Coordination chemistry crystal field theory

COLOR AND MAGNETISM IN COORDINATION CHEMISTRY CRYSTAL-FIELD THEORY (sections 23.5 and 23.6)... 

Kettle, S. F. A. (1969). Coordination Chemistry. Appleton, Century, Crofts, New York. A good introductory book that presents crystal field theory in a clear manner. 

Note to the student The AP chemistry exam does not emphasize complex ions or coordination compounds. There is nothing on the AP exam that involves the concepts of crystal-field theory, low versus high spin, valence bond theory, or other related areas. If you understand the questions presented here, then you are basically "safe" in this area of the exam. Most high school AP chemistry programs do not focus much on this area of chemistry because of time constraints. 

The model that largely replaced valence bond theory for interpreting the chemistry of coordination compounds was Ihe crystal field theory, first proposed in 1929 by Hans Bethe.11 As originally conceived, it was a model based on a purely electrostatic... 

Chapter 11 Coordination Chemistry Bonding, Spectra, and Magnetism 387 Bonding in Coordination Compounds 391 Valence Bond Theory 391 Crystal Field Theory 394 Molecular Orbital Theory 413 Electronic Spectra of Complexes 433 Magnetic Properties of Complexes 459... 

The crystal chemistry of many transition metal compounds, including several minerals, display unusual periodic features which can be elegantly explained by crystal field theory. These features relate to the sizes of cations, distortions of coordination sites and distributions of transition elements within the crystal structures. This chapter discusses interatomic distances in transition metal-bearing minerals, origins and consequences of distortions of cation coordination sites, and factors influencing site occupancies and cation ordering of transition metals in oxide and silicate structures, which include crystal field stabilization energies... 

Crystal field theory was developed, in part, to explain the colors of transition-metal complexes. It was not completely successful, however. Its failure to predict trends in the optical absorption of a series of related compounds stimulated the development of ligand field and molecular orbital theories and their application in coordination chemistry. The colors of coordination complexes are due to the excitation of the d electrons from filled to empty d orbitals d-d transitions). In octahedral complexes, the electrons are excited from occupied t2g levels to empty Cg levels. The crystal field splitting Ao is measured directly from the optical absorption spectrum of the complex. The wavelength of the strongest absorption is called Amax and it is related to Ao as follows. E = hv, so Ao = hv = Because en-... 

The failure of crystal field theory and VB theory to explain the spectrochemical series stimulated the development of ligand field theory, which applies qualitative methods of molecular orbital theory to describe the bonding and structure of coordination complexes. The terms ligand field theory and molecular orbital theory are often used interchangeably in inorganic chemistry today. 

One of the best sources is G. Wilkinson, R. D. Gillard, and J. A. McCleverty, editors. Comprehensive Coordination Chemistry, Pergamon Press, Elmsford, NY, 1987 Vol. 1, Theory and Background, and Vol. 2, Ligands, are particularly useful. Others include the books cited in Chapter 4, which include chapters on coordination compounds. Some older but still useful sources are C. J. Ballhausen, Introduction to Ligand Field Theory, McGraw-Hill, New York, 1962 T. M. Dunn, D. S. McClure, and R. G. Pearson, Crystal Field Theory, Harper Row, New York, 1965 and C. J. Ballhausen and H. B. Gray, Molecular Orbital Theory, W. A. Benjamin, New York, 1965. 

Werner s coordination theory, with its concept of secondary valence, provides an adequate explanation for the existence of such complexes as [Co(NH3)6]Cl3-Some properties and the stereochemistry of these complexes are also explained by the theory, which remains the real foundation of coordination chemistry. Since Werner s work predated by about twenty years our present electronic concept of the atom, his theory does not describe in modem terms the nature of the secondary valence or, as it is now called, the coordinate bond. Three theories currently used to describe the nature of bonding in metal complexes are (1) valence bond theory (VBT), (2) crystal field theory (CFT), and (3) molecular orbital theory (MOT). We shall first describe the contributions of G. N. Lewis and N. V. Sidgwick to the theory of chemical bonding. 

Solvent extraction of metals embodies all aspects of coordination chemistry rates, equilibria, stereochemistry, crystal field theory, covalent bonding, hard-soft acid-base theory, hydrogen bonding, steric hindrance, enthalpy and entropy. All of these basic principles can link together to produce pure metals on an industrial scale from dilute aqueous solutions — a remarkable achievement of elegant coordination chemistry. To achieve this result it is only necessary to form within the aqueous medium a neutral species containing the metal to be extracted. 

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