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We report the dimerization and oligomerization of ethylene using bis(phosphino)boryl supported Ni(II) complexes as catalyst precursors. By using alkylaluminum(III) compounds or other Lewis acid additives, Ni(II) complexes of the type (RPBP)NiBr (R = tBu or Ph) show activity for the production of butenes and higher olefins. Optimized turnover frequencies of 640 molethylene·molNi-1·s-1 for the formation of butenes with 41(1)% selectivity for 1-butene using (PhPBP)NiBr, and 68 molethylene·molNi-1·s-1 for butenes production with 87.2(3)% selectivity for 1-butene using (tBuPBP)NiBr, have been demonstrated. With methylaluminoxane as a co-catalyst and (tBuPBP)NiBr as the precatalyst, ethylene oligomerization to form C4 through C20 products was achieved, while the use of (PhPBP)NiBr as the pre-catalyst retained selectivity for C4 products. Our studies suggest that the ethylene dimerization is not initiated by Ni hydride or alkyl intermediates. Rather, our studies point to a mechanism that involves a cooperative B/Ni activation of ethylene to form a key 6-membered borametallacycle intermediate. Thus, a cooperative activation of ethylene by the Ni-B unit of the (RPBP)Ni catalysts is proposed as a key element of the Ni catalysis.

We report the dimerization and oligomerization of ethylene using bis(phosphino)boryl supported Ni(II) complexes as catalyst precursors. By using alkylaluminum(III) compounds or other Lewis acid additives, Ni(II) complexes of the type (RPBP)NiBr (R = tBu or Ph) show activity for the production of butenes and higher olefins. Optimized turnover frequencies of 640 molethylene·molNi–1·s–1 for the formation of butenes with 41(1)% selectivity for 1-butene using (PhPBP)NiBr, and 68 molethylene·molNi–1·s–1 for butenes production with 87.2(3)% selectivity for 1-butene using (tBuPBP)NiBr, have been demonstrated. With methylaluminoxane as a co-catalyst and (tBuPBP)NiBr as the precatalyst, ethylene oligomerization to form C4 through C20 products was achieved, while the use of (PhPBP)NiBr as the pre-catalyst retained selectivity for C4 products. Our studies suggest that the ethylene dimerization is not initiated by Ni hydride or alkyl intermediates. Rather, our studies point to a mechanism that involves a cooperative B/Ni activation of ethylene to form a key 6-membered borametallacycle intermediate. Thus, a cooperative activation of ethylene by the Ni–B unit of the (RPBP)Ni catalysts is proposed as a key element of the Ni catalysis.

Internet celebrity has become a phenomenon of great interest for scholars in the last few years. This is partly due to its impact in contemporary media ecosystems, and its influence in political, social, cultural, and commercial behaviors around the world. Meanwhile, some segments of the population continue to be marginalized by sociotechnical configurations that perpetuate structures of dominance in the digital sphere and on social media platforms. This is the case of immigrants, who often face diverse digital, symbolic, and physical borders that neglect their voice and agency. Thus, the present study aims to explore the creative practices of immigrant tiktokers who have achieved a significant following on this platform. Using a case study approach, we explore four immigrant creator profiles with a following of 17,000 to 500,000 through in-depth interviews and a multimodal content analysis of 252 of their videos to delve into their platformed practices on TikTok. The participants are Latin American immigrant creators living in the US and Spain, identified as part of a larger study on the uses of TikTok by Latinx immigrants in these two countries exploring 53 immigrant creator profiles with more than 10,000 followers. Their practices related to algorithmic (in)visibility, and their unfolding identities including their digital, creative, political, activist, cultural, and national personas are noteworthy, and suggest unique pathways to reclaim agency through social media influence and construct multi-dimensional microcelebrity identities beyond migratory status.

Internet celebrity has become a phenomenon of great interest for scholars in the last few years. This is partly due to its impact in contemporary media ecosystems, and its influence in political, social, cultural, and commercial behaviors around the world. Meanwhile, some segments of the population continue to be marginalized by sociotechnical configurations that perpetuate structures of dominance in the digital sphere and on social media platforms. This is the case of immigrants, who often face diverse digital, symbolic, and physical borders that neglect their voice and agency. Thus, the present study aims to explore the creative practices of immigrant tiktokers who have achieved a significant following on this platform. Using a case study approach, we explore four immigrant creator profiles with a following of 17,000 to 500,000 through in-depth interviews and a multimodal content analysis of 252 of their videos to delve into their platformed practices on TikTok. The participants are Latin American immigrant creators living in the US and Spain, identified as part of a larger study on the uses of TikTok by Latinx immigrants in these two countries exploring 53 immigrant creator profiles with more than 10,000 followers. Their practices related to algorithmic (in)visibility, and their unfolding identities including their digital, creative, political, activist, cultural, and national personas are noteworthy, and suggest unique pathways to reclaim agency through social media influence and construct multi-dimensional microcelebrity identities beyond migratory status.

The metaverse is presented as a possible new technological iteration for the Internet. The generation of virtual universes in which the physical and the digital converge raises the question of how education will be addressed in these new systems. We find, however, pioneering exercises such as Minecraft: Education Edition. This platform is a version based on the popular sandbox video game, which was originally created by a community of teachers. The aim of this research is to analyze and describe the idiosyncratic characteristics of Minecraft as an educational platform, framing it as one of the pioneering exercises in the metaverse. To this end, we have employed a methodology that combines Multimodal Discourse Analysis with Grounded Theory and the Constant Comparative Method. As conclusions, we observe how the Minecraft Education platform reinforces from its approach pre-existing aspects from the physical world, resizing them to adapt them to its connected digital environment. These are key elements such as the identity of the participants, their ability to act within the system, creativity through lessons as a guide to the educational objectives and the community as the backbone of the process. At the same time, it presents differential components, such as the use of avatars, the transition from textual literacy to multimodal literacy, game mechanics that boost creativity or transhuman capabilities that defy physical space-time. All in all, the platform is designed for teachers, parents and managers, to whom it offers a series of benefits. Therefore, the pedagogical action will depend on their judgment and execution, especially through the elaboration of lessons and worlds, the management of the sessions and their interaction in community environments. It is their responsibility to ensure that the educational experience is truly empowering or, on the contrary, that it ends up being governed by reproductive criteria linked to symbolic violence., El metaverso se presenta como una posible nueva iteración tecnológica para Internet. La generación de universos virtuales en los que convergen lo físico y lo digital pone sobre la mesa la cuestión de cómo se afrontará la educación en estos nuevos sistemas. Encontramos, no obstante, ejercicios pioneros como Minecraft: Education Edition. Esta plataforma es una versión basada en el popular videojuego sandbox, que fue creada originalmente por una comunidad de profesores. El objetivo de esta investigación es analizar y describir las características idiosincráticas de Minecraft como plataforma educativa, enmarcándola como uno de los ejercicios pioneros en el metaverso. Para ello, se ha empleado una metodología que combina el Análisis del Discurso Multimodal con la Grounded Theory y el Constant Comparative Method. Como conclusiones, se determina que la plataforma Minecraft Education refuerza desde su planteamiento cuestiones pre-existentes en el mundo físico, redimensionándolas para adaptarlas a su entorno digital conectado. Son claves como la identidad de los participantes, la agencia, la creatividad, con las lecciones como guía de los objetivos educativos, y la comunidad como vertebradora del proceso. Al mismo tiempo, presenta componentes diferenciales digitales, como el uso de avatares, la transición de la lectoescritura textual a la alfabetización en entornos multimodales, las mecánicas que impulsan la creatividad o las capacidades transhumanas que desafían el espacio-tiempo físico. Con todo, la plataforma está diseñada para profesores, padres y gestores, a los que ofrece una serie de prebendas. Por tanto, la acción pedagógica dependerá de su criterio y ejecución, especialmente a través de la elaboración de lecciones y mundos, la gestión de las sesiones, y la interacción en los entornos comunitarios. Queda bajo su responsabilidad que la experiencia educativa sea verdaderamente empoderadora o, por el contrario, esta se acabe rigiendo por criterios reproductivos y vincul

Today's digital ecosystems, in which social networking sites play a leading role, foster communicative phenomena of great interest, where diverse content creators make individual and collective experiences visible. In some cases, these communities give rise to cyberactivist movements, or become a trend, generating dialogue and debate on issues of interest to society. In other cases, they are presented as challenges promoted by brands and influencers, constituting true digital cultures of great impact on networks such as Twitter, Instagram, YouTube, TikTok or Snapchat. This topic has become an object of interest in the academic sphere due to its implications for understanding the interactions that characterize citizen participation and (self)representation. The purpose of this special issue is to explore the strategies, languages, codes and skills that make it possible to connect and make content visible so that it becomes a trend, exploring the new modes of expression and communication of various groups of creators and their communicative and multimodal skills within digital social media.

[EN] Book review:LÓPEZ VALERO, A., ENCABO FERNÁNDEZ, E., JEREZ MARTÍNEZ, I. y HERNÁNDEZ DELGADO, L. (COORDS.). Literatura infantil y lectura dialógica. La formación de educadores desde la investigación Barcelona: Octaedro, 2021., [ES] Reseña del libro:LÓPEZ VALERO, A., ENCABO FERNÁNDEZ, E., JEREZ MARTÍNEZ, I. y HERNÁNDEZ DELGADO, L. (COORDS.). Literatura infantil y lectura dialógica. La formación de educadores desde la investigaciónBarcelona: Octaedro, 2021.

The concept of metal–ligand cooperation opens new avenues for the design of catalytic systems that may offer alternative reactivity patterns to the existing ones. Investigations of this concept with ligands bearing a boron center in their skeleton established mechanistic pathways for the activation of small molecules in which the boron atom usually performs as an electrophile. Here, we show how this electrophilic behavior can be modified by the ligand trans to the boron center, evincing its ambiphilic nature. Treatment of diphosphinoboryl (PBP) nickel–methyl complex 1 with bis(catecholato)diboron (B2Cat2) allows for the synthesis of nickel(II) bis-boryl complex 3 that promotes the clean and reversible heterolytic cleavage of dihydrogen leading to the formation of dihydroborate nickel complex 4. Density functional theory analysis of this reaction revealed that the heterolytic activation of H2 is facilitated by the cooperation of both boryl moieties and the metal atom in a concerted mechanism that involves a Ni(II)/Ni(0)/Ni(II) process. Contrary to 1, the boron atom from the PBP ligand in 3 behaves as a nucleophile, accepting a formally protic hydrogen, whereas the catecholboryl moiety acts as an electrophile, receiving the attack from the hydride-like fragment. This manifests the dramatic change in the electronic properties of a ligand by tuning the substituent trans to it and constitutes an unprecedented cooperative mechanism that involves two boryl ligands in the same molecule operating differently, one as a Lewis acid and the other one as a Lewis base, in cooperation with the metal. In addition, reactivity towards different nucleophiles such as amines or ammonia confirmed the electrophilic nature of the Bcat moiety, allowing the formation of aminoboranes.

The efficient catalytic hydrosilylation of ketones and aldehydes has been investigated using a nickel pincer hydride complex supported by a diphosphino-boryl ligand (PBP). It was found that the presence of the boryl group within the skeleton of the ligand has a beneficial effect on the catalytic activities observed for ketones compared to related pincer systems. The analysis of the reaction mechanism allows for the synthesis and characterization of a nickel alkoxide derivative by insertion of the carbonyl moiety into the Ni−H bond. Combined experimental and theoretical analysis (DFT) support a reaction mechanism that involves the initial formation of an alkoxide complex followed by reaction with the silane to release the corresponding silyl ether and regenerate the catalyst.

The concept of metal–ligand cooperation opens new avenues for the design of catalytic systems that may offer alternative reactivity patterns to the existing ones. Investigations of this concept with ligands bearing a boron center in their skeleton established mechanistic pathways for the activation of small molecules in which the boron atom usually performs as an electrophile. Here, we show how this electrophilic behavior can be modified by the ligand trans to the boron center, evincing its ambiphilic nature. Treatment of diphosphinoboryl (PBP) nickel–methyl complex 1 with bis(catecholato)diboron (B2Cat2) allows for the synthesis of nickel(II) bis-boryl complex 3 that promotes the clean and reversible heterolytic cleavage of dihydrogen leading to the formation of dihydroborate nickel complex 4. Density functional theory analysis of this reaction revealed that the heterolytic activation of H2 is facilitated by the cooperation of both boryl moieties and the metal atom in a concerted mechanism that involves a Ni(II)/Ni(0)/Ni(II) process. Contrary to 1, the boron atom from the PBP ligand in 3 behaves as a nucleophile, accepting a formally protic hydrogen, whereas the catecholboryl moiety acts as an electrophile, receiving the attack from the hydride-like fragment. This manifests the dramatic change in the electronic properties of a ligand by tuning the substituent trans to it and constitutes an unprecedented cooperative mechanism that involves two boryl ligands in the same molecule operating differently, one as a Lewis acid and the other one as a Lewis base, in cooperation with the metal. In addition, reactivity towards different nucleophiles such as amines or ammonia confirmed the electrophilic nature of the Bcat moiety, allowing the formation of aminoboranes

The efficient catalytic hydrosilylation of ketones and aldehydes has been investigated using a nickel pincer hydride complex supported by a diphosphino-boryl ligand (PBP). It was found that the presence of the boryl group within the skeleton of the ligand has a beneficial effect on the catalytic activities observed for ketones compared to related pincer systems. The analysis of the reaction mechanism allows for the synthesis and characterization of a nickel alkoxide derivative by insertion of the carbonyl moiety into the Ni−H bond. Combined experimental and theoretical analysis (DFT) support a reaction mechanism that involves the initial formation of an alkoxide complex followed by reaction with the silane to release the corresponding silyl ether and regenerate the catalyst.

Platinum complexes have been often considered as the least reactive of the group 10 triad metals. Slow kinetics are behind this lack of reactivity but, still, some industrially relevant catalytic process are dominated by platinum compounds and sometimes different selectivities can be found in comparison to Ni or Pd. Nevertheless, during the last years, it has been reported that the catalytic behaviour of well-defined platinum derivatives can be improved through a judicious choice of their electronic and steric properties, leading to highly electrophilic or low-electron count platinum systems. In this feature article, we highlight some catalytic processes in which well-defined electrophilic platinum complexes or coordinatively unsaturated systems play an important role in their catalytic activity.

Platinum complexes have been often considered as the least reactive of the group 10 triad metals. Slow kinetics are behind this lack of reactivity but, still, some industrially relevant catalytic process are dominated by platinum compounds and sometimes different selectivities can be found in comparison to Ni or Pd. Nevertheless, during the last years, it has been reported that the catalytic behaviour of well-defined platinum derivatives can be improved through a judicious choice of their electronic and steric properties, leading to highly electrophilic or low-electron count platinum systems. In this feature article, we highlight some catalytic processes in which well-defined electrophilic platinum complexes or coordinatively unsaturated systems play an important role in their catalytic activity.

Microbial cooperation pervades ecological scales, from single-species populations to host-associated microbiomes. Understanding the mechanisms promoting the stability of cooperation against potential threats by cheaters is a major question that only recently has been approached experimentally. Synthetic biology has helped to uncover some of these basic mechanisms, which were to some extent anticipated by theoretical predictions. Moreover, synthetic cooperation is a promising lead towards the engineering of novel functions and enhanced productivity of microbial communities. Here, we review recent progress on engineered cooperation in microbial ecosystems. We focus on bottom-up approaches that help to better understand cooperation at the population level, progressively addressing the challenges of tackling higher degrees of complexity: spatial structure, multispecies communities, and host-associated microbiomes. We envisage cooperation as a key ingredient in engineering complex microbial ecosystems. Keywords: synthetic microbial communities; mutualism; cheaters; host-microbiome interactions; synthetic ecology