Macrocyclic ligands metal complexes

Some macrocyclic ligand anions and macrocyclic ligand metal complexes have also been intercalated in LDHs. For example, 5,10,15,20-tetra(4-sulfona-tephenyl)porphyrin anion is inserted into the interlayer by replacing Cl in a MgAl-HT (238). The gallery height (1.76 nm) is very close to the side length of the almost perfect square molecule of this porphyrin (1.80 nm), and thus the... 

Numerous metal complexes have been proven to be active electrocatalysts for C02 reduction.1,66-68 These catalysts can be conveniently grouped into three main families metal complexes with polypyridyl ligands, metal complexes with macrocyclic ligands, and metal complexes with phosphorus ligands. 

A typical example is seen in the addition of hydrogen cyanide to an imine to yield a cyanoamine (Fig. 4-29). Many of these reactions have been used to best advantage in the synthesis of macrocyclic ligands and complexes, and as such are considered in Chapter 6. A simple example of such a reaction is seen in the addition of HCN to the cobalt(m) complex indicated in Fig. 4-30. The starting complex is also readily prepared by a metal-directed reaction. 

Catenands (17) are interlocked macrocyclic ligands, which complex a variety of metal ions. ... 

Coordination OrganometalUc Chemistry Principles Electron Transfer Reactions Theory Macrocyclic Ligands Metal Ion Toxicity Oxides Solid-state Chemistry Polynuclear Organometallic Cluster Complexes Sulfur Organic Polysulfanes Thallium Organometallic Chemistry. 

Karakhanov s group has also been exploring poly(ethylene oxide)- and poly(alkene oxide)-copolymer-bound catalysts [99-102]. A notable aspect of this work is the design of polyethers like 39 that contain jS-cyclodextrins and calyx[4]- and calyx[6]arenes. Such polyethers couple the molecular recognition associated with these macrocycles with the catalytic activity of acac, phosphine, dipyridyl, and catechol ligands. Metals complexed to such ligands have been used in reactions like hydroformylation, Wacker oxidations, and arene hy-droxylation. 

Ogden, M. Spencer, P. New polyaza and polyammonium 33. ferrocene macrocyclic ligands that complex and electro-chemically recognize transition metal cations and phosphate anions in water. Chem. Commun. 1993, 13, 1046. 

BRIDGED MACROCYCLIC TRANSITION METAL COMPLEXES WITH MACROCYCLIC LIGANDS... 

Coordination chemistry of metalloporphyrins is a very large research field. The porphyrin macrocyclic ligand forms complexes with all transition metals, with many main group metals and many lanthanides. Metalloporphyrins easily bind various ligands in the axial positions above and below the porphyrin plane. The number of publications in the field amounts to several thousands a year. Fortunately, several review articles and monographs help manage this enormous research area. ... 

Novel electron-transfer reactions mediated by alkali metals complexed with crown ethers as macrocyclic ligands 98ACR55. 

The spectra and structure of transition metal complexes with tetradentate macrocyclic ligands. K. B. Yatsimirskii and Y. D. Lampeka, Russ. Chem. Rev. (Engl. Transl), 1980, 49,1003-1020 (191). 

A. W. Johnson Transition metal complexes of macrocyclic ligands, pp. 101-132 (83). 

The simple porphyrin category includes macrocycles that are accessible synthetically in one or few steps and are often available commercially. In such metallopor-phyrins, one or both axial coordinahon sites of the metal are occupied by ligands whose identity is often unknown and cannot be controlled, which complicates mechanistic interpretation of the electrocatalytic results. Metal complexes of simple porphyrins and porphyrinoids (phthalocyanines, corroles, etc.) have been studied extensively as electrocatalysts for the ORR since the inihal report by Jasinsky on catalysis of O2 reduction in 25% KOH by Co phthalocyanine [Jasinsky, 1964]. Complexes of all hrst-row transition metals and many from the second and third rows have been examined for ORR catalysis. Of aU simple metalloporphyrins, Ir(OEP) (OEP = octaethylporphyrin Fig. 18.9) appears to be the best catalyst, but it has been little studied and its catalytic behavior appears to be quite distinct from that other metaUoporphyrins [CoUman et al., 1994]. Among the first-row transition metals, Fe and Co porphyrins appear to be most active, followed by Mn [Deronzier and Moutet, 2003] and Cr. Because of the importance of hemes in aerobic metabolism, the mechanism of ORR catalysis by Fe porphyrins is probably understood best among all metalloporphyrin catalysts. 

Fig. 18. Plot of change in complex stability, Alogf , that occurs for the pairs of ligands cryptand-2,2,2 and EN ( ), and 18-aneN204 and EN (O), as a function of metal ion radius (20). The diagram shows how neutral oxygen donors tend to stabilize the complexes of large relative to small metal ions in macrocyclic ligands. Data from Ref. (11).

Complex formation between a metal ion and a macrocyclic ligand involves interaction between the ion, freed of its solvation shell, and dipoles inside the ligand cavity. The standard Gibbs energy for the formation of the complex, AGjv, is given by the difference between the standard Gibbs... 

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