1,720,965 research outputs found
Selective Stabilization of the Antiisomer of (eta-3-allyl)palladium and (eta-3-allyl)platinum Complexes
No full textA number of 2,9-disubstituted 1,10-phenanthrolines are synthesized. These are used as ligands in different cationic (eta3-allyl)palladium and -platinum complexes. It was found that while a syn configuration was by far the most stable one with the parent 1,10-phenanthroline, 2,9-substituents such as methyl, chloro, cyano, and propynyl induced a preference for the anti configuration. Since terminal nucleophilic addition to anti-eta3-allyl complexes will yield (Z)-alkenes, this observation opens up a potentially selective route to (Z)-alkenes. Using molecular mechanics calculations these effects may be rationalized
Molybdenum-catalyzed allylic substitution. Influence of 1,10-phenanthroline ligands on reactivity and selectivity
No full textSome new allylmolybdenum complexes containing 1,10-phenanthroline or 2,9-dimethyl-1,10-phenanthroline as Ligand have been synthesized and shown to have different geometries by NMR and X-ray diffraction analysis. The geometries of the complexes were elucidated by NMR techniques and confirmed by X-ray diffraction analysis. The catalytic activity and the influence on regio- and stereocontrol in the alkylation of allylic acetates have been investigated. The 2,9-dimethyl-1,10-phenanthroline complex was found to be a very efficient catalyst for selective conversion of (Z)-allyl acetates into (Z)-products
Quantum mechanical conformational analysys of beta-alanine zwitterion in aqueous solution
No full textEffects of Phenanthroline Type Ligands On the Dynamic Processes of (eta(3)-allyl)palladium Complexes - Molecular-structure of (2,9-dimethyl-1,10-phenanthroline)[(1,2,3-eta)-3-methyl-2-butenyl]-chlor Opalladium
No full textUsing saturation-transfer experiments and measurements of coalescence temperatures, the effects of phenanthroline ligands on the activation parameters for syn-anti isomerization, syn-anti proton exchange, and apparent rotation in six (eta3-allyl)palladium complexes have been studied. The rates of the processes are increased by the addition of ionic, coordinating ligands such as chloride indicating a pentacoordinated intermediate. By X-ray crystallography the structure of a potential intermediate of this type has been determined. Finally, using 2-(8-methoxy-1-naphthyl)-1,10-phenanthroline, it has been possible both to observe chiral induction on a deuterium-substituted eta3-allyl group and to find additional information on the mechanism of apparent rotation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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