Coordination compounds ligand field theory

Development of Coordination Chemistry Since 1930 Coordination Numbers and Geometries Nomenclature of Coordination Compounds Cages and Clusters Isomerism in Coordination Chemistry Ligand Field Theory Reaction Mechanisms... 

According to these principles, carbon ionization requires the loss of four electrons. In ionization, a coordination complex called a ligand may be formed in which a molecule or an ion donates a pair of electrons to a metal atom and ligands attach to the central ion electrostatically. For example, in (PtCU) " with four Cl ions are coordinated with the central Pt + ion. Such coordination compounds (and the lone pair the electron ligands donate) play a key role in defining the structural properties of metal complexes and ligand field theory has evolved to study their properties. 

Symmetry has a major role in two widely used and successful approaches of chemistry, viz., the crystal field and ligand field theories of coordination compounds. This topic has been thoroughly covered in textbooks and monographs on coordination chemistry. Therefore, it is mentioned here only in passing. 

Coordination Organometalhc Chemistry Principles Electronic Structure of Main-group Compounds Electronic Structure of OrganometaUic Compounds Electronic Structure of Clusters Ligand Field Theory Spectra Molecular Orbital Theory Symmetry Point Groups. 

Pauling used his valence bond approach to explain differences in magnetic behavior among coordination compounds by use of either 3d or 4d orbitals of the metal ion. Griffith and Orgel developed and popularized the use of ligand field theory, derived from the crystal field theory of Bethe and Van Vleck ° on the behavior of metal ions in crystals and from the molecular orbital treatment of Van Vleck. Several of these approaches are described in Chapter 10, with emphasis on the ligand field theory. 

In the following pages, the valence bond theory and the crystal field theory are described very briefly to set more recent developments in their historical context. The rest of the chapter describes the ligand field theory and the method of angular overlap, which can be used to estimate the orbital energy levels. These two supply the basic approach to bonding in coordination compounds for the remainder of the book. 

Use ligand field theory to order the energy levels in coordination compounds and to account for the spectrochemical series (Section 8.7). 

The application of organometallic compounds in medicine, pharmacy, agriculture and industry requires the accurate determination of these metals as part of their application. Most % complexes characterised by direct carbon-to-carbon metal bonding may be classified as organometallic and the nature and characteristics of the n ligands are similar to those in the coordination metal-ligand complexes. The -complex metals are the least satisfactorily described by crystal field theory (CFT) or valence bond theory (VBT). They are better treated by molecular orbital theory (MOT) and ligand field theory (LFT). There are several uses of metal 7i-complexes and metal catalysed reactions that proceed via substrate metal rc-complex intermediate. Examples of these are the polymerisation of ethylene and the hydration of olefins to form aldehydes as in the Wacker process of air oxidation of ethylene to produce acetaldehyde. 

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