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Metal–Organic Frameworks and Self-Assembled Supramolecular Coordination Complexes: Comparing and Contrasting the Design, Synthesis, and Functionality of Metal–Organic Materials

A wide array of forms of palladium has been utilized as precatalysts for Heck and Suzuki coupling reactions over the last 15 years. Historically, nearly every form of palladium used has been described as the active catalytic species. However, recent research has begun to shed light on the in situ transformations that many palladium precatalysts undergo during and before the catalytic reaction, and there are now many suggestions in the literature that narrow the scope of types of palladium that may be considered true “catalysts” in these coupling reactions. In this work, for each type of precatalyst, the recent literature is summarized and the type(s) of palladium that are proposed to be truly active are enumerated. All forms of palladium, including discrete soluble palladium complexes, solid-supported metal ligand complexes, supported palladium nano- and macroparticles, soluble palladium nanoparticles, soluble ligand-free palladium, and palladium-exchanged oxides are considered and reviewed here. A considerable focus is placed on solid precatalysts and on evidence for and against catalysis by solid surfaces vs. soluble species when starting with various precatalysts. The review closes with a critical overview of various control experiments or tests that have been used by authors to assess the homogeneity or heterogeneity of catalyst systems.

On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review

Artificial Organic Host Molecules for Anions

https://dr.ntu.edu.sg/bitstream/10356/96770/1/30.%20Application%20of%20Layered%20Double%20Hydroxides%20for%20Removal%20of%20Oxyanions.pdf

Application of layered double hydroxides for removal of oxyanions: A review

Recent Developments in the Preparation and Chemistry of Metallacycles and Metallacages via Coordination

Physical Factors in Anion Separations (B. Moyer & P. Bonnesen). Historical View on the Development of Anion Coordination Chemistry (B. Dietrich & M. Hosseini). Natural Anion Receptors: Anion Recognition by Proteins (S. Mangani & M. Ferraroni). Artificial Anion Hosts: Concepts for Structure and Guest Binding (F. Schmidtchen). Structural and Topological Aspects of Anion Coordination (J. Atwood & J. Steed). Thermodynamics of Anion Complexation (A. Bianchi & E. Garcia-Espana). Electrochemical Aspects of Anion Chemistry (A. Carbo). Photochemistry and Photophysics of Supramolecular Systems Containing Anions (L. Moggi & M. Manfrin). Anion Binding Receptors: Theoretical Studies (J. Wiorkiewicz-Kuczera & K. Bowman-James). Application Aspects Involving the Supramolecular Chemistry of Anions (J. Sessler, et al.). Supramolecular Catalysis of Phosphoryl Anion Transfer Processes (M. Hasseini). Index.

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Supramolecular chemistry of anions

A series of macrocyclic receptors were designed to probe the influence of four factors, hydrogen bonding, charge, dimensionality, and topology, on anion binding. Monocyclic and bicyclic polyammonium and polyamide receptors were synthesized from either 2,2‘-diaminodiethylamine derivatives (dien) or 2,2‘,2‘ ‘-aminoethylamine (tren) building blocks, plus aromatic or heterocyclic spacers. Supramolecular complexes of these hosts with three simple anion topologies were probed:  spherical (halides), trigonal planar (nitrate), and tetrahedral (sulfate). Results indicate a number of corollaries with transition-metal coordination chemistry in terms of binding concepts such as the chelate effect and dual valencies, as well as geometries for anion complexes that are strikingly similar to those observed in transition-metal coordination chemistry.

Alfred Werner Revisited: The Coordination Chemistry of Anions

Anion recognition is an active area of research in supramolecular chemistry. The rapidly increasing amount of structural data now allows anion coordination chemistry to be formalized in terms of coordination numbers and geometries based on hydrogen-bonding interactions between the host (ligand) and the guest (anion). This Minireview targets just one class of anion receptors, namely, amide-based ligands. The structural data for a series of five anion shapes are compiled according to coordination number, and distinct commonalities are observed within a given anion topology. The results also indicate a number of similarities between the coordination of anions and transition-metal ions.

Amide-based ligands for anion coordination.

Ammonium based anion receptors

The design of supramolecular hosts for anions began with simple diaza bicycles, named katapinands, and has evolved over the last 40 years to a number of elegantly designed receptors capable of binding many different anions. About the same time the term cryptand appeared in reference to another bicyclic compound that was selective for alkaline-earth ions. Since the first report these simple bicycles, a vast arena of hosts has appeared, including acyclic, monocyclic, and other multicyclic supramolecular receptors. Studies of these systems have revealed considerable information about anion coordination chemistry, including the fact that many of these complexes mimic their transition-metal corollaries in terms of coordination numbers. However, for anions interactions occur via H-bonding most often, rather than the coordinate covalent or dative bonds observed in transition-metal coordination. This critical review examines the design of enclosed, primarily bicyclic cryptands as hosts for anions, with a small scattering of higher polyhedra when deemed appropriate to the discussion. In order to show the development (evolution) of the field, key examples of early work will be noted and compared with more recent developments (136 references).

Kristin Bowman-James

Papers

Supramolecular chemistry of anions

Alfred Werner Revisited: The Coordination Chemistry of Anions

Amide-based ligands for anion coordination.

Ammonium based anion receptors

Cryptand-like anion receptors