section: Introductionmentioning

confidence: 99%

“…Figure8. Reaction scheme for the acid treatment of reduced silica:(6) siloxane-bridge cleavage,(7) hydrolytic removal of chemisorbed aluminum; (filled circle) silicon, (open circle) oxygen, (dashed circle) aluminum, (small open circle) hydrogen.…”

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confidence: 99%

Synthesis and characterization of a hydride-modified porous silica material as an intermediate in the preparation of chemically bonded chromatographic stationary phases

Sandoval¹,

Pesek²

1989

Anal. Chem.

113

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“…By comparison, this approach leads to higherCl values than the chlorination of silica with excess SiCl4 in refluxing toluene [Cl = 2.32 mol/m 2 (EV300)], [7] but lower Cl values than reached with the gas phase chlorination of silica with neat SiCl4 at high temperature (T >200 °C, Cl > 7 mol/m 2 ). [9] Treatment of SiO2-SiCl2 with LiInd* in a 1:1 solvent mixture of 1,4-dioxane / toluene and moderate heating to 60 °C for 24 h led to the indenyl-modified silicas SiO2-Si(Ind*)2.…”

Section: C6h3mentioning

confidence: 99%

Sequential Immobilization of Ansa-Hafnocene Complexes for Propene Polymerization

Arz¹,

Kratky²,

Günther³

et al. 2019

Preprint

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We report the immobilization of the ultrarigid ansa-hafnocene complexes rac-[Me2Si(Ind*)2HfCl2] (rac-1; Ind* = 7-(3',5'-Di-tert-butylphenyl)-4-methoxy-2-methylindenyl) on silica as hetereogeneous catalysts for propene polymerization. A sequential three-step synthesis on the siliceous surface led to pre-catalysts of the generalized structure SiO2-Si(Ind*)2HfCl2, which possess the silylene bridge of the substituted bis(indenyl) ligand directly attached to the surface. The immobilized pre-catalysts show very poor performance in the polymerization of propene, independent on the reaction conditions and the employed silica.Based on the results, we suggest that the close proximity of the catalyst to the surface combined with the steric congestion provoked by the ligand prevents a continuous polymerization, most likely due to a blockage of the catalytically active sites with growing polymer. TOC:

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“…In both cases the new groups serve to shield the unreacted silanols as well as the hydrolytically labile linkage that bonds the silane to the support. Although this steric protection has resulted in significantly improved bonded phases, the synthetic pro- In a different approach, bonded silicas bearing direct Si-C linkages have been developed (14)(15)(16). They involve the sequential reaction of the silica substrate with a chlorinating reagent (e.g., thionyl chloride) and a proper alkylating reagent (e.g., a Grignard or organolithium compound):…”

Section: Introductionmentioning

confidence: 99%

Hydrolytically stable bonded chromatographic phases prepared through hydrosilylation of olefins on a hydride-modified silica intermediate

Sandoval¹,

Pesek²

1991

Anal. Chem.

162

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A novel method for the preparation of bonded stationary phases Is described Hi which a hydrocarbonaeeous moiety Is bound to sMca surfaces through a direct sOIcon-carbon linkage. An established method Involving the chlorination and reduction of silica was used to prepare an Intermediate material containing fairly stable silicon hydride species. In the present report, such an Intermediate was reacted with terminal vinyl organic functionalities In the presence of a platinum catalyst. IR and NMR spectroscopic evidence confirmed the attachment of hydrocarbonaeeous ligands onto the sMca surface. Typical alkyl surface densities were 4.4 and 2.5 pmol/m2 for octyl and octadecyl groups, respectively. The extent of coverage was found to be strongly dependent on olefin concentration and reaction temperature. When compared to the corresponding organosllanlzatlon product, the bonded sMca was shown to have improved hydrolytic stabMty toward aqueous solutions containing trlfluoroacetlc acid.

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Herstellung oberflächenmodifizierter Adsorbentien

Cited by 39 publications

References 14 publications

Synthesis and characterization of a hydride-modified porous silica material as an intermediate in the preparation of chemically bonded chromatographic stationary phases

Synthesis and characterization of a hydride-modified porous silica material as an intermediate in the preparation of chemically bonded chromatographic stationary phases

Sequential Immobilization of Ansa-Hafnocene Complexes for Propene Polymerization

Hydrolytically stable bonded chromatographic phases prepared through hydrosilylation of olefins on a hydride-modified silica intermediate

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