Article
Chemistry, Physical
Massimo Melchiorre, Angela Amoresano, Peter H. M. Budzelaar, Maria E. Cucciolito, Fabio Mocerino, Gabriella Pinto, Francesco Ruffo, Angela Tuzi, Roberto Esposito
Summary: This work demonstrates the efficient conversion of neutral soybean oil and acidic waste cooking oil to biodiesel using a library of iron(III)-salen catalysts. The catalysts with acetate as a fifth ligand perform the best in the conversion process. The obtained biodiesel has a comparable iron content to biodiesels derived from other sources.
Article
Chemistry, Multidisciplinary
Raphael Robidas, Claude Y. Legault
Summary: A mechanism is proposed to explain the formation of benzobicyclo[3.2.0]heptane derivatives from 1,7-enyne derivatives bearing a terminal cyclopropane, which has been previously reported.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Callum R. Woof, Derek J. Durand, Natalie Fey, Emma Richards, Ruth L. Webster
Summary: The catalytic mechanism of iron-catalyzed alkene isomerization reaction was studied through a combination of experimental and theoretical approaches. The results suggest that the isomerization of alkenes can be achieved through the combination of a hydride source and an iron(II) beta-diketiminate pre-catalyst.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Review
Chemistry, Multidisciplinary
Justus Diekamp, Thomas Seidensticker
Summary: The recycling of homogeneous catalysts in a homogeneous matrix is a challenging task for many reactions aiming for industrial applications. Although various synthetic approaches for recyclable homogeneous catalysts exist, a concise overview of catalyst modifications is lacking in the literature. This review aims to fill this gap by summarizing the existing synthesis pathways for polar, non-polar, fluorous, and molecular-weight-enlarged catalysts and examining their modular and late-stage approaches. Additionally, the potential for a generally applicable tag library to facilitate catalyst modifications for specific recycling strategies is explored.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Review
Chemistry, Multidisciplinary
Tasneem Elkoush, Natasha D. Reich, Michael G. Campbell
Summary: In the past two decades, there has been a significant increase in the number of synthetically useful transformations catalyzed by silver, with dinuclear silver species commonly emerging as a key feature in these reactions. Understanding the role of dinuclear silver complexes in homogeneous catalysis can aid in the development of improved design principles for silver catalysts.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Multidisciplinary
C. -C. George Yeh, Christos Pierides, Guy N. L. Jameson, Sam P. de Visser
Summary: Thiol dioxygenases are important enzymes for human health, involved in detoxification and catabolism of toxic thiol-containing natural products. Recent studies show that differences in activity between CDO and MDO are due to variations in ligand coordination, with changes in substrate positioning and enzyme turnover caused by a positively charged Arg residue. The substrate scope of MDO with cysteinate and 2-mercaptosuccinic acid is explored and their reactivity is predicted.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Article
Chemistry, Multidisciplinary
Niklas F. Both, Anke Spannenberg, Haijun Jiao, Kathrin Junge, Matthias Beller
Summary: The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. Various aromatic and aliphatic esters were successfully hydrogenated at mild temperatures and low catalyst loadings using complexes 3 with KHBEt3 as additive, highlighting the efficiency of the novel catalytic system. Additionally, the versatility of the developed catalytic system was demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N-heteroarenes, and alkenes.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Bing Jiang, Marcos Gil-Sepulcre, Pablo Garrido-Barros, Carolina Gimbert-Surinach, Jia-Wei Wang, Jordi Garcia-Anton, Pau Nolis, Jordi Benet-Buchholz, Nuria Romero, Xavier Sala, Antoni Llobet
Summary: A cobalt complex with a kappa-N3P2 ligand is stable in air and exhibits good electrochemical behavior. It can catalyze the hydrogen evolution reaction and be regenerated with the addition of CoCp*(2).
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Francis Bru, Mathieu Lesieur, Albert Poater, Alexandra M. Z. Slawin, Luigi Cavallo, Catherine S. J. Cazin
Summary: The synthesis and isolation of [Pd(NHC)(PhC equivalent to CPh)] complexes were reported, which are new 14-electron Pd(0)-complexes that serve as key synthons for known palladium(0) and palladium(II) species and allow access to unprecedented mixed NHC-phosphite palladium(0) complexes. These complexes are also capable of catalyzing the facile hydrosilylation of allenes. DFT calculations provided insights into the relatively weak interaction between the metal and the diphenylacetylene ligand, comparing it with other ligands with varying coordinating power, structure, and electronic properties.
CHEMISTRY-A EUROPEAN JOURNAL
(2022)
Review
Chemistry, Inorganic & Nuclear
Miguel A. Chacon-Teran, Michael Findlater
Summary: alpha-Diimine and bis(arylimino)acenaphthene (BIAN) ligands and their iron complexes have been widely studied for their versatile applications in catalytic transformations, especially in reductive reactions. Spectroscopic and computational studies have revealed the importance of redox non-innocence and spin-state-crossing in the catalytic mechanisms.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2022)
Article
Chemistry, Physical
Froze Jameel, Matthias Stein
Summary: In the global effort to combat climate change, the design and development of new procedures for complex chemical multi-step reactions play a crucial role in the transformation of the chemical industry. Solvent effects on thermodynamics and kinetics are important considerations, with various roles including promoting intermediate formation but also compromising overall pathways. Solvent coordination is critical for the activity of reducing catalysts, impacting regioselectivity and reaction rates in complex multi-step reactions.
JOURNAL OF CATALYSIS
(2022)
Article
Chemistry, Multidisciplinary
Alexandra M. Zima, Oleg Y. Lyakin, Anna A. Bryliakova, Dmitrii E. Babushkin, Konstantin P. Bryliakov, Evgenii P. Talsi
Summary: Catalytic approaches to late-stage creation of new C-O bonds, especially via oxygenation of particular C-H groups in complex organic molecules, provide challenging tools for the synthesis of biologically active compounds and candidate drugs. The key role of the oxygen-transferring high-valent iron-oxygen species in selective oxygenation is now well established. In this Personal Account, recent data on the reactivity of bioinspired formally oxoiron(V) catalytically active sites toward organic substrates having C=C and C(sp(3))-H groups are analyzed, with a focus on the factors governing the oxidation chemo- and stereoselectivity.
Article
Chemistry, Physical
Lena Staiger, Tim Kratky, Sebastian Guenther, Ondrej Tomanek, Radek Zboril, Richard W. Fischer, Roland A. Fischer, Mirza Cokoja
Summary: Phosphanes have been found to increase both the reaction rate and selectivity towards olefins, with the ligand's steric and electronic effects playing a crucial role in catalyst performance.
Article
Chemistry, Multidisciplinary
George Dhimba, Alfred Muller, Koop Lammertsma
Summary: This study investigates the mechanisms of ligand rearrangement in octahedral chiral-at-metal complexes. The lowest energy cis isomer and its interconversion with other isomers are calculated. The connectivity of all enantiomeric minima and transition structures is summarized, and the influence of N-substitution on the favored pathway is evaluated.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Review
Chemistry, Organic
Pascal Matton, Steve Huvelle, Mansour Haddad, Phannarath Phansavath, Virginie Ratovelomanana-Vidal
Summary: Metal-catalyzed [2+2+2] cycloaddition is a powerful method for the rapid construction of functionalized 6-membered carbo- and heterocycles with high functional group tolerance. The reaction is usually regio- and chemoselective, but challenges remain for intermolecular reactions involving multiple alkynes.
SYNTHESIS-STUTTGART
(2021)
Article
Chemistry, Inorganic & Nuclear
William J. M. Blackaby, Katie L. M. Harriman, Samuel M. Greer, Andrea Folli, Stephen Hill, Vera Krewald, Mary F. Mahon, Damien M. Murphy, Muralee Murugesu, Emma Richards, Elizaveta Suturina, Michael K. Whittlesey
Summary: A new series of homoleptic Ni(I) bis-N-heterocyclic carbene complexes with different torsion angles between the ligands have been reported. The complexes exhibit a strongly anisotropic g-tensor and the first excited state energy ranges from 270 to 650 cm(-1). The magnetic relaxation is dominated by Raman and direct processes, and the temperature dependence of the relaxation does not correlate with the torsion angle.
INORGANIC CHEMISTRY
(2022)
Article
Chemistry, Physical
Thomas G. Linford-Wood, Mary F. Mahon, Matthew N. Grayson, Ruth L. Webster
Summary: This paper presents a synthetic study into the catalytic hydrogen/deuterium exchange of 1 degrees silanes, 2 degrees silanes, and 3 degrees siloxanes facilitated by iron-beta-diketiminato complexes (1a and 1b). Near-complete H/D exchange is observed for various aryl- and alkyl-containing hydro-silanes and hydrosiloxanes. The reaction tolerates alternative hydride source pinacolborane (HBpin) with quantitative H/D exchange. A synthetic and density functional theory (DFT) investigation suggests that a monomeric iron-deuteride is responsible for the H/D exchange.
Article
Chemistry, Multidisciplinary
Maximilian Fritz, Severine Rupp, Ciara I. Kiene, Sesha Kisan, Joshua Telser, Christian Wurtele, Vera Krewald, Sven Schneider
Summary: This study presents a new method for the conversion of dinitrogen to benzonitrile, which involves photoelectrochemical reduction of N-2 followed by N-benzoylation to achieve selective nitrogen transfer and produce nitrogenous organic products in photoelectrosynthesis.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Adam N. Barrett, Martin Diefenbach, Mary F. Mahon, Vera Krewald, Ruth L. Webster
Summary: In this study, gram-scale quantities of 2,4,6-tris(triphenylmethyl)-Dewar-1,3,5-triphosphabenzene were synthesized using an alkyne cyclotrimerization regime. It was found that this compound can undergo rearrangement and phosphorus migration reactions to form ring-contracted species. Additionally, novel crystallographically characterized products of other transformations were reported.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Nils Heppe, Charlotte Gallenkamp, Stephen Paul, Nicole Segura-Salas, Niklas von Rhein, Bernhard Kaiser, Wolfram Jaegermann, Atefeh Jafari, Ilya Sergueev, Vera Krewald, Ulrike I. Kramm
Summary: In order to achieve a future hydrogen economy, there is a need for non-precious metal catalysts for water splitting reactions that can be used globally. Metal-nitrogen-carbon (MNC) catalysts with active sites consisting of a metal center with fourfold coordination of nitrogen (MN4) have shown promising performance, but their optimization has been hindered by their low structural definition. By studying porphyrin model complexes, insights from well-defined molecules are transferred to MNC systems in order to evaluate the effect of porphyrin substituents on the electronic and electrocatalytic properties of MN4 centers for the hydrogen evolution reaction (HER) in aqueous electrolyte. The choice of substituent was found to impact their utilization on the carbon support and their electrocatalytic performance.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Lingmei Ni, Charlotte Gallenkamp, Stephan Wagner, Eckhard Bill, Vera Krewald, Ulrike I. Kramm
Summary: By using Mossbauer spectroscopy and quantum chemistry, researchers have established an active site model for metal-and nitrogen-doped carbon catalysts obtained through pyrolysis. They found that pyrrolic nitrogen coordination is the active site, and identified a previously unknown intermediate.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Review
Chemistry, Multidisciplinary
Thomas M. Hood, Samantha Lau, Ruth L. Webster
Summary: There is an increasing demand for reactions involving PH3, mainly because of the clean and safe generation of PH3 through the digestion of cheap metal phosphides with acids. This perspective highlights the current trends in forming new P-C/P-OC bonds with PH3 and discusses the challenges of selectivity and product separation in these reactions. The reactivity of PH3 with main group reagents is also emphasized, along with the renewed interest in alkali metal sources of H2P-.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Physical
Samantha Lau, Thomas M. Hood, Ruth L. Webster
Summary: In this Perspective, the challenges faced in catalytic hydrophosphination chemistry are discussed. The state of the art in stereoselective hydrophosphination and the scope and limitations of chemoselective hydrophosphination are highlighted. Progress in the chemistry of heavier homologues is also emphasized.
Article
Chemistry, Inorganic & Nuclear
Michael Papadakis, Alexandre Barrozo, Lea Delmotte, Tatiana Straistari, Sergiu Shova, Marius Reglier, Vera Krewald, Sylvain Bertaina, Renaud Hardre, Maylis Orio
Summary: Thiocarbohydrazone-based catalysts with potentially electrochemically active ligands can be easily tailored for optimization. In this study, a trinuclear nickel-thiocarbohydrazone complex is synthesized and characterized, showing an improved turnover rate compared to its mononuclear counterpart. DFT calculations reveal that the mechanism involved is metal-centered, unlike the metal-assisted ligand-centered mechanism in the mononuclear complex. Two possible mechanisms involving an initial double reduction of the system are proposed for this catalyst.
Article
Chemistry, Inorganic & Nuclear
Frederico F. Martins, Vera Krewald
Summary: The fixation and conversion of nitrogen gas is a major challenge in chemistry, and a recent push-pull approach has shown success in fine-tuning the electron density along the nitrogen-nitrogen bond. Using the complex trans-[ReICl(N2)(PMe2Ph)4] as a starting point, this study explores the electronic structure implications of this approach and demonstrates the relationship between Lewis acidity and the pulling effect of borane Lewis acids on the nitrogen-nitrogen bond. Additionally, it is found that the ligand trans to dinitrogen can weaken the dinitrogen bond. These electronic structure design principles are rooted in cooperative effects between a transition metal complex and a Lewis acid, and can be used to tailor complexes for desired thermal, electrochemical, or photochemical reactivity of nitrogen gas.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Moritz Buchhorn, Vera Krewald
Summary: The angular overlap model (AOM) is a parameterization scheme in ligand field theory (LFT) that can be used to predict spectroscopic data in transition metal complexes. This article presents AOMadillo, a software package that automates many steps of the AOM parameterization and performs least-squares fitting for efficient parameter evaluation.
JOURNAL OF COMPUTATIONAL CHEMISTRY
(2023)
Article
Chemistry, Physical
Adam Srut, Vera Krewald
Summary: In this study, transient absorption spectroscopy and excited state dynamics simulations were used to investigate the electronic and vibrational evolution of a mixed-valent excited state in the reduced form of the Creutz-Taube ion. The results revealed a series of excited states with weak metal-metal interaction, which dominated the electronic population at short time scales. A long-lived vibrational wave packet mainly confined to oscillations of the metal center-bridge distances was observed.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Multidisciplinary
Adam Srut, Benjamin J. Lear, Vera Krewald
Summary: The Marcus model is the foundation for modern discussion of electron transfer (ET). This study presents an ab initio approach for quantifying the ET coordinate and demonstrates its application in a series of dinitroradical anions. The results show that the energy separation between potential energy surfaces and the extent of electron localization can be used to track electron transfer and identify the precise nuclear motion leading to it. This approach allows for the separation of the intrinsic electron transfer coordinate from other structural relaxations and environmental influences, and the barrier separating the adiabatic minima is thin enough to enable heavy-atom tunneling in the ET process.
Article
Chemistry, Multidisciplinary
Benedict J. Elvers, Sebastian Paetsch, Siva S. M. Bandaru, Vera Krewald, Carola Schulzke, Christian Fischer
Summary: Heteroleptic molybdenum complexes with P2N2 and non-innocent dithiolene ligands were synthesized and electrochemically characterized. The reduction potentials of the complexes were adjusted by ligand-ligand cooperativity via non-covalent interactions. This finding was supported by electrochemical studies, UV/Vis spectroscopy, and temperature-dependent NMR spectroscopy. The observed behavior resembles enzymatic redox modulation through second ligand sphere effects.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Inorganic & Nuclear
Moritz Buchhorn, Vera Krewald
Summary: It has been widely believed that ammonia and amine ligands only interact with metals through sigma bonds and do not significantly interact via pi bonds. However, this study challenges this assumption by presenting evidence of significant pi interaction between ammonia ligands and copper ammine complexes. The results suggest that the pi interaction of ammonia ligands is comparable in strength to that of chloride ions.
DALTON TRANSACTIONS
(2023)