1,720,970 research outputs found
When SF5 outplays CF3: effects of pentafluorosulfanyl decorated scorpionates on copper (vol 12, pg 14618, 2021)
No full textCorrection for 'When SF5 outplays CF3: effects of pentafluorosulfanyl decorated scorpionates on copper' by Anurag Noonikara-Poyil et al., Chem. Sci., 2021, 12, 14618-14623, https://doi.org/10.1039/D1SC04846E
π‐Conjugated Triazenes and Nitriles: Simple Photoinduced Synthesis of Anilides Using Mild and Metal‐Free Conditions
No full textπ‐Conjugated Triazenes and Nitriles: Simple Photoinduced Synthesis of Anilides Using Mild and Metal‐Free Conditions
No full textTerminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate
No full textCopper plays an important role in alkyne coordination chemistry and transformations. This report describes the isolation and full characterization of a thermally stable, copper(I) acetylene complex using a highly fluorinated bis(pyrazolyl)borate ligand support. Details of the related copper(I) complex of HC≡CSiMe3 are also reported. They are three-coordinate copper complexes featuring η2-bound alkynes. Raman data show significant red-shifts in C≡C stretch of [H2B(3,5-(CF3)2Pz)2]Cu(HC≡CH) and [H2B(3,5-(CF3)2Pz)2]Cu(HC≡CSiMe3) relative to those of the corresponding alkynes. Computational analysis using DFT indicates that the Cu(I) alkyne interaction in these molecules is primarily of the electrostatic character. The π-backbonding is the larger component of the orbital contribution to the interaction. The dinuclear complexes such as Cu2(μ-[3,5-(CF3)2Pz])2(HC≡CH)2 display similar Cu-alkyne bonding features. The mononuclear [H2B(3,5-(CF3)2Pz)2]Cu(NCMe) complex catalyzes [3 + 2] cycloadditions between tolyl azide and a variety of alkynes including acetylene. It is comparatively less effective than the related trinuclear copper catalyst {μ-[3,5-(CF3)2Pz]Cu}3 involving bridging pyrazolates
Carbonyl and Isocyanide Complexes of Copper and Silver Supported by Fluorinated Poly(pyridyl)borates
No full textThe pyridine-based poly(pyridyl)borates
are a recent addition to
the scorpionate family. Furthermore, pyridyl ring substituted analogues
are also rare. The synthesis of a bis(pyridyl)borate featuring trifluoromethyl
substituted pyridyl donor arms and its utility in isocyanide and carbonyl
chemistry of copper(I) and silver(I) have been described together
with related molecules supported by a fluorinated tris(pyridyl)borate,
and a comparison to the better-known poly(pyrazolyl)borate relatives.
X-ray crystal structures of copper and silver complexes show that
the B-arylated, bis- and tris(pyridyl)borate ligands use only two
pyridyl moieties for metal ion coordination. Flanking B-aryl groups
close to metal sites are also a common feature in copper and silver
complexes supported by [Ph2B(6-(CF3)Py)2]− and [t-BuC6H4B(6-(CF3)Py)3]−. The CN stretching frequencies of the t-BuNC complexes
of Cu(I) and Ag(I) are notably higher than that of the free t-BuNC. The CO stretch of the analogous fluorinated poly(pyridyl)borate
ligand supported metal carbonyls lies closer to that of the free CO,
indicating the presence of fairly Lewis acidic metal sites. Metal
bound carbonyl stretching frequencies of comparable poly(pyridyl)borate
and poly(pyrazolyl)borate have been utilized to gauge the relative
donor properties of the two ligand families
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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