1,720,961 research outputs found
N,O versus O,O coordination in beta-imino diketonato complexes: Role of the metal center and of the imino substituent
No full textbeta-Imino carbonyl enolato metal(II) complexes of general formula [M((RCO)(R'CO)CC(R '') NH)(2)] (M = Mn, Fe, Co, Ni, Cu, Zn, Pd, R = R' = Me, R '' = CCl(3); M = Cu, Pd, R = R' = Me, R '' = PhCO; R = Me, R' = Ph, R '' = PhCO; R = R' = Ph, R '' = PhCO) are easily synthesized by the reaction of metal(II) acetates with the proper beta-enaminodiones in 1/2 molar ratio in ethanol at room temperature. In all the cases the trifunctional NOO beta-imino carbonyl enolate ligand acts as bidentate to give ML(2) complexes, whose structure depends on the metal center and on the nature of the substituent R '' at the imino carbon. With R '' = CCl(3) an O,O coordination is observed for all the metal centers but one, in fact palladium(II) exhibits an N,O coordination through the imino nitrogen and one keto oxygen. By contrast with R '' = PhCO the ligand is always coordinated through the imino nitrogen and one keto oxygen atom
Volatile square planar beta-imino carbonyl enolato complexes of Pd(II) and Ni(II) as potential MOCVD precursors
No full textA series of palladium(II) and nickel(II) [ML(2)] complexes (1-6: 1, Pd, L(Me); 2, Pd, L(iBu); 3, Pd, L(nBu): 4, Pd, L(nHe); 5, Ni, L(Me); 6, Ni, L(iBu)) has been synthesised by reacting the proper acetato salt with the beta-enamino ketoesters (MeCO)(MeOCO)C=C(NH(2))R (R = Me, i-Bu, n-Bu, n-hexyl). The chain length has practically no effect on the output of the synthetic procedure so that complexes are obtained always in good yields. They are all square planar and the potentially tridentate ligand is coordinated via the N,O donor atoms of the imino and keto groups. Their thermal behaviour has been fully studied and [Ni(L(Me))(2)] demonstrated to be a convenient precursor for the Metal Organic Chemical Vapour Deposition of Ni and NiO thin films
Base-promoted reactions of alpha-halogeno-alkylanilides
No full textHydride-promoted reactions of 2-halogeno-alkylcarboxanilides afford heterocyclic and acyclic condensation products, some of the latter compounds arising upon hydrolysis and/or rearrangement of the former ones. Competitive formation of dioxopiperazines versus oxazolidinone derivatives or their transformation products depends mainly upon the nature (primary, secondary or tertiary) of the halide moiety. Concurrent dehydrohalogenation of 2-bromo-isobutyranilides leads to unsaturated condensation products
Coordinating properties of the anionic ligand (MeCO)(2)C(-)C(X)Me (X = O or NH) toward transition metal(II) centers
No full textThe exchange reaction between transition metal(II) acetates and the protic nucleophiles 3-(1-aminoethylidene) pentane-2,4-dione (Hampd) or 3-acetylpentane-2,4-dione (Hacpd) affords the corresponding [M(ampd)(2)] (M = Ni (1), Pd (2)) or [M(acpd)(2)] (M = Mn (5), Fe (6), Ni (7), Cu (8), Pd (9)) complexes in fair to good yields. The reaction is performed in ethanol at room temperature, with addition of sodium carbonate in some cases. This last new synthetic procedure is applied for those complexes which easily undergo an extensive deacylation process. The factors determining the success of the exchange reaction and the resulting N, O or O, O coordination are fully discussed
One pot synthesis of unsaturated enaminoketoesters or of pyridines in the tin(IV) chloride-promoted reactions of beta-ketoesters with of alpha,beta-unsaturated nitriles
No full textTin(IV) chloride selectively promotes the nucleophilic attack of methyl acetoacetate to the cyano instead of the olefinic carbon atom of alpha,beta-unsaturated nitriles to give enaminoketoesters. In the presence of an excess of ketoester a second C-C bond formation occurs followed by cyclisation affording substituted pyridines in a selective cascade sequence
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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