Rollover cyclometalation - early history, recent developments, mechanistic insights and application aspects

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.“Rollover” cyclometalation constitutes a special case among the well-known class of cyclometalation reactions. An overview is given that covers the very first description of this reaction type, as well as recent developments. In addition, not only condensed-phase experiments are reviewed, but also investigations based on mass spectrometric techniques, together with “in silico” studies using DFT-based calculations are considered. While the latter two methods allow for a detailed analysis of the intrinsic factors that affect the reaction mechanisms, consideration of all three regimes permits to develop a coherent mechanistic picture and to address the often noted gap between condensed- and gas-phase studies. Moreover, the quite unexpected reactivity of “rollover” cyclometalated complexes in gas-phase experiments, as well as potential applications, e.g. in synthetic procedures, are discussed in some detail.DFG, EXC 314, Unifying Concepts in Catalysi

Untersuchungen zur Differenzierung der domestizierten und der Wildform von Sus scrofa in Lebensmitteln

In dieser Arbeit wurden zahlreiche DNA-analytische Untersuchungen wie PCR-RFLP, RAPD oder Sequenzierung an Haus- und Wildschweinen vorgenommen. Durch Vergleich von Mustern und Sequenzen wurde geprüft, ob es sich um individuelle Merkmale handelt oder um gruppenspezifische Marker, die für eine Differenzierung der domestizierten Form vom Wildschwein verwendet werden können. Untersucht wurden drei Gene, die in Zusammenhang mit dem äußeren Erscheinungsbild des Tieres gebracht werden das Melanocortin-1-Rezeptor-Gen, das Tyrosinase-Gen und das Immunorezeptor DAP10-Gen. Weiterhin wurde ein Gen, zwei nicht-codierende Bereiche und Introns untersucht, die nicht mit äußeren Merkmalen in Verbindung stehen das Cytochrom B-Gen, der D-Loop-Bereich und der repetetive Bereich des Mikrosatelliten S602 sowie Introns des Immunorezeptor DAP10-Gens. Besondere Aufmerksamkeit galt dabei dem cytB-Gen, da hier bereits eine RFLP-Analytik für die Differenzierung von Haus- und Wildschweinen etabliert war, die es zu untersuchen galt. Die DNA-Sequenzvergleiche zeigten bei den untersuchten Tieren der Art Sus scrofa eine große Homogenität im Vergleich zu den Unterschieden zwischen Tieren verschiedener Arten. Bei Sequenzabweichungen handelt es sich in der Regel um isolierte Punktmutationen, die von der Art her ausschließlich Substitutionen und keine Deletionen sind. Lediglich bei der repetetiven Sequenz ist eine unterschiedliche Anzahl an Repeats und einer daraus resultierenden unterschiedlichen Länge der DNA-Sequenz vorhanden, die jedoch nicht gruppenspezifisch ist. Eine Analytik zur Differenzierung der Formen beruht somit auf der Identifizierung von Punktmutationen. Bei Untersuchung der publizierten Differenzierungsmethoden oder Sequenzheterologien von Haus- und Wildschweinen zeigte sich, dass die Muster und Sequenzen innerhalb einer Form nicht homogen sind. Es gab bei jedem Marker mehrere Individuen einer Form, deren DNA-Sequenz von der der anderen Tiere abwich. Auch bei den weiteren untersuchten Sequenzen konnten keine Mutationen gefunden werden, die bei allen Individuen einer Form identisch waren. Die Sequenzheterogenität unter allen Individuen ist größer als die zwischen der Wild- und der domestizierten Form. Für die Differenzierung der Formen ist somit die Anwendung mehrerer Marker notwendig. Die genaueste Aussage über die Identität der Probe lässt sich aufgrund der Sequenzierung mehrerer DNA-Abschnitte vornehmen. Insgesamt konnten 14 Marker, die für die Unterscheidung der Formen geeignet sind, identifiziert werden. Einige wichtige Marker lassen sich über eine PCR-RFLP-Analyse identifizieren, für zwei Marker im D-Loop wurde ein Real-Time-PCR-System entwickelt

Completing the triad: Synthesis and full characterization of homoleptic and heteroleptic carbonyl and nitrosyl complexes of the group VI metals

Oxidation of M(CO)$_{6}$ (M = Cr, Mo, W) with the synergistic oxidative system Ag[WCA]/0.5 I$_{2}$ yields the fully characterized metalloradical salts [M(CO)$_{6}$]+˙[WCA]− (weakly coordinating anion WCA = [F-{Al(OR$^{F}$)$_{3}$}$_{2}$]$^{-}$, R$^{F}$ = C(CF$_{3}$)$_{3}$). The new metalloradical cations with M = Mo and W showcase a similar structural fluxionality as the previously reported [Cr(CO)$_{6}$]$^{+}$˙. Their reactivity increases from M = Cr < Mo < W and their syntheses allow for in-depth insights into the properties of the group 6 carbonyl triad. Furthermore, the reaction of NO$^{+}$[WCA]$^{-}$ with neutral carbonyl complexes M(CO)$_{6}$ gives access to the heteroleptic carbonyl/nitrosyl cations [M(CO)$_{5}$(NO)]$^{+}$ as salts of the WCA [Al(ORF)$_{4}$]$^{-}$, the first complete transition metal triad of their kind

Electronic correlations in organometallic complexes

We investigate an effective model for organometallic complexes (with potential uses in optoelectronic devices) via both exact diagonalisation and the configuration interaction singles (CIS) approximation. This model captures a number of important features of organometallic complexes, notably the sensitivity of the radiative decay rate to small chemical changes. We find that for large parameter ranges the CIS approximation accurately reproduces the low energy excitations and hence the photophysical properties of the exact solution. This suggests that electronic correlations do \emph{not} play an important role in these complexes. This explains why time-dependent density functional theory works surprisingly well in these complexes.Comment: 11 pages, 6 figure

Models of organometallic complexes for optoelectronic applications

Organometallic complexes have potential applications as the optically active components of organic light emitting diodes (OLEDs) and organic photovoltaics (OPV). Development of more effective complexes may be aided by understanding their excited state properties. Here we discuss two key theoretical approaches to investigate these complexes: first principles atomistic models and effective Hamiltonian models. We review applications of these methods, such as, determining the nature of the emitting state, predicting the fraction of injected charges that form triplet excitations, and explaining the sensitivity of device performance to small changes in the molecular structure of the organometallic complexes.Comment: To appear in themed issue of J. Mat. Chem. on the modelling of material

An Artificial SEI Layer Based on an Inorganic Coordination Polymer with Self-Healing Ability for Long-Lived Rechargeable Lithium-Metal Batteries

Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane solution of the phosphoric-acid derivative (CF$_{3}$CH$_{2}$O)$_{2}$P(O)OH (HBFEP), an artificial solid-electrolyte interphase (SEI) is generated on the Li-metal surface. Hence, HBFEP reacts on the surface to the corresponding Li salt (LiBFEP), which is a Li-ion conducting inorganic coordination polymer. This film exhibits – due to the reversibly breaking ionic bonds – self-healing ability upon cycling-induced volume expansion of Li. The presence of LiBFEP as the major component in the artificial SEI is proven by ATR-IR and XPS measurements. SEM characterization of HBFEP-treated Li samples reveals porous layers on top of the Li surface with at least 3 μm thickness. Li−Li symmetrical cells with HBFEP-modified Li electrodes show a three- to almost fourfold cycle-lifetime increase at 0.1 mA cm$^{-2}$ in a demanding model electrolyte that facilitates fast battery failure (1 M LiOTf in TEGDME). Hence, the LiBFEP-enriched layer apparently acts as a Li-ion conducting protection barrier between Li and the electrolyte, enhancing the rechargeability of Li electrodes

Efficient Room‐Temperature Activation of Methane by TaN+ under C−N Coupling

The thermal reaction of diatomic tantalum nitride cation [TaN]+ with methane has been explored using FT‐ICR mass spectrometry complemented by high‐level quantum chemical calculation; based on this combined experimental/computational approach, mechanistic aspects of this novel, highly efficient C−N coupling process have been uncovered. In distinct contrast to [TaN]+, its lighter congeners [VN]+ and [NbN]+ are inert towards methane under ambient conditions, and the origins of the remarkably variable efficiencies of the three metal nitrides are uncovered by CCSD(T) calculations.MeTa‐lated: Thermal activation of methane by [TaN]+ under C−N coupling and formation of H2 was detected by mass spectrometry and confirmed by quantum chemical calculations. The lighter congeners [VN]+ and [NbN]+ are inert towards methane under the same conditions. (In the picture the signal labeled with “×” arises from reactions with background contaminants.)Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137504/1/anie201606259-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137504/2/anie201606259.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137504/3/anie201606259_am.pd

Metal–metal cooperative bond activation by heterobimetallic alkyl, aryl, and acetylide PtII/CuI complexes

We report the selective formation of heterobimetallic PtII/CuI complexes that demonstrate how facile bond activation processes can be achieved by altering the reactivity of common organoplatinum compounds through their interaction with another metal center. The interaction of the Cu center with the Pt center and with a Pt-bound alkyl group increases the stability of PtMe2 towards undesired rollover cyclometalation. The presence of the CuI center also enables facile transmetalation from an electron-deficient tetraarylborate [B(ArF)4]− anion and mild C–H bond cleavage of a terminal alkyne, which was not observed in the absence of an electrophilic Cu center. The DFT study indicates that the Cu center acts as a binding site for the alkyne substrate, while activating its terminal C–H bond