1,720,966 research outputs found
Nickel upgrades nitrogen waste
No full textConversion of greenhouse gases and other pollutants to fine chemicals is a global challenge. First-row-transition-metal catalysts show promise as cost-effective tools to combat environmental impacts by managing the carbon and nitrogen cycle. Nitrogen oxyanions are experiencing renewed interest for their use as N1 feedstocks
Cooperative nitrile coordination using nickel and a boron‐containing secondary coordination sphere**
No full textMetal-ligand cooperation has emerged as a versatile tool for substrate activation in chemical reactivity. Herein, we provide the synthesis and characterization of a monoboranyl-containing analogue of the ubiquitous bulky diphosphine ligand, 1,2-bis(di-tert-butylphosphino)ethane, whose reactivity has been examined using nickel. Together, the pairing of nickel and boron provides a platform that allows for the cooperative coordination of organonitriles, giving unusual examples of intermolecularly bound dinickelacycles
Base metal chemistry and catalysis
No full textThis perspective provides an entry-level conversation concerning base metal catalysis as a green and sustainable solution in industrial and academic contexts. We establish a definition of “base metal,” challenging readers to consider the ethical implications of metal sourcing. We explore what it means to be “sustainable” and provide information on current efforts in synthetic chemistry. We provide examples of current catalytic trends and transformations in popular fields such as cross-coupling and small-molecule conversion, highlighting relevant base metal systems. Finally, we consider social context—for example, decisions related to catalyst development are often driven by factors including costliness, safety, social adoptability (whether society will accept its usage), and performance. How do we move base metal catalysis to the forefront? Is society concerned if materials are fabricated from cheaper and more abundant sources? How does the synthetic chemistry community guide this knowledge translation
Reactions of nickel boranyl compounds with pnictogen–carbon triple bonds
No full textThe catalytic conversion of unsaturated small molecules such as nitriles into reduced products is of interest for the production of fine chemicals. In this vein, metal–ligand cooperativity has been leveraged to promote such reactivity, often conferring stability to bound substrate – a balancing act that may offer activation at the cost of turnover efficiency. This report describes the reactivity of a [(diphosphine)Ni] compound with pnictogen carbon triple bonds (R–C[triple bond, length as m-dash]E; E = N, P), where the diphosphine contains two pendant borane groups. For E = N, cooperative nitrile coordination is observed to afford {Ni}2 complexes displaying B–N interactions, whereas for E = P, B–P interactions are absent. This work additionally outlines a structure–activity relationship that uses nitrile dihydroboration as a model reaction to unveil the effect of SCS stabilization, employing [(diphosphine)Ni] where the diphosphine contains 0, 1, or 2 pendant Lewis acid groups
Nickel complexes of allyl and vinyldiphenylphosphine
No full textMonodentate phosphine-ligated nickel compounds, e.g., [Ni(PPh3)4] are relevant as active catalysts across a broad range of reactions. This report expands upon the coordination chemistry of this family, offering the reactivity of allyl- and vinyl-substituted diphenylphosphine (PPh2R) with [Ni(COD)2] (COD = 1,5-cyclooctadiene). These reactions provide three-coordinate dinickelacycles that are intermolecularly tethered through adjacent {Ni}-olefin interactions. The ring conformation of such cycles has been studied in the solid-state and using theoretical calculations. Here, a difference in reaction outcome is linked to the presence of an allyl vs vinyl group, where the former is observed to undergo rearrangement, bringing about challenges in clean product isolation
Anomalous hydroboration at a four-coordinate Ni(II) diphenylvinylphosphine complex: Geometric impacts on solution equilibria
No full textFor coordination compounds, reliable control of metal geometry and spin state is of great interest, permitting control of reactivity and selectivity. As tuneable outputs, these observables are adjusted through thoughtful choice of ligand. This report examines a family of monophosphine-ligated nickel(II) dihalide compounds containing secondary coordination sphere borane groups. Interestingly, anomalous hydroboration of trans-[NiII(X)2(PPh2Vin)2] (Vin = vinyl) was witnessed upon treatment with HBCy2 (Cy = cyclohexyl), resulting in halide-directed Markovnikov hydroboration; these branched products were observed to be diamagnetic in solution. This outcome is in contrast with the linear ligand variants, which were prepared independently and show solution paramagnetism. Together, this report details an unusual hydroboration outcome and how this anomalous reactivity gives way to unique solution behavior of the resulting nickel(II) products simply by virtue of linear or branched secondary coordination sphere incorporation
So you want to develop a virtual lecture series? Lessons learned from the Global Inorganic Discussion Weekday (GIDW) – a Canadian initiative
Full text linkThe Global Inorganic Discussion Weekday (GIDW) is a virtual inorganic chemistry symposium series co-organized and co-hosted by Canadian inorganic chemists, Marcus Drover (University of Windsor) and Saurabh Chitnis (Dalhousie University). This perspective describes the mission of the GIDW event, its purpose, lessons learned, and offers an outline for other scientific disciplines that wish to organize similar virtual events at a time when physical conferencing is not safely possible.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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