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........ published in NEWSLETTER # 46

ENERGETICS OF ORGANOMETALLIC SPECIES
by Professor J.A. Marinho Simoes, Instituto Superior Tecnico, Lisboa (Portugal)

Thermochemical data are essential for the definition of energy profiles of chemical reactions or, in other words, for the prediction of kinetic and thermodynamic stability of molecules and molecular fragments. A wealth of energetic data (enthalpies of formation and bond dissociation enthalpies) has emerged in the last 15 years and has had a considerable impact on many areas of chemistry. Progress has been particularly noteworthy for organometallic species but the virtually infinite variety of combinations of metals with inorganic and organic ligands makes the already sizeable thermochemical data bank appear rather small for our needs. It is thus not surprising that the present research efforts in organometallic thermochemistry are stronger than ever, as reflected by a significant increase both in the number of publications and in the number of new groups working in this area.

Most techniques for probing the energetics of chemical bonds have been designed to tackle a relatively narrow range of problems and to deal with a given class of molecular species (saturated compounds, radicals, gas-phase ions, etc.). Each one of these techniques involves a number of assumptions that are important to understand, not only to assess the experimental results but also to use them correctly. This point may seem somewhat trivial, since it is common to many fields of science, but it is particularly important in the area of thermochemistry, where the diversity of experimental methods is large. Situations where an expert on a given technique is not aware of the capabilities of another, often complementary, technique, are not uncommon. More abundant are, of course, the cases where the non-specialist or even the advanced student lacks the required information to decide which method should be used to solve a particular problem.

The preceding paragraphs summarise the motivation for organising the NATO- ASI held in Curia, Portugal, in September 1991, and for editing the book under the above title. This book (NATO ASI SERIES C367) addresses a number of relevant questions in the field, such as (1) Why has the energetics of organometallic species became an area of recognised importance?; (2) What methods are available to obtain information on reaction enthalpies and bond `strengths'?; (3) What other methods are likely to be used in the future?; (4) Is the present thermochemical data bank satisfactory for our needs?; (5) How accurately can we estimate the energetics of organometallic reactions?; (6) Can theory offer reliable help?; (7) Which are the main problems to be tackled by the experimentalist? Some answers are provided by many of the leading scientists in the area of organometallic thermochemistry.

Reference books: B198, C67, C119, C155, C189, C193, C367, C385, E141, E206

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