scholarly journals Well-defined silica supported aluminum hydride: another step towards the utopian single site dream?

2015 ◽  
Vol 6 (10) ◽  
pp. 5456-5465 ◽  
Author(s):  
Baraa Werghi ◽  
Anissa Bendjeriou-Sedjerari ◽  
Julien Sofack-Kreutzer ◽  
Abdesslem Jedidi ◽  
Edy Abou-Hamad ◽  
...  

Reaction of triisobutylaluminum with SBA15700 at room temperature occurs by two parallel pathways involving either silanol or siloxane bridges.

1988 ◽  
Vol 121 ◽  
Author(s):  
Atsushi Ochi ◽  
H. KENT BOWEN ◽  
Wendell E. Rhine

ABSTRACTThe reaction between ammonia and aluminum hydride (AIH3) was investigated as a possible synthetic route to aluminum nitride (AIN), using tetrahydromran (THF) as the solvent. When an excess of ammonia was employed, a white powder was obtained which was converted to AIN by calcination. However, when a stoichiometric amount of ammonia was used, a soluble intermediate was obtained. This intermediate polymerized slowly at room temperature via a condensation reaction involving the elimination of hydrogen to give a gel that could be converted to AIN.


Tetrahedron ◽  
2011 ◽  
Vol 67 (2) ◽  
pp. 285-288 ◽  
Author(s):  
Jing-Jing Wu ◽  
Jian-Hang Cheng ◽  
Jian Zhang ◽  
Li Shen ◽  
Xu-Hong Qian ◽  
...  

2006 ◽  
Vol 84 (2) ◽  
pp. 214-224 ◽  
Author(s):  
Robert Tomaszewski ◽  
Rainer Vollmerhaus ◽  
Abdulaziz Al-Humydi ◽  
Qinyan Wang ◽  
Nicholas J Taylor ◽  
...  

Ethylene polymerization was studied using a variety of iminophosphonamide (PN2) complexes of zirconium. Bis(PN2) dichloride complexes [Ph2P(NR′)2]2ZrX2 (X = Cl; 1a: R′ = p-tolyl; 1b: R′ = Bn; 1c: R′ = C6F5) or dimethyl complexes (X = Me; 2a: R′ = p-tolyl; 2b: R′ = Bn) and cyclopentadienyl(PN2)zirconium dichloride complexes [η5-C5R′′5][R2P(NR′)2]ZrCl2 (3a: R′ = p-tolyl, R = Ph, R′′ = H; 3b: R′ = SiMe3, R = Et, R′′ = H; 3c: R′ = C6F5, R = Ph, R′′ = H; 3e: R′ = 3,5-(CF3)2Ph, R = Ph, R′′ = H; 3f: R′ = 3,5-(CF3)2Ph, R = Ph, R′′ = Me) or dimethyl analogs [η5-C5H5][R2P(NR′)2]ZrMe2 (4a: R′ = p-tolyl, R = Ph; 4b: R′ = SiMe3, R = Et) were evaluated under a range of conditions using methylaluminoxane (PMAO) activator. Complexes 1 and 2 behave as precursors to single-site polymerization catalysts under the conditions studied, while complexes 3 or dialkyls 4 show more complex behavior and formation of poly(ethylene) with a bimodal molecular weight distribution. In contrast, activation of dialkyl complexes 4 with [Ph3C][B(C6F5)4] and polymerization in the presence of small amounts of PMAO or TIBAL as scavenger, led to single-site behavior. PMAO reacts with the neutral dialkyls via ligand abstraction to produce a number of P-containing species that may explain the multi-site behavior observed when using this activator. Dialkyls 4 react cleanly with [Ph3C][B(C6F5)4] in haloarene or even dichloromethane solution to furnish the corresponding cationic alkyls 5, which were characterized by multinuclear NMR spectroscopy. Fluxional dinuclear species are formed in the presence of excess dialkyl and these are susceptible to C—H activation to form µ-Me,µ-CH2 complexes one of which could be isolated in pure form. The cationic alkyls initiate the polymerization of 1-hexene at room temperature in chlorobenzene solution, but extensive chain transfer occurs and the systems are not living.Key words: single site, early metal olefin polymerization catalysis.


1973 ◽  
Vol 51 (1) ◽  
pp. 33-41 ◽  
Author(s):  
R. U. Lemieux ◽  
K. James ◽  
T. L. Nagabhushan ◽  
Y. Ito

Hydrogénation of 2-oximino-α-D-arabino-hexopyranosides in the presence of palladium and hydrazine provided high stereoselectivity for the formation of 2-amino-2-deoxy-α-D-glucopyranosides including disaccharide structures. Similar yields of gluco-isomer were normally obtained on reduction by borane of 2-acetoximino-tri-O-acetyl-α-D-arabino-hexopyranosides in tetrahydrofuran. However, reduction of 2-O-(2-acetoximino-tri-O-acetyl-α-D-arabino-hexopyranosyl)-1,3-dibenzoylglycerol provided a ratio of about 3:2 of the gluco-to manno-isomers. Reductions with lithium aluminum hydride were not appreciably stereoselective. Treatment of isopropyl 2-oximino-α-D-arabino-hexopyranoside with hydrazine in the presence of palladium catalyst gave isopropyl 2-deoxy-α-D-arabino-hexopyranoside in a novel room-temperature Wolff–Kishner type reaction.Reduction of isopropyl tri-O-acetyl 2-oximino-α-D-lyxo-hexopyranoside both with borane and lithium aluminum hydride proceeded with slight stereoselectivity for the galacto-isomer.


2009 ◽  
Vol 54 (24) ◽  
pp. 5889-5893 ◽  
Author(s):  
Isao Shitanda ◽  
Atsushi Sato ◽  
Masayuki Itagaki ◽  
Kunihiro Watanabe ◽  
Nobuyuki Koura

1992 ◽  
Vol 70 (1) ◽  
pp. 128-134 ◽  
Author(s):  
Hsing-Jang Liu ◽  
Weide Luo

Glycidic thiolesters were shown to undergo regioselective reduction with Raney nickel to give 1,3-diols. With sodium borohydride at room temperature and lithium aluminum hydride at −78 °C, the reduction of glycidic thiolesters was found to proceed chemoselectively to furnish 2,3-epoxy alcohols. Keywords: glycidic thiolesters, reduction, 1,3-diols, 2,3-epoxy alcohols.


2016 ◽  
Vol 35 (19) ◽  
pp. 3288-3294 ◽  
Author(s):  
Baraa Werghi ◽  
Anissa Bendjeriou-Sedjerari ◽  
Abdesslem Jedidi ◽  
Edy Abou-Hamad ◽  
Luigi Cavallo ◽  
...  

2009 ◽  
Vol 60 (10) ◽  
pp. 668-671
Author(s):  
Isao SHITANDA ◽  
Atsushi SATO ◽  
Kunihiro WATANABE ◽  
Masayuki ITAGAKI ◽  
Nobuyuki KOURA

Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.


Sign in / Sign up

Export Citation Format

Share Document