Comparing Protonolysis and Transmetalation Reactions: Microcalorimetric Studies of C–AuI Bonds in [AuRL] Complexes

Producción CientíficaThe protonolysis of C–Au bonds in [AuRL] organometallic complexes has been studied by calorimetry for twelve R groups. The experimental data have been combined with DFT calculations to obtain Bond Dissociation Energy values (BDE). The C–Au BDE values show a good correlation with the corresponding isolobal C–H BDE values. The heat released in the protonolysis of [AuRL] has also been measured for R = Ph and L = P(OPh)3, PPh3, PMe3, PCy3, and IPr, and these values strongly depend on the trans influence of L because of the mutual destabilization of the L–Au and Au–C bonds. The enthalpy of the transmetalation reactions [AuR(PPh3)] + SnIBu3 → [AuI(PPh3)] + SnRBu3 for seven R groups have been measured and compared with the corresponding [AuR(PPh3)] protonolysis.Ministerio de Economía, Industria y Competitividad (Project CTQ2016-80913-P)Junta de Castilla y León (Project VA 051P17

Performance and ownership in the governance of urban water

In this paper the differences in terms of performance between public and the private governance in urban water management are investigated. A statistical ranking is implemented to determine programmatic efficiency differences in DEA, using an incomplete panel data that gathers information on 20 water utilities in Andalusia, in Southern Spain. In the model, labour and operational costs are considered as inputs. The volume of revenue water, the number of connections and the network length are used as outputs. The analysis indicates that private management is more efficient. The efficiency indicators adjusted by a variable related to quality are estimated and demonstrate that privatization of the service does not mean any loss in terms of quality. However, there are no significant differences between both types of management including as a desirable input hydraulic yield as a proxy of the degree of network renovation. A lower hydraulic efficiency in private management would suggest that the need to make significant investments could be an important factor when making the decision to privatize the management of the urban water service

In Situ Generation of ArCu from CuF2 Makes Coupling of Bulky Aryl Silanes Feasible and Highly Efficient

Producción CientíficaA bimetallic system Pd/CuF2, catalytic in Pd and stoichiometric in Cu, is very efficient and selective for the coupling of fairly hindered aryl silanes with aryl, anisyl, phenylaldehide, or pyridyl iodides of conventional size. The reaction involves the activation of the silane by CuII followed by disproportionation and transmetalation from the CuI(aryl) to PdII, on which coupling takes place. The CuIII formed in the disproportionation is reduced to CuI(aryl) by the aryl silane in excess, so that the CuF2 used is fully converted into CuI(aryl) and used in the coupling. Moreover, no extra source of fluoride is needed. Interesting size selectivity towards coupling is found in competitive reactions of hindered aryl silanes. Easily accessible [PdCl2(IDM)(AsPh3)] is by far the best catalyst, and the isolated products are esentially free of As or Pd (< 1 ppm). The mechanistic aspects of the process are experimentally examined and discussed.Ministerio de Economía, Industria y Competitividad (CTQ2013-48406-P)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA256U13

Sea baths as an example of sustainable architecture without an ecological footprint

By the last third of the nineteenth century, many sea bath structures were raised by the Spanish Levante, but currently only San Antonio´s sea bath, jutting out over the Mar Menor in Murcia, remains. The historical documentation about these seashore buildings located in Murcia and Alicante allowed us to study these architecture typologies as an approach to the design process intended to harmonize its products with nature. All the historical maps and plans, drawings and photographs convey a whole process of systematized execution with a minimum use of energy at each stage of the building process, its assembly and erection, in addition to the low maintenance and total future recycling. The adaptation of the architectural design to the coast is one of the most important aspects of these traditional constructions. This paper shows the study of different architectural, structural and constructive solutions characterized by the use of fixed and removable lightweight structures and the evolution of piling systems. The removable feature and the simplicity of the assembly allow us to talk about an example of sustainable architecture without ecological footprints

The cyclycal trend of local public service governance: evidence from urban water management in Spain

The level of public and private involvement in economic activity in societies has changed over time. One may talk about the existence of a cyclical trend in which the most important periods of public governance are replaced by periods in which private management dominates the situation. This phenomenon may also be observed in local areas. Some authors have pointed out the existence of an alternation in the provision of municipal services, resulting in periods dominated by governance compared to other stages dominated by private management. In order to illustrate this cyclical trend at local level, this paper intends to analyze the evolution of the governance of the Spanish water supply since the mid-nineteenth century to the present day. Recent evidence from the industry suggests the possibility that we may currently be witnessing a further change in the trend

Dramatic Mechanistic Switch in Sn/AuI Group Exchanges: Transmetalation vs. Oxidative Addition

Producción CientíficaThe mechanism of Ph/X exchange in reactions involving SnPhnBu3 and [AuXL] complexes switches dramatically from the usual concerted mechanism involving Ar/X mixed bridges when X = Cl, to an unexpected oxidative addition/reductive elimination pathway via an AuIII intermediate when X = vinyl

the intriguing behavior of an apparently simple coupling promoter ligand, PPh2(p-C6H4-C6F5), in their Pd complexes

ABSTRACT: Ligand PPh2(p-C6H4-C6F5), LHF, is an example of monodentate biphenyl phosphine that allows for cis coor-dination of two phosphines to Pd, as in complex cis-[Pd(C6F5)2Pd(LHF)2] (A). At 25 °C complex A undergoes easy reductive elimination to decafluorobiphenyl and, competitively, isomerizes to trans-[Pd(C6F5)2Pd(LHF)2] via a 3-coordinated interme-diate [Pd(C6F5)2Pd(LHF)]. Unexpectedly the direct reductive C6F5–C6F5 elimination is faster from the 4-coordinated complex A than from the 3-coordinated intermediate. The reason of this is that two cis LHF ligands play the role of a chelate with a large bite angle with tetrahedral distortion. As a matter of fact, using LHF in excess gives ΔG‡Pf-Pf = 23.1 kcal.mol-1, which ranks its efficiency for coupling and formation of the corresponding Pd0 catalyst as better than XantPhos or PhPEWO-F, and about the same as tBuBrettPhos. On the other hand, complex (µ-Cl)2[Pd2(C6F5)2(LHF)2] (B), obtained by reaction of (µ-Cl)2[Pd2(C6F5)2(tht)2] with LHF, presents in the 19F NMR COSY spectrum a very intriguing through space coupling pattern of the Fortho atoms of the C6F5 group in LHF and the C6F3Cl2-3,5 group on Pd. The inter-mitent coupling mechanism proposed is based on the switching of π-π stacking of C6F5 with one or another Ph group of LHF, which gives rise to enantiomers at the chiral P atom. Rotation around the P–biphenyl bond under hindrance of rotation around the C–C6F5 bond produces the intriguing selective coupling observed.Departamento de Química Física y Química InorgánicaCTQ2016-80913-PJCyL VA051P17VA062G1

Técnicas no destructivas aplicadas a la conservación de pinturas murales: la colorimetría. Recursos didácticos y patrones de estudio (2018)

Diseño de modelos de aprendizaje en el campo del diagnóstico de obras de arte con métodos no invasivos: aplicación de la colorimetría en el análisis del estado de conservación de pinturas murales y otros paramentos arquitectónicos

Uso de una herramienta de corrección automática en un curso de programación: Una experiencia docente

Ser capaz de programar se ha convertido en una competencia necesaria en un número importante de profesiones. Como consecuencia ha aumentado la demanda de cursos de programación en todos los niveles de enseñanza. Estos cursos suponen un desafío para los profesores involucrados ya que muchos estudiantes encuentran bastantes dificultades cuando empiezan a programar. Esto provoca un alto nivel de abandono en estas asignaturas. Para los profesores encargados de estas asignaturas suponen una alta carga de trabajo ya que deben corregir un gran número de ejercicios de programación. Las herramientas de corrección automática son una solución para estos problemas. Por un lado, los estudiantes disponen de una retroalimentación inmediata de su trabajo. Esto facilita el aprendizaje y aumenta su motivación. Por otro lado, la carga docente del profesor disminuye en gran medida. En este estudio describimos el proceso de implantación de una herramienta de corrección automática - CodeRunner - en un curso de programación. Los resultados han sido bastante buenos: ha aumentado la participación y ha bajado significativamente la tasa de abandono de la asignatura. Además, los estudiantes expresan una alta satisfacción con el uso de esta herramienta.A growing number of scientific and technological professions require the use of basic programming skills. In response to this need, educational institutions have begun to offer programming courses at all education levels. These courses pose a challenge for the teachers involved. Many students find learning to program difficult and the failure rates tend to be high. Additionally, these courses place significant demands on the instructors’ time as they must assess many programming exercises. Automatic assessment tools offer a solution to these problems. On one hand, students using these tools have immediate feedback on their work. This facilitates learning and increases their motivation. On the other hand, teachers devote less time to assess programming exercises, time that can be used in other teaching tasks. In this study we describe the use of an automatic assessment tool -CodeRunner- in an introductory programming course. The results have been quite good: students’ participation in lab sessions increased, and the drop-out rate decreased significantly. Additionally, students express a high degree of satisfaction when using this tool.Este trabajo ha sido financiado por el proyecto DPI2015-69585-R a través del Ministerio de Economía y Competitividad (MINECO)