02198nas a2200265   4500008004100000022001400041245012100055210006900176260011000245300001400355490000600369520120900375100001401584700001701598700002101615700002101636700001801657700001501675700002101690700002801711700002201739700001701761700002201778856013201800       2012                        eng d  a2044-475300aElectrostatic grafting of a triphenylphosphine sulfonate on SBA-15: application in palladium catalyzed hydrogenation0 aElectrostatic grafting of a triphenylphosphine sulfonate on SBA1  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a1188-11950 v23 a<p>A novel strategy for the immobilization of a sulfonate functionalized triphenylphosphine ligand by ion-ion interactions on an imidazolium modified SBA-15 is presented. A support containing electrostatically grafted triphenylphosphine as the ligand was reacted with PdCl2( CNPh)(2) and the resulting hybrid material catalyzed olefin hydrogenation under mild conditions. The catalyst exhibits excellent activity, selectivity and stability and it can be reused for at least ten times without any loss of activity. An analogous but covalently grafted palladium system does not show any hydrogenation activity under the same conditions. TEM images of the used catalyst clearly prove the absence of palladium nanoparticles. Additionally, XPS investigations prove that palladium( 0) is formed and the phosphine is oxidized. By AAS no palladium contamination down to 0.5 X 10(-4) mmol could be detected in the products and further leaching tests verified the reaction to be truly heterogeneous. This concept of non-covalent immobilization guarantees a tight bonding of the catalytically active species to the surface in combination with a high mobility, which should be favorable for other catalyses, too.</p>1 aWang, Lei1 aDehe, Daniel1 aPhilippi, Thomas1 aSeifert, Andreas1 aErnst, Stefan1 aZhou, Zhou1 aHartmann, Martin1 aTaylor, Robin, N. Klupp1 aSingh, Anand, Pal1 aJia, Mingjun1 aThiel, Werner, R.  uhttps://library.ncl.res.in/content/electrostatic-grafting-triphenylphosphine-sulfonate-sba-15-application-palladium-catalyzed-001852nas a2200217   4500008004100000022001400041245013200055210006900187260000800256490000800264520105300272653001601325653002401341653003601365653003001401653001801431100002401449700002001473700002201493856011901515       2023                        eng d  a1387-181100aEfficient olefin epoxidation with high turnover rates over ordered mesoporous silica nanoparticles with uniform manganese sites0 aEfficient olefin epoxidation with high turnover rates over order  cDEC0 v3623 a<p>Olefin epoxidation has been studied over a series of mesoporous manganese silicate nanoparticles and tBuOOH. Partial substitution of Si by Mn in silica framework leads to highly dispersed, distorted Mn(III) sites, confirmed by various physicochemical analyses. High conversion and stable styrene oxide, stilbene oxide and epoxy cyclohexane yield have been achieved with MS75 with 1:1.5 ratio of olefin: oxidant. However, at faster reaction rates lower styrene oxide yield is observed at lower Mn-containing catalyst (MS100). High TON, TOF over manganese sites shows accessible monomeric Mn sites. Attributed to high reactant density at redox-active Mn silicate sites due to facile diffusion across shallow pore depth channels of nanoparticulate om-MSx and surface hydrophobic characteristics. The catalysts were found to be stable under recycling and filtration experiments. The excellent stability against leaching of active manganese species indicates stable sites and good textural properties in om-MSx, essential for extended activity.</p>
10aepoxidation10aManganese silicates10aMesoporous silica nanoparticles10aOrdered mesoporous silica10apH adjustment1 aNegi, Sanjay, Singh1 aKhatri, Prateek1 aSingh, Anand, Pal  uhttps://library.ncl.res.in/content/efficient-olefin-epoxidation-high-turnover-rates-over-ordered-mesoporous-silica