Ligand influence

Oxidative carbonylation generates a number of important compounds and materials such as ureas, carbamates, 2-oxazolidinones, and aromatic polycarbonates. The [CuX(IPr)] complexes 38-X (X = Cl, Br, I) were tested as catalysts for the oxidative carbonylation of amino alcohols by Xia and co-workers [43]. Complex 38-1 is the first catalyst to selectively prepare ureas, carbamates, and 2-oxazolidinones without any additives. The important findings were the identity of the counterion and that the presence of the NHC ligand influenced the conversions. 2-Oxazohdinones were formed from primary amino alcohols in 86-96% yield. Complex 38-1 also catalysed the oxidative carbonylation of primary amines to ureas and carbamates. n-Propylamine, n-butylamine, and t-butylamine were transformed into the... 

Bulky substituents at tetravalent silicon centers are the structural key element of sterically overcrowded compounds with extraordinary properties Inter- and intramolecular interactions of the bulky ligands can be studied in detail and allow an assessment of the ligands influence on structure and reactivity. 

Ligand Influences in Copper-Dioxygen Complex-Formation and Substrate Oxidations... 

It would be tempting to apply the same rationale to the metathesis of 2-pentene isomers, but clearly, the steric requirements of methyl and ethyl are much less than that of isopropyl, and trade-offs involving cis-1,2-disubstitution vs. axial orientation are not clear neither is the important role of catalyst ligand influence. 

The 1,3-dipolar cycloaddition of nitrones to vinyl ethers is accelerated by Ti(IV) species. The efficiency of the catalyst depends on its complexation capacity. The use of Ti( PrO)2Cl2 favors the formation of trans cycloadducts, presumably, via an endo bidentate complex, in which the metal atom is simultaneously coordinated to the vinyl ether and to the cyclic nitrone or to the Z-isomer of the acyclic nitrones (800a). Highly diastereo- and enantioselective 1,3-dipolar cycloaddition reactions of nitrones with alkenes, catalyzed by chiral polybi-naphtyl Lewis acids, have been developed. Isoxazolidines with up to 99% ee were obtained. The chiral polymer ligand influences the stereoselectivity to the same extent as its monomeric version, but has the advantage of easy recovery and reuse (800b). 

It should be kept in mind that this type of study, treated here in terms of single complexes, acquires greater importance when carried out on a series of homologous complexes. This allows one to evaluate how the electronic and/or structural variations of the ligand influence the reorganization processes of the solvent molecules. In fact, such a comparison has recently led to a reinterpretation of the A °c parameter also in terms of the structural reorganisations of the first coordination sphere.18,19 For example, if one compares the A-Sr°c values for... 

In most cases, the ligands are present at far greater concentrations than the trace metals, (i.e., L (aq) M (aq)). Thus, ion associations between the trace metals and ligands influence the speciation of the former to a far greater extent than that of the latter. 

The geometries and spin multiplicities of models of the Mn -salen catalyst and the Mn -oxo intermediate have been studied using DFT. The Mn complexes have quintet ground states, while the nature of the salen ligand influences whether quintet, triplet, or singlet ground states are lowest in energy for the Mn -oxo intermediates. 

In the discussion of the property-specific control of a directing ligand in homogeneous transition-metal catalysis, one has to be sure that the results of the considered experiments are comparable. The ligand influences different intermediates of a catalytic system in more or less different ways. This can result in a somewhat contradic-... 

Brushite has a very wide distribution field, from about pH 5 to pH 13, with minimum Ca2+ solubilities at around 1 x 10 3 m between pH 7 and 11. At the solute concentrations modelled, only the CaOH+ complex influences the solubility of the solid phase. Monetite also has a very wide distribution field, from about pH 5 to pH 13, with minimum Ca2+ solubilities at around 1 x 10-3m between pH 7 and 11. At the solute concentrations modelled, only the CaOH+ complex influences the solubility of the solid phase. Octacalcium phosphate has a very wide distribution field, from about pH 5 to pH 14, with minimum Ca2+ solubilities at around 1 x 10 5 m around pH 12. At the solute concentrations modelled, only the CaOH+ complex influences the solubility of the solid phase. Low whitlockite has a very wide distribution field, from about pH 4 to pH 14, with minimum Ca2+ solubilities at around 1 x 10-8 M around pH 12. At the solute concentrations modelled, only the CaOH+ complex influences the solubility of the solid phase. Hydroxyapatite has a very wide distribution field, from about pH 4 to pH 14, with minimum solubilities at around 5 x 10 9 m around pH 12. At the solute concentrations modelled, only the CaOH+ and CaCO ligands influence the solubility of the solid phase. 

Additionally, the axial ligands influence the electronic structure of metalloporphyrins. It is known that axial ligation has a substantial influence on the redox (80,81) and photovoltaic (82) properties... 

How does the structure of the nonreplaced amine ligands influence the rate of base hydrolysis ... 

Variation in the P-Donor Ligand. INFLUENCE OF L VARIATION on Reaction Rates and Equilibria. The solvolytic Equation 4 in methanol (30%) water is first order (38). The... 

An extended (seven-sided) ternary complex model (Fig. 2B) was proposed by Samama et al. (1993) to accommodate mutant receptors that exhibited constitutive activity and to link receptor affinity with efficacy. This model includes the isomerization of the receptor between two conformational states, inactive (R) and active (R ), and only allows for the active R conformational state to interact with the G protein. Conceptually, the model allows for the receptor to toggle between on and off states where ligand or G protein manipulates the population size of these two conformational states, rather than affecting the activation strength of a particular conformational state. The different types of ligands influence... 

The spacer rigidity of the dithioether ligand influences the resulting framework in a spectacular manner. Indeed, the unsaturated dithioether ligand l,4-bis(phenythio)butyne, including a linear alkyne -CH2-C=C-CH2- array, reacts with Cul in MeCN to afford the colorless 3D polymer... 

H. Schreier, P. Moran, and I. W. Caras. Specific targeting of liposomes to cells using a GPI-anchored ligand influence of liposome composition on intracellular trafficking, J. Biol. Chem. 269 9090-9098 (1994). 

It was also of interest to us how changes in the organic residue of the carbyne ligand influence the stability and the behavior of carbyne complexes. Hence, we treated with boron tribromide a series of pentacarbonyl-[methoxy (aryl) carbene tungsten (0) complexes which were substituted at... 

The change to substituted allyl ligands influences the 48 49 equilibrium in the corresponding hafnium systems.53 Silver et al. have used the specific deprotonation at related methylallyl derivatives to generate the conjugated diene ligand in the coordination sphere of the metal. 

Another important manifestation of the ligand influence is the thermochemistry of the isomers of the CCs. The problem of isomerism of the CCs was a crucial... 

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