Ion-pair reversed-phase high-performance liquid chromatography was successfully coupled to negative-ion electrospray ionization mass spectrometry by using 60 × 0.20 mm i.d. capillary columns packed with 2.3-μm micropellicular, octadecylated poly(styrene/divinylbenzene) particles as stationary phase and gradients of acetonitrile in 50 mM aqueous triethylammonium bicarbonate as mobile phase. Systematic variation of the eluent composition, such as concentration of ion-pair reagent, anion in the ion-pair reagent, solution pH, and acetonitrile concentration led to the conclusion that most parameters have opposite effects on chromatographic and mass spectrometric performances. The use of acetonitrile as sheath liquid enabled the rapid and highly efficient separation and detection of phosphorylated and nonphosphorylated oligonucleotides ranging in size from 8 to 40 nucleotides. High-quality full-scan mass spectra showing little cation adduction were acquired from which the molecular masses of the separated oligonucleotides were calculated with an accuracy of 0.011%. With calibration curves being linear over at least 2 orders of magnitude, the lower limits of detection for a oligodeoxythymidine 16-mer were 104 fmol with full scan and 710 amol with selected-ion-monitoring data acquisition. The potential of ion-pair reversed-phase high-performance liquid chromatography−electrospray ionization mass spectrometry was demonstrated for mixed-sequence oligomers by the characterization of a reaction mixture from solid-phase synthesis of a 40-mer oligonucleotide.

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Imidazolium and benzimidazolium salts with an N-iminoyl and an NЈ-alkyl group are potential precursors for new bidentate [N,C] ligands which are of interest as novel steering ligands for applications of their metal complexes in homogeneous catalysis. Deprotonation of these azolium salts with potassium hydride does indeed occur, however, the initially formed imino-N-heterocyclic carbenes rearrange spontaneously under migration of the N-iminoyl group from the nitrogen to the former carbene carbon with the formation of 2-iminoyl(benz)imidazoles. These rearranged compounds are

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We report on new families of non-metallocene metal precatalysts for olefin polymerization with titanium, zirconium, vanadium and nickel as the active metal sites. The novel ligand design concept is based on iminohydroxamic acids and their derivatives as the principal chelating units. Various anionic and neutral [N,O] and [N,N] ligand systems are easily accessible by a modular synthetic sequence of imidoyl chlorides with substituted hydroxylamines or hydrazines, respectively. Steric protection of the metal coordination site, a necessary requirement for suppression of chain termination pathways of non-metallocene catalysts, is brought about by bulky aryl substituents on the imino nitrogen atoms. Crystal struc-