Ylide‐Functionalized Phosphines: Strong Donor Ligands for Homogeneous Catalysis

Phosphines are important ligands in homogenous catalysis and have been crucial for many advances, such as in cross‐coupling, hydrofunctionalization, or hydrogenation reactions. Herein we report the synthesis and application of a novel class of phosphines bearing ylide substituents. These phosphines are easily accessible via different synthetic routes from commercially available starting materials. Owing to the extra donation from the ylide group to the phosphorus center the ligands are unusually electron‐rich and can thus function as strong electron donors. The donor capacity surpasses that of commonly used phosphines and carbenes and can easily be tuned by changing the substitution pattern at the ylidic carbon atom. The huge potential of ylide‐functionalized phosphines in catalysis is demonstrated by their use in gold catalysis. Excellent performance at low catalyst loadings under mild reaction conditions is thus seen in different types of transformations.     

Reaction of trans-tetracyanodioxomolybdate(IV) with salicylaldehyde as an important stage in the Schiff base ligand formation. Kinetics and mechanism

The kinetics of the reaction between the protonated species of trans-[Mo(CN)4O2]4– and salicylaldehyde (Hsal) was studied in the 7.8–12.0 pH range in H2O-MeOH mixtures. Spectroscopic characterization of the product indicates that the aqua and cyano ligands are substituted by sal– with formation of the [Mo(CN)3O (sal- 2O,O)]2– ion. The formation quotient, Kf for the overall reaction=31 (±1) at 25°C. In the presence ofan excess of ligand, the rate law is of the formd[Mo(CN)3O(sal- 2O,O)2–]/dt =kobs[Mo(CN)4O (H2O)2–]. The kobs value is equal to 2.9 (±8)×10–3 at 25°C. The activation parameters H (kobs) and S (kobs) are 103 (±9)kJmol–1 and 45 (±8)JK–1mol–1, respectively. The amount of the product formed decreases with increasing pH but the rate of the product formation increases. The reaction mechanism and the possible formation of Schiff base ligands in the presence of amines are discussed.     

A thin chip microsprayer system coupled to Fourier transform ion cyclotron resonance mass spectrometry for glycopeptide screening

A thin polymer microchip was coupled with a Fourier transform ion cyclotron resonance (FTICR) 9.4 T mass spectrometer and the method was optimized in negative ion mode for glycopeptide screening. The interface between the polymer microchip and FTICR mass spectrometer consists of an in-laboratory conceived and designed mounting system that exhibits robust and controllable alignment of the chip toward the inlet of the mass spectrometer. The particular attribute of the polymer chip coupled to the FTICR mass spectrometer, to achieve an increase in ionization efficiency and sensitivity under the premise of high mass accuracy of detection, is highlighted by the large number of major and minor glycopeptide structures detected and identified in highly heterogeneous mixtures obtained from urine matrices. Glycoforms expressing various saccharide chain lengths ranging from tri- to dodecasaccharide, bearing up to three sialic acid moieties, could be detected and assigned based on the accuracy of the mass measurement (average mass deviation below 6 ppm) of their molecular ions. -Thin chipESI-FTICRMS is a potent novel system for glycomic screening of complex mixtures, as demonstrated for identification of singly sialylated O-glycosylated amino acids and peptides from urine matrices, and could be considered for general applicability in the glycoanalytical field.     

Ma?analytische Bestimmung von Lanthan mit Natriumwolframat in Anwesenheit von Adsorptionsindicatoren

Zusammenfassung Zur genauen und schnellen Bestimmung von Lanthan wird die Titration mit Natrium-wolframat unter Verwendung der Adsorptionsindicatoren Chlorphenolrot, o-Kresolrot und Methylrot, sowie der Gemische Methylrot + Bromkresolgrün und Chlorphenolrot + Anilinblau empfohlen. Der Fehler der Bestimmung beträgt höchstens 0,5%. Die Methode eignet sich zur Bestimmung von La³⁺ in reinen Salzen und zur Bestimmung der Summe von Seltenen Erdmetallen nach vorhergehender Abtrennung von anderen Schwermetallen, die mit Natriumwolframat einen schwerlöslichen Niederschlag bilden.

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Volumetric determination of lanthanum using sodium tungstate in presence of adsorption indicators

The accurate and rapid method described employs the following indicators: chlorophenol red, o-cresol red, methyl red, and the mixtures methyl red + bromocresol green and chlorophenol red + aniline blue. In all instances the error is smaller than 0.5%. The method is suitable for La³⁺ determination in lanthanum salts and also for the determination of the total amount of rare earths after separation from other heavy metals forming with sodium tungstate difficultly soluble precipitates.

     

Study of Lipophilicity and Application of Selected Topological Indexes in QSAR Analysis of Nicotinic Acid Derivatives. Part I

JPC – Journal of Planar Chromatography – Modern TLC - Selected nicotinic acid derivatives have been chromatographed on RP-HPTLC plates with methanol-water in different volume...     

Solar radiation, vitamin D and survival rate of colon cancer in Norway

Solar radiation contributes significantly to the status of serum calcidiol (25-hydroxyvitamin D3, 25-(OH)D3) in humans, even at the high latitudes of northern Norway. Thus, in late summer the serum concentration of calcidiol is roughly 50% larger than that in late winter, when the solar radiation in Norway contains too little ultraviolet radiation to induce any synthesis of vitamin D3 in human skin. This seems to influence the prognosis of colon cancer. We here report that the survival rate of colon cancer in men and women, assessed 18 months after diagnosis, is dependent on the season of diagnosis. A high serum concentration of calcidiol at the time of diagnosis, i.e. at the start of conventional therapy, seems to give an increased survival rate. This agrees with cell and animal experiments reported in the literature, as well as with epidemiological data from some countries relating colon cancer survival with latitude and vitamin D3 synthesis in skin. One possible interpretation of the present data is that, the level of calcidiol, or its derivative calcitriol (1alpha,25-dihydroxyvitamin D3, 1alpha,25-(OH)2D3), may act positively in concert with conventional therapies of colon cancer.     

Intermetallic interactions in face-to-face homo- and heterodinuclear bismacrocyclic complexes of copper(II) and nickel(II)

New face-to-face heterodinuclear complexes containing copper(II) and nickel(II) in identical tetraazamacrocyclic environments have been synthesized and characterized using ESI mass-spectrometry, X-ray diffraction, spectroscopic methods, and elemental analysis. These new bismacrocyclic systems were compared with the respective mono- and bismacrocyclic and [2]catenane homonuclear complexes. Interactions between the metal centers were monitored by magnetic and electrochemical measurements. Magnetic data indicate that all copper compounds studied behave as weakly interacting magnets. In the case of copper [2]catenane, the extent of magnetic interactions decreased when a benzocrown moiety was introduced between the macrocyclic units. On the basis of electrochemical data, the interactions between the metal centers were found to be substantially larger for the nickel complexes than for the corresponding copper ones. Interlocking of a benzocrown ether to form [2]catenane led to a nonequivalence of the metal centers and to the increase of donor abilities of the catenane compared to the respective bismacrocyclic complex. This is reflected by the shift of the first formal potential to less positive values. Intermetallic interactions for the heteronuclear nickel/copper complexes were found intermediary compared to the homonuclear ones. They were strengthened by shortening the spacer between the two tetraazamacrocyclic subunits which is a convenient way of fine-tuning the interactions. The increase of intermetallic interactions led to the increased stability of the intermediate mixed-valence states indicated by the higher values of comproportionation constants.     

Melting and high-temperature solid state transitions in cobalt(II) halides

Melting and high temperature solid-state transitions in CoCl₂ and CoBr₂ are widely discussed. On the basis of DSC and conductometric measurements it was found that melting process of CoCl₂ is preceded by a solid-state transition appearing about 20 K below the melting point of CoCl₂. Due to deconvolution of the thermograms, the enthalpy of fusion and that of solid-state transition were found to be 36.4 and 9.6 kJ mol^–1, respectively. Melting points of CoCl₂ and CoBr₂ were established to be 999.0 and 949.7 K, respectively. Hitherto unknown enthalpy of fusion of CoBr₂ was determined to be 27.2 kJ mol^–1. A solid-state transition in CoBr₂ at 650 K has been confirmed.