1,721,125 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
Assembling Metal Clusters with Covalent Linkers. Synthesis and Structure of a Roughly Planar Pt18 Derivative Containing Five Clusters Connected by sigma-Alkynyl Spacers
No full textSterically protected tri- and hexanuclear platinum clusters were used as building blocks for the high-yield synthesis of a first-generation dendrimer (see picture; tBu groups are omitted for clarity), which is chemically and thermally stable, and in which the cluster units are separated by conjugated 1,3,5-triethynylphenyl groups
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
Overcrowded organometallic platinum(II) complexes that behave as molecular gears
No full textIn gear: Dynamic 1H NMR studies on some organometallic platinum(II) compounds reveal a synchronism between rotation around the Pt-P bond and the oscillation of a phenanthroline ligand between two nonequivalent exchanging sites. The system behaves as a molecular-sized analogue of a mechanical gear (see picture; C gray, N blue, O red, P purple) whose dynamic properties can be tuned through small structural changes. (Figure Presented
Molecular Motion in Crystalline Naphthalene: Analysis of Multi-Temperature X-ray and Neutron Diffraction Data
No full textSingle crystals of h8-naphthalene have been examined by both X-ray and neutron diffraction over a range of temperatures from 5 to 295 K. The aim of this case study was to measure the anisotropic displacement parameters (ADPs) of carbons and hydrogens and to interpret them using the model of thermal motion proposed by Bürgi and Capelli (Acta Cryst. 2000, A56, 403). The traditional rigid-body analysis expresses the low-frequency motions in terms of molecular translations and librations only, whereas the Bürgi-Capelli treatment also includes the high-frequency internal modes. We show that a considerable improvement occurs by representing the internal modes by a single second-rank tensor and that a further improvement follows by including a Grüneisen parameter to account for volume thermal expansion. By applying the treatment to multi-temperature diffraction data, there is a considerable reduction in the ratio of number of adjustable parameters/number of independent observations
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
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