North catalyst system

The area of ethylene polymerization with late metal catalysts was rejuvenated when Brookhart and his group reported a family of new cationic Pd (II) and Ni(II) a-diimine catalysts (trademarked the Versipol catalyst system by DuPont) for the polymerization of ethylene, a-olefins, and cyclic olefins and the copolymerization of nonpolar olefins with a variety of functionalized olefins. These catalysts are now the focus of a joint development effort between the University of North Carolina at Chapel Hill and DuPont, and as can be seen from the scope of this review, they are being pursued at many other companies and universities. 

Titanium complexes have been shown to be active for the synthesis of cyclic carbonates or either di- or trithiocarbonates from epoxides and either carbon dioxide or carbon disulfide (Scheme 5.6). Titanium-catalysed synthesis of cyclic carbonates has been recently reviewed by North and coworkers. Titanium-salen complexes find application as catalysts, in combination with tetrabutylammonium bromide or tributylamine, for the synthesis of di- or trithiocarbonates from epoxides and carbon disulfide. It is worth highlighting that the catalyst loading can be reduced to 0.5 mol%, although 1 mol% of catalyst was required in order to achieve quantitative yields. The catalyst system showed a preference for dithiocarbonate formation for most of the epoxides studied. 

Very recently North s group revealed that the bimetallic aluminum(salen) complex 1 (Scheme 9) when used in conjunction with tetrabutylammonium bromide constitutes the only catalyst system capable of catalyzing the insertion of carbon dioxide into oxirane at 1 atm (760 mmHg) and at ambient temperature (25-30... 

A generation of millwrights and textile workers trained under Slater was the catalyst for the rapid proliferation of textile mills in the early nineteenth century. From Slater s first mill, the industry spread across New England to places like North Uxbridge, Massachusetts. For two decades, before Lowell mills and those modeled after them offered (30) competition, the Rhode Island System of small, rural spinning mills set the tone for early industrialization. 

Since 1981, three-way catalytic systems have been standard in new cars sold in North America.6,280 These systems consist of platinum, palladium, and rhodium catalysts dispersed on an activated alumina layer ( wash-coat ) on a ceramic honeycomb monolith the Pt and Pd serve primarily to catalyze oxidation of the CO and hydrocarbons, and the Rh to catalyze reduction of the NO. These converters operate with a near-stoichiometric air-fuel mix at 400-600 °C higher temperatures may cause the Rh to react with the washcoat. In some designs, the catalyst bed is electrically heated at start-up to avoid the problem of temporarily excessive CO emissions from a cold catalyst. Zeolite-type catalysts containing bound metal atoms or ions (e.g., Cu/ZSM-5) have been proposed as alternatives to systems based on precious metals. 

Admixture Systems North America Exclusive Synthesis Catalysts Care Specialties Aerosil Silanes Specially Acrylics... 

The SOFC system, however, has the potential to use natural gas directly, and thereby the opportunity to bypass the hydrogen source problem for stationary non-vehicle applications. The North Western University US patents on direct hydrocarbon oxidation are 2001/6,214,485 Bl, 2002/6,479,178 B2, 2003/0,118,879 and 2004/0,033,405, which deal with special catalysts and anodes. The parallel work at the University of Pennsylvania, http //www.upenn.edu/, is given in McIntosh S and Gorte (2003), correspondence address gorte seas.upenn.edu/. 

So far, our laboratories have primarily focused on the development, testing, and implementation of ccCA, but early success has been obtained in utilizing ccCA to solve chemical problems. For instance, a prototype version of ccCA was used by our group in collaboration with the experimental group of Professor T. Brent Gunnoe (then of North Carolina State University) to compute bond-dissociation enthalpies (BDEs) of ethylene, formaldehyde, methylene imine, carbodiimide, isocyanide, and their hydrogenated counterparts in order to probe useful correlations between the free BDEs of these model substrates and the proclivity of their insertion into the Ru(II)-phenyl bond of a catalyst-active species [108]. The BDEs of these small model systems provided a useful diagnostic to explain the thermochemical preferences of certain types of bond insertions. 

The most studied catalytic system is the one derived from 1,2-diamino-cyclohexane-derived Schiff base, presented for the first time by North and Belokon in 1998 for the cyanosilylation of aldehydes. In contrast to many catalysts known to date that require more than 10 mol% of loading and low temperatures, the catalyst 18 employed here was efficient at 0.1 mol% for a complete conversion at room temperature (0.01 mol% for 80% conversion. Scheme 7.14). Enantiomeric excesses from 30 to 86% were obtained from aromatic aldehydes and lower 44-46% enantiomeric excesses were observed from aliphatic ones (propanal and pivalaldehyde). 

The 1,2-addition of a cyanide ion to a carbonyl compound to form a cyanohydrin is a fundamental carbon-carbon bond-forming reaction in organic chemistry, and has frequently been at the forefront of advances in chemical transformations. In 2000, Belokon and North developed a catalytic system based on a vanadium-salen complex (Scheme 9.1). The synthesis of vanadium(iv) complex 1 was accomplished by refluxing a mixture of the corresponding Schiff base with vanadium(iv) sulfate and pyridine in ethanol under an argon atmosphere. A very low catalyst loading of 0.1 mol% was employed to convert aromatic and aliphatic aldehydes to cyanohydrin silyl ethers 3 with enantioselectivities of 68-95% after 24 h. Further investigations... 

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