1,720,975 research outputs found
Water soluble ruthenium cyclopentadienyl and aminocyclopentadienyl PTA complexes as catalysts for selective hydrogenation of alpha,beta-unsaturated substrates (PTA=1,3,5-triaza-7-phosphaadamantane)
No full textA series of half-sandwich Ru-cyclopentadienyl derivatives containing the cage-like water soluble monodentate phosphine 1,3,5-triaza-7-phosphaadamantane (PTA) was synthesized and tested in aqueous phase or biphasic homogeneous hydrogenation of activated olefins via hydrogen transfer or under hydrogen pressure at mild conditions. The hydrogen transfer results show higher activity for the Cp* derivatives (Cp* = C5Me5) than for the corresponding Cp complexes (CP = C5H5). Under H, pressure, all complexes show high selectivity to C=C double bond hydrogenation. The X-ray crystal structure featuring a protonated 2-aminoethylcyclopentadienyl Ru complex was also determined
Synthesis and characterisation of tetrahedro-tetraphosphorus complexes of rhenium - Evidence for the first bridging complex of white phosphorus
No full textReaction of white phosphorus with [(triphos)Re(CO)2(OTf)] (1) in dichloromethane affords the new tetraphosphorus complex [(triphos)Re(CO)2(η1-P4)](OTf) (2) [triphos = MeC(CH2PPh2)3; OTf = OSO2CF3]. Compound 2 reacts with a second equivalent of 1 to give the binuclear complex [{(triphos)Re(CO)2}2(μ,η1,η1-P4)](OTf)2 (3) in which a tetrahedro-P4 ligand behaves as tethering unit between two [(triphos)Re(CO)2]+ moieties. Complexes 2 and 3 represent the first soluble metal complexes of the tetraphosphorus molecule where the P4 ligand has not undergone any major modification
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
Reactions of the Rhenium(I) Fragment [{MeC(CH2PPh2)3}Re(CO)2]+. Synthesis and Characterization of a Stable Cationic η2-H2Complex of Rhenium
No full textReaction of Re(CO)3(PPh3)2Cl with MeC(CH2PPh2)3 (triphos) gives (triphos)Re(CO)2Cl (1) which is converted to the hydride (triphos)Re(CO)2H (2) by treatment with LiAlH4. An X-ray diffraction analysis of 2 shows that the rhenium atom is octahedrally coordinated by triphos, which occupies a triangular face of the coordination polyhedron, by two carbonyl groups and by a terminal hydride ligand. Treatment of 2 with Me3OBF4 results in the evolution of methane and formation of the unsaturated complex [(triphos)Re(CO)2]BF4(4) which is stabilized by an agostic interaction between the rhenium center and a phenyl C-H bond of triphos. The η2-H2 complex [(triphos)Re(CO)2(H2)]BF4(3) is obtained either by protonation of 2 or by addition of H2 to the agostic complex 4. The presence of an intact dihydrogen ligand in 3 is unambiguosly shown by 1H NMR spectroscopy [T1min= 8.6 ms (CD2Cl2, 300 MHz, -58 °C); Jhdof 30.8 Hz for the monodeuteriated isotopomer [(triphos)Re(CO)2(HD)]- BF4(3-d1)]. Vinylidene derivatives of the formula [(triphos)Re(CO)2({C=C(H)R}]BPh4(R = Ph, 8; CO2Et, 9; C6H13, 10) are obtained by reaction of either the η2-H2 complex 3 or the agostic complex 4 with terminal alkynes in the presence of NaBPh4. The preference for the coordination of neutral groups at rhenium in the [(triphos)Re(CO)2]+ fragment follows the order N2 < C-H(agostic) < H2 < HC≡CR < CH3CN < CO. All the reactions described have been carried out in tetrahydrofuran or dichloromethane. © 1995, American Chemical Society. All rights reserved
Activation of 2-propyn-1-ols by the rhenium(I) fragment [{MeC(CH2PPh2)(3)}Re(CO)(2)](+). Synthesis and characterization of cationic Re(I) complexes containing unsaturated eta(1)-carbon ligands
No full textThe [{MeC(CH2PPh2)3}Re(CO)2. auxiliary has been found to activate 1-ethynyl-1-cyclohexanol and 1-phenyl-2-propyn-1-ol
yielding a variety of h1-carbon ligands, which includes hydroxyvinylidene, alkenylvinylidene, alkoxycarbene, h1-Csp-enynyl,
secondary allenylidene, acyl, hydroxycarbene and alkoxycarbene groups. The reactivity of the allenylidene complex [{MeC(CH2PPh2)3}Re(CO)2{C.C.C(H)Ph}]. toward water and methanol has been investigated
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
Phosphinic platinum complexes with 8-thiotheophylline derivatives: Synthesis, characterization, and antiproliferative activity
No full textThe platinum mixed-phosphine complexes (SP-4,2)-[PtCl(8-MTT)(PPh3)(PTA)] (2) and cis-[Pt(8-MTT)(2)(PPh3)(PTA)] (3) (MTTH2 = 8-(methylthio)theophylline, PTA = 1,3,5-triaza-7-phosphaadamantane) have been prepared from the precursor cis-[PtCl2(PPh3)(PTA)] (1), which has been fully characterized by X-ray diffraction determination. Antiproliferative activity tests indicated that the presence of one lipophilic PPh3 and one hydrophilic PTA makes 1-3 more active than the analogues bearing two PPh3 or two PTA. The reactivity of cis-[PtCl2(PPh3)(2)], cis-[PtCl2(PTA)(2)], and cis-[PtCl2(PPh3)(PTA)] with the bis(thiopurines) bis(S-8-thiotheophylline)methane (MBTTH2), 1,2-bis(S-8-thiotheophylline)ethane (EBTTH2), and 1,3-bis(S-8-thiotheophylline)propane (PBTTH2) has also been investigated. New binuclear complexes have been prepared and identified by spectroscopic techniques and their antiproliferative activities on T2 and SKOV3 cell lines evaluated
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
Backward synthesis of rhenium(I)γ-hydroxyvinylidene and γ-methoxy-vinylidene complexes and their conversion to the allenylidene [Re=C=C=CPh2(CO)2(MeC(CH2Ph2)3](OSO2CF3).
No full textThe reactivity of the rhenium() allenylidene complex [Re{C C CPh2}(CO)2(triphos)](OTf ) (1) [triphos =
MeC(CH2PPh2)3] towards ionic nucleophiles and electrophiles has been explored. Nucleophiles regioselectively attack
the Cγ carbon atom leading to the formation of σ-alkynyl complexes, while electrophiles attack the Cβ atom yielding
carbyne complexes. The sequential addition of OH and H to 1 at low temperature gave the γ-hydroxyvinylidene
complex [Re{CC(H)C(OH)Ph2}(CO)2(triphos)](OTf ) which regenerated 1 above 40 C via H2O elimination
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