Faraday Discussions最新文献

{"title":"Mechanistic understanding of N2 activation: a comparison of unsupported and supported Ru catalysts†","authors":"Yves Ira A. Reyes, Kai-Shiang Yang, Ho Viet Thang, Carmine Coluccini, Shih-Yuan Chen and Hsin-Yi Tiffany Chen","doi":"10.1039/D2FD00172A","DOIUrl":"https://doi.org/10.1039/D2FD00172A","url":null,"abstract":"<p >N<small>₂</small> dissociative adsorption is commonly the rate-determining step in thermal ammonia synthesis. Herein, we performed density functional theory (DFT) calculations to understand the N<small>₂</small> dissociation mechanism on models of unsupported Ru(0001) terraces, Ru B5 sites, and polar MgO(111)-supported Ru<small>₈</small> cluster mimicking a B5 site geometry, denoted (Ru<small>₈</small>(B5-like)/MgO(111)). The activation energy of N<small>₂</small> dissociative adsorption on the Ru<small>₈</small>(B5-like)/MgO(111) model (<em>E</em><small>_a</small> = 0.33 eV) is much lower than that on the unsupported Ru(0001) terrace (<em>E</em><small>_a</small> = 1.74 eV) and Ru B5 (<em>E</em><small>_a</small> = 0.62 eV) models. The lower N<small>₂</small> dissociation barrier on Ru B5 sites is facilitated by the enhanced σ donation and π* back-donation between N<small>₂</small>(σ, π*) and Ru(d) orbitals resulting in the stronger activation of the molecular side-on N<small>₂</small>* dissociation precursor. The Ru<small>₈</small>(B5-like)/MgO(111) also exhibits enhanced σ donation because of the B5-like cluster geometry. Furthermore, the Ru cluster of the bare Ru<small>₈</small>(B5-like)/MgO(111) model is positively charged. This induced an unusual π donation from N<small>₂</small>(π) to Ru(d) orbitals as revealed by analyses of the density of states and partial charge densities. The combined σ and π donation resulted in an increased synergistic π* back-donation. The total interactions between N<small>₂</small>(σ, π, π*) and Ru(d) resulted in an overall electron transfer to the adsorbed N<small>₂</small> from the Ru atoms in the B5-like site with no direct involvement of the MgO(111) substrate. Analyses of bond stretching vibrations and bond lengths show that the N<small>₂</small>(σ, π, π*) and Ru(d) interactions lead to a weaker N–N bond and stronger Ru–N bonds. These correspond to a lower barrier of N<small>₂</small> dissociation on the Ru<small>₈</small>(B5-like)/MgO(111) model, where the highest red-shift of N–N vibration and the longest N–N bond length were observed after side-on N<small>₂</small>* adsorption. These results demonstrate that an electron-deficient Ru catalyst are not always inhibited from donating electrons to adsorbed N<small>₂</small>. Rather, this study shows that the electron deficiency of Ru can promote π* back-donation and N<small>₂</small> activation. These new insights may therefore open new avenues to design supported Ru catalysts for nitrogen activation.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"243 ","pages":" 148-163"},"PeriodicalIF":3.4,"publicationDate":"2023-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3994212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"H-Bonding leading to latent initiators for olefin metathesis polymerization†‡","authors":"Artur Brotons-Rufes, Naeimeh Bahri-Laleh and Albert Poater","doi":"10.1039/D2FD00163B","DOIUrl":"https://doi.org/10.1039/D2FD00163B","url":null,"abstract":"<p >Ruthenium–NHC based catalysts, with a chelated iminium ligand <em>trans</em> to the N-heterocyclic carbene (NHC) ligand, that polymerize dicyclopentadiene (DCPD) at different temperatures are monitored using Density Functional Theory calculations to unveil the reaction mechanism, and subsequently how important are the geometrical and electronic features <em>vs.</em> the non-covalent interactions in between. The balance is very fragile and H-bonds are fundamental to explain the different behaviour of latent catalysts. This computational study aims to facilitate future studies of new generations of latent initiators for olefin metathesis polymerization, with the 3D and mainly the 2D Non-Covalent Interaction plots the characterization tool for H-bonds.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"244 ","pages":" 252-268"},"PeriodicalIF":3.4,"publicationDate":"2023-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2023/fd/d2fd00163b?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3694280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Switching on/off molybdenum nitride catalytic activity in ammonia synthesis through modulating metal–support interaction†","authors":"Amanda Sfeir, Camila A. Teles, Maya Marinova, Hérve Vezin, Jean-Philippe Dacquin, Axel Löfberg, Said Laassiri and Sébastien Royer","doi":"10.1039/D2FD00154C","DOIUrl":"https://doi.org/10.1039/D2FD00154C","url":null,"abstract":"<p >Modulating the interaction between Mo nanoparticles and their support is an elegant approach to finely tune the structural, physico-chemical, redox and electronic properties of the active site. In this work, a series of molybdenum nitride catalysts supported on TiO<small>₂</small>, and SBA-15 has been prepared and fully characterized. The results of characterization confirmed the high dispersion of Mo and the formation of small molybdenum nanoparticles in both the 10-Mo-N/SBA-15 and 10-Mo-N/TiO<small>₂</small> catalysts. In this context, we have shown that the catalytic activity of Mo species was strongly impacted by the nature of the catalytic support. Amongst the studied supports, SBA-15 was found to be the most appropriate for Mo dispersion. In comparison, when supported on a reducible oxide (TiO<small>₂</small>), Mo species showed poor catalytic activity in both ammonia synthesis and decomposition and were prone to quick deactivation in the ammonia synthesis reaction. Evidence of charge transfer from the reducible support to the active phase, indicative of possible SMSI behaviour, has been observed by XPS and EPR. Differences in the oxidation states, redox behaviours, and electronic properties have been further studied by means of EPR, H<small>₂</small>-TPR and H<small>₂</small>-TPD.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"243 ","pages":" 126-147"},"PeriodicalIF":3.4,"publicationDate":"2023-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2023/fd/d2fd00154c?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3994210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A conformational equilibrium in the nitrogenase MoFe protein with an α-V70I amino acid substitution illuminates the mechanism of H2 formation†","authors":"Dmitriy A. Lukoyanov, Zhi-Yong Yang, Krista Shisler, John W. Peters, Simone Raugei, Dennis R. Dean, Lance C. Seefeldt and Brian M. Hoffman","doi":"10.1039/D2FD00153E","DOIUrl":"https://doi.org/10.1039/D2FD00153E","url":null,"abstract":"<p >Study of α-V70I-substituted nitrogenase MoFe protein identified Fe6 of FeMo-cofactor (Fe<small>₇</small>S<small>₉</small>MoC-homocitrate) as a critical N<small>₂</small> binding/reduction site. Freeze-trapping this enzyme during Ar turnover captured the key catalytic intermediate in high occupancy, denoted E<small>₄</small>(4H), which has accumulated 4[e<small>^?</small>/H<small>⁺</small>] as two bridging hydrides, Fe2–H–Fe6 and Fe3–H–Fe7, and protons bound to two sulfurs. E<small>₄</small>(4H) is poised to bind/reduce N<small>₂</small> as driven by mechanistically-coupled H<small>₂</small> reductive-elimination of the hydrides. This process must compete with ongoing hydride protonation (HP), which releases H<small>₂</small> as the enzyme relaxes to state E<small>₂</small>(2H), containing 2[e<small>^?</small>/H<small>⁺</small>] as a hydride and sulfur-bound proton; accumulation of E<small>₄</small>(4H) in α-V70I is enhanced by HP suppression. EPR and <small>⁹⁵</small>Mo ENDOR spectroscopies now show that resting-state α-V70I enzyme exists in two conformational states, both in solution and as crystallized, one with wild type (WT)-like FeMo-co and one with perturbed FeMo-co. These reflect two conformations of the Ile residue, as visualized in a reanalysis of the X-ray diffraction data of α-V70I and confirmed by computations. EPR measurements show delivery of 2[e<small>^?</small>/H<small>⁺</small>] to the E<small>₀</small> state of the WT MoFe protein and to both α-V70I conformations generating E<small>₂</small>(2H) that contains the Fe3–H–Fe7 bridging hydride; accumulation of another 2[e<small>^?</small>/H<small>⁺</small>] generates E<small>₄</small>(4H) with Fe2–H–Fe6 as the second hydride. E<small>₄</small>(4H) in WT enzyme and a minority α-V70I E<small>₄</small>(4H) conformation as visualized by QM/MM computations relax to resting-state through two HP steps that reverse the formation process: HP of Fe2–H–Fe6 followed by slower HP of Fe3–H–Fe7, which leads to transient accumulation of E<small>₂</small>(2H) containing Fe3–H–Fe7. In the dominant α-V70I E<small>₄</small>(4H) conformation, HP of Fe2–H–Fe6 is passively suppressed by the positioning of the Ile sidechain; slow HP of Fe3–H–Fe7 occurs first and the resulting E<small>₂</small>(2H) contains Fe2–H–Fe6. It is this HP suppression in E<small>₄</small>(4H) that enables α-V70I MoFe to accumulate E<small>₄</small>(4H) in high occupancy. In addition, HP suppression in α-V70I E<small>₄</small>(4H) kinetically unmasks hydride reductive-elimination without N<small>₂</small>-binding, a process that is precluded in WT enzyme.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"243 ","pages":" 231-252"},"PeriodicalIF":3.4,"publicationDate":"2023-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3936035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Poster list","authors":"","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"241 ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3879604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Boosting the activity of Mizoroki–Heck cross-coupling reactions with a supramolecular palladium catalyst favouring remote Zn⋯pyridine interactions†","authors":"Naba Abuhafez and Rafael Gramage-Doria","doi":"10.1039/D2FD00165A","DOIUrl":"https://doi.org/10.1039/D2FD00165A","url":null,"abstract":"<p >Transition metal catalysis benefitting from supramolecular interactions in the secondary coordination sphere in order to pre-organize substrates around the active site and reach a specific selectivity typically occurs under long reaction times and mild reaction temperatures with the aim to maximize such subtle effects. Herein, we demonstrate that the kinetically labile Zn⋯N interaction between a pyridine substrate and a zinc–porphyrin site serving for substrate binding is a unique type of weak interaction that enables identification of supramolecular effects in transition metal catalysis after one hour at a high reaction temperature of 130 °C. Under carefully selected reaction conditions, supramolecularly-regulated palladium-catalyzed Mizoroki–Heck reactions between 3-bromopyridine and terminal olefins (acrylates or styrenes) proceeded in a more efficient manner compared to the non-supramolecular version. The supramolecular catalysis developed here also displayed interesting substrate-selectivity patterns.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"244 ","pages":" 186-198"},"PeriodicalIF":3.4,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2023/fd/d2fd00165a?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3693584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"List of participants","authors":"","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"241 ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3879608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Site-selective methylene C–H oxidation of an alkyl diamine enabled by supramolecular recognition using a bioinspired manganese catalyst†","authors":"Arnau Vicens, Laia Vicens, Giorgio Olivo, Osvaldo Lanzalunga, Stefano Di Stefano and Miquel Costas","doi":"10.1039/D2FD00177B","DOIUrl":"https://doi.org/10.1039/D2FD00177B","url":null,"abstract":"<p >Site-selective oxidation of aliphatic C–H bonds is a powerful synthetic tool because it enables rapid build-up of product complexity and diversity from simple precursors. Besides the poor reactivity of alkyl C–H bonds, the main challenge in this reaction consists in differentiating between the multiple similar sites present in most organic molecules. Herein, a manganese oxidation catalyst equipped with two 18-benzo-6-crown ether receptors has been employed in the oxidation of the long chain tetradecane-1,14-diamine. <small>¹</small>H-NMR studies evidence simultaneous binding of the two protonated amine moieties to the crown ether receptors. This recognition has been used to pursue site-selective oxidation of a methylenic site, using hydrogen peroxide as oxidant in the presence of carboxylic acids as co-ligands. Excellent site-selectivity towards the central methylenic sites (C6 and C7) is observed, overcoming selectivity parameters derived from polar deactivation by simple amine protonation and selectivity observed in the oxidation of related monoprotonated amines.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"244 ","pages":" 51-61"},"PeriodicalIF":3.4,"publicationDate":"2023-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2023/fd/d2fd00177b?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3936058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Poster list","authors":"","doi":"10.1039/d3fd90046k","DOIUrl":"https://doi.org/10.1039/d3fd90046k","url":null,"abstract":"","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136259102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Poster list","authors":"","doi":"10.1039/d3fd90054a","DOIUrl":"https://doi.org/10.1039/d3fd90054a","url":null,"abstract":"","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135263171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}