Effect of ligand structure

In hetero-Diels-Alder reactions, the effect of ligand structure and acidity on the catalytic activity of lanthanide catalysts has been reviewed.191 The effect of different C(2)-symmetric bisoxazolines on the zinc(II)-catalysed hetero-Diels-Alder reaction of ethyl glyoxylate with conjugated 1,3-dienes has been investigated.192 The hetero-Diels-Alder reaction 4-dimethylamino-2-phenyl-l-thiabuta-1,3 -diene with methyl acrylate and /V-cnoyloxazolidinone produces cw-3,4-disubstituted 3,4-dihydro-2//-... 

To assess the effect of ligand structure, several measurements are necessary the emission energy, the lifetime, and the emission quantum yield. Furthermore, it is essential that details on precisely how the data have been obtained be given. Demas and Crosby220) have pointed out the necessity for this reporting. In the absence of specific details, discrepancies between reported values are difficult to assess. From the data in the following sections it will be seen that there is a wide variation in the quantities reported. 

Sparteine appears to be the best ligand examined to date in studies on the effect of ligand structure on the enantioselective deprotonation.304 The f-butoxycarbonyl group stabilizes the anion and renders a-protons more acidic. 

J. Rosenqvist, K. Axe, S. Sjoberg, and P. Person, Adsorption of dicarboxylates on nano-sized gibbsite particles effects of ligand structure on bonding mechanisms, Colloids Surf. A 220, 91-104(2003). 

Figure 5.7 The effect of ligand structure on reduction potentials in some macrocyclic complexes of iron, (a) The effect of unsaturation (b) the effect of increased conjugation (E, represents the measured reduction potential under the conditions used as these were not the standard conditions, a value of the standard potential was not obtained, but E, can be taken as a good approximation of the standard potential)...

Santostefano, M., H. Liu, X.H. Wang, K. Chaloupkaand S. Safe. Effect of ligand structure on formation and DNA binding properties of the transformed rat cytosolic aryl hydrocarbon receptor. Chem. Res. Toxicol. 7 544-550, 1994. 

A second study provided an analysis of the effect of ligand structure on the reductive elimination of diaryl ethersJ ... 

Harder TE, Walker SD, Martinelli JR, Buchwald SL (2005) Catalysts for Suzuki-Miyaura Coupling Processes Scope and Studies of the Effect of Ligand Structure. J Am Chtan Soc... 

In either case, the polymerization behavior of this catalyst would be expected to be sensitive to propylene pressure and reaction temperature. Indeed, higher pressures and lower temperatures favor formation of isotactic pentads. The effect of ligand structure on catalyst behavior and polymer properties for 2-arylindene metallocene catalysts has been extensively studied. 

Naga, N. Imanishi, Y. Copolymeiization of ethylene and cyclopentene with zirconocene catalysts Effect of ligand structure of zirconocenes. Macromol. Chem. Phys. 2002, 203,159-165. 

The effects of ligand structure, such as N-alkylated chain length, degree of N-substitution, and the distance between the two amino groups, that is, methylene-diamine (mn), ethylenediamine (en), trimethylenediamine (tn) and some kinds of polymethylenediamine (bn, hn), were extensively studied. In addition, ethylenediamine derivatives containing ether linkages and polyamines such as triamine and tetramine are also mentioned. Scheme 2 depicts the relationships between the abbreviations and the structure of representative ligands studied in this work. 

Tang W, Matyjaszewski K. Effect of ligand structure on activation rate constants in ATRP. Macromolecules 2006 39 4953 959. 

Figure 7 Effect of ligand structure on /Catrp for a series of copper-based catalysts. Reprinted from Tang, W. Kwak, Y. Braunecker, W. etal. J. Am. Chem. Soc. 2008, 130,10702-10713," ° with permission from the ACS.

This approach has been applied in an MM study of the effect of ligand structure on the one-electron reduction of ten hexa-amine Co(III) complexes. A plot of AU versus reduction potential revealed the expected trend, although the correlation was poor (r = 0.781). The poor correlation can be attributed in large part to the differences in the electronic contribution from ammonia to primary and secondary amine moieties. An excellent correlation (r = 0.999) is obtained, however, if the data is restricted to a subset of ligands bearing constant donor atom types, e.g., primary amines. 

Walker, J. R. Martinelli and S. L. Buchwald, Catalysts for Suzuki-Miyaura coupling processes Scope and studies of the effect of ligand structure, J. Am. Chem. Soc., 2005,127(13), 4685-4696. 

Discussion of the effect of ligand structure on protein-carbohydrate affinity requires an evaluation of complex stability constants. A munber of biophysical techniques are appropriate for the study of protein-carbohydrate interaction many of the more enlightening strategies are the topics of separate chapters elsewhere in this volume. We describe below three techniques used extensively in glycobiology— inhibition of hemagglutination, enzyme-linked lectin assay (ELLA), and isothermal titration microcalorimetry—and we consider the types of information provided by each technique in order to facilitate appropriate interpretation of the data. 

Fig. 1 Effect of ligand structures on ATRP activation rate constants (fcaot) with ethyl 2-bro-moisobutyrate (EtBriB) activated by Cu Br complexes in the presence of MeCN at 35 °C. N2 red, N3 black-, N4 blue-, amine/imine solid-, pyridine operv, mixed left-half solid-, linear open square-, branched filled triangle-, cyclic open circle. Reprinted with permission from American Chemical Society [41]...

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