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71.
Lewis M. Broomfield David Boschert Joseph A. Wright David L. Hughes Manfred Bochmann 《Journal of organometallic chemistry》2009,694(25):4084-4089
Potassium salts of the new 2-phosphinomethyl-1H-pyrroles, K[R2PCH2C4H3N] (R = Ph, Cy) react with (η3-allyl)nickel bromide to give the chelate complexes (R2PCH2C4H3N)Ni(allyl), whereas the sterically hindered 2-diphenylphosphinomethyl-5-t-butyl-1H-pyrrole and (η3-allyl)nickel bromide afford a phosphine adduct (HNC4H2-5-But-2-CH2PPh2)Ni(allyl)Br which is stabilized by an intramolecular NHBr hydrogen bond. The addition of B(C6F5)3 to (R2PCH2C4H3N)Ni(allyl) leads to an electrophilic attack in 5-position of the pyrrole ring, to give the thermally unstable zwitterions (η3-C3H5)Ni[NC4H3(2-CH2PR2)-5-B(C6F5)3] which catalyse the isomerisation of 1-hexene. The addition of B(C6F5)3 is reversible, and slow ligand rearrangement to Ni(N-P)2 products appears to be the major catalyst deactivation pathway. 相似文献
72.
Simon Maher Sarfaraz U. Syed David M. Hughes John R. Gibson Stephen Taylor 《Journal of the American Society for Mass Spectrometry》2013,24(8):1307-1314
Previous experimental and theoretical work identified that the application of a static magnetic (B) field can improve the resolution of a quadrupole mass spectrometer (QMS) and this simple method of performance enhancement offers advantages for field deployment. Presented here are further data showing the effect of the transverse magnetic field upon the QMS performance. For the first time, the asymmetry in QMS operation with B x and B y is considered and explained in terms of operation in the fourth quadrant of the stability diagram. The results may be explained by considering the additional Lorentz force (v x B) experienced by the ion trajectories in each case. Using our numerical approach, we model not only the individual ion trajectories for a transverse B field applied in x and y but also the mass spectra and the effect of the magnetic field upon the stability diagram. Our theoretical findings, confirmed by experiment, show an improvement in resolution and ion transmission by application of magnetic field for certain operating conditions. Figure
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A scheme is outlined for the separation of Li, K, Rb, Cs, Sr, Ba, Ce, Nd, Sm and Eu from silicate materials. The elements are separated by cation-exchange to provide groups suitable for mass spectrometric analysis, and are then further purified by anion-exchange. Results obtained by isotopic dilution analysis are reported for G-1, W-1, and the Harwell meteorite-in these measurements the alkali metals were determined separately from the other elements. Requirements are discussed for combining the procedures to form a more comprehensive method for use with a single sample. 相似文献
75.
The family of ligands containing an N2O2S2 core, namely, 1,2-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)ethane (H2L1), 1,3-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)propane (H2L2), 1,4-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)butane (H2L3), and 1,2-di(3-Me-5-t-Bu-salicylaldamino-o-phenylthio)ethane (H2L4), have been prepared and complexed with a variety of vanadium chlorides and alkoxides to afford complexes of the form [V(X)L1] (X = O (1), Np-tol (2), Cl (3)), [V(O)(L2,3)] (L2 (4), L3 (5)), and [V(L4)] (6). Crystal structure determinations of H2L1 and H2L4 show the molecule to be centrosymmetric about the bridging ethane moiety, with structural determination of 1 and 3 revealing isostructural monomeric complexes in which the ligand chelates in such a way as to afford pseudo-octahedral coordination at the vanadium center. Prolonged reaction of H2L1 with [V(Np-tol)(OEt)3] led, via oxidative cleavage of the C-S bond, to the bimetallic complex [V2L1(3-Me,5-t-Bu-salicylaldimino-o-phenylthiolate)2] [VL'] (7), as characterized by single-crystal X-ray crystallography. 7 was also isolated from the reaction of H2L4 and [VO(On-Pr)3]. The ability of 1-7 to catalyze the homopolymerization of ethylene and the copolymerization of ethylene/1-hexene in the presence of dimethylaluminum chloride (DMAC) has been assessed: screening reveals that for ethylene homopolymerization 1-7 are all highly active (>1000 g/mmol.h.bar), with the highest activity (ca. 11 000 g/mmol.h.bar) observed using catalyst 3; the use of trimethyl aluminum (TMA) or methylaluminoxane (MAO) as the cocatalyst led only to poorly active systems producing negligible polymer. Analysis of the polyethylene produced showed high molecular weight linear polymers with narrow polydispersities. For ethylene/1-hexene copolymerization, activities as high as 1,190 g/mmol.h.bar were achieved (4); analysis of the copolymer indicated an incorporation of 1-hexene in the range of 5-13%. 相似文献
76.
Enda Bergin David L. Hughes Christopher J. Richards 《Tetrahedron: Asymmetry》2010,21(11-12):1619-1623
Reaction of (η5-cyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt with Hg(OAc)2 (2.3 equiv) in 1:1 MeOH/CH2Cl2 followed by the addition of LiCl resulted in the formation of (η5-1,2-dichloromercuricyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt (33%) and its 1,3-isomer (6%). Following conversion into their corresponding diiodides these compounds were desymmetrised by Suzuki reactions with ArB(OH)2 employing [(R)-BINAP]PdCl2, with the highest ee of 24% being obtained for (η5-1-iodo-3-(2-methoxyphenyl)cyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt. 相似文献
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Ohne Zusammenfassung 相似文献
80.
Crystal and molecular structure of 5,12a-diacetyloxytetracycline 总被引:1,自引:0,他引:1