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1.
Corina Andronescu Justus Masa Richard D. Tilley John J. Gooding Wolfgang Schuhmann 《Current Opinion in Electrochemistry》2021
The complex interplay of restricted mass transport leading to local accumulation or depletion of educts, intermediates, products, counterions and co-ions influences the reactions at the active sites of electrocatalysts when electrodes are rough, three-dimensionally mesoporous or nanoporous. This influence is important with regard to activity, and even more to selectivity, of electrocatalytic reactions. The underlying principles are discussed based on the growing awareness of these considerations over recent years. 相似文献
2.
The effect of changes of ionic strength on the partition of an analytically important weak acid between a variety of aqueous and immiscible organic phases has been studied with respect to new measurements on dithizone (3-mercapto-1,5-diphenylformazan) and di(p-tolyl)thiocarbazone. A linear relationship has been deduced between the pH at which 50% extraction takes place and Sr,o (the solubility of the reactant in the organic phase), and confirmed by measurements of pH, and Sr,o for a large number of organic solvents. The solubilities of the reagents in water, Sr, are also reported. The form of the relationship between pH and log D, and between pH and log Sr,o is the same whether a solution of dithizone consists of a single species or a mixture of thiol and thione forms in tautomeric equilibrium. 相似文献
3.
This empirical analysis of CD data for 7-membered lactams includes examples of all twelve possible structural types in which the lactam is fused to a cyclohexane ring as part of a polycyclic compound. The CD behaviour of several classes of lactams shows ‘dOgura's sign rule’ to be an over-simplification. The signs and values of Δ? for lactams in which the second ring is fused at the 3,4- or 6,7-positions of the lactam ring show considerable deviations from the “normal’ values for 4,5- or 5,6-fused lactams.No simple pattern of group contributions emerged from this analysis, but a correlation of CD behaviour with the torsion angle in the C-CO-NH-C structural component is suggested, on the basis of a study of Dreiding models, and is supported by the result of an X-ray crystallographic analysis of one of the lactams.This study of CD data is extended to a smaller group of lactones with a seven-membered ring, most of which show Cotton effects opposite in sign and of smaller magnitude than those of the corresponding lactams. 相似文献
4.
Reaction of the 1-substituted-3-cyano-isothioureas 6 with hydroxylamine gave mixtures of the 5-amino-3-substituted-amino-1,2,4-oxadiazoles 1 and the isomeric 3-amino-5-substituted-amino-1,2,4-oxadiazoles 8 in which 1 usually predominated. The structural assignment of these products is discussed. In a second method, the 2-hydroxy-1-methyl-1-phenyl-guanidine 15 was converted to the corresponding 3-disubstituted-amino-5-trichloromethyl-1,2,4-oxadiazole 16 , a precursor to the 5-amino derivatives 17 by nucleophilic displacement of the trichloromethyl group. 相似文献
5.
New hafnocene triarylstannyl complexes were prepared and were shown to undergo clean thermal decompositions via alpha-aryl-elimination to produce the corresponding stannylene and a hafnocene aryl complex. The rate of the decomposition is highly dependent on the nature of the ancillary ligand, with the stabilities of the CpCp*Hf(SnPh(3))X compounds following the order X = NMe(2) > Np (alpha-agostic) > OMe > Cl > Me. Mechanistic information suggests that alpha-aryl-elimination may be viewed as a concerted process involving nucleophilic attack of the migrating aryl group onto the electrophilic metal center. 相似文献
6.
The scandium dihydrosilyl complexes Cp*(2)ScSiH(2)R (R = Mes (4), Trip (5), SiPh(3) (6), Si(SiMe(3))(3) (7); Mes = 2,4,6-Me(3)C(6)H(2), Trip = 2,4,6-(i)()Pr(3)C(6)H(2)) and Cp*(2)ScSiH(SiMe(3))(2) (8) were synthesized by addition of the appropriate hydrosilane to Cp*(2)ScMe (1). Studies of these complexes in the context of hydrocarbon activation led to discovery of catalytic processes for the dehydrogenative silation of hydrocarbons (including methane, isobutene and cyclopropane) with Ph(2)SiH(2) via sigma-bond metathesis. 相似文献
7.
S. De Rossi E. Iguchi M. Schiavello R. J. D. Tilley 《Reaction Kinetics and Catalysis Letters》1977,6(2):201-208
The oxidation of propene was studied on several tungsten oxides which contained small amounts of Ti, Ta, Nb and Sn. Only the Sn-containing specimen was found to be selective in the conversion of propene to acrolein. The catalytic results are correlated with crystal structures determined by electron microscopy.
, Ti, Ta, Nb Sn. , , Sn, . , .相似文献
8.
Jian Yang Vernica Postils Michael I. Lipschutz Meg Fasulo Christophe Raynaud Eric Clot Odile Eisenstein T. Don Tilley 《Chemical science》2020,11(19):5043
A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]+, is a precursor to efficient catalysts for the hydrosilation of alkenes with a variety of hydrosilanes under mild conditions and low catalyst loadings. DFT studies reveal the presence of two coupled catalytic cycles based on [(NPN)NiH]+ and [(NPN)NiSiR3]+ active species, with the latter being more efficient for producing the product. The preferred silyl-based catalysis is not due to a more facile insertion of alkene into the Ni–Si (vs. Ni–H) bond, but by consistent and efficient conversions of the hydride to the silyl complex.A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]+, is a precursor to efficient catalysts for the hydrosilation of alkenes with hydrosilanes under mild conditions and low catalyst loadings. 相似文献
9.
10.
Following the discovery of a ternary GeW oxide with the Mo5O14 structure, a large number of ternary MWO systems were surveyed to investigate the frequency of occurrence of this structure type. Samples were prepared by heating tungsten oxides and the appropriate ternary element or a suitable compound of the ternary element in evacuated silica ampoules at 1373°K for 1 week. The compositions investigated were close to M0.02W0.98O2.80. Oxides with the Mo5O14 structure were found in many systems across the whole of the periodic table, from Li to Bi. Some aspects of the formation of these phases and the way in which they could affect the course of reduction of WO3 to W metal are discussed. 相似文献