21129-09-9Relevant articles and documents
The Structure of Metallomicelles
Griffiths,Fallis,Willock,Paul,Barrie,Griffiths,Williams,King,Heenan,Goergl, Richard
, p. 2022 - 2028 (2004)
The morphology of micelles formed by two novel metallosurfactants has been studied by small-angle neutron scattering (SANS) and small-angle-X-ray scattering (SAXS). The two surfactants both contain a dodecyl chain as the hydrophobic moiety, but differ in the structure of the head group. The surfactants are CuII complexes of monopendant alcohol derivatives of a) the face-capping macrocycle 1,4,7-triazacyclanonane (tacn), and b) an analogue based upon the tetraazamacrocycle 1,4,7,10-tetraazacyclododecane. Here, neutron scattering has been used to study the overall size and shape of the surfactant micelles, in conjunction with X-ray scattering to locate the metal ions. For the 1,4,7,10-tetraazacyclododecane-based surfactant, oblate micelles are observed, which are smaller to the prolate micelles formed by the 1,4,7-triazacyclononane analogue. The X-ray scattering analysis shows that the metal ions are distributed throughout the polar head-group region, rather than at a well-defined radius; this is in good agreement with the SANS-derived dimensions of the micelle. Indeed, the same model for micelle morphology can be used to fit both the SANS and SAXS data.
Well-defined Cp*Co(III)-catalyzed Hydrogenation of Carbonates and Polycarbonates
Dahiya, Pardeep,Gangwar, Manoj Kumar,Sundararaju, Basker
, p. 934 - 939 (2020/12/15)
We herein report the catalytic hydrogenation of carbonates and polycarbonates into their corresponding diols/alcohols using well-defined, air-stable, high-valent cobalt complexes. Several novel Cp*Co(III) complexes bearing N,O-chelation were isolated for the first time and structurally characterized by various spectroscopic techniques including single crystal X-ray crystallography. These novel Co(III) complexes have shown excellent catalytic activity to produce value added diols/alcohols from carbonate and polycarbonates through hydrogenation using molecular hydrogen as sole reductant or iPrOH as transfer hydrogenation source. To demonstrate the developed methodology's practical applicability, we have recycled the bisphenol A monomer from compact disc (CD) through hydrogenation under the established reaction conditions using phosphine-free, earth-abundant, air- and moisture-stable high-valent cobalt catalysts.
Straightforward synthesis of MTW-type magnesium silicalite for CO2 fixation with epoxides under mild conditions
Wen, Haimeng,Xie, Jingyan,Zhou, Yang,Zhou, Yu,Wang, Jun
, p. 5725 - 5735 (2019/10/23)
Aluminum-free magnesium silicalite with MTW topology (Mg-Si-ZSM-12) was fabricated via a straightforward hydrothermal synthesis route involving an initial acid co-hydrolysis step. Mg incorporation endowed superior basic properties to the MTW framework, as illustrated by CO2 sorption and temperature programmed desorption plus the activity in a typical basic reaction, Knoevenagel condensation. Mg-Si-ZSM-12 catalyzed the coupling of atmospheric CO2 with epoxides and led to the efficient production of cyclic carbonates with high yield and selectivity at relatively low temperature (down to 60 °C). The present strategy afforded a zeolitic solid base with regular 12-membered ring microporous channels that has potential application in CO2 fixation.
Novel chromium (III) complexes with N4-donor ligands as catalysts for the coupling of CO2 and epoxides in supercritical CO2
Cuesta-Aluja, Laia,Djoufak, Mary,Aghmiz, Ali,Rivas, Raquel,Christ, Lorraine,Masdeu-Bultó, Anna M.
, p. 161 - 170 (2013/12/04)
New neutral and cationic chromium(III) complexes with N4 Schiff base ligands have been prepared and characterized. These complexes are active catalysts for the cycloaddition of CO2 and styrene oxide in CH 2Cl2 solutions, affording epoxide conversions in a 39-92% range, with encouraging cyclic carbonate yields (up to 63%). It is to notice that the cationic species were significantly more active than their neutral analogs. Addition of tetrabutylammonium halides improved the selectivity toward styrene carbonate (87% yield). Dichloromethane could be avoided using solvent free or supercritical carbon dioxide as a solvent (scCO2) and, moreover, this improved the catalytic activity of the cationic complexes (TOF up to 652 h-1). Using scCO2, these chromium catalysts afforded the rapid and selective formation of cyclic carbonates from the coupling of CO2 to various linear terminal epoxides, such as epichlorydrin, propylene oxide and long chain terminal oxiranes. Coupling of cyclohexene oxide and carbon dioxide led to mixtures of poly(cyclohexene) carbonate and cyclic carbonate depending on the conditions (pressure and co-catalyst/catalyst ratio). Poly(cyclohexene) carbonate was isolated with a productivity 388 g/g Cr. Selective formation of the cyclic cyclohexene carbonate was obtained working under scCO2 conditions.
