Structure elucidation of the unprecedented asymmetric bis-chelate complex [Pd(1,3-bis(di(o-methoxy-m-methylphenyl)phosphino)propane)2]2+ in the solid state and in solution

Complexes of the type [Pd(ligand)(2)](anion)(2) were prepared with a series of bidentate di(o-methoxyphenyl)phosphine ligands with increasing steric bulk on the meta position of the phenyl groups: m-H (L1); m-MeO (L2); and m-Me (L3). The solid-state structure of [Pd(L2)(2)](OTs)(2) revealed that the two ligands are symmetrically coordinated to Pd(2+). In the solid state structure of [Pd(L3)(2)](OTs)(2) however, the two ligands are unsymmetrically coordinated to Pd(2+), yielding an unprecedented conformation of this bis-chelate P(4)Pd(2+) complex. (1)H-(1)H-COSY and NOESY analysis and a (31)P-NMR simulation showed that the asymmetric structure of [Pd(L3)(2)](OTs)(2) is retained in solution.     

Automated mass spectrometric analysis of urinary and plasma serotonin

Serotonin emerges as crucial neurotransmitter and hormone in a growing number of different physiologic processes. Besides extensive serotonin production previously noted in patients with metastatic carcinoid tumors, serotonin now is implicated in liver cell regeneration and bone formation. The aim was to develop a rapid, sensitive, and highly selective automated on-line solid-phase extraction method coupled to high-performance liquid chromatography–tandem mass spectrometry (XLC-MS/MS) to quantify low serotonin concentrations in matrices such as platelet-poor plasma and urine. Fifty microliters plasma or 2.5 μL urine equivalent were pre-purified by automated on-line solid-phase extraction, using weak cation exchange. Chromatography of serotonin and its deuterated internal standard was performed with hydrophilic interaction chromatography. Mass spectrometric detection was operated in multiple reaction monitoring mode using a quadrupole tandem mass spectrometer with positive electrospray ionization. Serotonin concentrations were determined in platelet-poor plasma of metastatic carcinoid patients (n = 23) and healthy controls (n = 22). Urinary reference intervals were set by analyzing 24-h urine collections of 120 healthy subjects. Total run-time was 6 min. Intra- and inter-assay analytical variation were <10%. Linearity in the 0–7300 μmol/L calibration range was excellent (R² > 0.99). Quantification limits were 30 and 0.9 nmol/L in urine and plasma, respectively. Platelet-poor serotonin concentrations in metastatic carcinoid patients were significantly higher than in controls. The urinary reference interval was 10–78 μmol/mol creatinine. Serotonin analysis with sensitive and specific XLC-MS/MS overcomes limitations of conventional HPLC. This enables accurate quantification of serotonin for both routine diagnostic procedures and research in serotonin-related disorders.     

Subpicosecond pulse generation from a 1.56 μm mode-locked VECSEL

Near-transform-limited subpicosecond pulses at 1.56 μm were generated from an optically pumped InP-based vertical-external-cavity surface-emitting laser (VECSEL) passively mode-locked at 2 GHz repetition rate with a fast InGaAsNSb/GaAs semiconductor saturable absorber mirror (SESAM). The SESAM microcavity resonance was adjusted via a selective etching of phase layers specifically designed to control the magnitude of both the modulation depth and the intracavity group delay dispersion of the SESAM. Using the same VECSEL chip, we observed that the mode-locked pulse duration could be reduced from several picoseconds to less than 1 ps with a detuned resonant SESAM.     

Negative electrorheological responses of micro-polar fluids in the finite spin viscosity small spin velocity limit. I. Couette flow geometries

Negative electrorheological responses induced by micro-particle electrorotation in two-dimensional Couette flow geometries are analyzed by a set of continuum modeling field equations originating from anti-symmetric/couple stress theories in the finite spin viscosity small spin velocity (FSV) limit. Analytical solutions are obtained for the first time to express the spin velocity, linear velocity, and effective viscosity in terms of the electric field strength, driving shear rate, boundary condition selection parameter, and spin viscosity. Good agreement is achieved between the FSV theoretical predictions presented herein and the experimental measurements reported in recent literature for the effective viscosity for low driving shear rates.     

Nickel N‐heterocyclic carbene complexes in the vinyl polymerization of norbornene

Vinyl polymerized norbornene has some useful properties such as good mechanical strength, optical transparency and heat resistance. Several transition metal complexes have been described in the literature as active catalysts for the vinyl polymerization of norbornene. We now report the use of three types of nickel(II) complexes with N‐heterocyclic carbene (NHC) ligands in the catalytic vinyl polymerization of norbornene under a range of conditions. Specifically, two nickel complexes bearing a chelating bis(NHC) ligand, two nickel complexes bearing two chelating anionic N‐donor functionalized NHC ligands as well as one diiodidonickel(II) complex with two monodentate NHC ligands were tested. The solid‐state structure of bis(1,3‐dimethylimidazol‐2‐ylidene)diiodidonickel(II), as determined by X‐ray crystallography, is presented. The highest polymerization activity of 2.6 × 10⁷ g (mol cat)^?1 h^?1 was observed using the latter nickel complex as catalyst, activated by methylaluminoxane. The norbornene polymers thus obtained are of high molecular weight but with rather low polydispersity. Copyright © 2010 John Wiley & Sons, Ltd.     

Derivatization Procedures for Reducing Oligosaccharides,Part 3: Preparation of Oligosaccharide Glycosylamines,and Their Conversion Into Glycosaccharide - Acrylamide Copolymers

Abstract

Reducing oligosaccharides were converted in good yields into the corresponding primary glycosylamines by treatment with aqueous ammonium bicarbonate. The glycosylamines were then acryloylated and the obtained oligosaccharide N-acryloyl glycosylamines were copolymerized with acrylamide. High molecular weight, linear copolymers were obtained, which were useful as antigens in immunoassays.     

Highly Selective Iron‐Catalyzed Synthesis of Alkenes by the Reduction of Alkynes

Herein, the iron‐catalyzed reduction of a variety of alkynes with silanes as a reductant has been examined. With a straightforward catalyst system composed of diiron nonacarbonyl and tributyl phosphane, excellent yields and chemoselectivities (>99 %) were obtained for the formation of the corresponding alkenes. After studying the reaction conditions, and the scope and limitations of the reaction, several attempts were undertaken to shed light on the reaction mechanism.