Lewis acid-base properties

Senanayake, G. (2012). Gold leaching by copper(II) in ammoniacal thiosulphate solutions in the presence of additives. Part I A review of the effect of hard-soft and Lewis acid-base properties and interactions of ions. Hydrometallurgy, 115-116, 1-20. doi 10.1016/j. hydromet.2011.11.011... 

It is hoped that the terms donor and acceptor strengths will be reserved for inferences made about Lewis acid-base properties from data in the gas phase or poorly solvating solvents. This is to be contrasted with the more complex phenomena contributing to acidity and basicity. 

The Lewis acid-base properties of these ionic liquids are determined by the chloroaluminate species. The equilibrium of the chloroaluminate liquid is primarily described by two equilibria at x AICI3 below 0.67 ... 

The ligand of a metal complex and the solvent molecule compete with each other, as Lewis bases, to interact with the central metal ion. At the same time, the metal ion and the solvent molecule compete with each other, as Lewis acids, to interact with the ligand. Thus, the behavior of a metal complex is easily influenced by the Lewis acid-base properties of solvents. In an aprotic solvent, which is of weak acid-... 

Most ions constituting ionic liquids can be categorized according to their Lewis acid/base properties (i.e., their capability to accept or to donate an electron pair) nevertheless, some ions may be considered according to the Bronsted definition, i.e., on the basis of their ability to accept or donate a proton. Typical ionic liquids are those based on neutral or very weakly basic anions (BF4, PF, NOf, CHsSO, 4 f2N ) and neutral (tetraalkylammonium, dialkyl-pyrrolidium, trialkylsulfonium) or weakly acidic cations (1,3-dialkylimidazolium and 1,2,3-trialkylimidazolium) (Figure 4.1). 

Strategy I. Redox non-innocent ligands used to modify the Lewis acid-base properties of the metal... 

We discussed the Lewis acid-base properties of hydrated metal ions, which are a type of complex ion, in Section 18.8, and we examined complex-ion equilibria in Section 19.4. In this section, we consider the bonding, structure, and properties of complex ions. 

The Lewis acid-base properties of zeolites received a growing interest recently. A series of works " suggested that the infrared and XPS spectra of adsorbed pyrrole can characterize both the Lewis basicity and the Lewis acidity of alkali-exchanged zeolites. The zeolite base strength decreases with an increase in Si/AI ratio of the framework, and increases when the electropositivity of the counter alkali cation is raised. The Lewis acid strength of counter cations increases with Si/AI ratio and decreases with electropositivity. In other words, the alkali-exchanged zeolites have both Lewis acid and Lewis base centres and provide an easy way to tune up the relative strengths of these two sites. 

The model of Krygowski and Fawcett [Kr 75], developed for the description of the solvent effect and taking into account exclusively the Lewis acid-base properties of the solvent, also appears suitable for the description of the solvent dependence of the chemical shift. For example, this model reflects well the results of the Na resonance studies by Erlich et al referred to earlier [Er 70, Er 71, Gr 73]. In addition to the interaction between the sodium ion and the solvent, it also points to the dependence of the chemical shift on the concentration as a result of ion-pair formation. However, the authors themselves [Fa 76] reported that the model was unsuitable for the description of other NMR data reflecting the solvent effect. 

Oxides, especially those of Al, Si, Fe, and Mg, are essential components of the earth s minerals their surface sites may have either Bronsted or Lewis acid-base properties. The weathering of rocks and the formation of soils are processes at the solid/liquid interface between minerals and natural waters or solutes from the medium in which solid phases are either formed, altered, or dissolved. Dissolution of solid minerals is controlled by slow surface reactions rather than... 

The extent of association can vary with the nature of the organic groups attached to the metal, probably because of electronic influences which modify the Lewis acid-base properties of the metal. Thus, /7-nitrophenyl trithiastibocane molecules assemble into dimers only, 173 [431]. 

The catalytic activities were found to be well correlated with the Lewis acid-base properties. UIO-66-NH2 showed the highest catalytic activity among the investigated MOFs-based materials with a maximum of 96% Ygj, obtained at 100°C, 20 bar after 4 h in the presence of chlorobenzene as solvent. Nevertheless the contribution of homogeneous reaction cannot be excluded in this case. 

Isosteric and the closely related isoelectronic relationships are still widely used by inorganic chemists as an effective predictor of new molecules [109]. These isoelectronic relationships provide a good guide to the occurrence and structures of the predicted molecules, although the variation in the charges of the ions can influence their Lewis acid/base properties and their redox properties. Table 3... 

Lewis acid-base properties of polar condensed-phase... 

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