1,721,040 research outputs found
Hydrogen transfer reduction of polyketones catalyzed by iridium complexes: a novel route towards more biocompatible materials.
No full textA novel glycerol valorization route: chemoselective dehydrogenation catalyzed by iridium derivatives
No full textDehydrogenation of glycerol to dihydroxyacetone is catalyzed by Ir(diene)(N-N)X (diene = 1,5-hexadiene, 1,5-cyclooctadiene; N-N = 1,10-phenanthroline, 2,2′-bipyridine and substituted derivatives; X = Cl, I). The reactions are performed under hydrogen transfer conditions, using acetophenone as the hydrogen acceptor
Dehydrogenation of glycerol to dihydroxyacetone catalyzed by iridium complexes with P-N ligands
No full textThe chemoselective dehydrogenation of glycerol was catalyzed by organoiridium derivatives of the type [HIr(cod)L] (cod = 1,5-cyclooctadiene; L = Pr-N(CH2CH2PPh2)2, Et2NCH2CH2N(CH2CH2PPh2)2, o-Me2NC6H4PPh2) using hydrogen acceptors such as acetophenone, cyclohexanone, styrene and benzaldehyde. The catalytic reactions were performed in the absence of a basic cocatalyst in order to avoid decomposition of the desired product, i.e. dihydroxyacetone. Acceptor-less dehydrogenation was also observed either in the absence of a hydrogen acceptor, or as a parallel route, when the reaction was performed in the presence of acetophenon
Iron complexes with polydentate phosphines as unusual catalysts for alcohol oxidation
Full text linkThe iron(II) compounds [Fe(triphos)(CH3CN)3](OTf)2 (triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane; OTf = CF3SO3) (1), [Fe(dppm)2(CH3CN)2](OTf)2 (dppm = bis(diphenylphosphino)methane) (2), [Fe(dppe)2(CH3CN)2](OTf)2 (dppe = 1,2-bis(diphenylphosphino)ethane) (3), [Fe(dppp)(CH3CN)4](OTf)2 (dppp = 1,3-bis(diphenylphosphino)propane) (4) and [Fe(PSP)(CH3CN)3](OTf)2 (PSP = bis(2-(diphenylphosphino)ethyl)sulfide) (5) were synthesized and characterized by NMR and (2, 3 and 4) also by X-ray crystallography. Such complexes catalyzed the selective oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones. The catalytic reactions were performed in acetonitrile in mild experimental conditions (r.t. or 50 °C) using tert-butylhydroperoxide (TBHP) as oxidizing agent. By following the reaction of complex 4 with the oxidant by UV–visible spectroscopy, it was possible to evidence formation of the corresponding iron-peroxide intermediate. Comparison of ESI-MS spectra acquired on a solution of 1 or 4 before and after TBHP addition suggests ligand oxidation to iron-phosphine oxide complexes
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
Donor properties of diphosphine ligands in tungsten carbonyl complexes: synchrotron radiation XPS measurements and DFT calculations
No full textSynchrotron radiation XPS measurements of W 4f and P 2p core level binding energies in the series W(CO)4(P−P) (P−P = dppm (1), dppe (2), dppp (3), dppb (4), dmpe (5), F-dppe (6); dppm = bis(diphenylphosphino)methane, dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane, dmpe = 1,2-bis(dimethylphosphino)ethane, F-dppe = 1,2-bis(bis(pentafluorophenyl)phosphino)ethane) are reported. The results are interpreted in terms of effects of the chelate ring size and of the nature of substituents of the P atoms. The trend of XPS data show an excellent agreement with the results of DFT calculations, obtained by the ΔSCF approach. Further analysis of the Kohn−Sham eigenvalues calculated at the ground-state level has assessed the role played by the initial state effects
[Rh(CO)4]-, [Rh5(CO)15]- and bimetallic clusters as catalysts for the carbonylation of nitrobenzene to methyl phenylcarbamate
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