Comparison between phosphine and NHC-modified Pd catalysts in the telomerization of butadiene with methanol – a kinetic study combined with model-based experimental analysis

The authors thank the European Community within its project SYNFLOW (FP7; grant agreement n8 NMP2-LA-2010-246461) for financial support.The telomerization of butadiene with methanol was investigated in the presence of different palladium catalysts modified either with triphenylphosphine (TPP) or 1,3-dimesityl-imidazol-2-ylidene (IMes) ligand. When pure butadiene was used as substrate, a moderate selectivity for the Pd-TPP catalyst toward the desired product 1-methoxy-2,7-octadiene (1-Mode) of around 87 % was obtained, while the IMes carbene ligand almost exclusively formed 1-Mode with 97.5 % selectivity. The selectivity remained unchanged when the pure butadiene feed was replaced by synthetic crack-C4 (sCC4), a technical feed of 45 mol% butadiene and 55 mol% inerts (butenes and butanes). The TPP-modified catalyst showed a lower reaction rate, which was attributed to the expected dilution effect caused by the inerts. Surprisingly, the IMes-modified catalyst showed a higher rate with sCC4 compared to the pure feed. By means of a model-based experimental analysis, kinetic rate equations could be derived. The kinetic modeling supports the assumption that the two catalyst systems follow different kinetic rate equations. For the Pd-TPP catalyst, the reaction kinetics were related to the Jolly mechanism. In contrast, the Jolly mechanism had to be adapted for the Pd-IMes catalyst as the impact of the base seems to differ strongly from that for the Pd-TPP catalyst. The Pd-IMes system was found to be zero order in butadiene at moderate to high butadiene concentrations and first order in base while the nucleophilicity of the base is influenced by the methanol amount resulting in a negative reaction order for methanol.PostprintPeer reviewe

Mechanism of the Water-Gas Shift Reaction Catalyzed by Efficient Ruthenium-Based Catalysts: A Computational and Experimental Study

Supported ionic liquid phase (SILP) catalysis enables a highly efficient, Ru‐based, homogeneously catalyzed water‐gas shift reaction (WGSR) between 100 °C and 150 °C. The active Ru‐complexes have been found to exist in imidazolium chloride melts under operating conditions in a dynamic equilibrium, which is dominated by the [Ru(CO)3Cl3]− complex. Herein we present state‐of‐the‐art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride, which effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate‐limiting step involves water is supported by using D2O in continuous catalytic WGSR experiments. The resulting mechanism constitutes a highly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution

The Emergence of the Pro-Nicene Alliance

This chapter narrates the emergence of the pro-Nicene alliance by arguing that it was a consensus-building movement. It begins by tracing the history of other consensus-building movements in the fractured theological landscape of the years 325-61 in order to demonstrate their development of various consensus-building tactics, which were ultimately used unsuccessfully. The impetus for the pro-Nicene alliance itself was dissatisfaction with, or the failure of, these previous efforts. Pro-Nicenes adopted four tactics of previous consensus-building efforts and deployed them successfully: (1) defining itself as the center between extreme positions, (2) promoting a minimalist creed that nonetheless ruled out extremes to be avoided, (3) acknowledging that the meaning of a creed was not self-evident and producing supplementary material to insure its correct interpretation, and (4) securing imperial patronage. The chapter then turns to shifts in thinking which occurred in the early 360s and made consensus between former opponents possible, taking Athanasius of Alexandria and Basil of Caesarea as paradigmatic examples of these shifts. The chapter concludes by narrating the consolidation and ascendency of the pro-Nicene alliance in the late 370s and early 380s

Hosting the Council in Nicaea: Material needs and Solutions

This chapter examines the physical surroundings and circumstances of the first ecumenical council at Nicaea. The first part summarizes what we know of the city of Nicaea, what it looked like in the early fourth century, and if it had the necessary infrastructure to host a large gathering. The chapter also considers why the council was moved to Nicaea from Ancyra as well as why Nicaea was favored over the nearby imperial capital of Nicomedia. The next part focusses on the location, character, and size of the venue of the council, the palace of Nicaea. After a more general discussion of the complex, the author attempts to shed light on the physical form of the hall in which the bishops gathered by reviewing the evidence for audience halls known from other imperial and private palaces. Both the possibility of the council taking place in a large basilica-like setting and an alternative of the bishops convening inside a rotunda are considered. Finally, there is a brief comparison of the setting of the Nicaean council and contemporary Christian meeting places

The Twenty Canons of the Council of Nicaea

Apart from the very important profession of faith, the Council of Nicaea also promulgated twenty canons, most of which do not receive the same attention in research as the Nicene Creed, although these were already highly esteemed in ancient times. First of all, this chapter provides a brief review of their textual transmission. Besides the original Greek text, which has been handed down in canonical collections and writings of ecclesiastical writers, there are some translations into other ancient languages (Latin, Syriac, Coptic). Then after dividing the twenty canons into various thematic groups (for example, laws pertaining to the clergy, sacraments, ecclesiastical jurisdiction), the second part explains each canon with the aid of previous research literature and interpretations in order to provide a short overview of their purpose and content. The third part deals with the reception of the canons in the early Church by councils, bishops, and ecclesiastical writers, and asks what importance was attributed to the Nicene canons in various canonical sources. Finally, some desiderata for future research are discussed