1,720,966 research outputs found
Protonation of platinum(II) pyrazolates: synthesis, characterization and X-ray crystal structure of [Pt(dppe)(Hpz-N)(2)][BF4](2)center dot CHCl3 center dot H2O (Hpz-N = unsubstituted pyrazole)
No full textProtonation reactions of [Pt(dppe)(pz-N)(2)] (1) carried out either with HBF4(aq) or with [18-crown-6 .H3O][BF4], afford the new pyrazole adduct [Pt(dppe)(Hpz-N)(2)][BF4](2) (3) characterized by analytical, infrared and multinuclear NMR data. Deprotonation of 3 as well as protonation of 1, under controlled conditions, give the known binuclear Pt(II) pyrazolato complex [Pt(dppe)(mu -pz-N,N'](2)[BF4](2) (2). Competitive formation of mono-, 3, and dinuclear, 2, compounds is discussed. The structure of a solvate of complex 3, (C33H35B2N4OF8Cl3P2Pt), was solved by X-ray diffraction. The platinum atom exhibits a distorted square-planar geometry (P-Pt-P angle 85.3(1)degrees and N-Pt-N angle 87.0(4)degrees). The geometry around the B atom is tetrahedral. The hydrogen bonds between the pyrazole rings and one BF4- orientate the pyrazoles roughly in the same direction, away from the coordination plane. (C) 2001 Published by Elsevier Science Ltd
Mono-and dinuclear complexes of platinum(II) with chiral diphosphines: Pt(P-Pʹ)Cl2 and [Pt(P-Pʹ)(μ-OH)]2[BF4]2(P-Pʹ = prolophos, N-(diphenylphosphino)-2-((diphenylphoshpinoxy)methyl)pyrrolidine, and butaphos, 1-(diphenylphosphinoxy)-2-(N-ethyl-N-(diphenylphosphino)amino)butane). Crystal and molecular structure of Pt{S-prolophos-P, Pʹ)Cl2
No full textThe mononuclear complexes Pt(P-P')Cl2, 1 and 2, where P-P' are the chiral ligands (S)-N-(diphenylphoshino)-2-((diphenylphosphinoxy)methyl)pyrrolidine, S-prolophos, and (R)-1-(diphenylphosphinoxy)-2-(N-ethyl-N-(diphenylphosphino)amino)butane, R-butaphos, respectively, were prepared and characterized in solution by H-1, C-13, P-31, Pt-195, and two-dimensional correlation spectra. Only one conformer is observed in solution at room temperature. The structure of complex 1, Pt{S-prolophos}Cl2, was solved by X-ray diffraction: C29H29Cl2NOP2Pt, orthorhombic, space group P2(1)2(1)2(1), a = 16.557 (6) angstrom, b = 15.697 (6) angstrom, c = 10.948 (5) angstrom, Z = 4, and V = 2845 (2) angstrom 3. The structure was was refined to a conventional R factor of 0.040 (R(w) = 0.049) for 2700 observed reflections with I > 3-sigma(I). The ligand P-P' is coordinated in an endobidentate fashion to the platinum atom, which exhibits a slightly distorted square-planar geometry. The seven-membered ring adopts a twist-boat conformation. Treatment of complexes 1 and 2 with silver tetrafluoroborate in methanol solution afforded the dinuclear species [(P-P')Pt(mu-OH)2Pt(P-P')][BF4]2 (3, P-P' = prolophos, and 4, P-P' = butaphos). The dinuclear unit is maintained even in the gas phase, as shown by the MS-FAB spectrum of complex 4. Complex 1, in the presence of tin(II) chloride, was found to catalyze the hydroformylation of styrene to (R)-(-)-2-phenylpropanal with 37% optical purity
X-RAY CRYSTAL-STRUCTURE OF [1,2-BIS(DIPHENYLPHOSPHINO)ETHANE]BIS(3,5-DIMETHYL-PYRAZOLE-N)PLATINUM(I I) TETRAFLUOROBORATE DICHLOROMETHANE SOLVATE, [(PH2PCH2CH2PPH2)PT(3,5-ME2PZH)2][BF4]2.CH2CL2
No full textThe crystal structure of the compound [(Ph2PCH2CH2PPh2)Pt(3,5-Me2pzH)2][BF4]2·CH2Cl2 has shown that the ligands around the Pt atom are approximately in a square planar coordination, whereas the pyrazole rings point roughly in the same direction, away from the coordination plane. This unusual conformation is probably due to the hydrogen bonds with fluorine atoms of the BF4- anion. Bond distances and angles are compared with those in other pyrazole 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
Tin(IV) and organotin(IV) complexes containing the anion of some 1-R'-3-methyl-4-acyl-5-pyrazolones. Crystal structure of bis(1-phenyl-3-methyl-4-benzoylpyrazolon-5-ato)-dimethyl tin(IV)
No full textVariations 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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