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  • Inorganic Chemistry  (83,671)
  • Chemical Engineering  (17,982)
  • LUNAR AND PLANETARY EXPLORATION  (14,409)
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  • 1
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publication Date: 2023-06-23
    Description: The aim of this second Eng Special Issue is to collect experimental and theoretical re-search relating to engineering science and technology. The general topics of Eng are as follows: electrical, electronic and information engineering; chemical and materials engineering; energy engineering; mechanical and automotive engineering; industrial and manufacturing engineering; civil and structural engineering; aerospace engineering; biomedical engineering; geotechnical engineering and engineering geology; and ocean and environmental engineering. Therefore, the following editorial is a selection of representative works of these topics.
    Keywords: &nbsp ; Environment Management ; Environmental Engineering ; Chemical Engineering ; Materials Engineering&nbsp ; bic Book Industry Communication::T Technology, engineering, agriculture::TB Technology: general issues ; bic Book Industry Communication::T Technology, engineering, agriculture::TB Technology: general issues::TBX History of engineering & technology
    Language: English
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  • 2
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    De Gruyter | De Gruyter
    Publication Date: 2024-04-05
    Description: The essential principles of green chemistry are the use of renewable raw materials, highly efficient catalysts and green solvents linked with energy efficiency and process optimization in real-time. Experts from different fields show, how to examine all levels from the molecular elementary steps up to the design and operation of an entire plant for developing novel and efficient production processes.
    Keywords: Process Engineering ; Chemical Engineering ; Technical Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment::RNU Sustainability ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TD Industrial chemistry and manufacturing technologies::TDC Industrial chemistry and chemical engineering ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TQ Environmental science, engineering and technology
    Language: English
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  • 3
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    Frontiers Media SA
    Publication Date: 2024-04-04
    Description: The Frontiers in Chemistry Editorial Office team are delighted to present the inaugural “Frontiers in Chemistry: Rising Stars” article collection, showcasing the high-quality work of internationally recognized researchers in the early stages of their independent careers. All Rising Star researchers featured within this collection were individually nominated by the Journal’s Chief Editors in recognition of their potential to influence the future directions in their respective fields. The work presented here highlights the diversity of research performed across the entire breadth of the chemical sciences, and presents advances in theory, experiment and methodology with applications to compelling problems. This Editorial features the corresponding author(s) of each paper published within this important collection, ordered by section alphabetically, highlighting them as the great researchers of the future. The Frontiers in Chemistry Editorial Office team would like to thank each researcher who contributed their work to this collection. We would also like to personally thank our Chief Editors for their exemplary leadership of this article collection; their strong support and passion for this important, community-driven collection has ensured its success and global impact.
    Keywords: Green and Sustainable Chemistry ; Analytical Chemistry ; Theoretical and Computational Chemistry ; Polymer Chemistry ; Medicinal and Pharmaceutical Chemistry ; Organic Chemistry ; Nanoscience ; Catalysis and Photocatalysis ; Supramolecular Chemistry ; Electrochemistry ; Inorganic Chemistry ; Chemical Biology ; thema EDItEUR::P Mathematics and Science::PD Science: general issues
    Language: English
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  • 4
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-02-10
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-01-27
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-01-27
    Description: Polynitrogens have the potential for ultrahigh-performing explosives or propellants because singly or doubly bonded polynitrogens can decompose to triply bonded dinitrogen (N2) with an extraordinarily large energy release. The large energy content and relatively low activation energy toward decomposition makes the synthesis of a stable polynitrogen allotrope an extraordinary challenge. Many elements exist in different forms (allotropes)—for example, carbon can exist as graphite, diamond, buckyballs, or graphene. However, no stable neutral allotropes are known for nitrogen, and only two stable homonuclear polynitrogen ions had been isolated until now—namely, the N3− anion (1) and the N5+ cation (2). On page 374 of this issue, Zhang et al. (3) report the synthesis and characterization of the first stable salt of the cyclo-N5− anion, only the third stable homonuclear polynitrogen ion ever isolated. Author: Karl O. Christe
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Publication Date: 2016-03-19
    Description: Exploiting binding affinities between molecules is an established practice in many fields, including biochemical separations, diagnostics, and drug development; however, using these affinities to control biomolecule release is a more recent strategy. Affinity-controlled release takes advantage of the reversible nature of noncovalent interactions between a therapeutic protein and a binding partner to slow the diffusive release of the protein from a vehicle. This process, in contrast to degradation-controlled sustained-release formulations such as poly(lactic-co-glycolic acid) microspheres, is controlled through the strength of the binding interaction, the binding kinetics, and the concentration of binding partners. In the context of affinity-controlled release--and specifically the discovery or design of binding partners--we review advances in in vitro selection and directed evolution of proteins, peptides, and oligonucleotides (aptamers), aided by computational design.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pakulska, Malgosia M -- Miersch, Shane -- Shoichet, Molly S -- Canadian Institutes of Health Research/Canada -- New York, N.Y. -- Science. 2016 Mar 18;351(6279):aac4750. doi: 10.1126/science.aac4750.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering and Applied Chemistry, Institute of Biomaterials and Biomedical Engineering, and Donnelly Centre, University of Toronto, Toronto, Ontario, Canada. ; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada. ; Department of Chemical Engineering and Applied Chemistry, Institute of Biomaterials and Biomedical Engineering, and Donnelly Centre, University of Toronto, Toronto, Ontario, Canada. Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26989257" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Engineering ; Combinatorial Chemistry Techniques ; Delayed-Action Preparations/*chemistry ; Directed Molecular Evolution ; *Drug Design ; Humans ; Lactic Acid/*chemistry ; Microspheres ; Polyglycolic Acid/*chemistry ; Proteins/*administration & dosage
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-09-09
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-11-11
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2014-10-04
    Description: Ethanol toxicity in the yeast Saccharomyces cerevisiae limits titer and productivity in the industrial production of transportation bioethanol. We show that strengthening the opposing potassium and proton electrochemical membrane gradients is a mechanism that enhances general resistance to multiple alcohols. The elevation of extracellular potassium and pH physically bolsters these gradients, increasing tolerance to higher alcohols and ethanol fermentation in commercial and laboratory strains (including a xylose-fermenting strain) under industrial-like conditions. Production per cell remains largely unchanged, with improvements deriving from heightened population viability. Likewise, up-regulation of the potassium and proton pumps in the laboratory strain enhances performance to levels exceeding those of industrial strains. Although genetically complex, alcohol tolerance can thus be dominated by a single cellular process, one controlled by a major physicochemical component but amenable to biological augmentation.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4401034/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4401034/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lam, Felix H -- Ghaderi, Adel -- Fink, Gerald R -- Stephanopoulos, Gregory -- R01 GM035010/GM/NIGMS NIH HHS/ -- R01-GM035010/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2014 Oct 3;346(6205):71-5. doi: 10.1126/science.1257859. Epub 2014 Oct 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. Whitehead Institute for Biomedical Research, Cambridge, MA, USA. ; Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. ; Whitehead Institute for Biomedical Research, Cambridge, MA, USA. gfink@wi.mit.edu gregstep@mit.edu. ; Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. gfink@wi.mit.edu gregstep@mit.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25278607" target="_blank"〉PubMed〈/a〉
    Keywords: *Biofuels ; Cation Transport Proteins/genetics ; Cell Culture Techniques ; Cell Membrane/metabolism ; Chemical Engineering ; *Drug Resistance, Fungal/genetics ; Ethanol/*metabolism/pharmacology ; Fermentation ; Genetic Engineering ; Glucose/metabolism ; Hydrogen-Ion Concentration ; Phosphates/*metabolism ; Potassium Compounds/*metabolism ; Proton Pumps/genetics ; Proton-Translocating ATPases/genetics ; Saccharomyces cerevisiae/drug effects/genetics/*metabolism ; Saccharomyces cerevisiae Proteins/genetics ; Up-Regulation ; Xylose/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 11
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2014-11-29
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Langer, Robert S -- Gura, Trisha -- New York, N.Y. -- Science. 2014 Nov 28;346(6213):1146. doi: 10.1126/science.346.6213.1146.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Trisha Gura is a freelance writer who lives in Boston. For more on life and careers visit www.sciencecareers.org.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25430772" target="_blank"〉PubMed〈/a〉
    Keywords: Biotechnology ; *Career Choice ; Chemical Engineering ; *Entrepreneurship ; *Science
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 12
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2012-11-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Savage, Phillip E -- New York, N.Y. -- Science. 2012 Nov 23;338(6110):1039-40. doi: 10.1126/science.1224310.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Chemical Engineering Department, University of Michigan, Ann Arbor, MI 48109, USA. psavage@umich.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23180853" target="_blank"〉PubMed〈/a〉
    Keywords: *Biofuels ; Cell Culture Techniques ; Chemical Engineering ; Chlorophyta/*chemistry/growth & development ; *Hot Temperature ; *Hydrostatic Pressure ; *Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 13
    Publication Date: 2007-11-17
    Description: Artificial biochemical circuits are likely to play as large a role in biological engineering as electrical circuits have played in the engineering of electromechanical devices. Toward that end, nucleic acids provide a designable substrate for the regulation of biochemical reactions. However, it has been difficult to incorporate signal amplification components. We introduce a design strategy that allows a specified input oligonucleotide to catalyze the release of a specified output oligonucleotide, which in turn can serve as a catalyst for other reactions. This reaction, which is driven forward by the configurational entropy of the released molecule, provides an amplifying circuit element that is simple, fast, modular, composable, and robust. We have constructed and characterized several circuits that amplify nucleic acid signals, including a feedforward cascade with quadratic kinetics and a positive feedback circuit with exponential growth kinetics.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, David Yu -- Turberfield, Andrew J -- Yurke, Bernard -- Winfree, Erik -- New York, N.Y. -- Science. 2007 Nov 16;318(5853):1121-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Computation and Neural Systems, California Institute of Technology, MC 136-93, 1200 East California Boulevard, Pasadena, CA91125, USA. dzhang@dna.caltech.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18006742" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Catalysis ; Chemical Engineering ; *Computers, Molecular ; DNA/*chemistry ; Entropy ; Equipment Design ; Feedback, Physiological ; Mice ; Nanotechnology ; Nucleic Acid Hybridization ; Rabbits
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 14
    Keywords: Biomass conversion ; Biotechnology ; Chemical Engineering ; Chemistry industry ; Industrial Chemistry ; Kent ; Riegel ; biochemical engineering
    Description / Table of Contents: Substantially revising and updating the classic reference in the field, this handbook offers a valuable overview and myriad details on current chemical processes, products, and practices. No other source offers as much data on the chemistry, engineering, economics, and infrastructure of the industry. The Handbook serves a spectrum of individuals, from those who are directly involved in the chemical industry to others in related industries and activities. It provides not only the underlying science and technology for important industry sectors, but also broad coverage of critical supporting topics. Industrial processes and products can be much enhanced through observing the tenets and applying the methodologies found in chapters on Green Engineering and Chemistry (specifically, biomass conversion), Practical Catalysis, and Environmental Measurements; as well as expanded treatment of Safety, chemistry plant security, and Emergency Preparedness. Understanding these factors allows them to be part of the total process and helps achieve optimum results in, for example, process development, review, and modification. Important topics in the energy field, namely nuclear, coal, natural gas, and petroleum, are covered in individual chapters. Other new chapters include energy conversion, energy storage, emerging nanoscience and technology. Updated sections include more material on biomass conversion, as well as three chapters covering biotechnology topics, namely, Industrial Biotechnology, Industrial Enzymes, and Industrial Production of Therapeutic Proteins.
    Pages: Online-Ressource (XIV, 1562 pages)
    ISBN: 9780387278438
    Language: English
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 61-67 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Risk assessments have been performed to determine the risk associated with the transportation of hazardous wastes through a city. In the course of these assessments, a number of modeling issues arose relating to transportation accident rates, the characterization of incidents, the effect of thermal radiation, the impact of exposure to toxic chemicals, and the threshold for acceptable risk. This paper discusses these issues.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. S3 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 98-103 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents the design of ribbon wound pressure vessels useful for Ammonia, Urea and Methanol plants. The design is to create a thin shell of 1/5 the total wall thickness required, weld it to the end pieces, and wind 4 to 8 mm thick ribbons of 80 mm width at an angle of 15 to 30 degrees on the inner shell, using a prestress. The ribbons are welded at the ends and an even number of layers are wound cross-helically on to the shell. With more than 7000 vessels over the pressure range of 50 to 350 atmospheres in use in the various chemical industries in China over the past 30 years, their safety record has been excellent. Of particular interest has been the application of this technology in the Ammonia and Urea plants, where the design allows fabrication of these vessels at substantial reduction in cost, and early delivery, when compared to the mono wall technology.
    Additional Material: 6 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 20-22 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Most audits try to look at a representative selection of the plant procedures and equipment. An alternative is a survey, a look in depth at selected procedures (such as those for testing alarms and trips, issuing permits-to-work, controlling modifications, taking samples or testing relief devices) or selected equipment (such as level glasses or equipment for handling LPG). If the procedure or equipment is well-chosen, surveys may make a bigger contribution to safety, per person-hour, than a conventional audit.
    Additional Material: 1 Tab.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 39-42 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Under OSHA 1910.119, all Process Safety Management (PSM) facilities are required to keep their pressure relief system design information current. This article demonstrates why a pressure relief system design verification effort must be based on an equipment list, rather than a relief device list, in order to ensure that every piece of equipment is adequately protected. The formerly common practice of simply checking the design bases of all existing relief devices is deficient is deficient since this technique does not systematically ensure that every piece of equipment is protected.The “Berwanger Method” is a step by step process for designing or analyzing a pressure relief system to meet OSHA 1910.119 Process Safety Information (PSI) and Process Hazard Analysis (PHA) mandates. The method uses a relational database which tracks the relationships between protected equipment, potential overpressure scenarios, and protective devices.The challenge facing an operating company does not end once the design basis has been “verified” - the design basis information must also be maintained and be readily accessible to avoid costly reinvention of the wheel down the road. The “Berwanger Method” also addresses these maintenance issues.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 49-60 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper reports on a comprehensive literature search and small scale experimental work on the reaction characteristics of phosphorous trichloride and water. More than 30 tests were conducted, including both closed and open test cells. The water to phosphorus trichloride molar ratio was varied from 1 to 25. When in contact, water and phosphorus trichloride will form two liquid layers with a reaction starting at the interface. The impact of variables on reaction rates including the interface surface area, layer depth, and stirring were investigated experimentally. A reaction rate model that fits all the measured data is presented. Case studies illustrating the use of this data for emergency relief systems and vent containment design are presented in reference. [1].
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  • 21
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 68-73 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two major accidents in the 80's: the summit Tunnel Fire, England and Piper Alpha disaster, an offshore platform in the North Sea; and very recently, possible explosion of the Boeing, TWA flight 800 at New York, makes it imperative that further research into the mechonisms of the ignition of flammable vapor/air mixture in contact with hot surfaces needs to be done. There have been a number of studies of ignition by hot surfaces, but in all these studies the ignition sources were wire, sphere or strip, i.e., most of them were flat surfaces. But to the authors' knowledge, other variables which affect the ignition mechanism such as irregular geometrical shapes have not been studied. The purpose of this paper is to examine how the degree of confinement (or, configuration), size and orientation, of the heated surface affects the ignition temperature of the flammable vapors. The results were obtained by experimentnal and by computational fluid dynamics.
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  • 22
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. S3 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 23
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 9-15 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design and deflagration pressure relief vents is based on correlations developed for various types of combustible materials and for enclosures of different strengths. The primary guideline for deflagration vent design in the US is NFPA 68 Guide for Venting of Deflagrations [5]. That document gives guidance for the design of vents for enclosures containing flammable gases, specifically hydrogen, coke oven gas, propane, and methane. Application of the guide to other gases is achieved using the KG value. Values of KG are published for a relatively small number of gases, as seen in Table D-1 of NFPA 68. This work present KG data on several additional gases obtained in a laboratory scale test vessel along with analysis of the results with respect to published values of fundamental burning velocity.
    Additional Material: 9 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 23-31 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In May 1996, the Flammable and Combustible Liquids Code Committee of the National Fire Protection Association (NFPA) proposed for adoption by the Association a new edition of NFPA 30, Flammable and Combustible Liquids Code. This new edition was the culmination of two and one-half years' work by the Committee and included one of the most significant changes to that document in some twenty years: the incorporation of mandatory fire protection criteria for warehouses and other inside areas that store flammable and combustible liquids in containers and portable tanks.
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  • 25
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 17 (1998), S. 32-38 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes the development of a risk ranked Inspection Recommendation procedure that is used by one of Exxon's chemical plants to prioritize repairs that have been identified during equipment inspection.As part of the Company's Safety Management Practices initiative in the late 1980's a procedure was put into place to ensure that an Inspector's repair recommendations were properly addressed by the organization. The initial procedures were successful at “systematizing” the documentation and stewardship-to-completion of the Inspector's recommendation, however, there were complications with the original process: (1)The Inspector made a simple High, Medium or Low assessment of the priority/criticality of the recommendation. Frequently, this resulted in disagreements with Operations about the true priority of the recommendation.(2)If there was agreement on the priority of the recommendation, there was still disagreement on the relative rank within the priority-which high priority was the highest priority?(3)With limited funds to spend on repairs, it was (and is) important to make sure that the money was being spent on the highest risk items that had the greatest risk reduction/cost benefit ratio.To address these concerns, the procedure was modified to incorporate a risk assessment of the recommendation by both the Inspector and Operations. In the new procedure, the Inspector describes the deficiency that he/she finds and assesses the probability of failure within a certain time-frame. Operations must assess the consequences, from an environmental, safety and economics standpoint, were the failure to occur. These assessments are combined in the typical risk equation (risk = probability × consequences) to arrive at a severity index which serves to rank the recommendation relative to the other recommendations. Because Operations participates in the assessment there is very little disagreement about the priority of the recommendation. The severity index puts the recommendations in order so it is quite clear which are the highest priority recommendations. This process has helped to focus the entire organization on those deficiencies that represent the greatest risk with the result that less time and money is spent correcting items that have a low risk/cost benefit ratio, allowing these savings to be used to reduce the higher risks in the plant.
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    Process Safety Progress 17 (1998), S. 124-126 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple analytical method is presented for estimating the hybrid minimum ignition energy (HMIE) of dust-gas mixtures, based on the assumed generality of Bartknecht's well-known test data for mixtures of propane with a series of dusts in air. Since the HMIE equation requires input data which might be unavailable, the use of conservative default methods is discussed.
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    Process Safety Progress 17 (1998), S. 138-148 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A large and potentially hazardous decrease in aldehyde autoignition temperature (AIT) occurs with increased pressure. The AIT-pressure curve determined in a 5 L stainless steel sphere was similar for propionaldehyde and butyraldehyde in air, falling from about 185°C at atmospheric pressure to 90°C at 140 psia. Reduction of oxygen concentration had little effect on propionaldehyde AIT. At 100°C and 140 psia, autoignitions accompanied by at least a doubling of pressure were observed above 4% oxygen. In the presence of a few grams of free liquid, propionaldehyde vapor ignited in air at initial conditions significantly below the AIT. The mechanism appears to involve rapid Fe-catalyzed exothermic liquid-phase oxidation leading to autoignition of the adjacent heated gas layer. An acetaldehyde vapor-air mixture in the presence of free liquid and rust exploded at room temperature when air pressure was increased to 95 psia; this result is discussed with reference to a cylinder overpressurization that occurred while making up an ostensibly sub-LFL calibration mixture with compressed air. Propionaldehyde's limiting oxygen concentration (LOC) was investigated in the near-autoignition region using the same 5L apparatus; the findings are discussed with reference to an overpressurization incident in an air-liquid partial oxidation reactor. The general results are used to illustrate the application of LOC in partial oxidation processes subject to autoignition and to discuss elements of the current ASTM draft test method for LOC, which does not address test difficulties associated with condensable and/or reactive gas systems.
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    Process Safety Progress 17 (1998), S. F3 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Process Safety Progress 17 (1998), S. 157-170 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Risk analysis in chemical process industries is an elaborate exercise involving several steps from preliminary hazard identification to development of credible accident scenarios, to preparation of strategies for prevention or control of damage.All this requires substantial inputs of time and money. In order to get an approximate yet workable assessment of risk at much lesser costs, indices have been developed which link typical findings of elaborate risk analysis to scales of risk. The scales, in turn, provide workable measures of hazards/risks/safety.In the past, indices have been reported for swift risk assessment - the noteworthy among them include Dow fire and explosion index, Mond fire, explosion and toxicity index, IFAL index, and mortality index. A few rapid ranking techniques have also been proposed.This paper presents a new system of methodologies for Hazard Identification and Ranking (HIRA). The system consists of two indices: one for fire and explosion hazards and another for the hazard due to likely release of toxic chemical. The magnitudes of these indices indicate the severity of the likely accident; in terms of the size of the impacted area.HIRA has been applied to a typical chemical process industry - a sulfolane plant - and its performance has been compared with that of the Dow's and the Mond's indices. The study reveals that HIRA is more sensitive and accurate than the other indices.
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    Process Safety Progress 17 (1998), S. 200-208 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    Process Safety Progress 17 (1998), S. 213-218 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On October 31, 1987 a crane lifting a heat exchanger convection section failed and severed a 4″ loading line and a 2″ pressure relief line to an HF alkylation reactor settler drum at a petroleum refinery in Texas City, Texas. Vapors were emitted under pressure for about two hours and the vessel was plugged and drained aproximately 44 hours later. A plume from this accidental release passed through residential areas, damaging some vegetation (brown lawns), and spawning a class action law suit. An extensive analysis was conducted to determine the total inventory loss and to model the blowdown process and the concentrations of HF in the plume. Since the discharge rate was decreasing with time, a peak concentration of HF in the emitted vapors occurred just before the water spray mitigation system became fully operative. Consequently, the mitigation efforts were more effective late in the response when concentrations were already low. The predicted plume concentrations are consistent with observed vegetation damage effects, with concentrations below Emergency Response Planning Guideline Level 3 past 3/4 mile from the source. These results support a policy of sheltering in place during such an event.
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fifty-five gallon steel drum of a liquid organic peroxide pressurized and ruptured in the mix room of a manufacturing plant. The head of the drum blew off and the ejected material ignited. The resulting fire was extinguished by the building sprinkler system and operating personnel. Although there were no injuries, the fire caused significant damage in the mix room. The investigation of this incident, its likely cause, and the corrective actions will be discussed.
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    Process Safety Progress 17 (1998), S. 238-242 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Brazoria County Petrochemical Council, 13 companies that are working together to enhance relations between industry and the community, united in a joint effort at complying with the EPA's Risk Management Program. One of the significant issues the group had to address was the need to develop meaningful hazard assessment for presentation to the public. The EPA's “Table Look-Up Approach” found in the Offsite Consequence Analysis Guidance document is certainly a good tool; however, the built-in conservatism results in over-estimates of potential hazard areas. Much more meaningful results are shown to be obtained using one of the hazard release models.The value of using a credible scenario with realistic meteorological data is demonstrated through the consistently smaller areas predicted by the PHAST Model for planning purposes. Realistic scenarios/failure modes and realistic model parameters are important so that the risk to the public is not overstated. Proprietary models such as PHAST are invaluable in providing more meaningful consequences for planning purposes.
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    Process Safety Progress 17 (1998), S. 263-271 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Some of the hazards encountered by process plant operators involve the operation of in-line valves to control, start, and to stop flow. Torque required to operate valves may vary according to valve wheel size, in-line pressure, and valve flange position (open/closed). This study determined how valve wheel size, in-line pressure and valve position (open/closed) affect torque required to actuate a valve. Data were gathered with each combination of size, pressure and position for 336 valves in an operating petrochemical process facility. The results indicate that the main effects of valve wheel size, the in-line pressure, and open/closed valve position significantly affect operational torque requirements. In addition, the interaction between position and pressure was significant for operational torque. The implication of these results is that operators are exposed to operational torque requirements that exceed maximum acceptable capabilities that have been determined in previous studies.
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    Process Safety Progress 17 (1998), S. 288-296 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ammonia storage tank was built at the BASF Antwerp site in 1969 on land reclaimed from the sea. After several years of operation uneven foundation settlement, of up 2, occurred. In order to assure stability of this area for the next operation period (at least 10 years) measures were taken to ensure continued safe operation. One key measure was strain gauge monitoring at the location of maximum stress.
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    Process Safety Progress 17 (1998), S. 297-301 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Baker-Strehlow methodology was developed to provide an objective approach to prediction of blast pressures from vapor cloud explosions. The complete methodology was first published in 1994 [1]. Since then, it has evolved through ongoing research and use in VCE hazard analyses, facility siting studies and accident investigations. This article gives a brief overview of a paper on recent developments in the Baker-Strehlow methodology presented at the 31st Loss Prevention Symposium in Houston on March 9-13, 1997. Because the entire paper is too lengthy to be presented here, the following discussions may be lacking in some details. A copy of the complete paper can be obtained from the American Institute of Chemical Engineers (AIChE).Since the Baker-Strehlow method was first published, it has been used extensively in VCE hazard assessments in refineries and chemical plants. As expected, many practical lessons have been learned during the course of the hazard assessments, and the Baker-Strehlow method has evolved as a result. The changes have been evolutionary, not revolutionary. In keeping with the goals of the original study in which the methodology was developed, all changes have been incorporated with the intent of achieving an objective methodology to provide consistent prediction of VCE blast effects.The revisions to the Baker-Strehlow method resulting from experience gained during plant walk-downs and hazard assessments include: Systematic identification of “potential explosion sites” or “PESs,”Selection of the level of confinement for mixed zones of 2D and 3D confinement,Deciding on flame expansion when confinement is elevated above the vapor cloud,Selecting the reactivity for a fuel that is a mixture of fuels with differing reactivities,Predicting blast loads when there are multiple PES's within a vapor cloud considering different ignition source locations.
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    Process Safety Progress 17 (1998), S. 83-85 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Safety, health and loss prevention are major areas of interst for the American Institute of Chemical Engineers (AIChE). There has been an evolution of these concerns over the years in the Institute just as it has in industry. This article chronicles this evolution.
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    Process Safety Progress 17 (1998) 
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    Keywords: Chemistry ; Chemical Engineering
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    Process Safety Progress 17 (1998), S. 1-8 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent guidelines released by the U.S. EPA define a worst-case scenario as a release under stable atmospheric conditions defined as Pasquil-Gifford stability class F. Unfortunately, very few tests at F stability have been available heretofore to provide a basis for models. Recent test data with propane releases by the German research organization TUV provide a set of 60 experiments conducted specifically to define the effects of atmospheric stability class on dispersion. Of these, 25 tests were at F stability. A comparable number were at each other stability class A through E. In addition 23 tests were at wind speeds under 1.5 m/s in stable atmospheres. This paper reports on adjustments made to our models based on these new data by reducing the originally-postulated sensitivity to stability class. In spite of considerable scatter in the TUV data, particularly between two different types of propane analyzers, the model allows us to extract information by averaging over the tests.
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    Process Safety Progress 17 (1998), S. 16-19 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A multi-disciplinary team developed a guideline for determining access restriction zones around vented solids handling equipment. The guideline provides a method for ensuring the discharge from a vented explosion will not cause injury to personnel. The steps in this method include: calculating the extent of external hazards from vented explosions; identifying potential areas where personnel could be exposed to a hazard; identifying ways to eliminate or reduce the hazard area; and establishing and documenting any access restrictions needed. Hazard zone calculations use the latest knowledge from research into fireball size, flame length and external pressure equations in VDI 3673. The guideline provides guidance for using this information. Options for mitigating or reducing external hazards from vented explosions are also described. As part of the project, the team audited several solids handling systems to look for potential oversights in existing restricted access areas. Some of the team's learnings from these audits are reviewed.
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    Process Safety Progress 17 (1998), S. 43-48 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper defines situation awareness (SA) and discusses its importance to operator-machine system safety and functioning in the context of process control activities. Specifically, identified are relationships of human detection of critical process cues converying the status of automated control systems and operator interpretation of the meaning and relevance of such information to the potential for negative incidents in chemical processing. Beyond individual operator SA in interacting with control systems, intra- and inter- work team SA are discussed for supporting individual attainment of process control responsibilities. Factors critical to team SA are discussed. “Road blocks” to team SA are also analytically examined. Lastly, methods for assessing individual and team SA are reviewed and vehicles for relating outcomes of these methods to changes in process control operator and team behavior to improve human-machine system safety and performance are relayed.
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    Process Safety Progress 17 (1998) 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    Process Safety Progress 17 (1998), S. 74-81 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The knowledge of the ingition behavior of dust-air mixtures due to electrical sparks (MIE, Minimum Ignition Energy) and hot surfaces (MIT, Minimum Ignition Temperature) is important for risk assessments in chemical production plants. The ignition behavior determines the extent and hence the cost of preventive protection measures.This paper describes the use of the minimum ignition energy and minimum ignition temperature as very important safety indexes in practice.Based on the latest results from large scale experiments on pneumatic filling of silos with polymeric materials and new results of full scale filling tests using Flexible Intermediate Bulk Containers (FIBC) manufactured from a variety of materials, guidance can be given to ensure safe operation in different situations such as filling, emptying operations, type of powder handled.The aim of this paper is to assist people dealing with product. It reflects the present state of the art and current knowledge of the assessment and measures associated with powder handling.
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    Process Safety Progress 17 (1998), S. 104-106 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In mid-1997, an Advanced Process Control (APC) scheme was implemented at a resins manufacturing complex with the goal of minimizing flare fuel gas usage while maintaining sufficient energy (BTU/SCF flare gas) to be in environmental regulatory compliance. Prior to APC implementation, the flare system was manually controlled by plant operators with minor attention paid to the minimization of fuel gas usage. Since implementation, APC has saved the plant thousands of dollars in fuel gas costs and reduced unnecessary combusted fuel gas emissions.Hazard analysis techniques were used in the development of the control scheme. An overview of the APC used, the economic evaluation, and the hazard analysis techniques used in the project are presented here.
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    Process Safety Progress 17 (1998), S. 107-123 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the risk assessment parlance, especially with reference to chemical process industries, the term “domino effect” is used to denote “chain of accidents,” or situations when a fire/explosion/missile/toxic load generated by an accident in one unit in an industry causes secondary and higher order accidents in other units. The multi-accident catastrophe which occurred in a refinery at Vishakhapatnam, India, on September 14, 1997, claiming 60 lives and causing damages to property worth over Rs 600 million, is the most recent example of the damage potential of domino effect.But, even as the domino effect has been documented since 1947, very little attention has been paid towards modeling this phenomena. In this paper we have provided a conceptual framework based on sets of appropriate models to forecast domino effects, and assess their likely magnitudes and adverse impacts, while conducting risk assessment in a chemical process industry. The utilizability of the framework has been illustrated with a case study.
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    Process Safety Progress 17 (1998) 
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    Keywords: Chemistry ; Chemical Engineering
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    Process Safety Progress 17 (1998), S. 149-154 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article deals with fire protection for water miscible flammable liquids stored in plastic containers packaged in boxes located on pallets. A series of fire tests was conducted with palletized rack storage arrangements using in-rack sprinkler protection at various levels. The intent of the paper is to present data from this test series for these types of commodities. The paper will identify various existing water miscible flammable liquid products stored in this fashion and provide background information for protecting this type of storage as it relates to NFPA 30 Flammable and Combustible Liquids Code. The test data indicates that further research work is needed in the area of plastic containers for use with the storage of combustible and flammable liquids. Included in the paper are discussions concerning possible protection strategies and suggestions for future research which would benefit those involved in risk management of this type of commodity.
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    Process Safety Progress 17 (1998), S. 176-183 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The safest method to prevent fires and explosions of flammable mixtures in the first place. This method requires detailed knowledge of the flammability region as a function of the fuel, oxygen, and nitrogen concentrations. A triangular flammability diagram is the most useful tool to display the flammability region, and to determine if a flammable mixture is present during plant operations.This paper describes how to draw and use a flammability diagram. A procedure to estimate the flammability region using the available and sometimes limited data is discussed. The paper also shows how to use the flammability diagram with plant operations involving inerting and purging, and from bringing vessels into and out of service. A compilation of flammability diagrams for 30 materials, based on previously published data is provided.An automated apparatus for acquiring data for a flammability diagram is described. The apparatus consists of a 20-L sphere with an automated gas mixing system, a fuse-wire ignition system, and a high speed pressure measurement and data acquisition system. Data derived from the apparatus includes flammability limits, maximum pressure during combustion, and the maximum pressure rate. The effect of fuse-wire ignitor dynamics on the results is studied. A flammability diagram for methane drawn from data obtained from the apparatus, is presented.
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    Process Safety Progress 17 (1998), S. 86-97 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Regulatory issues related to material safety have made the accurate measurement and/or prediction of flash points essential. The flash point is one of the major physical properties used to determine the fire and explosion hazards of a liquid. Flash points are used by virtually all governmental entities worldwide to define “flammable” and “combustible” materials for shipping and safety regulations.A model is described here for the calculation of closed cup flash points for multicomponent, single liquid phase, mixtures. The model is based upon rigorous vapor/liquid equilibrium calculations supplemented with information about the lower flammable limits (LFL's) and heats of combustion (ΔHc's) for the mixture's constituent components. The closed cup flash points predicted with this model are typically within ± 5°C of the experimentally reported values. Such a model is useful as a means of verifying experimental data and as a tool for screening product formulations prior to experimental flash point determination. The model should considerably enhance the safety evaluation portion of the product development cycle, thus leading to shortened product time-to-market cycles. While flash points calculated with this model are in excellent agreement with experiment, experimental determination is still encouraged for critìcal safety applications.
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    Process Safety Progress 17 (1998), S. 134-137 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: National Advisory Committee's Acute Exposure Guideline Levels (AEGLs) for ammonia are critically evaluated. The technical bases for concern about AEGL-2 and AEGL-3 values derived by the committee are summarized recommendations made.
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    Process Safety Progress 17 (1998), S. 127-133 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An explosion and flash fire in a fixed bed reactor occurred at a municipal wastewater treatment plant (WWTP). Two employees were injured in the accident. The accident occurred in an ozone treatment building where ozone was used to treat odors from the offgas of the sludge concentration units. Excess ozone manually was routed to the fixed bed reactor (ozone destruct unit) where the ozone is catalytically transformed into oxygen before being discharged to the atmosphere.An investigation of the accident was conducted to determine the root cause of the explosion and flash fire and identify corrective actions which the WWTP management could undertake to prevent a recurrence. This investigation included site inspections, interview with the injured employees, sampling and analysis of various materials, an explosion dynamics analysis, and a root cause analysis.It was concluded that cooling oil from one of the ozone generation units entered the main ozone gas line due to a crack in one of the reactor's dielectric tubes. The cooling oil was vented into the ozone destruct unit when an employee opened a ball valve on the main ozone gas line. The cooling oil, essentially a saturated hydrocarbon mixture, reacted exothermically when it contacted the manganese dioxide catalyst. The exothermic reaction resulted in an explosion which propelled the access panel outwards and dispersed the catalyst pellets. A flash fire followed the explosion. The flash fire burned two employees and caused thermal damage to a nearby control panel.Although this accident was the first of its kind at this facility, this was not the first time that the ozone generator had experienced a failure of a dielectric tube. Thus, there was a significant probability that a dielectric tube failure could leak cooling oil into the main ozone gas line. This failure event could, in turn, result in another explosion and flash fire. The WWTP staff neither designed nor fabricated the ozone generator-destructor system. Therefore, it did not seem appropriate for the WWTP staff to modify the ozone system. Instead, it was recommended that the ozone destruct unit be taken out of service. The WWTP management acted on this recommendation.
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    Process Safety Progress 17 (1998), S. 171-175 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An explosion occurred in a petroleum product storage tank at a refinery. The liquid petroleum product was a heavy oil used as an asphalt extender. There were no injuries, but the cleanup was costly. The storage tank was one of several which received the product stream from a dehydration unit. The accident occurred shortly after the refinery was brought back on-line following a shutdown for schduled maintenance.This was the first incident of this kind to occur at this facility. Analysis of the process data and eyewitness observations indicated that the dehydration tower, which was supposed to be maintained at a minimum of 100°C during the shutdown, was allowed to drift below 100°C for an unknown period of time. This deviation enabled liquid water to enter the storage tank. Three operational factors contributed to the accident. Corrective actions were recommended to prevent a recurrence of a similar incident.
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  • 53
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    Process Safety Progress 17 (1998), S. 184-189 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust explosions have been with us for a long time. The first record of a dust explosion occurred in Turin, Italy, on December 14, 1785 [1]. The detailed record of this event is left to us by Count Morozzo. The event took place in Mr. Giacomelli's bakery. We know from his account that the weather was unseasonably dry, that a boy who worked in the bakery was using a shovel to stir and transfer the flour to a chute from a store room to the bakery and he had a lighted lamp to work by. The rest, as the saying goes, is history. No one was killed, and the building was saved by the sagacious fact of having plenty of windows. Since that first record, of course, there have been many explosions with much loss of life and significant economic consequences.
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  • 54
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    Process Safety Progress 17 (1998), S. 190-195 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The RSST DIERS vent sizing methodology is revised to provide realistic design equations for reactive systems consistent with available large-scale experience. Using easy to obtain RSST data such as rate of temperature rise and rate of pressure rise excellent agreement is illustrated for hybrid, vapor and gassy reactive systems.
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  • 55
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    Process Safety Progress 17 (1998), S. 196-199 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: From the 1960s onwards, the chemical and oil industries developed and used a number of new safety techniques which, in time, became second nature to those who applied them. They included the use of QRA for deciding priorities, Hazop and audits for identifying problems, inherently safer design for avoiding hazards, and more thorough investigation of incidents for identifying underlying causes. However, it has not yet become second nature to remember the accidents of the past and the actions needed to prevent them happening again.I joined industry in 1944 and moved to production in 1952. Then, and for at least 15 years afterwards, safety was a non-technical subject that could be left to arts graduates and elderly foremen. There was concern that people should not be hurt - great attention was paid to the lost-time accident rate - but there was no realization, that it was a subject worthy of systematic study by experienced technologists.This view changed at the end of the 1960s. A new generation of plants had been built, operating at higher temperatures and pressures and containing larger inventories of hazardous chemicals; the result was a series of fires and explosions and a worsening fatal accident rate. Figure 1 shows the situation in ICI, at the time the UK, s largest chemical company. Other companies experienced a similar state of affairs.As a result in 1968, I was appointed one of the company's first technical safety advisers, an unusual appointment at the time for someone with my experience, and if the reason for my appointment had not been so obvious I would have wondered what I had done wrong. I and my colleagues tried to apply the same sort of systematic thinking to safety that we applied in our other professional work. We developed some new concepts and techniques and adopted others. A common feature of our ides, realized only in restrospect, was that they consisted of more than mere problem-solving techniques. Once people had got used to these new concepts and used them a few times, they began to look at a whole range of problems in a different way.
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  • 56
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    Process Safety Progress 17 (1998), S. W3 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 57
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    Process Safety Progress 17 (1998), S. 259-262 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Case histories of 65 incidents in runaway reactions and emergency relief in Taiwan were analyzed and classified into several categories according to their causes, materials involved, equipment types, reaction types, and ignition sources. The cases in reactors and storage tanks were examined in more detail owing to the higher probability or larger potential hazard in these two types of equipments. The most common consequence of the incidents are explosions, fires, and atmospheric release of toxic chemicals. The most severe case was a thermal explosion from an organic peroxide storage area which caused the death of 33 persons. Popping and direct releasing of process chemicals to the atmosphere from relieving devices cause the greatest environmental concerns to the community close to the plants. Runaway reactions in batch type reactors occur frequently due to various operational mistakes. Heat of reaction is the most frequent ignition source of runaway reactions and emergency relief.
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  • 58
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    Process Safety Progress 17 (1998), S. 272-277 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: EPA's Risk Management Program regulation, promulgated in June 1996 as 40 CFR Part 68 requires subject industries to submit Risk Management Plans by June 1999. This plan requires hazard assessment of the operations of a facility using worst case scenarios and alternative releases. EPA has provided an Off-site Consequence Analysis (OCA) guidance to help facilities in their hazard assessment.OxyChem will be significantly impacted by the RMP rule. This paper outlines OxyChem's general experience and its strategy in planning to comply with this rule. OxyChem's approach in the development of the scenarios required by the rule is described in this paper. Limitations involved in the use of EPA's look-up tables or a single modeling solution for conducting all of the OCA are discussed. A three tiered OCA approach is presented as a possible alternative.
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  • 59
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    Process Safety Progress 17 (1998), S. 209-212 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: HFC-227ea (CF3CHFCF3;1, 1, 1, 2, 3, 3, 3-heptafluoropropane) is an effective replacement for Halon 1301 in fire suppression systems, providing rapid extinguishment of flames through a combination of physical and chemical mechanisms. The vast majority of applications for HFC-227ea involve the protection of Class A hazards, which are characterized by low fuel loadings and low energy output, with fire sizes often in the range of 5-10 kW. Mid- and large-scale testing has demonstrated that HFC-227ea, at its minimum design concentration of 7.0% v/v, is effective at extinguishing fires typical of those expected to occur in electronic data processing (EDP) facilities, telecommunication facilities and anechoic chambers. The levels of HF produced following extinguishment of typical Class a fires with HFC-227ea were well below the estimated mammalian LC50 and the human Dangerous Toxic Load (DTL), and do not appear to present a threat to electronic equipment.
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    Process Safety Progress 17 (1998), S. 219-224 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sandia National Laboratories (Sandia) has refined a process for developing inherently safer system designs based on methods used by Sandia to design detonation safety into nuclear weapons. The process was created when Sandia realized that standard engineering practices did not provide the level of safety assurance necessary for nuclear weapon operations, with their potential for catastrophic accidents. A systematic approach, which relies on mutually supportive design principles integrated through fundamental physical principles, was developed to ensure a predictably safe system response under a variety of operational and accident-based stesses. Robust, safe system designs result from this thematic approach to safety, minimizing the number of safety critical features. This safety assurance process has two profound benefits: the process avoids the need to understand or limit the ultimate intensity of off-normal environments and it avoids the requirement to analyze and test a large array of accident environment scenarios (e.g., directional threats, sequencing of environments, time races, etc) to demonstrate conformance to all safety requirements.
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    Process Safety Progress 17 (1998) 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
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  • 62
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    Process Safety Progress 17 (1998), S. 233-237 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method is described to enhance the management of process safety risks such that the number and type of safety systems protecting against any hazard are consistently predicated upon risk. Further, that such an assignment of safety systems can be made consistent throughout an organization. This consistency is gained through standardization of qualitative risk ranking and by setting company guidelines.
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  • 63
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    Process Safety Progress 17 (1998), S. 243-258 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Research was carried out to develop improved protection guidelines for silane handling systems through enhanced understanding of the behavior of releases of this pyrophoric gas. The approach involved addressing three aspects of the problem: the prompt ignition behavior of silane; the reactivity characteristics of quiescent silane/air mixtures; and the rates of reaction of silane leaked into enclosures with and without explosion venting, in the presence of ventilation air flow. A first conclusion, reached from tests in a ventilated cabinet, was that, contrary to prevailing belief, the ventilation flow has no measurable effect on the prompt ignition of the release. From experiments in a 5.1-liter (311-in.3) sphere it was found that silane/air mixtures of concentrations between 1.4 and 4.1% (by volume) are explosive but stable. In this case, piloted ignition tests yielded laminar burning velocities up to 5 m/s (1000 ft/min). Mixtures between 4.5 and 38% (the maximum reached in the tests) were found to be metastable, and would undergo spontaneous ignition after a delay ranging from 15 to 120 seconds, with the shorter values corresponding to higher silane concentrations. Experiments were also performed in a 0.645-m3 (22.8-ft3) vessel both with and without explosion venting, to measure the rates of energy release associated with impulsively-started silane leaks from 1/8 and 1/4-in. (3.2 and 6.4-mm) lines. A method for the prediction of the venting requirements of partial-volume deflagrations (PVD) was evolved into a tool to quantify the pressure rise from ignition of silane leaks in enclosures. These results represent a significant step toward updating existing design recommendations which prescribe ventilation requirements that are based on outdated and, in some instances, misinterpreted data.
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    Process Safety Progress 17 (1998), S. 278-287 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas explosion simulators are often used as tools in process plant design. This article presents some properties of gas explosions found using the EXSIM simulation software on three offshore modules with a total of nearly 10,000 simulations. The selected results are chosen for their supposed applicability to structural design in the process industries.Generalized data are presented for the effect of gas cloud size, explosion impulse vs. explosion pressure, pressure and impulse vs. duration, the probability of a “short” explosion, loading rate, pressure-time “shape” function, and the effect of introducing louvers.
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  • 65
    ISSN: 0009-2940
    Keywords: Alkoxopalladium(II) ; Conformational analysis ; Hydrogen bonding ; Two-dimensional and cage structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of palladium acetate with two equivalents of di- and triethanolamines RN(CH2CH2OH)2 in the presence of a base affords the new chelate-stabilized alkoxo Pd(II) complexes [Pd(OCH2CH2N(R)CH2CH2OH)2] [R = Me (1), Et (2), n-Bu (3), benzyl (4) or CH2CH2OH (5)]. These N,O-ligated complexes are isolated in high yield as yellow, crystalline solids and are thermally stable despite the presence of several β-hydrogen atoms in the ligand system. Both complexes possess a square-planar palladium coordination geometry with the two oxygen atoms positioned mutually trans. The most notable difference in the molecular structures is that 1 forms a two dimensional network of intermolecular O-H≡O hydrogen bonds, whereas 5 forms intramolecular O-H⃛O hydrogen bonds, which cage the palladium center. In solution 1-4 exist as a diastereoisomeric mixture (a racemic enantiomeric pair SNSN, RNRN and a mesomeric form RNSN) in a 1:1 molar ratio, and this ratio is independent of temperature in nonalcoholic solvents, When complexes 1-4 are dissolved in protic solvents (e.g. MeOH) the diastereomeric excess is temperature-dependent due to an exchange process between the meso diastereoisomer and the (racemic) enantiomeric pair. Thermodynamic parameters for this process in a mixture of MeOH-toluene have been determined with NMR and show this process to be influenced by the steric nature of the alkyl substituent (R) on nitrogen. A conformational analysis based on 1H-NMR coupling constants within the N,O-chelate ring of complexes 1-4 provides details on the solution structure of the ring in both diastereoisomers.
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  • 66
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 13-22 
    ISSN: 0009-2940
    Keywords: Carbamates ; Catalysis ; Substituted nitrobenzenes ; Palladium ; Reductive carbonylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1, 10-phenanthroline)2(triflate)2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. the selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion ot the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid function.
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  • 67
    ISSN: 0009-2940
    Keywords: Isothiazole complexes ; Dinuclear silver(I) complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of isothiazole-based potential ligands bearing substituents with additional donor sites in the 5-position of the heterocycle was synthesized [3-Me-5-R-C3HNS; R = CH=N(CH2)2py (1), CH=NCH2py (2), CH2N(CH2CH2NEt2)2 (4), (CH2)2SMe (5)]. Upon reaction with AgO3SCF3 they formed complexes [(1)AgOSO2CF3]2 (6), [(2)AgOSO2CF3]2 (7), [(4)Ag]2+2(O3SCF-3)2 (8) and [(5)AgOSO2CF3]2 (9), respectively. 6, 8 and 9 were shown by X-ray structural analyses to consist of dimeric units L2Ag2+2, either discrete (8), coordinated by terminal CF3SO-3 units (6). In 8 and 9 the isothiazole moiety is bonded to the metal center via the ring-N. The coordination potential of the isothiazole heterocycle is discussed.
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  • 68
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 115-118 
    ISSN: 0009-2940
    Keywords: Gold complexes ; Bromonium complex ; Halogenonium complex ; Halogen, two-coordinate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of (R3P)AuX (X = Cl, Br, I) with [(R3P)Au]+ BF-4 obtained from (R3P)AuCl and AgBF4 in tetrahydrofuran, lead to cationic binuclear gold(I) complexes of the general formula ([(R3P)Au]2X}+ BF-4. A number of chloro- (R = Ph, o-Tol, Mes, Bzl, Et), bromo- (R = Ph, o-Tol, Mes) and iodo-bridged (R = Ph, Mes) complexes of this type have been isolated and identified on the basis of their analytical and spectroscopic data. The crystal structure of bis[(triphenylphosphane)gold(I)]bromonium tetrafluoroborate was determined by single-crystal X-ray diffraction. The cations contain two-coordinate bromine atoms with an Au-Br-Au angle of 96.83(3)°.
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  • 69
    ISSN: 0009-2940
    Keywords: Arene complexes ; Ruthenium compounds ; Electrophilic substitution ; Lithiation ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6-ligands of (η4-1,5-COD)(η6-1,3,5-cyclooctatriene)Ru (1) or (η4-1,5-COD)(η6-naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono- and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)-(COD)Ru as starting materials. These facilitate a rapid bromine-lithium exchange reaction with nBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (-)-menthyl] enantiomerically pure or diastereomeric complexes containing CO2R* groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)-(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of simple alkenes at room temperature.
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 145-154 
    ISSN: 0009-2940
    Keywords: Fluorocarbons ; C-F bond activation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The main reaction pathways which lead to the breaking of C-F bonds in perfluoroalkanes and -arenes are discussed. Emphasis is placed on recent developments and on the mechanistic patterns that emerge.
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  • 71
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metal-vapor reactions of Co atoms with 1,3-tBu2CpH (1a), 1,3-tBu2CpH (1a), 1,2,4-tBu3CpH (1b) and EtMe4CpH (1c) are described. With 1a the two mononuclear complexes [(η5-tBu2Cp) (η4-tBu2-1,3-cyclopentadiene)Co] (2a) and [(η5-tBu2Cp)2Co] (3a) were isolated, together with the dinuclear cobalt cluster [{(η5-tBu2Cp)Co}2H3] (4a) and trace amounts of the tetranuclear cluster [{(η5-tBu2Cp)CoH}4] (5a). The molecular structures of 3a and 4a were determined by X-ray diffraction. Reaction of 1b with Co atoms afforded a single product, the dinuclear cluster [{(η5-tBu3Cp)Co}2H3] (4b), whose molecular structure was determined by single-crystal X-ray diffraction. Both, 4a and 4b exhibit extremely short Co-Co distances [2.244(1) (4a) and 2.242(1) Å (4b)], as found for the Me5Cp analog [{(η5-Me5Cp)Co}2H3] (4c). Reaction of an isomeric mixture of Me4EtCpH (1c) with Co atoms furnished the mononuclear sandwich [ (η5-Me4EtCp)(η4-Me4Et-1,3- cyclopentadiene)Co] (2b), the trinuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}3H4] (6a) and the tetranuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}4H4] (5c). The molecular structure of 5c was determined by X-ray crystallography and revealed a tetrahedral arrangement of the cobalt atoms. The electrochemical behavior of the dinuclear complexes 4a-4c was studied by cyclic voltammetry. Reversible redox couples were found for all three compounds, with a correlation between the degree of alkyl substitution and their respective cathodic shifts. Compounds 4a and 4b react with CO to yield the mononuclear and dinuclear complexes [ (η5- CpR)Co(CO)2] (R=1,3-tBu2, 1,2,4-tBu3) (7a and 7b) as well as [{(η5-CpR)CO}2(CO)2] (8a and 8b). Reaction of the trinuclear hydridocobalt cluster 6a and its Me5Cp analog 6b with AgBF4 in the presence of PEt3 yielded the heteronuclear clusters [{η5-Me4CPR)Co}3AgP(Et)3H4]+[BF4]- (R=Et, Me) (9a and 9b). 9a was structurally characterized by X-ray crystallography.
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 45-48 
    ISSN: 0009-2940
    Keywords: Metallated methyl isopropenyl ether ; Tetrahydrofurans ; 1-Oxabicyclo[4.3.0]heptanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl isopropenyl ether (1) has been metallated at low temperature with a 1:1 molar mixture of n-BuLi/t-BuOK in THF-hexane, and subsequently functionalized with a variety of electrophilic reagents. At temperatures higher than - 30°C, the metallated methyl isopropenyl ether (2) decomposes with formation of allene. When the suspension of 2 is allowed to warm up to room temperature in the presence of an additional equivalent of n-BuLi, the intermediary allene is converted into 1-propynyllithium (2c), which reacts with propylthiocyanate to give 1-propylthio-1-propyne (4). Some of the functionalization products were subjected to acidic hydrolysis affording the expected methyl ketones.
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 55-62 
    ISSN: 0009-2940
    Keywords: Diastereoselective hydrogenation ; Folic acid ; Immobilized optically active rhodium(I)/diphosphane catalysts ; Leucovorin ; HPLC analysis of 5-formyltetrahydrofolic acid derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the hydrogenation of the C=N bonds in the pyrazine ring of the vitamin folic acid (1) optically active rhodium(I)/diphosphane complexes immobilized on supports such as silica gel or Al2O3 were used. The reduction was carried out at 50 bar hydrogen pressure in an aqueous solution buffered to pH 7. Thus, 5,6,7,8-tetrahydrofolic acid (2) was obtained which contains a new asymmetric center at C-6 of the pterine system. Therefore, in combination with the (S) configuration of the natural L-glutamic acid part of the molecule two diastereomers with (6S,S) and (6R,S) configuration arise. The relatively unstable tetrahydrofolic acid (2) was converted into its 5-formyl derivative folinic acid (4) by treatment with methyl formate/formic acid in a 5:1 mixture of DMSO/pyridine. The Ca salt of folinic acid (4) is the widely used drug leucovorin. The diastereomers were separated by silica gel HPLC. To the column bovine serum albumine (BSA) is covalently bound. With optically active rhodium(I)/diphosphane catalysts, immobilized on silica gel supports, a diastereoselectivity of up to 90% could be achieved in the hydrogenation of folic acid (1).
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  • 74
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 405-408 
    ISSN: 0009-2940
    Keywords: Hexahydro-closo-hexaborates ; Boron ; Bridging ligands ; NMR spectroscopy ; Gold ; Copper ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By reaction of (PPh3)3 CuCl and PPh3AuCl with [B6H6]2- in organic media, dinuclear complexes are formed containing the hexaborate as a bridging ligand coordinated to the metal centers by opposite B3 facets of the B6 cluster in a trihapto mode. This is verified by single-crystal X-ray structural analysis of the isotypical (Paā) compounds [Cu2μ-bis-η3-B6H6)(PPh3)2] (1) and [Au2(μ-bis-η3-B6H6)(PPh3)2)] (2) which showed the metal centers to be very close to the B3 plane [1.92 (1), 2.10 (2) Å. The 11B NMR spectra of the two compounds feature doublets, at δ= -15.32 in 1 and at -11.51 in 2, which are significantly shifted downfield in comparison to [B6H6]2- (δ= -17.2).
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  • 75
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 425-429 
    ISSN: 0009-2940
    Keywords: Silver complexes ; Crown compounds ; Thioethers ; 1,3-Dithioles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of two crown thioethers 2,5,8,10,12-pentathiabicyclo[7.3.0]dodeca-1)9)-ene-11-thione (L) and -11-one (L') with Ag1 has been investigated by structural methods. Both thioethers act as tridentate ligands coordinating the silver ion in a trigonal fashion. In the case L, the 11- thione sulfur is coordinated additionally by another silver ion, to yield a polymeric chain with a distorted-tetrahedral geometry about the metal ion. Despite differing only in its carbonyl chalcogen, L' forms six-coordinated, monomeric complexes.
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  • 76
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 433-442 
    ISSN: 0009-2940
    Keywords: Metallobiosites ; Metalloproteins ; Metalloenzymes ; Dinucleating ligands ; Transition metals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Awareness of the asymmetric nature of numerous dinuclear metallobiosites and of the ability of the individual metal ions to have quite distinct roles in the functioning of the metalloenzyme concerned has led to a search for carefully designed unsymmetric dinucleating ligands that will give dinuclear complexes capable of acting as models for the metallobiosites. This review surveys progress made in the design and synthesis of complexes capable of serving as models for donor atom, coordination number and geometric asymmetries found at dinuclear metal centres.
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  • 77
    ISSN: 0009-2940
    Keywords: Alkali metal organophosphanylamide ; Carbon-potassium bonding ; Phosphazane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metalation of bis(diphenylphosphanyl)amine [HN-(PPh2)2,1 with KOtBu at 95°C in toluene affords a pale yellow precipitate of potassium bis(diphenylphosphanyl)amide (3a). On addition of liquid N,N,N′,N“,N“-pentamethyldiethylenetriamine (PMDTA, 4) the precipitate dissolves in toluene at 115°C to give a yellow solution, from which yellow-green blocks of [(Ph2P)2NK·PMDTA] (3b) are obtained. X-ray analysis reveals that the coordination sphere of potassium consists of the chelating triamine ligand and [N(PPh2)2]- as N-donor as well as η1 and η2 C-donor with two phenyl fragments. No phosphorus coordination of [N(PPh2)2]- is observed.
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  • 78
    ISSN: 0009-2940
    Keywords: Phosphaalkynes ; Triorganoaluminium compounds ; Cooligomerization ; Cage compounds ; Aluminium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When the trialkylaluminium reagents 5 are allowed to react with phosphaalkynes 4 in n-pentane, a highly selective phosphaalkyne cyclotrimerization with incorporation of two organometallic units occurs (→ 6). The tetracyclooctane derivatives 6a-e represent the first examples of phosphorus-aluminium-carbon cage compounds. The polycyclic products 6 are able to function as ligands in transition-metal complexes (→ 7), which is illustrated by the reactions of 6b, c with nonacarbonyldiiron and pentacarbonyl(tetrahydrofuran)tungsten, respectively.
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  • 79
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 283-289 
    ISSN: 0009-2940
    Keywords: Zinc ; Sulfonate ligands ; Perchlorates ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempts are reported to incorporate sulfonate and perchlorate anions as ligands in zinc complexes of tripodal ligands. Using tris(benzimidazolylmethyl)amine (BIMA) only the aqua complexes [ (BIMA)Zn-OH2](RSO3)(ClO4) and [(BIMA)Zn-OH2](RSO3)2(R=CH3, CF3, p-tolyl) were accessible. Using substituted pyrazolylborates (Tp*), the same three sulfonate anions were found to be ligands in the complexes Tp*Zn-OSO2R. Spectroscopic evidence for perchlorate coordination in Tp*ZnClO4 · 2 DMSO conflicts with crystallograpic evidence against it in Tp*ZnClO4 · pyridine. The crystal structures of [(BIMA)Zn-OH2](CH3SO3)2, TpCum,MeZn-OS02CH3, TPtBu,MeZn-OSO2C6H4-p-CH3, and [TpCum,MeZn · NC5H5]ClO4 were determined.
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  • 80
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 295-298 
    ISSN: 0009-2940
    Keywords: Rhenium ; Oxides ; Alkyl ligands ; Dirhenium compounds ; Metal-metal interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most alkylrhenium(VII) oxides, e.g. ((cyclo)-C3H5)Re03 (2) are rather sensitive to temperature and moisture with the prominent exception of methyltrioxorhenium (1). The corresponding alkylrhenium(VI) oxides of formula [RR′(O)- Re(μ-O)]2 [R=R′=(cyclo)-C3H5 (3), iPr (4); R=CH3, R′=C2H5 (5), R=CH3, R′=iPr (6)] are much more stable in this regard. They can be handled in air at room temperature. They were synthesized from Re207 and dialkylzinc precursors, fully characterized and are available in much higher yields than their ReVII congeners. Mixed tetraalkyltetraoxodirhenium(VI) complexes (R # R′) synthesized from 1 and dialkylzinc compounds form as a mixture of cis/trans isomers. They are oily liquids at room temperature. The Re=O and Re-Re stretching force constants as a measure of the bond strengths, were determined from IR and Raman data.
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  • 81
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 335-340 
    ISSN: 0009-2940
    Keywords: Allylsilanes ; Superbases ; Metalations ; Stereoselectivity ; Cyclizations ; Silicon ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When treated with two equivalents of a butyllithium/potassium tert-butoxide mixture, terminal olefins carrying unprotected hydroxy or carboxy groups generate allylmetal intermediates which can be trapped with chlorotrimethylsilane to afford functionalized (Z)-2-alkenyltrimethylsilanes. One equivalent of the superbasic reagent suffices if the unsaturated alcohols are first protected as acetals before being subjected to the metalation/silylation/hydrolysis sequence.
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  • 82
    ISSN: 0009-2940
    Keywords: Metallacycloalkanes ; Metallacycloalkenes ; Osmium ; Iron ; Cyclic ketones ; Metallacycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the bis(triflates) [F3CSO3-(CH)m-O3SCF3] [m = 5-10, 12, 14, 16 (1a-i) with Na2[Os(CO)4] in dimethyl either affords the osmacycloalkanes 2a, 2b and 2f-i (m = 5, 6, 10, 12, 14, 16), diosmacycloalkanes 3a-i (m = 5-10, 12, 14, 16), and triosmacycloalkanes 4a-i (m = 5-10, 12, 14, 16). The structure of 3f was investigated by an X-ray structural analysis. This 22-membered disomacycle crystallizes in the space group Pā with Z = 1. If the unsaturated cis-4-octen-1,8-diyl bis(trifluoromethanesulfonate) (5) is treated with Na2[Os(CO)4] the diosmacyclooctadeca-5,14-diene 6 is obtained. By treating the bis(triflates) 1a, b with Na2[Fe(CO)4] the corresponding ferracycloalkanes are formed only in situ. Insertion of carbon monoxide into the M-C σ bonds leads to the cyclic ketones 7a, d and to the diketone 8d.
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  • 83
    ISSN: 0009-2940
    Keywords: Pyrrolidinephosphanes ; 3-Hydroxypyrrolidine ; 3-Diphenylphosphanylpyronlidine ; Salt effects ; Polymorphism ; Homogeneous catalysis ; Palladium ; Asymmetric catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of both enantiomers of 3-diphenylphosphanulpyrrolidiine (2) and several N-substituted derivatives together with two PdIi complexes of this ligand is reported. Form L-malic acid and L-hydroxyproline both enantiomers of 3-hydroxypyrrolidine are prepared without any problems due to epimerization. KPPh2 in the presence of LiCl is shown to be the most effective reagent for the synthesis of 2. The reported X-ray structure determination sof Pdl2 complexes show a rather rigid bicyclic hetero-norbornane skeleton. The flexibility of the other parts of the molecules is obvious in several polymorphs revealed by this method. This polymorphism is additionally investigated by a 31P-CP-MAS study. From solution 1-, 13C- and 31P-NMR studies it is concluded that the bicyclic hetero-norbornane skeleton is retained in solution.
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  • 84
    ISSN: 0009-2940
    Keywords: Trichlorosilylation ; Dichlorophosphanes ; Silylphosphanes ; Amino(silyl)phosphanes ; Silicon /Reductions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of hexachlorodisilane and of trichlorosilane/triethylamine with alkyl-and dialkylaminodichlorophosphanes RPCl2 1a-i [R = iPr: a; (Me3Si)2CH: b; R=1-adamantly: c: R=tBu: d; R=Et2N: e; R=iPr2M: f] furnish bis(trichlorosilyl)-phosphanes RP(SiCl3)2 3a-f. However, when less bulky substituents are attached to the phosphorus atom, so that there is little steric crowding, the double reductive silylations leading from 1 to 3 are accompanied by side reactions and decomposition of 3. Therefore, only 3b, 3c, 3d, and 3f wre isolated in a pure state. These compounds are more readily prepared by the; trichlorosilane/triethylamine method. 1H-, 31P- and 29Si-Nmr spectra confirm their constitution. The structure of solid 3f, the first aminobis(trichlorosilyl)phosphane, was determined by X-ray crystallography. 3f contains a phosphorus atom in a pyramidal environment surrounded by two silicon atoms and a planar nitrogen atom of the diisopropylamino group.
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  • 85
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 417-420 
    ISSN: 0009-2940
    Keywords: Gallium ; Low-valent compounds ; Gallium-gallium bond ; Terminal triphenytriazenido ligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrakis[bis(trimethylsilyl)methyl]digallane (4) 1 reacts with 1,3-diphenyltriazene to yield two compounds, which were both characterized by a crystal structure determination. The gallium-gallium bond is retained in the yellow derivate [(H5C6)2N3](R)Ga-Ga(R)[N3(C6H5)2 2 [R = CH(SiMe3)2], which is formed by a ligand exchange reaction and shows two terminal chelating triazenido ligands besides two bis(trimethylsilyl)methyl groups; the Ga—Ga bond length is 245.79(6) pm. The second product is the orange dialkyl(diphenyltriazenido)gallium derivative R2Ga[N3(C6H5)2] 3, where the triazene has reacted as an oxidant by the cleavage of the Ga—Ga bond and probably by release of elemental hydrogen.
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  • 86
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 463-472 
    ISSN: 0009-2940
    Keywords: Hypervalent compounds ; Tellurium ; Polycations ; Molecular Orbital Theory ; Band structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Approximate MO and band structure calculation are used to analyze the bonding in the recently synthesized paramagnetic, semiconducting phase [Te15Br4]2+. The [Te15Br4]2+ chains are very similar to those in the tellurium subhalide Te2Br. The electronic structure and bonding within these chains is analysed and the possibility of hypervalency in both [Te15Br4][MoOBr4]2 and Te2Br is discussed. The bonding in the classically hypervalent molecule TeBr42- and a model Te3Br24- is compared to that of the infinite system. Our calculations indicate that both [Te15Br4][MoOBr4]2 and Te2Br contain weakly hypervalent Te atoms and that the interesting electronic properties of [Te15Br4][MoOBr4]2 arise within the distinct sublattices, which do not interact significantly.
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  • 87
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 479-488 
    ISSN: 0009-2940
    Keywords: Heterobimetallic complexes ; Carbene complexes ; Alkynes ; Coupling reaction ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequential reaction of the dimethylamino(trimethylsilylethylnyl)carbene complexes [(CO)5M'=C(NMe2)C≡CSiMe3] [M' = W (1a)] with KF/THFMeOH, nBuLi and transition metal halides, [XMLn], affords heterobimetallic propynyliden complexes of the type [(CO)5M'=C(N-Me2)C≡CMLn] [MLn = Ni(PPh3) Cp (4a, b). Ni(PMe2Ph)2- {Mes) (Mes=2,4,6-C6H2Me3) (5a), Rh(CO)(PPh3)2 (6a), Fe(CO)2Cp (7a,b)]. In contrast, reaction of 1a with MeLi · LiBr and [IFe(CO)2Cp] yields the novel N-metallated complex [(CO)5W=C{N(ME)Fe(CO)2Cp}C≡CSiMe3] (8a). The complexes [(CO)5M'=C(NMe2)C≡CMLn=Fe(CO)2Cp (7a, b), Ru(CO)2Cp (10a,b), Ru(CO)(PPh3)Cp (11a), Mn(CO)5 (12a), Re(CO)5 (13a)] are accessible by Pd-catalyzed coupling of the C-stannylated carbene complexes [(CO)5M'=C-(NMe2)C≡CSnBu3] (9a, b) with [XMLn]. The related monomethylaminocarbene complexes [(CO)5M'=C(NHMe)C≡ CSnBu3] (16a, b), obtained by stannylation of [(C))5M'=C(NHMe)C=CH] (15a, B) with Bu3SnNEt2, react with [IFe(CO)2Cp] to give the bimetallic complexes [(CO)5M'=C(NHMe)C≡CFe(CO)2Cp] (17a, b). The complexes 4a, 5a, 7a and 10a were characterized by X-ray structural analysis. The spectroscopic and structural data suggest that the two metal centers in 4-7, 10-13, and 17 interact only weakly.
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  • 88
    ISSN: 0009-2940
    Keywords: Rhenium ; Technetium ; 8a-Amino-6-methyl-ergoline ; Chelates ; Structure elucidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Current research in radiopharmaceutical chemistry is aimed at the design of technetium-based receptor-binding radiotracers because of the excellent nuclide properties of the isotope 99mTc. Tc tracers and the corresponding complexes of rhenium, as the inactive surrogate of Tc, are required to imitate organic agonists or antagonists of the receptor. We have started studies with ergolines, which are known to be dopamine substitutes. The present report deals with the functionalization of 8α-amino-6-methyl-ergoline (2) with a 2-mercaptoacetyl group, and the subsequent synthesis of the first rhenium complex containing a pendent ergoline moiety [Re- O(SSS)(RS)] (HSSSH = HS-CH2CH2-S-CH2CH2-SH and RSH = 8a-amino-N-(2-mercaptoacetyl)-6-methyl-ergoline) (4). The molecular structure of the rhenium complex was determined by X-ray crystal structure analysis.
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  • 89
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 859-862 
    ISSN: 0009-2940
    Keywords: Yttrium ; Lanthanum ; Samarium ; Lanthanides ; Aminotroponiminate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of N-isopropyl-2-(isopropylamino)troponimine, [(i-Pr)2ATI]H, with KH in THF affords [(i-Pr)2ATI]K. This is a useful starting material for the preparation of the mono-, bis- and tris-substituted compounds [[i-Pr)2ATI]YCl2-(THF)2}2, [(i-Pr)2ATI2Y[O(2,6,t-Bu2C6H3)] and [(i-Pr)2-ATI]3Ln (Ln = Y, La, Sm), which can be obtained from ([i-Pr)2ATI]K and LnX3 and LnX3 (X = Cl, I), or Y[O(2,6-t-BuC6H3)]3. All compounds have been characterized by spectroscopic methods. The monosubstituted yttrium complex {[(i-Pr)2ATI]YCl2(THF)2}2 has also been investigated by single crystal X-ray diffraction.
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  • 90
    ISSN: 0009-2940
    Keywords: C-H activation ; Alkyne complexes ; Cyclopentadienyl cobalt ; Fluxionality ; Hydrido complexes ; Clusters ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vicinal C-H bonds of the cycloalkenes CnH2n (n = 5-8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a-5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a-c: n = 5-7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon-carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) å in 5c d; 1.464(8), 1.499(5) Å in 8b, c]. Three dynamic processes - alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange - are operational in the trinuclear 5a-d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
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  • 91
    ISSN: 0009-2940
    Keywords: Mercury ; Lanthanides ; Lanthanoid(II) complexes ; (N-2,6-Diisopropylphenyl)(N-trimethylsily)amide complexes ; Bis(trimethylsilyl)amide complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mercury(II) amide complex Hg[N(SiMe3)(2,6-iPr2C6H3)]2 (1) was prepared by reaction of HgBr2 with Li[N(SiMe3) 2,6-iPr2C6H3)] in diethyl ether solvent. Redox transmetallation reactions of 1 with elemental samarium, europium or ytterbium in THF solvent (THF = tetrahydrofuran), generated the novel divalent complexes Ln[N(SiMe3)(2,6-iPr2C6H3]2(THF)2 with Ln = Sm (2), Eu (3) and Yb (4). 4 was also synthesized by reaction of elemental ytterbium, HgPh2 and HN(SiMe3)(2,6-Me3)2]2(THF)2 [Ln = Sm (5), Yb (6)] by reaction of the metals with HgPh2 and HN(SiMe3)2. Thermal desolvation of 4 under high vacuum gave Yb(N)(SiMe3)2,6-iPr2C6H3)]2 (THF) (7), whereas under identical conditions 6 yielded the solvent-free complex [Yb[N{SiMe3)2]2]2. (8). The new compounds 1-4 and 7 are hydrocarbon soluble and 171Yb-NMR spectra were recorded for 4, 6, 7 and 8. X-ray crystal structure determinations of 2 and 4 revealed four-coordinate, distorted tetrahedral metal environments augmented by weak Ln…ipso-C(aryl) interactions.
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  • 92
    ISSN: 0009-2940
    Keywords: Biaryls ; Boron ; Chirality ; Cooperative Effects ; Lewis acids ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of Lewis acid binaphthyl systems, substituted in 2-or 2,2′-position, are synthesized by lithiation of 2,2′-dibromo-1,l ′-binaphthyl (5), followed by addition of various electrophiles. Stepwise lithiation and subsequent borylation with trimethyl borate leads to the bromoboronic acid 6, which can be stabilized by esterification with pinacol giving 7. By increasing the reaction mixture to 2 equiv. of n-butyllithium and 2 equiv. of methyl borate the path to the binaphthylmonoboronic acid ester 9 is opened up. A further increase in the quantity of electrophile also leads to the binaphthylbisboronic acid ester 12. The 2,2′-disubstituted silyl, germyl, and stannyl derivatives 13a-15a are accessible in good yields. Treatment with boron halides leads exclusively to methyl/halogen exchange, giving the bidentate Lewis acids 13b-15b, the former of which can be bridged by oxygen.Only in case of the bis(tributylstannyl)binaphthyl 16a does ipso substitution occur in the presence of boron trichloride, giving the bis(dichloroboryl)-substituted binaphthyl 16b which can then be hydrolysed to 11. The structures of the majority of the compounds were investigated by X-ray diffraction. In case of the 2,2′-disubstituted compounds 13a-15a the naphthyl groups are orientated perpendicular to each other. The intra- and intermolecular interactions are dominated by this binaphthyl system. In case of the oxygenbridged compounds 13c and 14c the angle between the naphthyl planes decreases to about 70°. This also has an effect on the packing of the molecule; in this instance the orientation of two naphthyl in neighbouring molecules is nearly parallel. The structure of the diboronic acid is dominated by intra- and intermolecular hydrogen bonding.
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  • 93
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 951-954 
    ISSN: 0009-2940
    Keywords: Phosphane-boranes ; Medium-sized rings ; Ring opening and closure ; Temperature-dependent NMR studies ; Phosphorus ; Boron ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A phosphane-borane (3) with the P-B bond integrated into a seven-membered ring was prepared from 4-pentenyl-diphenylphosphane (4) by hydroboration using 9-borabicyclononane (9-BBN). The product was confirmed to have a ring structure in the solid state by single crystal X-ray diffraction. The P-B distance of 2.057(2) Å is indicative of a standard donor-acceptor bond similar to the type found in homologous five- and six-membered rings. The room-temperature 31P-NMR signal of the compound in various solvents (δ ≈ - 15) is not compatible with the cyclic structure and suggests that ring opening occurs as the compound is dissolved. Variable-temperature NMR work corroborated this assumption, and the enthalpy of ring closure was determined to be ΔH = -30.5(4) kJmol-l. In CD2C12 at -90°C, δ31P is shifted to +3.5 ppm to low field, suggesting virtually complete ring closure under these conditions.
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  • 94
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 963-968 
    ISSN: 0009-2940
    Keywords: Fluorine ; Macrocycles ; Complexes ; Sodium ; Barium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new fluoro macrocycles BenzoFN2O3 and F(N2O2)2C2H4 were synthesized in the reactions of 1,3-bis(bromomethyl)-2-fluorobenzene with benzo-diaza-15-crown-5 and 1,2-bis(diaza-12-crown-4)ethane, respectively, in 30% yield each. Close CF...metal ion interactions in the respective alkaline metal complexes in solution are evidenced by characteristic shifts of the 19F-NMR resonances of up to δ = 18.7 relative to the free ligand and by a decrease of the 1J(CF) coupling constant of up to 20 Hz, which is most pronounced in BenzoFN2O3 · Li+ and F(N2O2)2C2H4 · K+. In BenzoFN2O3· Li+ a1J(19F-7Li) of 15.5 Hz was observed, which is indicative very close CF...Li+ interactions in solution. In the X-ray crystal structures of BenzoFN2O3 · Na+ [CF⃛Na+ 246.8(2) pm], 26-fluoro-4,7,13,16-tetraoxa-1, 10-diazatricyclo[ 8.8.7.1 20,24 ] - hexacosa-20,22,24(26)triene · Na+ (CF⃛Na+ 267.1(2) pm) and 21 -fluoro-3,6,9,12,15,18-hexaoxabicyclo[ 18.3.1 1,20]heneicosa- l(24),20,22-triene. Ba2+ [CF⃛Ba2+ 299.0(3) pm] short CF⃛metal interactions were found. Such close CF⃛metal ion interactions do not result in a lengthening of the C-F bonds, which is not a sign of weak CF⃛metal ion interactions, since a Cambridge Structural Database search revealed that a shortening of the C-O bond length is also not observed in crown ether complexes of alkaline metals.
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  • 95
    ISSN: 0009-2940
    Keywords: Phosphorus heterocycles ; 1H-Phosphirenes ; Nucleophilic substitution reactions at 1H-phosphirenes ; Metal-complexation of functionalized 1H-phosphirenes ; Carbonyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The halogen atoms in the 1-chloro-1H-phosphirenes, 5a-c, are easily substituted on reaction with organolithium and Grignard reagents, 14a-p, with formation of the corresponding O-, N-, C-, Si-, and Ge-substituted 1H-phosphirenes, 15a-t. C1/H exchange reactions also occur on reaction with lithium metal hydrides (5a → 17). Furthermore, substitution reactions are also realized with the alkali metal borates, 18a-g (→19a-g); the same is true for reactions with trimethylsilyl cyanide and azide (→22a-d). Some of the substitution products have been characterized in the form of their metal complexes, 16, 23, 24, and 25.
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  • 96
    ISSN: 0009-2940
    Keywords: Germatranes ; Organotrihalogenogermanes ; Organometallic (Si, Ge, Sn) reagents ; Transmetallation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trialkylstannyl esters of tris(2-hydroxyalkyl)amines, N(CH2CHROSnAlk3)3 (9-11 (R = H, Me; Alk = Et, Bu), react with X3GeC(R1)(R2)COOR3 (12-17) (X = Cl or Br; R1, R2=H, Me, Ph, SiMe3, COOEt; R3=Me, Et) to give esters of α-germatranylcarboxylic acids, N(CH2CHRO)3GeC(R1)(R2)-COOR3 (1-8), in high yields. The synthesis of esters 12-17 is reported. Esters of α-germatranyldiphenylacetic acid 24 and 25 can be obtained by treatment of diphenylketene with Et3SnOMe to give in situ Et3SnC(Ph2)COOMe (23), followed by reaction with GeCl4 to give in situ Cl3GeC(Ph2)COOMe (22 and further reactions with 9 or 11, respectively. Reduction of germatrane 6 with LiAlH4 in diethyl ether leads to cleavage of the germanium-carbon bond with subsequent formation of (2-hydroxyethyl)trimethylsilane. The crystal structures of 3, 6 and 7 are reported. 1-Acyloxygermatranes 26 and 27 are obtained by treatment of 1-methoxygermatrane (28) with diphenyl- and dichloroacetic acid, respectively.
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  • 97
    ISSN: 0009-2940
    Keywords: Tin - Nitrogen cage compounds ; Sn—X—Sn intramolecular bridges ; Distannylamine pyridine adduct ; Tin ; Moessbauer spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(dimethylchlorostannyl)amine (2a) reacts with pyridine in a 3:4 molar ratio to produce the tin-nitrogen containing bicyclo[3.1.1]heptane (3) with elimination of the adduct Me2SnCl2·2 py. Treatment of the distannylamine 2,6-[Pr2H3N(SnMe2Cl)2 (4) with pyridine, however, leads to the formation of the 1:1 pyridine adduct 4 and this can be regarded as a model to explain the route to 3. The molecular structures of 3 and 5 were determined by multinuclear magnetic resonance spectroscopy in solution, as well as by X-ray structure analysis of their crystals. Typical structural features for both compounds are intramolecular Sn—X—Sn bridges. Support for the structures comes from MS fragmentation patterns, IR spectra, and the Mössbauer spectra.
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  • 98
    ISSN: 0009-2940
    Keywords: 1,2,4-Diazaphospholes ; Phosphiranes, alkylidene- ; 2-Phosphabutadienes ; Phosphorus heterocycles ; pyrazolines, thermolysis ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5-alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-phosphapyrazolines) are thermally much more stable than related compounds without the exocyclic double bond. Thermolysis reactions typically occur in the range 110-150°C in toluene solution, and different, mostly competing, reaction pathways are observed. Thermal extrusion of nitrogen from 8a-g gives rise to β-phosphanaylsiloxyalkenes 10, benzo[c]-phosphole derivatives 11, 14 and 115, (β-siloxyalkylidene)-Phosphiranes 12, and dihydro-1,3-oxaphospholes 13. The thermolysis of 5-alkylidene-4,5-dihydro-4-trimethylsilyl-3-trimethylsilyloxy-3H-1,2,4-dizaphospholes 17 afforded three products, including the highly substituted and stable 2-phosphabutadienes 18 formed by nitrogen extrusion and rearrangement. Finally, the 4-chloro-3-trimethylsilyloxy-substituted heterocycle 21 was transformed at 170°C into 4H-1,2,4-diazaphosphole 23. The structures of 13c and 18a were determined by single-crystal X-ray diffraction.
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  • 99
    ISSN: 0009-2940
    Keywords: Boron ; Diazaboroles ; Carbenes ; Heterocycles ; Imidazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Bromo-2,3-dihydro-1H-1,3,2-diazaboroles (3a-c) were synthesized by cyclocondensation of dilithiated 1,4-diazabutadienes (5a-c) with boron tribromide in hexane. 3a was also obtained by sodium amalgam reduction was conducted in ether solvents, diboroxane (2) resulted as the main product. Compound 3a and 1,3-dialkyl-4,5-dimethylimidazol2-ylidenes (6a, b) underwent halide displacement to afford the borolylimidazolium salts 7a, b. Compounds 2, 3a-c, and 7a, b were characterized by elemental analyses and spectroscopic methods (1H, 11B, 13C NMR; Ir; MS). The molecular structures of 2 and 7a were established by single-crystal X-ray diffraction analyses.
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  • 100
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 725-728 
    ISSN: 0009-2940
    Keywords: Dendrimers ; Metal complexes ; Nanostructures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Strong multiple complexation of transition metal ions, Cu(II), Zn(II) and Ni(II) with different generations of well-defined poly(propylene imine) dendrimers as multi(tridentate) ligands has been used to construct nanoscopic assemblies of defined structure and size incorporating a distinct number of metal ions from 2 up to 32.
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