Coordination ability of solvents

The process actually involves two bimolecular processes, each of which requires solvent participation. However, the first step may also be a first-order step in which H20 coordinates only after X leaves. Although the reaction has been shown as if it takes place in water, other solvents could also be used, and a great difference in the overall rate of reaction should be expected. Because the coordinating abilities of solvents are different, the rates of the substitution reactions depend on the solvent chosen. Although many reactions are more complicated than suggested by the SN1 and SN2 models, there are many substitution reactions for which these rate laws (the so-called limiting cases) are applicable. 

Fig. 6.4 Schematic illustrations of the difference between coordination ability of solvent molecules to metal center in a 8-SAP and b 8-TDH structures. The author considers that the solvent molecules might be difBcult to coordinate to metal center in 8-TDH stmctures owing to their stmctural stabihty...

Those in which solvent molecules are directly involved in formation of the ion association complex. Most of the solvents (ethers, esters, ketones and alcohols) which participate in this way contain donor oxygen atoms and the coordinating ability of the solvent is of vital significance. The coordinated solvent molecules facilitate the solvent extraction of salts such as chlorides and nitrates by contributing both to the size of the cation and the resemblance of the complex to the solvent. 

In addition to influencing the reactivity, the coordinating ability of the solvent affects the mechanism of CO insertion. Thus, when a poorly coordinating solvent is employed together with a good nucleophile L, the... 

Kinetic studies have been made of the reaction of CpMo(CO)j R (R = Me, Et, CH2Ph, and CH2CH=CH2) (48, 80, 81) and 7r-X2C9H5Mo(CO)jMe (X = H or OMe) (108) with a variety of P donor ligands L. Solvents employed ranged from nonpolar hexane to polar THF and MeCN. Generally, the mechanism is very sensitive to the coordinating ability of the solvent and the nucleophilicity of L. 

The preparation of ZnSe materials is an area of interest and study. The coordinating ability of the solvent used in the solvothermal synthesis of zinc selenide was demonstrated to play an important role in the nucleation and growth of nanocrystalline ZnSe.604 Thermolysis of bis [methyl( -hexyl)di-seleno]carbamato]zinc gave highly monodispersed particles characterized by electronic spectroscopy, photoluminescence, X-ray diffraction, and electron microscopy.605... 

The efficiency of the extraction depends on the coordinating ability of the solvent, and on the acidity of the aqueous solution which determines the concentration of the metal complex. Coordinating ability follows the sequence ketones > esters > alcohols > ethers. Many metals can be extracted as fluoride, chloride, bromide, iodide or thiocyanate complexes. Table 4.5 shows how the extraction of some metals as their chloro complexes into diethyl ether varies with acid concentration. By controlling... 

As discussed in section 2.4.4 the coordinating ability of a solvent will often affect the rate of nucleation and crystal growth differently between two polymorphs. This can be used as an effective means of process control and information on solvent effects can often be obtained from polymorph screening experiments. There are no theoretical methods available at the present time which accurately predict the effect of solvents on nucleation rates in the industrial environment. 

The carbocupration of methoxyallene affords a (Z)- or (E)-enol ether depending on the solvent used [52], In THF, the reaction exhibits Z-selectivity because the coordination ability of THF excludes the intramolecular chelation effect of the methoxy group, which may be responsible for the E-selectivity for the reaction in ether (Scheme 10.49). 

There is a wide range of possibilities for adjusting the solubility characteristics of ionic liquids, and this is one of their potential advantages for optimized performance in biphasic or multiphasic catalysis (/). Because of the generally weak coordinating ability of the anions, most catalysts can be isolated in the solvent in a stable state without loss of activity. The product selectivity can sometimes be improved as well by the phase isolation. Because the catalyst is concentrated in the ionic phase, the reaction volume can be much smaller than in classical... 

If the metathesis is done at 5.5 < pH > 6, decomposition is 5%, but reaches 50% when the pH is lowered to 5.0. At pH > 7 the compound appears to form several different hydrolysis products, depending upon the concentration and solution pH, which are not completely characterized, but show different 31PNMR and UY/visible spectra.1 The visible spectrum of the Ni11 complex depends upon the coordinating ability of the solvents, which... 

They argue that the similar coordinating ability of these phusphoryl (—P=0) solvents (and to a lesser extent their dielectric constants) is more important than their chemical differences (supposed autoionization and chloride ion transfer in phosphorus oxychloride). 

The solvating ability of solvents depends not only on their general polarity, which is a non-specific property, but in a large part to their ability to interact in a specific manner with the solute. This may take place by the donation of a nonbonding pair of electrons from a donor atom of the solvent towards the formation of a coordinate bond with the solute, therefore exhibiting Lewis basicity, or the acceptance of such a pair from a solute, an exhibition of Lewis acidity of a protic or protogenic solvent towards the formation of a hydrogen bond between it and... 

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