1,721,564 research outputs found
Reactivity of Cu(I) Nacnac Complexes Toward Polypnictogen Compounds
No full textThe nacnac Cu(I) compound [LCu(MeCN)] (2) (L = [{N(C6H3Me2-2,6)C(Me)}(2)CH](-)) was reacted with complexes containing aromatic cyclo-E-5 ([Cp*Fe(eta(5)-E-5)], E = P (1a), As (1b), Cp* = eta(5)-C5Me5), cyclo-P-4 ([Cp'''Co(eta(4)-P-4)] (3), Cp''' = eta(5)-(C5H2Bu3)-Bu-t) and cyclo-E-3 ligands ([Cp'''Ni(eta(3)-E-3)], E = P (4a), As (4b)) yielding the heterometallic complexes [(Cp*Fe)(mu,eta(5:2)-E-5)(LCu)] (E = P (5a), As (5b)), [(Cp*Fe)(mu(3),eta(5:2:1)-E-5)(LCu)(2)] (E = P (6a), As (6b)), [(Cp'''Co)(mu,eta(4:2)-P-4)(LCu)] (7), [(Cp'''Co)(mu(3),eta(4:2:1)-P-4)(LCu)(2)] (8), and [(Cp'''Ni)(mu,eta(3:2)-E-3)(LCu)] (E = P (9a), As (9b)). These complexes are rare examples of the coordination of a group 11 metal to aromatic cyclo-E-n (E = P, As; n = 3-5) ligands. All products were comprehensively characterized by crystallographic and spectroscopic methods. Their dynamic behavior in solution was studied by VT (variable-temperature) NMR spectroscopy, and their electronic structures were elucidated by DFT calculations
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
NHCs as Neutral Donors towards Polyphosphorus Complexes
Full text linkThe first adducts of NHCs (=N-heterocyclic carbenes) with aromatic polyphosphorus complexes are reported. The reactions of [Cp*Fe(eta(5)-P-5)] (1) (Cp*=pentamethyl-cyclopentadienyl) with IMe (=1,3,4,5-tetramethylimidazolin-2-ylidene), IMes (=1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene) and IDipp (=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) led to the corresponding neutral adducts which can be isolated in the solid state. However, in solution, they quickly undergo a dissociative equilibrium between the adduct and 1 including the corresponding NHC. The equilibrium is influenced by the bulkiness of the NHC. [Cp '' Ta(CO)(2)(eta(4)-P-4)] (Cp ''=1,3-di-tert-butylcyclopentadienyl) reacts with IMe under P atom abstraction to give an unprecedented cyclo-P-3-containing anionic tantalum complex. DFT calculations shed light onto the energetics of the reaction pathways
Supramolecular Chemistry and Halogenation Reactions of Pentaphosphaferrocenes
Full text linkThis thesis deals with the supramolecular chemistry and halogenation reactions of pentaphosphaferrocenes. In chapter 1, an introduction into supramolecular chemistry in general and that of polyphosphorus ligands in particular is given, followed by an outline of the research objectives (chapter 2).
Chapter 3 deals with the variation of the Cp ligand of the pentaphosphaferrocene and the effects on the self-assembly reactions with Cu salts. In chapter 4, the application of [(CpCr)2As5] as a template molecule is discussed. In chapter 5, triple decker complexes [(CpCr)2As5] and [(CpMo)2P4S] are applied as templates in the self-assembly of different pentaphosphaferrocenes and Cu salts. Chapter 6 focusses on the self-assembly of pentaphosphaferrocenes with Au salts. Chapter 7 deals with the iodination of pentaphosphaferrocene and its higher homologues.
The thesis treasury, chapter 8, deals with further results not yet suitable for publication and obtained in the fields of supramolecular chemistry of CuGaCl4, two further polypnictogen complexes and Au salts, polyphospholyl ligands and Cu salts, early transition metal complexes of polyphospholyl ligands, as well as further halogenation reactions of pentaphosphaferrocenes.
In chapter 9, a comprehensive conclusion is presented
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