1,721,171 research outputs found
A Stable Palladium(I) Dimer with One 14e- Palladium Center and its Reversible Reaction with CS2, Affording a New Complex with a Planar Four-Coordinate Carbon
No full textTrue new stable dinuclear Pd(I) complexes, [Pd-2(mu-PBu(t)2),(PPh(3))(3)]X and [Pd-2(mu-PBu(2)(t))(PPh(3))(2)(mu,eta(2): eta(2)-CS2)]X(X = BF4, CF3SO3), have been synthesized and characterized. The former has one 14e Pd center, and the latter, which has been characterized by X-ray diffraction, contains a CS2 molecule with a four-coordinate planar CS2 carbon
Multinuclear NMR, X-ray, and DFT Studies on RhCl(diene)(phosphoramidite) Complexes
No full textNMR, X-ray, and DFT studies on several [RhCl(diene)(phosphoramidite)] complexes suggest that both electronic and steric effects affect the nature of the olefin, chloride, and P-donor bonding. The X-ray study of [RhCl(1,5-COD)(phosphoramidite)] (phosphoramidite = (Binol)PN(CH(CH 3)Ph)2) reveals an intramolecular selectivity in the back-bonding in which the C-C bond of the olefin trans to the Cl ligand is preferentially elongated. Two types of dynamic processes have been detected at ambient temperature in CD2Cl2 solution using 2-D NOESY methods: presumed phosphoramidite dissociation and diolefin rotation. The former is observed with both 1,5-COD and NBD. The latter is more selective in that the intramolecular dynamics for the NBD analogues are relatively fast, but those for the 1,5-COD compounds, barely detectable. DFT calculations suggest that the diolefin rotation proceeds over a tetrahedral transition state and that there is a smaller energy barrier for the NBD complexes relative to the analogous 1,5-COD species. Two bis phosphoramidite salts of the form [Rh(1,5-COD) (phosphoramidite)2]BF4 are reported
Proton Lability in Highly Hindered Dinuclear Palladium(I) mu-Phosphido-Secondary Phosphine Complexes. Crystal Structures of [Pd2(mu-PBut2)(PCy2H)3(CO)]BF4 and [Pd2(mu-PBut2)(PCy2H)2(mu,eta2,eta2-isoprene)]BF4
No full textThe reactions of the dinuclear cationic complexes [Pd-2(mu-PBu(2)(t))(PR(3))(4)](+) (PR(3) = PCy(2)H, PMe(3)) with CO or isoprene proceed with substitution of one or two phosphine ligands giving the corresponding [Pd-2(mu-PBu(2)(t))(PR(3))(3)(CO)](+) and [Pd-2(mu-PBu(2)(t)) (mu,eta(2),eta(2)-isoprene)(PR(3))(2)](+) cations. [Pa-2(mu-PBu(2)(t))(PCy(2)H)(3)(CO)](+) equilibrates in solution to a mixture of monocarbonyl derivatives arising from bridging phosphido/terminal phosphine interchange. The complexes were characterized by multinuclear 1-D and 2-D NMR spectroscopy. The crystal and molecular structures of [Pd-2(mu-PBu(2)(t))(PCy(2)H)(3)(CO)]BF4 and [Pd-2(mu-PBu(2)(t))(PCy(2)H)(2)(mu,eta(2),eta(2)-isoprene)]CF3SO3 were solved by single-crystal X-ray diffraction studies
Preparative, X-ray and NMR Studies of Phosphide-Bridged Palladium(I) Dimers. A New Complex with an eta2-Bridging PHCy2 Ligand
No full textThe preparation of several new Pd(I) cationic dinuclear complexes containing bridging PCy2 or PBu(t)2 ligands and terminal phosphine ligands is described. One of these, [Pd2(mu-PCy2)(mu-PHCy2)(PEtCy2)2]+ (7), contains a Pd-H-P bridging unit, a relatively rare type of bonding. The cationic complexes [Pd2(mu-PBut2)(PHCy2)4]+ (5) and [Pd2(mu-PBut2)(PMe3)4]+ (8) have been isolated and characterized via P-31 NMR and X-ray crystallographic studies. The structures reveal large distortions presumably of steric origin. Relevant crystallographic parameters for two complexes are as follows: for [5]BF4, C56H110BF4P5Pd2, monoclinic, space group P2(1)/c, with a = 20.929(5) angstrom, b = 15.244(5) angstrom, c = 20.860(6) angstrom, beta = 75.01(2)-degrees, V = 6429(2) angstrom 3; for [8]CF3SO3, C21H54F3O3P5Pd2S, monoclinic, space group C2/c, with a = 29.810(3) angstrom, b = 11.181(1) angstrom, c = 23.126(4) angstrom, beta = 105.99(9)-degrees, Z = 8, V = 7410(1) angstrom 3
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
- …
