Adventures in the Coordination Chemistry of Di‐2‐pyridyl Ketone and Related Ligands: From High‐Spin Molecules and Single‐Molecule Magnets to Coordination Polymers, and from Structural Aesthetics to an Exciting New Reactivity Chemistry of Coordinated Ligands

Abstract

The coordination chemistry of di-2-pyridyl ketone and related ligands is reviewed. An outline of the variety of such ligands is presented. References are given to methods for the synthesis of ligands that are not available on the market. The activation of the carbonyl group(s) of some of the ligands towards further reactions seems to be an emergent area of synthetic inorganic chemistry. The coordination chemistry of each ligand with metals is briefly described. Emphasis is placed on structural features and physical properties (mainly magnetic) of the resulting metal clusters and coordination polymers. The structural diversity of the complexes stems from the ability of the deprotonated diol-or hemiketal-type Organization of This Microreview and General InformationThis Microreview presents a focused overview of the coordination chemistry of ligands with the general formulae X-CO-X, X-CO-Y, X-CO-CO-X, and X-CO-X-CO-X, where X and Y are donor groups. We mainly describe the polynuclear metal complexes (clusters) and coordination polymers that have derived from the use of these ligands and the organic chemistry of their metal complexes. From the viewpoint of properties, emphasis is placed on the magnetism of the metal complexes. Much of the chemistry, both published and unpublished, that is reported comes from our group; however, detailed reference to all appropriate work by others is provided. The Microreview aims not to be comprehensive in terms of a discussion of every known cluster or coordination polymer containing a ligand derived from the above-mentioned molecules; rather, it aims to provide [ ‡] ligands to adopt a variety of bridging coordination modes depending on the number of carbonyl groups, the nature of the extra donor groups in the molecule and on the reaction conditions. Employment of a second organic or inorganic ligand in this chemistry gives an extraordinary structural flexibility in the resulting mixed-ligand systems. The initial use of 1,1Ј-carbonyldiimidazole and 1,1Ј-oxalyldiimidazole in copper(II) chemistry, which leads to unprecedented coordination polymers containing alcoholysis and/or hydrolysis "fragments" of the ligands, is also illustrated.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) the reader with some idea of the range of chemistry that has been carried out (and indeed remains still to do) with these ligands. The article contains eight sections, including this one. The next section is introductory: the reader can find brief, general information on the two classes of compounds that are frequently mentioned in this Microreview, namely metal clusters and polymers, as well as a short discussion of the organic chemistry of metal complexes, which is currently a popular topic in inorganic chemistry. The last part of Section 2 provides a "hors d'oeuvre" of the ligands that are discussed in detail in Sections 3-7. Section 8 provides initial conclusions and perspectives for future research. Sections 2 and 3 are divided into parts for clarity. The organization of this ...

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