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A series of iron(II) bis(triflate) complexes containing tripodal tetradentate nitrogen ligands with pyridine and dimethylamine donors of the type [N(CH(2)Pyr)(3-n)()(CH(2)CH(2)NMe(2))(n)] [n = 0 (tpa, 1), n = 1 (iso-bpmen, 3), n = 2 (Me(4)-benpa, 4), n = 3 (Me(6)-tren, 5)] and the linear tetradentate ligand [(CH(2)Pyr)MeN(CH(2)CH(2))NMe(CH(2)Pyr), (bpmen, 2)] has been prepared. The preferred coordination geometry of these complexes in the solid state and in CH(2)Cl(2) solution changes from six- to five-coordinate in the order from 1 to 5. In acetonitrile, the triflate ligands of all complexes are readily displaced by acetonitrile ligands. The complex [Fe(1)(CH(3)CN)(2)](2+) is essentially low spin at room temperature, whereas ligands with fewer pyridine donors increase the preference for high-spin Fe(II). Both the number of pyridine donors and the spin state of the metal center strongly affect the intensity of a characteristic MLCT band around 400 nm. The catalytic properties of the complexes for the oxidation of alkanes have been evaluated, using cyclohexane as the substrate. Complexes containing ligands 1-3 are more active and selective catalysts, possibly operating via a metal-based oxidation mechanism, whereas complexes containing ligands 4 and 5 give rise to Fenton-type chemistry. 相似文献
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Britovsek GJ England J Spitzmesser SK White AJ Williams DJ 《Dalton transactions (Cambridge, England : 2003)》2005,(5):945-955
A series of Fe(II), Mn(II), Co(II) and Ru(II) complexes containing bis(imino)pyridine or bis(amino)pyridine ligands and weakly coordinating triflate (OTf-) or non-coordinating SbF6- anions have been prepared. The complexes have been fully characterized including several solid-state structure analyses. Two unusual mono-chelate six-coordinate bis(imino)pyridine Fe(II) and Mn(II) complexes have been observed. The catalytic properties of the complexes for the oxidation of cyclohexane with H2O2 have been evaluated. Only the Fe(II) complexes have shown catalytic activity, which is mainly due to Fenton-type free radical auto-oxidation. 相似文献
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van Meurs M Britovsek GJ Gibson VC Cohen SA 《Journal of the American Chemical Society》2005,127(27):9913-9923
Highly active transition metal ethylene polymerization catalysts across the transition series have been investigated for their ability to catalyze chain growth on zinc. In reactions of various catalysts with ZnEt(2), product distributions range from Schulz-Flory to Poisson, with several catalysts showing intermediate behavior. A statistical modeling program is introduced to correlate product distributions with the relative rates of propagation, chain transfer to zinc, and beta-H transfer. Six regimes have been identified, ranging from Schulz-Flory to pure Poisson where chain transfer to metal is the only termination process, through to combined alkane/alkene distributions where beta-H transfer is competitive with chain transfer to metal. It is concluded that, while catalyzed chain growth (CCG) is favored by a reasonable match between the bond dissociation energies of both the main group and transition metal alkyl species, the M-C bond energies of the bridging alkyl species, and hence the stabilities of any hetero-bimetallic intermediates or transition states, are key. The latter are strongly influenced by the steric environment around the participating metal centers, more bulky ligands leading to a weakening of the bonds to the bridging alkyl groups; CCG is thus usually more favored for sterically hindered catalysts. 相似文献
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Energy spectra for decaying 2D turbulence in a bounded domain 总被引:1,自引:0,他引:1
We use results derived in the framework of the replica approach to study the liquid-glass thermodynamic transition. The main results are derived without using replicas and applied to the study of the Lennard-Jones binary mixture introduced by Kob and Andersen. We find that there is a phase transition due to the entropy crisis. We compute both analytically and numerically the value of the phase transition point T(K) and the specific heat in the low temperature phase. 相似文献
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Ugolotti J Hellstrom S Britovsek GJ Jones TS Hunt P White AJ 《Dalton transactions (Cambridge, England : 2003)》2007,(14):1425-1432
The reaction of 8-hydroxyquinoline (HQ) with B(C(6)F(5))(3) leads to the formation of the zwitterionic compound (C(6)F(5))(3)BQH (1), involving a proton migration from O to N. Compound 1 can be converted thermally to (C(6)F(5))(2)BQ (2), which can also be prepared from (C(6)F(5))(2)BCl and HQ. The reaction of HQ with (C(6)F(5))B(OC(6)F(5))(2) generates initially (C(6)F(5))(OC(6)F(5))BQ (3), which easily hydrolyses to give the diboron compound ((C(6)F(5))BQ)(2)O (4). Compounds 1, 2 and 4 have been fully characterised, including X-ray analysis. The spectroscopic properties of these compounds, including photoluminescence (PL) have been investigated and compared with the non-fluorinated luminescent boron compound (C(6)H(5))(2)BQ and also with AlQ(3). The changes in luminescent behaviour upon fluorination of these boron quinolinate compounds have been rationalised using computational studies. 相似文献
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Taylor RA Law DJ Sunley GJ White AJ Britovsek GJ 《Chemical communications (Cambridge, England)》2008,(24):2800-2802
The use of ligands with proximate hydrogen bonding substituents in the oxidation of platinum(II) dimethyl complexes with H2O2 leads to the exclusive formation of an unusual cis-dihydroxo platinum(IV) complex, which can dehydrate to form a trinuclear metalla-azacrown complex. 相似文献
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