Crystal structure of 1,1,2,2-tetramethyl-1,2-bis(2,3,4,5-tetramethylcyclopenta-2,4-dien-1-yl)disilane

The mol­ecular structure of the title compound, C22H38Si2, features a trans arrangement of the cyclo­penta­dienyl rings to avoid steric strain [C-Si-Si-C torsion angle = -179.0 (5)°]. The Si-Si bond length is 2.3444 (4) Å. The most notable inter­molecular inter­actions in the mol­ecular packing are C-H...[pi] contacts that lead to the formation of wave-like supra­molecular chains along the b axis

Crystal structure of 1-hydroxy-2,2,6,6-tetramethylpiperidin-1-ium trifluoromethanesulfonate

In the cation of the title salt, C9H20NO+·CF3O3S-, the six-membered heterocyclic ring displays a chair conformation. In the crystal, centrosymmetric pairs of cations and anions are linked by N-H...O and O-H...O hydrogen bonds to form rings with a R44(14) graph-set motif

Ansa-Titanocenkomplexe zur Untersuchung der fundamentalen Schritte in der lichtgetriebenen Wasserspaltung

Diese Arbeit beschäftigt sich mit der Spaltung von Wasser an Titanocenkomplexen. Ziel war es, ein fundamentales Verständnis über die Oxidations- bzw. Reduktionsprozesse zu erlangen, die am Metallzentrum bzw. Wasser stattfinden. Es konnte gezeigt werden, dass die formale Abstraktion eines H-Radikals von Wasser, unter Bildung einer Ti-O-Bindung, möglich ist. Diese wurde dann in einem weiteren Schritt unter Verwendung von Licht gespalten, wodurch der ursprünglich eingesetzte Titankomplex wieder erhalten wurde. Diese Reaktionsfolge stellt ein Beispiel für einen Zyklus der Wasserspaltung dar

Crystal structure of 1,1,2,2-tetramethyl-1,2-bis(2,3,4,5-tetramethylcyclopenta-2,4-dien-1-yl)disilane

The molecular structure of the title compound, C22H38Si2, features a trans arrangement of the cyclopentadienyl rings to avoid steric strain [C—Si—Si—C torsion angle = −179.0 (5)°]. The Si—Si bond length is 2.3444 (4) Å. The most notable intermolecular interactions in the molecular packing are C—H...π contacts that lead to the formation of wave-like supramolecular chains along the b axis

Crystal structures of two ansa-titanocene trifluoromethanesulfonate complexes bearing the Me2Si(C5Me4)2 ligand

The crystal structures of two ansa-titanocene trifluoromethanesulfonate complexes bearing the Me2Si(C5Me4)2 ligand are reported, namely [dimethylbis(η5-tetramethylcyclopentadienyl)silane](trifluoromethanesulfonato-κ2O,O′)titanium(III) toluene monosolvate, [Ti(CF3O3S)(C20H30Si)]·C7H8, 1, and chlorido[dimethylbis(η5-tetramethylcyclopentadienyl)silane](trifluoromethanesulfonato-κO)titanium(IV), [Ti(CF3O3S)(C20H30Si)Cl], 2. Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetrahedral geometry, with the trifluoromethanesulfonate anion acting as a bidentate or monodentate ligand in 1 and 2, respectively. In 1, weak π–π stacking interactions involving the toluene solvent molecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed

Highly selective visible light-induced Ti–O bond splitting in an ansa-titanocene dihydroxido complex

Irradiation of a substituted ansa-titanocene(IV) dihydroxido complex with visible light induces Ti–O bond dissociation. In contrast to previous studies on structurally similar unbridged complexes, no side reactions are observed and formation of the Ti(III) species is highly selective. The formation of OH radicals was proved using a biradicaloid species

A Model of a Closed Cycle of Water Splitting Using <i>ansa</i>-Titanocene(III/IV) Triflate Complexes

A series of <i>ansa</i>-titanocene triflate complexes are described as model compounds for the elementary steps of light-driven overall water splitting. Titanocene­(III) triflate complexes are readily obtained by reaction of a titanocene source with Yb­(OTf)₃. Subsequent reactions with water and with/without TEMPO as hydrogen scavenger are studied. The as-obtained titanocene­(IV) compounds can be photoreduced to give titanocene­(III) triflate complexes, which can undergo further hydrolysis to form a closed catalytic cycle of water splitting. No further degradation of the photoreduced species was observed because of the presence of the OTf group. The stability of the system was evaluated in an experiment with high concentrations of water and TEMPO. X-ray crystallography on all titanocene complexes, EPR and NMR spectroscopy, and DFT were used to support our observations

Hacia la transdiciplinariedad

En este número de Polis, el tema monográfico de Lente de Aproximación lo hemos dedicado al tema de la pluri, inter y transdisciplinariedad. La importancia del tema es indudable. Estamos viviendo una revolución del conocimiento en todas las áreas que se manifiesta en una heterogeneidad casi inconmensurable de discursos y publicaciones, que asemeja al mito borgiano de la biblioteca de Babel. Sin embargo, esta proliferación está acompañada de una profunda insatisfacción respecto a las ciencias, especialmente las sociales. De una parte, experimentamos la fragmentación de la imagen de la realidad en múltiples visiones parciales provenientes de la diversidad de las ciencias y de cada una de ellas. De otra, somos cada vez más concientes que nuestras investigaciones son demasiado simples y esquemáticas para intentar aprehender una realidad polisémica y cada vez más fluyente. Asimismo, hay una presión creciente a convertir las investigaciones en ciencia aplicada, en tecnología útil para los gobiernos y empresas. Habitualmente dichas investigaciones están construidas sobre supuestos y teorías cuestionables desde el punto de vista científico, pero las cuales minimizan la conflictividad social. Es así que ciertos conceptos -como el de “capital social”- han adquirido gran relevancia porque permiten análisis y mediciones útiles para programas de políticas sociales