Complexes central atom concepts

A metal sandwich compound does not strictly fit our previous concept of an ABfl-type molecule, since the ligand atoms interact strongly with each other as well as with the central atom. It is desirable to extend the discussion to these molecules, however, since they provide clear and important examples of how to treat the situation in which the ligands in a complex are themselves polyatomic entities with an internal set of MOs perturbed by interaction with the AOs of the central atom. 

Truly, the redox reaction concept in its simplest form, transfer of one or several electrons between two species, is much easier to apply to the central atoms of inorganic complexes and relatively simple covalent inorganic compounds with their well-defined oxidation states than to the carbon atoms of organic molecules. Nevertheless oxidation states of the latter can be defined using very simple rules (see, e.g. Hendrickson et al., 1970) and immediately reveal the possible redox nature of any transformation at a carbon atom. It is also true that redox mechanisms other than electron transfer—hydrogen atom or hydride transfer, oxygen transfer, displacement, etc.—should by their very... 

The concept of hypervalent bonding is assumed to decrease the electron density on the central silicon atom upon complexation. 

Electron counting in transition metal complexes (18 e rule) is an useful tool to understand their stability and structure, although it does not apply to all transition metal complexes—only for a majority of compounds containing 7i-acceptor ligands. The 18 electron rule is an extension of the idea of the octet rule, which applies to atoms having only s and p orbitals. The idea is that the molecule will be stable when the central atom has the same electronic structure as noble gases of the same row. A similar concept can be applied to transition metal complexes having d electrons. The compound is considered most stable when the total number of electrons around the atom becomes the... 

One focus of the book is the hydroformylation process, the process involved in the first commercial implementation of aqueous-phase catalysis with its detailed descriptions of fundamental laws, special process features, and the present state of the art. Further focal points of the book are basic research on the complex catalysts (central atoms, ligands) and on the influence of the reaction conditions, solvents, and co-solvents, and a survey of other aqueous two-phase concepts and of proposed applications, with experimental examples and details. Environmental aspects are also considered. 

In most coordination compounds it is possible to identify a central or core atom or ion that is bonded not simply to one other atom, ion or group through a coordinate bond, but to several of these entities at once. The central atom is an acceptor, with the surrounding species each bringing (at least) one lone pair of electrons to donate to an empty orbital on the central atom, and each of these electron-pair donors is called a ligand when attached. The central atom is a metal or metalloid, and the compound that results from bond formation is called a coordination compound, coordination complex or often simply a complex. We shall explore these concepts further below. 

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