Catalyst precursors for ethylene polymerization based on novel mono- and bi-nuclear pyridylimine-type palladium(II) complexes with long straight chain alkyl substituents at the imino nitrogen
作者:Rui Chen、Selwyn F Mapolie
DOI:10.1016/s1381-1169(02)00456-9
日期:2003.2
attached to the imino nitrogen are described. These complexes were evaluated as catalyst precursors for ethylene polymerization under relatively mild reaction conditions. Unlike N-aryl substituted pyridylimine-type analogues, these complexes when activated with methylaluminoxane (MAO) were capable of producing highly linear polyethylene with high molecular weights, the values of which can be tuned from
Metallomicelles as catalysts of the hydrolysis of carboxylic and phosphoric acid esters
作者:Paolo Scrimin、Paolo Tecilla、Umberto Tonellato
DOI:10.1021/jo00001a033
日期:1991.1
Lipophilic ligands 2-4 have been synthesized. In the presence of Cu(II) ions, they form metallomicelles that are catalytically active in the cleavage of the p-nitrophenyl esters of acetic, hexanoic, and dodecanoic acids. Catalysis was also observed in the cleavage of p-nitrophenyl diphenyl phosphate. The apparent pK(a) of the Cu(II)-coordinated hydroxyl of ligand 2a, in the micellar aggregate, is 7.7, as estimated from the rate vs pH profiles for both classes of esters: this suggests that the hydroxyl is involved as a nucleophile in the hydrolytic cleavage, which proved to be really catalytic process. The ligand bearing the free hydroxyl (2a) is more effective in the cleavage of carboxylate esters than ligands with the methylated alcoholic group (2b) or devoid of it (4); the opposite behavior is observed in the cleavage of the phosphate triester. A rationale is offered that calls for the difference in the coordination ability to the metal center of phosphate and carboxylate esters.
Synthesis and antitubercular activity of substituted phenylmethyl- and pyridylmethyl amines
A total of 42 benzyl- and pyridylmethyl amines were synthesized either by reductive amination of aromatic/heteroaromatic aldehydes with amines or by conjugate addition of amines to the cinnamates followed by reduction of the ester group with lithium aluminium hydride to the respective propanolamines. All the synthesized compounds were evaluated against both avirulent and virulent strains of Mycobacterium
A micellar approach is proposed to build a series of systems featuring an "off-on-off" fluorescentwindow response with changes in pH. The solubilizing properties of micelles are used to self-assemble, in water, plain pyrene with lipophilized pyridine and tertiary amine moieties. Since these components are contained in the small volume of the same micelle, pyrene fluorescence is influenced by the basic