Metals bases concept

The strength of the complexation is a function of both the donor atom and the metal ion. The solvent medium is also an important factor because solvent molecules that are potential electron donors can compete for the Lewis acid. Qualitative predictions about the strength of donor-acceptor complexation can be made on the basis of the hard-soft-acid-base concept (see Section 1.2.3). The better matched the donor and acceptor, the stronger is the complexation. Scheme 4.3 gives an ordering of hardness and softness for some neutral and ionic Lewis acids and bases. 

The subject is also closely related to fuel-ash corrosion which in most cases is caused by a layer of fused salts such as sulphates and chlorides Attention has been focused on the electrochemistry of this type of corrosion and the relevant thermodynamic data summarised in the form of diagrams . Fluxing and descaling reactions also resemble in some respects reactions occurring during the corrosion of metals in fused salts. A review of some of the more basic concepts underlying corrosion by fused salts (such as acid-base concepts and corrosion diagrams) has appeared. ... 

Concept A variety of metal-based chiral catalysts effect enantioselective chemical transformations that allow for concise and efficient synthesis of optically pure organic molecules. These transformations,... 

Classification of biologically important metal ions and ligands according to the hard-soft acid-base concept and their general characteristics... 

Solid surfaces lie at the interface of two historically distinct regimes. On the one hand, a surface can be thought of as a perturbation on a crystalline solid. Hence ideas based on the properties of condensed matter can be used to develop interaction potentials. For example, in a bulk metal the concept of a free electron gas is well developed, and simple potentials based on these ideas have been extended to include surfaces Unfortunately, these ideas are... 

When interaction between the metal-based components is weak, polynuclear transition metal complexes belong to the field of supramolecular chemistry. At the roots of supramolecular chemistry is the concept that supramolecular species have the potential to achieve much more elaborated tasks than simple molecular components while a molecular component can be involved in simple acts, supramolecular species can performIn other words, supramolecular species have the potentiality to behave as molecular devices. Particularly interesting molecular devices are those which use light to achieve their functions. Molecular devices which perform light-induced functions are called photochemical molecular devices (PMD). Luminescent and redox-active polynuclear complexes as those described in this chapter can play a role as PMDs operating by photoinduced energy and electron transfer processes. ... 

From 1720 on, the pages of the Paris Academy Memoires reveal an evergrowing practice of describing neutral salts in terms of the acid and the base they contain. In Hombergs work at the beginning of the century, the alkalies were almost the only base mentioned. Slowly the earths become important, as they took over the role of the Renaissance concept of matrix, the womb in which salts grow in the earth. The vitriols are recognized as neutral salts with a metallic base. 

In order to produce higher-order products, there has been a focus on transition-metal-based electrocatalysts containing multiple metal centers to facilitate multielectron transfers. This approach is based on the concept that a multielectron mechanism is required to produce highly reduced species [31], However, while multielectron charge-transfer catalysts have been demonstrated to affect the 2 e reduction of CO2 to CO and formate, more highly reduced products are only sporadically observed. 

Special catalysts have also been studied and developed for low-temperature and clean-gas applications They comprehend both metal-oxide-based and noble-metal-based catalysts and apply novel design concepts, as presented in a subsequent paragraph... 

TABLE 2.1 Classification of Biologically Important Metal Ions and Ligands According to the Hard—Soft Acid—Base Concept and their General Characteristics... 

Electrocatalysis in metallic corrosion may be classified into two groups Adsorption-induced catalyses and solid precipitate catalyses on the metal surface. In general, the bare surface of metals is soft acid in the Lewis acid-base concept and tends to adsorb ions and molecules of soft base forming the covalent binding between the metal surface and the adsorbates. The Lewis acidity of the metal surface however may turn gradually to be hard as the electrode potential is made positive, and the bare metal surface will then adsorb species of hard base such as water molecules and hydroxide ions in aqueous solution. Ions and molecules thus adsorbed on the metal surface catalyze or inhibit the corrosion processes. Solid precipitates, on the other hand, are produced by the combination of hydrated cations of hard acid and anions of hard base forming the ionic bonding between the cations and the anions on the metal surface. 

---