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91.
It is well known that metalloenzymes are able to catalyze chemical reactions with a very high activity and selectivity|1–3|. Therefore the synthesis of complexes between transition metal derivatives and structurally ordered macromolecular ligands to give catalytic systems having high activity and stereoselectivity is of large interest from both applicative and speculative point of view. In this connection the main aim of this article is to emphasize the role of the constitutional and configurational order of the macromolecular ligand in determining the properties of the corresponding complexes with transition metal derivatives. This is of particular importance for designing catalytic systems displaying peculiar features as far as activity, selectivity and stereochemistry are concerned. Moreover a better insight into environment and coordination sphere of the polymer attached metal derivative can be of great help for mechanistic studies of the reactions involved. 相似文献
92.
Armstrong DS Arvieux J Asaturyan R Averett T Bailey SL Batigne G Beck DH Beise EJ Benesch J Bimbot L Birchall J Biselli A Bosted P Boukobza E Breuer H Carlini R Carr R Chant N Chao YC Chattopadhyay S Clark R Covrig S Cowley A Dale D Davis C Falk W Finn JM Forest T Franklin G Furget C Gaskell D Grames J Griffioen KA Grimm K Guillon B Guler H Hannelius L Hasty R Allen AH Horn T Johnston K Jones M Kammel P Kazimi R King PM Kolarkar A Korkmaz E Korsch W Kox S Kuhn J Lachniet J Lee L Lenoble J 《Physical review letters》2007,99(9):092301
93.
There are many reports1 of the pyrolysis of fluorinated organic compounds, including the defluorination of cyclic fluorocarbons over iron to give aromatic compounds. Extending this technique we have investigated the flow pyrolysis of some readily accessible unsaturated fluorocarbons, such as I, II, and III, and found these to be synthetically useful routes to fluorinated dienes, cyclobutenes, and furans. Pyrolyses were carried out using a nitrogen flow over platinum, iron or caesium fluoride heated at 430–700°. The various products can all be rationalized in terms of intermediate allylic radicals, and the solid substrate influences which allylic radicals are formed.We are also investigating the chemistry of those now accessible compounds, such as IV, V, and VI, and some of the preliminary results are described. For example the fluoride ion induced dimerisation of IV gave two major products VII and VIII via a particular interesting mechanism. 相似文献
94.
Zhu H Ahmidouch A Anklin H Arenhövel H Armstrong C Bernet C Boeglin W Breuer H Brindza P Brown D Bültmann S Carlini R Chant N Cowley A Crabb D Danagoulian S Day DB Eden T Ent R Farah Y Fatemi R Garrow K Harris C Hauger M Honegger A Jourdan J Kaufmann M Khandaker M Kubon G Lichtenstadt J Lindgren R Lourie R Lung A Mack D Malik S Markowitz P McFarlane K McKee P McNulty D Milanovich G Mitchell J Mkrtchyan H Mühlbauer M Petitjean T Prok Y Rohe D Rollinde E Rondon OA Roos P Sawafta R Sick I Smith C 《Physical review letters》2001,87(8):081801
We report the first measurement using a solid polarized target of the neutron electric form factor G(n)(E) via d-->(e-->,e(')n)p. G(n)(E) was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia ( 15ND3). The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility in quasifree kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find G(n)(E) = 0.04632+/-0.00616(stat)+/-0.00341(syst) at Q2 = 0.495 (GeV/c)(2). 相似文献
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97.
Carlo Carlini Marco Martinelli Elisa Passaglia AnnaMaria Raspolli Galletti Glauco Sbrana 《Macromolecular rapid communications》2001,22(9):664-668
Novel catalytic systems based on bis‐(chelate)nickel(II) precursors, such as bis(α‐nitroacetophenonate)nickel(II) [Ni(naph)2] and bis(2,6‐diisopropylbenzenesalicylaldiminate)nickel(II) [Ni(dipbs)2], and methylaluminoxane (MAO) as the cocatalyst were employed for the polymerization of methyl methacrylate (MMA). Reaction parameters were examined. Under proper conditions, the Ni(dipbs)2/MAO system allowed to obtain poly(MMA) with a very high productivity (TOF up to 70 000 h–1) and a remarkable syndiospecificity degree (rr > 80%) at room temperature without addition of an ancillary Lewis base. 相似文献