Entwicklung von Katalysatoren für die Alkinmetathese: Synthese funktionalisierter Molybdänbenzylidinkomplexe und verwandter Spezies

The present dissertation focused on the variation of the ligand environment of molybdenum benzylidyne complexes as potential alkyne metathesis initiators. In order to improve the robustness of these complexes, several strategies were explored. In the first place, functionalisation of the benzylidyne unit (CAr) with ether groups resulted in para-methoxybenzylidyne and trimethoxybenzylidyne derivatives [Mo(CAr)(OC(CF3)2Me)3] (Ar = 4-MeO-C6H4, 2,4,6-(MeO)3C6H2). These complexes formed 1D-polymeric chains in the solid state promoted by intermolecular contacts between the methoxy group at the para-position and the metal centre of the adjacent molecule. In the second place, a series of complexes of the type [Mo(CMes)(L)(OC(CF3)2Me)3] (Mes = 2,4,6-trimethylphenyl, L = acetonitrile, 2,4,6-trimethoxybenzonitrile, acetone, pyridine, 2,2'-bipyridine, trimethylphosphane, and 1,3,4,5-tetramethylimidazoline carbene) was synthesised by addition of coordinating ligands (L) to [Mo(CMes)(OC(CF3)2Me)3]. Stability tests revealed no observable degradation of the 2,2'-bipyridine and the carbene adducts upon exposure to air. Furthermore, selected alkynes (such as 1-heptyne, 3-hexyne, phenylacetylene, tolan, and ynediamines) were reacted stoichiometrically with [Mo(CMes)(OC(CF3)2Me)3] in an attempt to isolate intermediate metallacyclic species. Only the reaction with ynediamines yielded unusual paramagnetic molybdenacyclobutadiene complexes; otherwise, alkylidyne cross-metathesis products were generated, e.g. [Mo(CPh)(OC(CF3)2Me)3]. The catalytic activity in alkyne metathesis was determined for all investigated alkylidyne complexes in terms of TON and TOF values.Die vorliegende Arbeit befasste sich mit der Veränderung der Ligandensphäre von Molybdänbenzylidinkomplexen, die als Alkinmetatheseinitiatoren fungieren sollen. Dabei wurden mehrere Strategien mit dem Ziel untersucht, die Beständigkeit dieser Komplexe zu erhöhen. Zunächst wurden die para-Methoxybenzylidin- und Trimethoxybenzylidinderivate [Mo(CAr)(OC(CF3)2Me)3] (Ar = 4-MeO-C6H4, 2,4,6-(MeO)3C6H2) erzeugt, wobei die Benzylidineinheit (CAr) mit Ethergruppen funktionalisiert werden konnte. Diese Komplexe gestalteten sich im Festkörperzustand als 1D-Polymerketten, bedingt durch die Bildung von intermolekularen Wechselwirkungen zwischen der Methoxygruppe an der para-Position und dem Metallzentrum des Nachbarmoleküls. Zweitens wurde eine Reihe von Komplexen des Typs [Mo(CMes)(L)(OC(CF3)2Me)3] (Mes = 2,4,6-Trimethylphenyl; L = Acetonitril, 2,4,6-Trimethoxybenzonitril, Aceton, Pyridin, 2,2'-Bipyridin, Trimethylphosphan und 1,3,4,5-Tetramethylimidazolincarben) durch die Anlagerung von koordinierenden Liganden (L) an [Mo(CMes)(OC(CF3)2Me)3] synthetisiert. Stabilitätsuntersuchungen zeigten, dass keine Zersetzung der 2,2'-Bipyridin- und Carbenaddukte bei Kontakt mit Luft beobachtet werden konnte. Darüber hinaus wurden ausgewählte Alkine (1-Heptin, 3-Hexin, Phenylacetylen, Tolan und Indiamine) stöchiometrisch mit [Mo(CMes)(OC(CF3)2Me)3] umgesetzt, um intermediäre metallazyklische Spezies zu isolieren. Lediglich die Reaktion mit Indiaminen führte zu ungewöhnlichen paramagnetischen Molybdänacyclobutadienkomplexen; in den anderen Fällen wurden Alkylidin-Kreuzmetatheseprodukte erzeugt, z. B. [Mo(CPh)(OC(CF3)2Me)3]. Die katalytische Aktivität in Alkinmetathesereaktionen wurde anhand von TON- und TOF-Werten für alle untersuchten Alkylidinkomplexe beschrieben

Gramática aplicada a ELE: la perífrasis “ir a + infinitivo” y el futuro sintético

La presencia en español de dos construcciones —la perífrasis «IR A+Infinitivo» y las formas verbales sintéticas terminadas en –rá— que pueden alternarse en determinados contextos como mecanismos para expresar la futuridad en español ha llevado a una generalización en el uso de tales construcciones descuidando la vertiente pragmática de las mismas, y, en consecuencia, se ha tendido a ofrecer al estudiante de ELE una consideración básicamente gramatical de los usos de la perífrasis y del futuro sintético. En este sentido, el objetivo de nuestra propuesta busca establecer las principales divergencias de carácter pragmático que —creemos— deberían incorporarse a la explicación de estos contenidos gramaticales

Los géneros discursivos desde la perspectiva del ELE

Afrontar el proceso de adquisición de una lengua extranjera supone una tarea global que culmina en el dominio de la misma en múltiples variables situacionales. En el siguiente trabajo proponemos una incipiente caracterización de la conversación telefónica como subgénero discursivo que se enmarca en el ámbito del desarrollo de las destrezas orales. Pretendemos con ello acotar un marco específico en el que las características interaccionales propias de los textos conversacionales aparecen en algunos aspectos dislocadas, así como proponer una aplicación didáctica mediante la imbricación de este género textual con el uso de ciertos recursos cinematográficos en la clase de ELE

Revisió del gènere Agave L. a Catalunya

Màster en Biodiversitat, Universitat de Barcelona, Facultat de Biologia. Curs: 2018. Tutor:Ignasi Soriano Tomàs. Directors: Jordi López-Pujol i Neus Ibáñez Cortina.The genus Agave L. has about 200 species naturally distributed in the Neotropics. Most of the described species are, however, native to Mexico (ca. 75%), with many of these being endemic. Agave is a genus with a long tradition of uses, mainly alimentary, medicinal, and industrial (e.g. as a fiber plant). The most common agave in the Iberian Peninsula but also in Catalonia is A. americana, that was already introduced in the 16th century, and which is widely naturalized (at least since 18th century). Many other agaves were introduced subsequently to Catalonia (and other places of Europe), mostly during 19th and 20th centuries. Current floras and alien catalogues of Catalonia and the Iberian Peninsula only include a few Agave species, and the lack of taxonomical consensus point towards a need for a revision of the genus. Up to 12 taxa are catalogued in the present work, together with a dicotomical key and distribution maps for all of them. Some insights on the history of the introduction of the genus into Catalonia and the Iberian Peninsula are also provided

Dangers at Sea and Maritime Conflict Management in the Crown of Aragon of the First Two Trastàmara (1410-1458)

La tesi titulada Els perills de la mar. Pirateria, captiveri i gestió del conflicte marítim a la Corona d’Aragó (1410-1458) ofereix un quadre diversificat de la gestió de la pirateria, del cors, de la defensa costanera i del conflicte marítim en general a la Corona d’Aragó de la primera meitat del segle xv. El present article resumeix la seva estructura, la metodologia aplicada, el seu contingut, així com també la seva aportació a la historiografia nacional i internacional que ha abordat aquestes temàtiques amb anterioritat, sobretot a partir dels tres nuclis marítims més importants de la Corona: les ciutats de Barcelona, València i Mallorca.The PhD dissertation titled Dangers at Sea. Piracy, Captivity and Maritime Conflict Management in the Crown of Aragon (1410-1458) offers a diversified picture of the management of piracy, privateering, coastal defence and maritime conflicts in general in the Crown of Aragon during the first half of the 15th century. This article summarizes its structure, the applied methodology, its content and also its contribution to earlier national and international historiography, investigating these issues mainly based on the history of the three most important maritime centres of the Crown: the cities of Barcelona, Valencia and Majorca

The Westerly Index as complementary indicator of the North Atlantic oscillation in explaining drought variability across Europe

This paper analyses the influence of different atmospheric circulation indices on the multi-scalar drought variability across Europe by using the Standardized Precipitation Evapotranspiration Index (SPEI). The monthly circulation indices used in this study include the North Atlantic oscillation (NAO), the East Atlantic (EA), the Scandinavian (SCAN) and the East Atlantic-Western Russia (EA-WR) patterns, as well as the recently published Westerly Index (WI), defined as the persistence of westerly winds over the eastern north Atlantic region. The results indicate that European drought variability is better explained by the station-based NAO index and the WI than by any other combination of circulation indices. In northern and central Europe the variability of drought severity for different seasons and time-scales is strongly associated with the WI. On the contrary, the influence of the NAO on southern Europe droughts is stronger than that exerted by the WI. The correlation patterns of the NAO and WI with the SPEI show a spatial complementarity in shaping drought variability across Europe. Lagged correlations of the NAO and WI with the SPEI also indicate enough skill of both indices to anticipate drought severity several months in advance. As long as instrumental series of the NAO and WI are available, their combined use would allow inferring European drought variability for the last two centuries and improve the calibration and interpretation of paleoclimatic proxies associated with drought

Assessment of vapor pressure deficit variability and trends in Spain and possible connections with soil moisture

The Vapor Pressure Deficit (VPD) is one of the most relevant surface meteorological variables; with important implications in ecology, hydrology, and atmosphere. By understanding the processes involved in the variability and trend of the VPD, it is possible to assess the possible impacts and implications related to both physical and human environments, like plant function, water use efficiency, net ecosystem production, atmospheric CO2 growth rate, etc. This study analysed recent temporal variability and trends in VPD in Spain between 1980 and 2020 using a recently developed high-quality dataset. Also, the connection between VPD and soil moisture and other key climate variables (e.g. air temperature, precipitation, and relative humidity) was assessed on different time scales varying from weekly to annual. The objective was to determine if changes in land-atmosphere feedbacks connected with soil moisture and evapotranspiration anomalies have been relevant to assess the interannual variability and trends in VPD. Results demonstrate that VPD exhibited a clear seasonality and dominant positive trends on both the seasonal (mainly spring and summer) and annual scales. Rather, trends were statistically non-significant (p > 0.05) during winter and autumn. Spatially, VPD positive trends were more pronounced in southern and eastern of Spain. Also, results suggest that recent trends of VPD shows low contribution of variables that drive land-atmosphere feedbacks (e.g. evapotranspiration, and soil moisture) in comparison to the role of global warming processes. Notably, the variability of VPD seems to be less coupled with soil moisture variability during summertime, while it is better interrelated during winter, indicating that VPD variability would be mostly related to climate variability mechanisms that control temperature and relative humidity than to land-atmosohere feedbacks. Overall, our findings highlight the importance of assessing driving forces and physical mechanisms that control VPD variability using high-quality climate datasets, especially, in semiarid and sub-humid regions of the world

Long-term precipitation in Southwestern Europe reveals no clear trend attributable to anthropogenic forcing

We present a long-term assessment of precipitation trends in Southwestern Europe (1850-2018) using data from multiple sources, including observations, gridded datasets and global climate model experiments. Contrary to previous investigations based on shorter records, we demonstrate, using new long-term, quality controlled precipitation series, the lack of statistically significant long-term decreasing trends in precipitation for the region. Rather, significant trends were mostly found for shorter periods, highlighting the prevalence of interdecadal and interannual variability at these time-scales. Global climate model outputs from three CMIP experiments are evaluated for periods concurrent with observations. Both the CMIP3 and CMIP5 ensembles show precipitation decline, with only CMIP6 showing agreement with long term trends in observations. However, for both CMIP3 and CMIP5 large interannual and internal variability among ensemble members makes it difficult to identify a trend that is statistically different from observations. Across both observations and models, our results make it difficult to associate any declining trends in precipitation in Southwestern Europe to anthropogenic forcing at this stage