Die Umsetzung von [Nb6Cl12]-Cluster-Komplexverbindungen mit Neutralliganden: Synthesen, Strukturen, intermolekulare Wechselwirkungen und Folgereaktionen

Im Rahmen dieser Arbeit wird die Synthese und Charakterisierung von 153 neuartigen Niobcluster-Komplexverbindungen mit neutralen Liganden beschrieben. Es wurden erstmalig T-förmige CH-π-, Anion-π- und Lone-Pair-π-, Chalkogen-Chalkogen-Wechselwirkungen, sowie Halogen-, Chalkogen- und Pnikogen-Brücken in Niobcluster-Verbindungen beobachtet. Mit den Verbindungen [Nb6Cl14(Pyz)4] und [Nb6Cl14(Pyr-4-CN)4] werden Ausgangsverbindungen vorgestellt, durch die über 90 neue Cluster-Verbindungen synthetisiert werden konnten, u.a. die ersten Niobcluster-Verbindungen mit neutralen S- und Se-Liganden.In this work the synthesis and characterization of 153 novel niobium cluster complexes with neutral ligands is described. For the first time T-shaped CH-π, anion-π and lone-pair-π, chalcogen-chalcogen interactions, as well as halogen, chalcogen and pnicogen bridges in niobium cluster compounds were observed. With the compounds [Nb6Cl14(Pyz)4] and [Nb6Cl14(Pyr-4-CN)4], starting compounds are presented which allowed the synthesis of over 90 new cluster compounds, including the first niobium cluster compounds with neutral S and Se ligands

Hexanuclear Niobium Cluster Compounds with Protonated N‐Base Cations

Octahedral clusters of the [M6X12] type offer numerous possibilities to form structural arrangements through different choices of bonding situations. In this paper a series of new cluster compounds of the transition metal niobium is described, which consist of the [Nb6Cl18]2–, and in one case [Nb6Cl18]3–, anion and protonated N‐base cations ([MIm‐H]+, [nPr3N‐H]+, [TMGu‐H]+, and [Tzn‐H]+). They all are prepared using water scavenger compounds [SOCl2 or (Ac)2O] under oxidising conditions, resulting in two‐electron (or one‐electron, respectively) oxidized cluster units with respect to the starting material [Nb6Cl14(H2O)4]·4H2O. Of five members of this group single‐crystal X‐ray structures were determined. The cluster anions exist in all structures as discrete units. The acidic H atoms of all N‐bases are hydrogen bonded to H acceptors, in 4 cases to outer, exo bonded Cl atoms of the cluster unit and in one case to the O atom of a co‐crystallized THF molecule. In [TMGu‐H]2[Nb6Cl18] chains of cluster anions exist hydrogen‐bonded through bridging [TMGu‐H]+ cations. ESI mass spectra of [MIm‐H]2[Nb6Cl18]·2SOCl2 and [TMGu‐H]2[Nb6Cl18] show the expected isotopic distribution patterns for the anions together with other peaks associated to chloride mass losses and/or reduction processes

Intraligand Charge Transfer Enables Visible‐Light‐Mediated Nickel‐Catalyzed Cross‐Coupling Reactions

We demonstrate that several visible‐light‐mediated carbon−heteroatom cross‐coupling reactions can be carried out using a photoactive NiII precatalyst that forms in situ from a nickel salt and a bipyridine ligand decorated with two carbazole groups (Ni(Czbpy)Cl2). The activation of this precatalyst towards cross‐coupling reactions follows a hitherto undisclosed mechanism that is different from previously reported light‐responsive nickel complexes that undergo metal‐to‐ligand charge transfer. Theoretical and spectroscopic investigations revealed that irradiation of Ni(Czbpy)Cl2 with visible light causes an initial intraligand charge transfer event that triggers productive catalysis. Ligand polymerization affords a porous, recyclable organic polymer for heterogeneous nickel catalysis of cross‐coupling reactions. The heterogeneous catalyst shows stable performance in a packed‐bed flow reactor during a week of continuous operation

Footprints of Inversions at Present and Past Pseudoautosomal Boundaries in Human Sex Chromosomes

The human sex chromosomes have stopped recombining gradually, which has left five evolutionary strata on the X chromosome. Y inversions are thought to have suppressed X–Y recombination but clear evidence is missing. Here, we looked for such evidence by focusing on a region—the X-added region (XAR)—that includes the pseudoautosomal region and the most recent strata 3 to 5. We estimated and analyzed the whole set of parsimonious scenarios of Y inversions given the gene order in XAR and its Y homolog. Comparing these to scenarios for simulated sequences suggests that the strata 4 and 5 were formed by Y inversions. By comparing the X and Y DNA sequences, we found clear evidence of two Y inversions associated with duplications that coincide with the boundaries of strata 4 and 5. Divergence between duplicates is in agreement with the timing of strata 4 and 5 formation. These duplicates show a complex pattern of gene conversion that resembles the pattern previously found for AMELXY, a stratum 3 locus. This suggests that this locus—despite AMELY being unbroken—was possibly involved in a Y inversion that formed stratum 3. However, no clear evidence supporting the formation of stratum 3 by a Y inversion was found, probably because this stratum is too old for such an inversion to be detectable. Our results strongly support the view that the most recent human strata have arisen by Y inversions and suggest that inversions have played a major role in the differentiation of our sex chromosomes

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements