313 research outputs found
Complexes (R=Organyl): Stepwise versus Concerted Mechanism in Copper‐Mediated Trifluoromethylation
No full textIntramolecular Phenyl Transfer from Boron to Lithium, Sodium, and Copper: Defining the Limits of Transmetalation
No full textAbstract Transmetalation is a key elementary step in organometallic chemistry, for which reason there is a keen interest in better understanding the factors governing this reaction. We have previously reported the unusual transfer of a phenyl anion from boron to lithium in the gas‐phase dissociation of [LiBr( t Bu)(Ph)Bpin] − ( Chem. Eur. J . 2024 , 43 , e202303653). Here, we use a combination of gas‐phase fragmentation experiments and quantum chemical calculations to probe the reactivity of the related adducts [MX(R)(Ph)Bpin] − (R= n Bu, t Bu, Ph; X=Cl, Br, I, BF 4 , BPh 4 ; M=Li, Na, K, Cu). We find the transfer of Ph − to be much favored over that of n Bu − and t Bu − . The tendency toward transmetalation is decreased for anions X − that strongly bind to the metal center M. Likewise, it is diminished for more electropositive/less electronegative metals M. According to our theoretical calculations, the coordination of a single molecule of tetrahydrofuran to the metal M also lowers the propensity for transmetalation, thereby approaching the behavior in solution. Thus, our results reveal a subtle interplay of different effects influencing the tendency toward transmetalation.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/50110000165
Modular Ion Mobility Calibrants for Organometallic Anions Based on Tetraorganylborate Salts
No full textThe Thomas Iron Company, 1854-1904 : chartered under the laws of Pennsylvania
No full textThis book presents the history of the Thomas Iron Company. It was prepared for the stockholders of the Company in commemoration of the company\u27s 50th anniversary. The history of the company and its founders, as well as other notable figures are described. Also, the expansion of the company and its development in the area is also provided in detail
Dissecting Transmetalation Reactions at the Molecular Level: Phenyl Transfer in Metal Borate Complexes
No full textHexanuclear Copper(I) Hydride from the Reduction-Induced Decarboxylation of a Dicopper(II) Formate
No full text(R=allyl)**
No full textHigh‐valent tetraalkylcuprates(iii) and ‐argentates(iii) are key intermediates of copper‐ and silver‐mediated C−C coupling reactions. Here, we investigate the previously reported contrasting reactivity of [RM( iii )Me(3)](−) complexes (M=Cu, Ag and R=allyl) with energy‐dependent collision‐induced dissociation experiments, advanced quantum‐chemical calculations and kinetic computations. The gas‐phase fragmentation experiments confirmed the preferred formation of the [RCuMe](−) anion upon collisional activation of the cuprate(iii) species, consistent with a homo‐coupling reaction, whereas the silver analogue primarily yielded [AgMe(2)](−), consistent with a cross‐coupling reaction. For both complexes, density functional theory calculations identified one mechanism for homo coupling and four different ones for cross coupling. Of these pathways, an unprecedented concerted outer‐sphere cross coupling is of particular interest, because it can explain the formation of [AgMe(2)](−) from the argentate(iii) species. Remarkably, the different C−C coupling propensities of the two [RM( iii )Me(3)](−) complexes become only apparent when properly accounting for the multi‐configurational character of the wave function for the key transition state of [RAgMe(3)](−). Backed by the obtained detailed mechanistic insight for the gas‐phase reactions, we propose that the previously observed cross‐coupling reaction of the silver complex in solution proceeds via the outer‐sphere mechanism
Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl
No full textGrignard reagents RMgCl and their so-called turbo variant, the highly reactive RMgCl center dot LiCl, are of exceptional synthetic utility. Nevertheless, it is still not fully understood which species these compounds form in solution and, in particular, in which way LiCl exerts its reactivity-enhancing effect. A combination of electrospray-ionization mass spectrometry, electrical conductivity measurements, NMR spectroscopy (including diffusion-ordered spectroscopy), and quantum chemical calculations is used to analyze solutions of RMgCl (R=Me, Et, Bu, Hex, Oct, Dec, iPr, tBu, Ph) in tetrahydrofuran and other ethereal solvents in the absence and presence of stoichiometric amounts of LiCl. In tetrahydrofuran, RMgCl forms mononuclear species, which are converted into trinuclear anions as a result of the concentration increase experienced during the electrospray process. These trinuclear anions are theoretically predicted to adopt open cubic geometries, which remarkably resemble structural motifs previously found in the solid state. The molecular constituents of RMgCl and RMgCl center dot LiCl are interrelated via Schlenk equilibria and fast intermolecular exchange processes. A small portion of the Grignard reagent also forms anionic ate complexes in solution. The abundance of these more electron-rich and hence supposedly more nucleophilic ate complexes strongly increases upon the addition of LiCl, thus rationalizing its beneficial effect on the reactivity of Grignard reagents.Deutsche Forschungsgmeinschaft [KO 2875/4-1
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