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2- 2-(4-Methoxyphenyltelluro)ethyl thiophene (L-1) bis 2-(2-thienyl)ethyl telluride (L-2) and their metal complexes; crystal structure of trans-dichlorobis{2-(2-(4-methoxyphenyltelluro)ethyl) thiophene-Te}palladium(II) and {bis 2-(2-thienyl)ethyll telluride} dichloro(p-cymene)ruthenium(II)
No full textThe reaction of ArTe- (Ar = 4-MeOC6H4) and Te2- generated in situ by borohydride reduction of Ar2Te2 and Te, respectively, with 2-(2-thienyl)ethyl chloride has resulted in 2-[2-(4-methoxyphenyltelluro)ethyl]thiophene (L-1) and bis[2-(2-thienyl)ethyl] telluride (L-2), respectively. Their complexes [AgNO3(L-1)] (1) [PdCl2(L-1)(2)] (2) [PtCl2(L-1)(2)] (3) [HgBr2(L-1)](2) (4) [Ru(p-cymene)Cl-2(L-1)] (5) [Ru(p-cymene)Cl-2(L-2)] (6) and [PdCl2(L-2)(2)] have been synthesized. The ligands and complexes exhibit characteristic H-1 and C-13{H-1} NMR spectra. Both the ligands coordinate only through Te in all the complexes. The single crystals of 2 and 6 are characterized by X-ray diffraction. Compound 2 has square planar geometry around Pd and trans arrangement of ligands. The Pd-Te bond distances 2.5951(7) and 2.5872(7) Angstrom are longer than the values expected due to strong trans influence. The unique intermolecular secondary Te...Cl interaction (distance = 3.450/3.449 Angstrom) between neighbouring molecules has been observed in the crystal structure of 2. The distance between Pd atoms of two neighbouring molecules 3.2143(10) Angstrom has also been found less than the sum of van der Waal's radii 3.26 Angstrom. These secondary interactions in 2 result in the formation of a dimeric species, which remains intact even in the solution. Compound 6 is a half sandwich having three coordination sites occupied by two Cl atoms and the Te atom of L-2 with Ru-Te bond distance of 2.6528(9) Angstrom and Ru-Cl, 2.415(2)/2.422(2) Angstrom
Multidentate hybrid organotellurium ligands 1-(4-methoxyphenyltelluro)-2-[3-(6-methyl-2-pyridyl)propoxy]ethane (L-1) 2-methyl-6-{3-[2-({2-[3-(6-methyl-2-pyridyl)propoxy]-ethyl}telluranyl)et hoxy]propyl}pyridine (L-2) and their metal complexes: formation of 20-membered metallomacrocycle by L-1
No full text4-MeOC6H4Te-Na+ and Te2- generated in situ by reduction of (4-MeOC6H4Te)(2) and elemental Te, respectively, with sodium borohydride on reaction with 2-[3-(2-chloroethoxy)propyl]-6-methylpyridine in N-2 atmosphere results in 1-(4-methoxyphenyltelluro)-2-[3-(6-methyl-2-pyridyl)propoxy]ethane (L-I) 2-methyl-6-{3-[2-({2-[3-(6-methyl-2-pyridyl)propoxy]ethyl}telluranyl)eth oxy]propyl}pyridine (L 2) as viscous oils. Their proton and carbon-13 NMR spectra are characteristic. The L 2 shows signs of decay within few days. The complexes [PdCl2(L-I)](2) (1), [PtCl2(L-I)](2) (2), [HgBr2(L-I)] (3), [PdCl2(L-2)](2) (6), [PtCl2(L-2)](2) (7) and [(PdCl2)(3)(L-2)(2)](8) have been synthesized and found to give characteristic 1 H and 13 C NMR spectra. The 3 on crystallization from acetone:hexane (2: 1) mixture gives MeOC6H4HgBr (4) and [RTe+-HgBr2]Br- (R = -CH2CH2OCH2CHCH2-(2-(6-CH3-C5H3N))) (5). The crystals of 1, 2 and 4 are subjected to X-ray diffraction and their structures are solved. The I and 2 are 20-membered metallomacrocycles and do not dissociate in solution. The crystals of I and 2 have chloroform and benzene, respectively, in the lattice whereas 4 is a linear ArHgBr type species. The Pd/Pt in 1 and 2 has square planar geometry. The Pd-Te and Pd-N bond lengths in 1 are 2.530(1)/2.5313(9) and 2.097(4) and 2.101(4) angstrom, respectively
Tellurated heterocycles, 2-[(2-thienyltelluro)methyl]tetrahydrofuran (L-1) and [(2-thienyltelluro)methyl]tetrahydro-2H-pyran (L-2): synthesis and complexation reactions with Pd(II), Pt(II), Hg(II), Ru(II) and Cu(I) single crystal structures of [Ru(p-cymene)Cl-2(L-1)] and cis-[PdCl2(L-2)(2)]
No full text2-Thienyllithium (ThLi) reacts with elemental Te to give ThTeLi which on reaction with tetrahydrofurfurylchloride and 2-(bromomethyl) tetrahydro-2H-pyran at -78 degrees C results in L-1 and L-2. Their complexes [PdCl2(L-1)(2)] (1), [PtCl2(L-1)(2)](2), [HgBr2(L-1)(2)](3), [Ru(p-cym-ene)Cl-2(L-1)] (4), [CuBr(L-1)] (5), [PdCl2(L-2)(2)](6), [PtCl2(L-2)(2)](7), [HgBr2(L-2)(2)](8) and [Ru(p-cymene)Cl-2(L-2)] (9). Both the ligands and all nine complexes have characteristic H-1 and C-13 NMR spectra which reveal that in most of the complexes the two ligands L-1 and L-2 coordinate through Te only. This is corroborated by single crystal structures of 4 and 6. The 4 is a half sandwich compound, in which coligands of p-cymene are Cl and L-1 (monodentate coordinated through Te). The Ru-Te bond length is 2.6340(7) Å. In the 6 Pd has nearly square planar geometry and molecules of ligand L-2 are cis to each other, which is something rare with the monodentate telluride ligands. The Pd-Te bond lengths are 2.538(2) and 2.517(2) Å. The crystal structure of 6 also shows presence of secondary (TeCl)-Cl-. . . interactions in the crystal lattice. The Pd-Pd distance in 6 becomes 3.188(3) Å, less than 3.26 Å (sum of vander Waal's radii). The ligation of L-1 and L-2 is compared with those of related ligands
First example of bimetallic complex of platinum(II) with a hybrid organotellurium ligand [(4-MeOC6H4Te)CH2CH2OCH2CH2CH2(2-C5H4N)] (L1) containing 20-membered metallomacrocycle ring: synthesis and crystal structure
No full text1-(4-Methoxyphenyltelluro)-2-[3-(6 methyl-2 pyridyl)propoxy]ethane (L1) and its complexes [MCl2(L1)]2 (M = Pd or Pt) have been synthesized. The single crystal X-ray diffraction of [PtCl2(L1)]2 · 2CHCl3 shows a bimetallic complex of platinum(II) containing a 20-membered metallomacrocycle ring, which remains stable in solution as shown by molecular weight and conductance measurements. The Pt–Te and Pt–N bond lengths are 2.5409(3) and 2.087(5) Å, respectively. The protons of CH2 linked to Te show a deshielding > 1 ppm on the formation of the two complexes
Reactions of hybrid organotellurium ligands 1-(4-methoxyphenyltelluro)-2- 3-(6-methyl-2-pyridyl) propoxy ethane (L-1) and 1-ethylthio-2- 2-thienyltelluro ethane (L-2) with mercury(II) bromide: formation of complexes and their decomposition
No full textTwo tellurium ligands 1-(4-methoxyphenyltelluro)-2-[3 -(6-methyl-2-pyridyl)propoxy]ethane (L-1) and 1-ethylthio-2-[2-thienyltelluro]ethane (L-2) have been synthesized by reacting nucleophiles [4-MeO-C6H4Te-] and [C4H3S-2-Te-] with 2-[3-(6-methyl-2-pyridyl)propoxy]ethylchlo ride and chloroethyl ethyl sulfide, respectively. Both the ligands react with HgBr2 resulting in complexes of stoichiometry [HgBr2 (.) L-1/L-2] (1/4), which show characteristic NMR (H-1 and C-13{H-1}). On crystallization of I from acetone-hexane (2:1) mixture, the cleavage of L-1 occurs resulting in 4-MeOC6H4HgBr (2) and [RTe+ -> HgBr2]Br- (3) (where R = -CH2CH2OCH2CH2CH2-(2-(6-CH3-C5H3N))). The 2 is characterized by X-ray diffraction on its single crystal. It is a linear molecule and is the first such system which is fully characterized structurally. The Hg-C and Hg-Br bond lengths are 2.085(6) and 2.4700(7) angstrom. The distance of four bromine atoms (3.4041(7)-3.546(7) angstrom) around Hg (cis to C) is greater than the sum of van der Waal's radii 3.30 angstrom. This mercury promoted cleavage is observed for an acyclic ligand of RArTe type for the first time and is unique, as there appears to be no strong intramolecular interaction to stabilize the cleavage products. The 4 on crystallization shows the cleavage of organotellurium ligand L-2 and formation of a unique complex [(EtS(CH2)(2)SEt)HgBr(mu-Br)Hg(Br)(mu-Br)(2)Hg(Br)(mu-Br)BrHg(EtS(CH2)(2 )SEt)] (.) 2HgBr(2) (5), which has been characterized by single crystal structure determination and H-1 and C-13 {H-1} NMR spectra. The elemental tellurium and [C4H3SCH2](2) are the other products of dissociation as identified by NMR (proton and carbon-13). The cleavage appears to be without any transmetalation and probably first of its kind. The centrosymmetric structure of 5 is unique as it has [HgBr3](-) unit, one Hg in distorted tetrahedral geometry and one in pseudo-trigonal bipyramidal one. The molecule of 5 may also be described as having [(EtSCH2CH2SEt)HgBr](+) [HgBr3](-) units, which dimerize and co-crystallize with two HgBr, moieties. There are very weak Hg (...) Br interactions between co-crystallized HgBr, units and rest of the molecule. [Hg(3)-Br(1)/Hg(3)-Br(4) = 3.148(1)/3.216(1) angstrom]. The bridging Hg (...) Br distances, Hg(2)-Br(4)', Hg(2)'-Br(4) and Hg(1)-Br(2), are from 2.914(1) to 3.008(1) angstrom
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
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