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Stereochemical configuration is determined by the relationship of atoms in three dimensional space, yet remains most commonly represented in two-dimensional media such as printed publications or computer screens. Recommendations are provided for the display of three-dimensional stereochemical information in two-dimensional diagrams in ways that avoid ambiguity and are likely to be understood correctly by all viewers. Examples are provided for all types of stereochemical configuration, with explanation of which styles are preferred and which should be avoided. Principal recommendations include:
- Know your audience: Diagrams that have a wide audience should be drawn as simply as possible.
- Avoid ambiguous drawing styles.
- Avoid the use of perspective diagrams and class-specific drawing styles (Fischer projections, Haworth projections, etc.) when structures are to be interpreted by computers.
- Use solid wedges to indicate bonds that project above the plane of the paper and hashed wedges to indicate bonds that project below the plane of the paper; in both cases, the bonds must be oriented with the narrow end at the stereogenic center.
- Avoid connecting stereogenic centers with a stereobond.
Pure Appl. Chem., Vol. 78, No. 10, pp. 1897–1970, 2006
IUPAC Recommendations 2006
© 2006 IUPAC
IUPAC permission is acknowledged
Abstract
Until 1960, catalysts based on coordination compounds were little used and they were mainly employed on the laboratory scale. Since then, however, there has been a rapid emergence of new catalytic systems, mainly due to developments in Organometalic Chemistry, due in large part to the use of organometallic complexes (and / or coordination compounds) in three industrially important reactions: the Ziegler, Wacker and Oxo processes. Appropriate combinations of ligands (electronic and stereo effects) strongly influence the structure and the reactivity of catalytically active complexes. With the increasing knowledge of the coordination chemistry, in particular Organometalic Chemistry, it is possible to get the exact structure of the complex which will catalyze a reaction. Nowadays, the use of “clean” chemical reactions is a requirement, not only in the chemical industry, but also in the laboratory. By using highly efficient and selective catalysts it is possible to save energy and raw material, which is the case of complexes of transition metals. In order to understand catalysis by transition metals it is necessary to know the chemistry of the complexes involved: organic reagents are primarily coordinated to the metal as ligands (i.e., are activated) and are then converted to products through various types of reactions. It is therefore necessary to review some fundamental aspects such as structure, binding and reactions of metal complexes to better understand the phenomena involved in catalysis.
Keywords
catalysis, catalysts, catalytic systems, coordination compounds, organometallic compounds, ligands, coordination sphere, chemical structure, chemical bonds, metal complexes
Author
Regina Buffon
Universidade Estadual de Campinas, Instituto de Química
Translated by
João C. de Andrade
Revised by
Carol H. Collins
