6,971 research outputs found
Neutrons in chemistry : contributions of single crystal neutron diffraction to coordination chemistry
No full text1. Introduction
Single crystal neutron diffraction is the technique of choice for unambiguously and accurately locating hydrogen atoms even in the presence of nearby “heavy atoms”. Recent advances in instrumentation and neutron sources are opening up new possibilities: in particular the use of fairly small crystals and short data collection times.
2. Results and Discussion
We will report three examples to illustrate the power of this technique in inorganic chemistry:
1) the first unambiguous structural evidence for non-conventional hydrogen bonding between a water molecule and a metal center in trans-[PtCl2(NH3)(N-glycine)]∙H2O.[1]
2) The coordination geometries of the binary platinum hydrides [Pt2(P-P)2(H)3]+ (P-P = dppb: 1,4–Bis(diphenylphosphino)butane and dpe: 1,2–Bis(diphenylphosphino)ethane).
3) The unambiguous location of deuterium atoms in the deuterated form of RuH2(η2-H2)2(PCyp3)2 (Cyp = cyclopentyl) complex as a proof of the metal-mediated C-H activation.[2]
3. References
[1] Silvia Rizzato, Jacqueline Bergès, Sax A. Mason, Alberto Albinati and Jiří Kozelka, Angew. Chem. Int. Ed., in press.
[2] M. Grellier, L. Vendier, B. Chaudret, A. Albinati, S. Rizzato, S. A. Mason and S. Sabo-Etienne J. Am. Chem. Soc., 2005,127 (50), 17593
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
Steric and polar effects in free-radical reactions. - An unusual type of azocoupling by free radical decomposition of diazonium salts
No full textA new free-radical azocoupling has been accomplished by decomposition of diazonium salts with monoelectronic reducing agents in the presence of 4-methyl-3-penten-2-one. Steric and polar factors are responsible of the unusual behaviour. © 1980
An Experimental and Theoretical Study of the Electronic and Molecular Structure of [Zn4(μ4-S){μ-S2P(OC2H5)(2)}(6)]: the First Molecular Model of ZnS
No full textThe electronic and molecular structure of hexakis[μ-(O,O′-diethyl dithiophosphate-S:S′)]-μ4-thiotetrazinc, [Zn4(μ4-S){μ-S2P(OC2H5)2}6] (1), has been investigated by combining X-ray diffraction measurements, UV–vis absorption spectroscopy and density functional calculations. The title compound is characterized by a Zn4(μ4-S)(μ-S12) core consisting of a S atom at the center of a distorted tetrahedron of Zn ions, each of them placed at the center of an irregular tetrahedron of S atoms. Theoretical results point out that 1, at variance to the isostructural [Zn4(μ4-S){μ-S2As(CH3)2}6] recently investigated by Albinati et al. [Inorg. Chem. 38 (1999) 1145], can be considered a well tailored molecular model of ZnS. Theoretical outcomes also indicate that the low energy region of the UV absorption spectrum of 1 includes transitions having a ligand-to-metal-charge transfer nature involving the excitation of an electron from the occupied μ4-S 3p based atomic orbitals to the empty Zn 4s based levels
[Poesia] Três poemas de Alberto Secama
No full textThree poems by Alberto Secama. About the author: Alberto Secama is an Angolan poet who has poems published on many websites and on facebook:https://www.facebook.com/Xungurra/abouthttp://www.pordentrodaafrica.com/cultura/africa-em-verso-rio-kwanza-por-alberto-secamahttp://www.pordentrodaafrica.com/cultura/africa-em-verso-zong-por-alberto-secamahttp://www.pordentrodaafrica.com/cultura/coluna-africa-em-verso-o-sol-la-fora-por-alberto-secamaTres poemas de Alberto Secama. Sobre el autor: Alberto Secama es un poeta angoleño que tiene poemas publicados en varios sitios y en el facebook:https://www.facebook.com/Xungurra/abouthttp://www.pordentrodaafrica.com/cultura/africa-em-verso-rio-kwanza-por-alberto-secamahttp://www.pordentrodaafrica.com/cultura/africa-em-verso-zong-por-alberto-secamahttp://www.pordentrodaafrica.com/cultura/coluna-africa-em-verso-o-sol-la-fora-por-alberto-secamaTrês poemas de Alberto Secama. Sobre o autor: Alberto Secama é um poeta angolano que possui poemas publicados em vários sites e no facebook:https://www.facebook.com/Xungurra/abouthttp://www.pordentrodaafrica.com/cultura/africa-em-verso-rio-kwanza-por-alberto-secamahttp://www.pordentrodaafrica.com/cultura/africa-em-verso-zong-por-alberto-secamahttp://www.pordentrodaafrica.com/cultura/coluna-africa-em-verso-o-sol-la-fora-por-alberto-secam
Orizzonti mantovani. Spunti e dinamiche paesaggistiche ne L'Illustrissimo di Alberto Cantoni
No full textIn the literary production of Alberto Cantoni, short story writer and novelist between the nineteenth and twentieth centuries, the novel L'Illustrissimo is highly important both because it is the last publication of the author, from Pomponesco, a small town a few kilometers south of Mantua, both because it summarizes in a single text the different nuances and different directions that his writing has taken over the course of his literary career, also due to a writing and processing time that embraces the entire span of years of his career itself. In the foreground, in addition to the numerous and brilliant characters, one of the protagonists is the Mantuan landscape which, not a simple background, becomes a true literary parameter which in different and significant ways affects the purposes and mechanisms of the novel
Stable olefin complexes of Pt(II) containing trichlorostannate(II) ligands: Structure of(Ph4As)[Pt(SnCl3)3(1,5 - COD)]
No full textPlenary Session: Luis Alberto Urrea
No full texta) Plenary Session: Luis Alberto Urrea, Mexican American Chicago Writer
Luis Alberto Urrea is a 2005 Pulitzer Prize finalist for non-fiction and member of the Latino Literature Hall of Fame. He is a prolific and acclaimed writer who has used his dual-culture life border experiences to explore the complex and interconnected Mexican-US American reality. The critically acclaimed and best-selling Mexican-born author of 13 books, Urrea has won numerous awards for his poetry, fiction and essays.
Moderator: Dr. Héctor García, Loyola University Chicag
O duplo significado do sentir e do pensar nas obras de Alberto Caeiro e Descartes
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-Graduação em LiteraturaA pretensão desta dissertação intitulada O duplo significado do sentir e do pensar nas obras de Alberto Caeiro e Descartes é investigar a relação entre o sentir e o puro pensar, usando como referência a poesia O Guardador de Rebanhos, de Alberto Caeiro, que apresenta de forma evidente o tema; e como este assunto é tratado nas Meditações Metafísicas de René Descartes, também de forma claramente visível. Podemos perceber em ambos os autores, uma diplopia, uma espécie de duplo olhar sobre a relação sentir e puro pensar. No primeiro capítulo vou falar sobre a tese do duplo olhar de Descartes, a respeito da relação sentir e puro pensar na leitura de Merleau-Ponty, salientando a visão de natureza. No segundo capítulo, parto da leitura das três primeiras Meditações Metafísicas para caracterizar a tensão que se pode verificar entre Descartes e Alberto Caeiro quando se referem ao puro pensar. O foco principal de Descartes, nas três primeiras Meditações, é o pensar puro, e neste ponto Alberto Caeiro critica o pensar puro. No terceiro capítulo, analisando as três últimas Meditações, percebe-se que há uma virada no pensamento de Descartes, no qual o autor inverte seu ponto de vista, aproximando-se da idéia de Alberto Caeiro. No quarto capítulo, mostrarei a leitura que outros autores fazem acerca do sentir e do pensar na obra de Alberto Caeiro, mostrando que assim como Descartes, este também ostenta uma diplopia, não do sentir, mas do pensar. The pretension of this work entitled O duplo significado do sentir e do pensar nas obras de Alberto Caeiro e Descartes is to investigate the relationship between the feeling and the pure thinking, using as reference the poetry O Guardador de Rebanhos, by Alberto Caeiro, that presents in an evident way this theme; and as this subject is treated in René Descartes' Metaphysical Meditations, also in a clearly visible way. It is possible to notice in both authors, the diplopy, a sort of double look about the relationship between feeling and pure thinking. The thesis about Descartes'double look regarding the relation of feeling and pure thinking, in Merleau-Ponty reading, pointing out the nature vision, will be treated in the first chapter. In the second chapter, I start from the reading of the first three Metaphysical Meditations to characterize the tension that can be verified between Descartes and Alberto Caeiro when they refer to the pure thinking. Descartes' main focus in the first three Meditations is pure thinking and, in this point, Alberto Caeiro criticizes pure thinking. In the third chapter, analyzing the last three Meditations, it is possible to notice that there is an alteration in Descartes' thought, in which the author inverts his point of view, approaching of Alberto Caeiro's idea. In the fourth chapter, I will show the reading that other authors do concerning feeling and thinking in Alberto Caeiro's work, showing that as well as Descartes, this also shows a diplopy, not of feeling, but of thinking
Reactions of Cyclopalladated Benzylidene-aniline Schiff's Base Complexes. Selective Synthesis of 2′-Substituted Schiff's Base Derivatives and the X-Ray Crystal Structure of the Dimer [Pd(μ-OAc)(5′-OCH3[BOND]C6H3CH[DOUBLE BOND]NC6H4-4-CH3)]2
No full textThe 2′-cyclopalladated imine complex equation image, reacts with CO in MeOH to afford the 2′-substituted aryl imine 2′-CO2CH3-5′-OCH3[BOND]C6H3CH[DOUBLE BOND]NTol (Tol = C6H4-4-CH3). The product of this reaction can be altered by changing the bridging ligand from AcO to Cl, in which case only the 5-membered ring heterocyclic compound equation image is obtained. [Pd(μ-OAc)(1a)]2 with 2 equiv. of Ph3P and CO (1 atm) gives the heterocyclic equation image which arises from two CO insertion reactions, whereas [PdX(1a)]2 (X = AcO, Cl) with 4 equiv. of C[TRIPLE BOND]NBut and 4 equiv. of Ph2PCH2CH2PPh2 affords the heterocyclic ketenimine equation image [PdCl(1a)]2 reacts with CH2[DOUBLE BOND]CHCO2CH2CH3 to afford 2′([BOND]CH[DOUBLE BOND]CHCO2CH2CH3)-5′-OCH3C6H3CHO, and [Pd(μ-OAc)(1a)]2 with I2 to give 2′-I-5′-OCH3C6H3CHO. Excess CH3O2CC[TRIPLE BOND]CCO2CH3 reacts with various substituted cyclopalladated Schiff's bases in MeOH to afford equation image which we formulate as possessing two Pd[BOND]C bonds, and one coordinated ester O atom. The X-ray crystal structure of [Pd(μ-OAc)(1a)]2 has been determined; relevant bond lengths [Å] and bond angles [°] are: Pd[BOND]O(1), 2.139(6), Pd[BOND]O(2), 2.026(6), Pd[BOND]N, 2.039(6), Pd[BOND]C(2′), 1.951(8), Pd[BOND]Pd, 3.113(1), N[BOND]Pd[BOND]C(2′), 80.9(3), N[BOND]Pd[BOND]O(1), 97.5(2), C(2′)[BOND]Pd[BOND]O(2), 91.7(3), O(1)[BOND]Pd[BOND]O(2), 89.2(2)
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