Molecular Structures of Transition Metal Complexes

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Molecular structures of transition metal complexes of siloles and germoles show that the diene system is 7 -coordinated to the metal <1986OM910, 1987JOM(335)91, 1993CB1385, 20000M4720>. 

C.J. Ballhausen, Molecular Electronic Structures of Transition Metal Complexes, McGraw-Hill, New York, 1979. 

Molecular modelling of transition metal complexes (TMC), reproducing characteristic features of their stereochemistry and electronic structure, is in high demand in relation with studies and development of various processes of complex formation with an accent on ion extraction, ion exchange, isotope separation, neutralization of nuclear waste, and also when studying structure and reactivity of metal-containing enzymes. Solving these techno-... 

Ballhausen, C. J. Molecular Electronic Structure of Transition Metal Complexes McGraw-Hill New York, NY, 1979. 

A valuable approach toward the determination of solution structures is to combine molecular mechanics calculations with solution experimental data that can be related to the output parameters of force field calculations 26. Examples of the combination of molecular mechanics calculations with spectroscopy will be discussed in Chapter 9. Here, we present two examples showing how experimentally determined isomer distributions may be used in combination with molecular mechanics calculations to determine structures of transition metal complexes in solution. The basis of this approach is that the quality of isomer ratios, computed as outlined above, is dependent on the force field and is thus linked to the quality of the computed structures. That is, it is assumed that both coordinates on a computed potential energy surface, the... 

Ballhausen, CJ (1979) Molecular electronic structures of transition metal complexes. McGraw-Hill, London... 

B. A. Frenz and J. A. Ibers Molecular structures of transition metal hydride complexes, pp. 33-74 (111). 

As different the ligand field and AI approaches are, as different are the cultures of the respective proponents. It is very instructive to recall here a comment that Carl BaHhausen made in the preface of his wonderful book Molecular Electronic Structures of Transition Metal Complexes about the relation of LFT to microscopic first-principles physics Unfortunately the temptation is to elaborate an approximate theory and to introduce an increasing number of loosely defined effects in order to explain the movements of the parameters. .. there is little reason to expect that deeper insight can be gained in this way. ... 

Molecular Electronic Structures of Transition Metal Complexes II... 

Ballhausen s latest book [30], Molecular Electronic Structures of Transition Metal Complexes appeared in 1979, 25 years after his first article. It can be seen as his answer to the question What is a molecule - in particular a transition metal complex He starts with his conclusion from a series of articles on the chemical bond [31], Chemistry is one huge manifestation of quantum mechanics . He then introduces the Bom-Oppenheimer approximation as the basis for applying electronic and nuclear coordinates, and lets the picture of a molecule unfold itself with the concepts of electronic states, potential surfaces, transitions, vibronic couplings, etc. The presentation is traditional, but contains many refinings in the discussion of a molecule s ground state as well as its excited states. The world of transition metal complexes is favoured through the choice of examples. 

Molecular symmetry and ways of specifying it with mathematical precision are important for several reasons. The most basic reason is that all molecular wave functions—those governing electron distribution as well as those for vibrations, nmr spectra, etc.—must conform, rigorously, to certain requirements based on the symmetry of the equilibrium nuclear framework of the molecule. When the symmetry is high these restrictions can be very severe. Thus, from a knowledge of symmetry alone it is often possible to reach useful qualitative conclusions about molecular electronic structure and to draw inferences from spectra as to molecular structures. The qualitative application of symmetry restrictions is most impressively illustrated by the crystal-field and ligand-field theories of the electronic structures of transition-metal complexes, as described in Chapter 20, and by numerous examples of the use of infrared and Raman spectra to deduce molecular symmetry. Illustrations of the latter occur throughout the book, but particularly with respect to some metal carbonyl compounds in Chapter 22. 

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