1,720,993 research outputs found
Unsymmetrical Platinum(II) Phosphido Derivatives: Oxidation and Reductive Coupling Processes Involving Platinum(III) Complexes as Intermediates
No full textReaction of the trinuclear [NBu4]2[(R F)2Pt(μ-PPh2)2Pt(μ-PPh 2)2Pt(RF)2] (1, RF = C6F5) with HCl results in the formation of the unusual anionic hexanuclear derivative [NBu4]2[{(R F)2Pt(μ-PPh2)2Pt(μ-PPh 2)2Pt(μ-Cl)}2] (4, 96 e- skeleton) through the cleavage of two Pt-C6F5 bonds. The reaction of 4 with Tl(acac) yields the trinuclear [NBu4][(R F)2Pt(μ-PPh2)2Pt(μ-PPh 2)2Pt(acac)] (5, 48 e- skeleton), which is oxidized by Ag+ to form the trinuclear compound [(RF) 2Pt(μ-PPh2)2Pt(μ-PPh2) 2Pt(acac)][ClO4] (6, 46 e- skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II), which displays a Pt-Pt bond. The reduction of 6 by [NBu4][BH4] gives back 5. The treatment of 6 with Br- (1:1 molar ratio) at room temperature gives a mixture of the isomers [(PPh2RF)(RF)Pt(μ-PPh 2)(μ-Br)Pt(μ-PPh2)2Pt(acac)], having Br trans to RF (7a) or Br cis to RF (7b), which are the result of PPh2/C6F5 reductive coupling. The treatment of 5 with I2 (1:1 molar ratio) yields the hexanuclear [{(PPh2RF)(RF)Pt(μ-PPh2)(μ-I) Pt(μ-PPh2)2Pt(μ-I)}2] (8.96 e- skeleton), which is easily transformed into the trinuclear compound [(PPh 2RF)(RF)Pt(μ-PPh2)(μ-I) Pt(μ-PPh2)2Pt(I)(PPh3)] (9, 48 e- skeleton). Reaction of [(RF)2Pt(μ-PPh 2)2Pt(μ-PPh2)2Pt(NCMe) 2] (10) with I2 at 213 K for short reaction times gives the trinuclear platinum derivative [(RF)2Pt(μ-PPh 2)2Pt(μ-PPh2)2Pt(I)2] (11, 46e skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II) and with a Pt-Pt bond, while the reaction at room temperature and longer reactions times gives 8. The structures of the complexes have been established by multinuclear NMR spectroscopy. In particular, the 195Pt NMR analysis, carried out also by 19F-195Pt heteronuclear multiple-quantum coherence, revealed an unprecedented shielding of the 195Pt nuclei upon passing from Pt(II) to Pt(III). The X-ray diffraction structures of complexes 4, 5, 6, 9, and 11 have been studied. A detailed study of the relationship between the complexes has been carried ou
Behavior of Neutral Phosphido Derivatives of Platinum and Palladium toward Silver Centers
No full textThe reaction of the neutral binuclear complexes [(R(F))(2)Pt(mu-PPh(2))(2)M(Phen)1 (phen = 1,10-phenanthroline, R(F) = C(6)F(5); M = Pt, 1; M = Pd, 2) with AgClO(4) or [Ag(OClO(3))(PPh(3))] affords the trinuclear complexes [AgPt(2)(mu-PPh(2))(2)(R(F))(2)(Phen)(OClO(3))] (7a) or [AgPtM(mu-PPh(2))(2)(RF)(2)(Phen)(PPh(3))] [ClO(4)] (M = Pt, 8; M = Pd, 9), which display an "open-book" type structure and two (7a) or one (8,9) Pt Ag bonds. The neutral diphosphine complexes [(R(F))(2)Pr(mu-PPh(2))(2)m(P P)] (P P = 1,2-bis(diphenylphosphino)methane, dppm, M = Pt, 3; M = Pd, 4; P P = 1,2-bis(diphenylphosphino)ethane, dppe, M = Pt, 5; M = Pd, 6) react with AgClO(4) or [Ag(OClO(3))(PPh(3))], and the nature of the resulting complexes is dependent on both M and the diphosphine. The dppm Pt Pt complex 3 reacts with [Ag(OClO(3))(PPh(3))], affording a silver adduct 10 in which the Ag atom interacts with the Pt atoms, while the dppm Pt Pd complex 4 reacts with [Ag(OClO(3))(PPh(3))], forming a 1:1 mixture of [AgPdPt(mu-PPh(2))(2)(RF)(2)(OClO(3))(dppm)] (11), in which the silver atom is connected to the Pt-Pd moiety through Pd (mu-PPh(2)) Ag and Ag-P(k'-dppm) interactions, and [AgPdPt(mu-PPh(2))(2) (R(F))(2)(OClO(3))(PPh(3))(2)] [ClO(4)] (12). The reaction of complex 4 with AgClO(4) gives the trinuclear derivative 11 as the only product. Complex 11 shows a dynamic process in solution in which the silver atom interacts alternatively with both Pd-mu PPh(2) bonds. When P-P is dppe, both complexes 5 and 6 react with AgClO(4) or [Ag(OClO(3))(PPh(3))], forming the saturated complexes (M = Pt, 13; Pd, 14), which are the result of an oxidation followed by a PPh(2)/C(6)F(5) reductive coupling. Finally, the oxidation of trinuclear derivatives [(R(F))(2)Pt(II)(mu-PPh(2))(2)Pt(II)(mu-4PPh(2))(2)Pt(II)L(2)] (L(2) = phen, 15; L = PPh(3), 16) by AgClO(4) results in the formation of the unsaturated 46 VEC complexes [(R(F))(2)Pt(III)(mu-PPh(2))(2)Pt(III)(mu-PPh(2))(2)Pt(II)L(2)][ClO(4)](2) (17 and 18, respectively) which display Pt(III)-Pt(III) bonds
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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