Spontaneous Reductive Elimination at Iridium(III) Induced by the Strong π‐Acceptor Ligand Trifluorophosphane

The reaction of the cyclometalated five‐coordinate 16 VE iridium(III) compound [IrCl(H)(P(tBu)2C6H4‐κ2P,C)(P(tBu)2Ph)] (1) with the strong π‐acceptor ligand trifluorophosphane resulted quickly in the quantitative formation of the new iridium(I) complex trans‐[IrCl(PF3)(P(tBu)2Ph)2] (2). This unexpected spontaneous reductive elimination was already observed in reactions of 1 with the very strong π‐acceptor ligands CO and NO+. First indications during reactions of 1 with lesser strong π‐acceptor ligands like alkyl or arylphosphanes did not show this inversion behavior of the cyclometalation. The title species 2 was characterized by spectroscopic methods and its molecular structure in the crystal was confirmed by X‐ray crystallography

Reactivity of Cyanide and Thiocyanate Towards the Nitrosyl Carbonyl [Co(CO)3(NO)]

The reaction of equimolar amounts of [Co(CO)3(NO)] and [PPN]CN, PPN+ = (PPh3)2N+, in THF at room temperature resulted in ligand substitution of a carbonyl towards the cyanido ligand presumably affording the complex salt PPN[Co(CO)2(NO)(CN)] as a reactive intermediate species which could not be isolated. Applying the synthetic protocol using the nitrosyl carbonyl in excess, the title reaction afforded unexpectedly the novel complex salt PPN[Co2(μ‐CN)(CO)4(NO)2] (1) in high yield. Because of many disorder phenomena in crystals of 1 the corresponding NBu4+ salt of 1 has been prepared and the molecular structure of the dinuclear metal core in NnBu4[Co2(μ‐CN)(CO)4(NO)2] (2) was determined by X‐ray crystal diffraction in a more satisfactory manner. In contrast to the former result, the reaction of [PPN]SCN with [Co(CO)3(NO)] yielded the mononuclear complex salt PPN[Co(CO)2(NO)(SCN‐κN)] (3) in good yield whose molecular structure in the solid was even determined and its composition additionally confirmed by spectroscopic means

Wie arbeiten Schüler in den naturwissenschaftlichen Fächern ? : Lernforschung in der Schule und im Schülerlabor Biologie als Grundlage zukünftiger Schulentwicklung

Wissenschaftsmethodische Kompetenzen und ein wissenschaftstheoretisches Verständnis der Naturwissenschaften sind Teil einer naturwissenschaftlichen Bildung. Ob Schülerinnen und Schüler diese Kompetenzen bis zum Ende ihrer Schullaufbahn überhaupt entwickeln ist aber weitgehend unbekannt. Am Institut für Biologiedidaktik arbeitet seit 2001 die Arbeitsgruppe „Wissenschaftliche Arbeitsweisen im Biologieunterricht“ an dem Ziel, aus der Sicht der Fachdidaktik Biologie grundlegende Variablen des naturwissenschaftlichen Arbeitsprozesses bei Schülern zu identifizieren, modellhaft abzubilden und theoretisch zu fassen. Ein wichtiges Instrument war dabei – neben der Feldforschung – die Einrichtung eines Schüler-Labors zur Erforschung von Schülergruppen unter standardisierten Bedingungen

An End-to-End Performance Comparison of Seven Permissioned Blockchain Systems

The emergence of more and more blockchain solutions with innovative approaches to optimising performance, scalability, privacy and governance complicates performance analysis. Reasons for the difficulty of benchmarking blockchains include, for example, the high number of system parameters to configure and the effort to deploy a blockchain network. In addition, performance data, which mostly comes from system vendors, is often intransparent. We investigate and evaluate the performance of seven permissioned blockchain systems using different parameter settings in a reproducible manner. We employ an end-to-end approach, where the clients sending the transactions are fully involved in the data collection approach. Our results highlight the peculiarities and limitations of the systems under investigation. Due to the insights given, our work forms the basis for continued research to optimise the performance of blockchain systems.Comment: 14 pages, 5 figures, 20 tables, Middleware Conferenc

Coinage Metal Complexes of Bis(quinoline-2-ylmethyl)phenylphosphine-Simple Reactions Can Lead to Unprecedented Results

The different coordination behavior of the flexible yet sterically demanding, hemilabile P,N ligand bis(quinoline-2-ylmethyl)phenylphosphine (bqmpp) towards selected Cu-I, Ag-I and Au-I species is described. The resulting X-ray crystal structures reveal interesting coordination geometries. With [Cu(MeCN)(4)]BF4, compound 1 [Cu-2(bqmpp)(2)](BF4)(2) is obtained, wherein the copper(I) atoms display a distorted square planar and square pyramidal geometry. The steric demand and pi-stacking of the ligand allow for a short Cu...Cu distance (2.588(9) angstrom). Cu-I complex 2 [Cu4Cl3(bqmpp)(2)]BF4 contains a rarely observed Cu4Cl3 cluster, probably enabled by dichloromethane as the chloride source. In the cluster, even shorter Cu...Cu distances (2.447(1) angstrom) are present. The reaction of Ag[SbF6] with the ligand leads to a dinuclear compound (3) in solution as confirmed by P-31{H-1} NMR spectroscopy. During crystallization, instead of the expected phosphine complex 3, a tris(quinoline-2-ylmethyl)bisphenyl-phosphine (tqmbp) compound [Ag-2(tqmbp)(2)](SbF6)(2) 4 is formed by elimination of quinaldine. The Au(I) compound [Au-2(bqmpp)(2)]PF6 (5) is prepared as expected and shows a linear arrangement of two phosphine ligands around Au-I

Cytotoxic Activity of Some Half‐sandwich Rhodium(III) Complexes Containing 4,4’‐disubstituted‐2,2’‐bipyridine Ligands

The synthesis and characterization of three compounds [Rh(η5-C5Me5)Cl(N^N)]PF6 (N^N=4,4’-disubstituted-2,2’-bipyridines, 1–3) are described. The cationic complexes contain the bidentate ligands N^N=4,4'-di-tert-butyl-2,2'-bipyridine (1), N^N=4,4'-dinonyl-2,2'-bipyridine (2) and N^N=4,4'-diamino-2,2'-bipyridine (3). The complex salts were obtained by the bridge-splitting reaction from the precursor [{Rh(η5-C5Me5)(μ-Cl)Cl}2] and subsequent salt metathesis affording their corresponding hexafluorido phosphate salts. All compounds were characterized by elemental analysis and spectroscopic means. Additionally, the molecular structure of compound 3 in the solid was determined by a single-crystal X-ray diffraction study. The cytotoxicity of all three compounds was examined by MTT assay against two cancer cell lines – HT-29 (colon adenocarcinoma) and MCF-7 (human breast adenocarcinoma) - and normal human fibroblast cells (GM5657T). Compound 1 has moderate cytotoxicity against both cell lines, while compound 2 is seven to nine times more cytotoxic than cisplatin against MCF-7 and HT-29, respectively. In contrast to cisplatin, both compounds are more active against cancer cells than fibroblasts, thus showing some cancer selectivity

Molecular Methods Used for the Identification of Potentially Probiotic Lactobacillus reuteri Strains

Forty potentially probiotic Lactobacillus strains as well as reference strains of different genera were grown under standardised conditions. Cell masses were harvested and DNA was isolated. For identification, all strains were subjected to genus-specific polymerase chain reaction (PCR), and the affiliation with the genus Lactobacillus was confirmed for all isolates. Using two species-specific primer-pairs for Lactobacillus reuteri, specific amplicons were observed for eight of the forty investigated strains. For differentiation, these eight strains as well as the reference strains of the species L. reuteri and closely related species were subjected to randomly amplified polymorphic DNA (RAPD)-PCR using fourteen arbitrary primers. Two selected strains as well as probiotic and common reference strains were further investigated applying pulsed field gel electrophoresis (PFGE). With the latter two methods, individual profiles were found for most strains, but no difference between probiotic and common strains could be made out

Cytotoxic Activities of Half‐sandwich M(III) Complexes (M=Rh, Ir) Bearing Chloro‐substituted Bidentate‐coordinated Phenanthroline or Terpyridine Ligands

The synthesis and characterization of four compounds [M(η5-C5Me5)(N^N)Cl]PF6 [N^N=4,7-dichloro-1,10-phenanthroline with M=Rh, 1, and M=Ir, 2, and N^N=4'-(4-chlorophenyl)-2,2':6',2''-terpyridine in the κ2N,N'-coordination mode with M=Rh, 3, and M=Ir, 4] are described. All compounds were characterized by spectroscopic means and their molecular structures in the crystal were confirmed by single-crystal X-ray diffraction studies. The cytotoxicity of all compounds was evaluated by MTT assay against the three cancer cell lines HeLa (cervical carcinoma), HT-29 (colon adenocarcinoma) and MCF-7 (human breast adenocarcinoma). The complexes 3 and 4 display promising activity with IC50 values of 1 μM. The rhodium(III) complex 1 also shows highly improved cytotoxicity compared to cisplatin against the cancer cell lines HT-29 and MCF-7. In contrast to this, the iridium(III) complex 2 is even less active against the HeLa cell line than cisplatin