1,720,960 research outputs found
Reactivity of the zwitterionic ligand EtNHC(S)Ph2PNPPh 2C(S)NEt towards [Ru3(CO)12]. Sulfur transfer and ligand fragmentation leading to the methideylamide [-N(Et)-CH(R)-] μ3-bridging moiety
No full textThe reaction of EtNHC(S)Ph2PNP+Ph2C(S) N-Et (HEtSNS) with [Ru3(CO)12] has been carried out under two different experimental conditions: in the first case [Ru 3(CO)12], previously turned into the labile intermediate [Ru3(CO)10(CH3CN)2], afforded, at room temperature in dichloromethane, the trinuclear clusters [Ru 3(CO)11(CNEt)] (1), {Ru3(CO) 9(μ-H)[(μ-S:κ-P)Ph2PNPPh2C(S)NEt]} (2), {Ru3(CO)9(μ-H)[(μ-S:κ-P)Ph 2PNP(S)Ph2]} (3) and {Ru3(CO) 10[(μ-κ2P)Ph2PNHPPh2]} (4). Ligand fragmentation occurs via loss of EtNC or EtNCS, without sulfur transfer to the cluster core. In the second case, [Ru3(CO)12] reacted with HEtSNS in toluene at 70 °C, giving the trinuclear clusters 4, {Ru3(CO)7(CNEt)(μ3-S)[(μ2-N: η1-C:κ1-P)Ph2PNPPh 2C(H)NEt]} (5), {Ru3(CO)8)(μ3-S) [(μ2-N:η-C:κ-P)Ph2PNPPh2C(H)NEt]} (6) and {Ru3(CO)6(μ3-CO)(μ3-S) (EtNC)[(μ-κ2P) Ph2PNHPPh2]} (7). The last three compounds derive from ligand fragmentation and sulfur transfer to the metal cluster. All compounds were characterized by spectroscopy (NMR, IR) and the molecular structures of 2, 5 and 7 were determined by single-crystal X-ray diffraction. Cluster 2 preserves the original Ru3 triangular core in which an edge is bridged by a hydride ligand and by the sulfur atom of the Ph2PNPPh2C(S)NEt ligand. Cluster 5 shows an open triangle of Ru atoms capped by a μ3-sulfide and by the unprecedented methideylamide -N(Et)CH(R)-μ3-bridging moiety of the Ph 2PNPPh2C(H)NEt ligand. It formally derives from cluster 6 by substitution of ethyl isonitrile with one CO molecule. Finally, cluster 7 displays a Ru3(μ3-S)(μ3-CO) trigonal bipyramidal core. © 2009 The Royal Society of Chemistry
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
Oxidative Addition of Iodomethane to Charge-Tuned Rhodium(I) Complexes
No full textThe zwitterionic Rh(I) monocarbonyl complex [Rh(EtSNS)(CO)] (1, EtSNS =EtNC(S)Ph(2)P=NPPh(2)C(S)NEt(-)) was reacted with iodomethane in dichloromethane, yielding the stable acetyl-Rh(III) complex [Rh(EtSNS)(COCH(3))I] (4). Complex 4 was characterized in solution and in the solid state by X-ray diffraction analysis.. The rate constant of the reaction [5.48 (7) x 10(-2) M(-1) s(-1) at 25 degrees C CH(2)Cl(2)] and the activation parameters Delta H(double dagger) [28(3) kJ mol(-1)] and Delta S(double dagger)[-173(10) J mol(-1) K(-1)] were determined, confirming a nucleophilic addition mechanism. The rate constant was obtained by monitoring the acetylic product by (1)H NMR, under second-order conditions ([Rh]/[CH(3)I]=1). Complex 1 can be mono- and biprotonated with HX (X=PF(6), OTf, NO(3)), forming [Rh(HEtSNS)(CO)]X (2 center dot X) and [Rh(H(2)EtSNS)(CO)]X(2) (3 center dot X(2)), respectively. A decrease of the calculated DFT Mulliken atomic population on the Rh atom is observed along the series 1 > 2 > 3 in accordance with the variation of the coordinated CO stretching frequency. Compounds 2 center dot X were also reacted with iodomethane, forming complexes [Rh(HEtSNS)(COCH(3))I]X (5 center dot X), stable in solution for a short time, that transform by deprotonation into 4 and into unidentified decomposition products. The rate constants were determined under pseudo-first-order conditions due to the lower reactivity [2 center dot NO(3)=24.6 (6) x 10(-5) M(-1) s(-1); 2 center dot OTf=12.7 (3) x 10(-5) M(-1) s(-1); 2 center dot PF(6)=2.50 (6) x 10(-5) M(-1) s(-1)]. The activation parameters for 2 center dot PF(6) were also determined. The influence of the counterion could be explained assuming that the different non-metal-coordinated anions form hydrogen bonding with the NH group of 2 center dot X, which in turn causes a variation of the electron density on the Rh center. A good correlation between the CO stretching frequencies and the rate constants was observed. The experimental rate constant for complex 1 is 1 order of magnitude higher than the one calculated using the linear regression function obtained for the 2 center dot X series (experimental=5.48 x 10(-2) M(-1) s(-1); calculated=1.29 x 10(-3) M(-1) s-(1)), pointing out that the monoprotonated complexes react more slowly than expected. Both steric and electronic effects were examined and held responsible for this reduced reactivity. Complexes 3 center dot X(2) reacted too slowly, yielding complex 4 and unidentified decomposition products, hindering the determination of the rate constants
A Neutrally Charged Trimethylmanganese(III) Complex: Synthesis, Characterization, and Disproportionation Chemistry
No full textVariations 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
- …
