Metal template reaction

Metal template reactions, 1, 416, 433 equilibrium kinetic, 1, 434 thermodynamic, 1, 434 Metal tolerance amino acid complexes, 2, 964 plants, 2, 963 Metal toxicity... 

The structures of the dihydro-octa-aza[14]annulene complexes (149) have been reported. The second example of single macrocycles capable of encompassing two metal atoms has been published. The complexes (150) and (151) have been prepared by metal template reactions of acetone and... 

Probably the most important effect contributed by metal coordination to ligands is stereochemical in nature. Because of the rather strict coordination geometry imposed by metal ions, ligands can be held in suitable juxtaposition for reactions to take place between them. This phenomenon is the hallmark of metal template reactions and is also a crucial feature of metal enzyme reactions, where high specificity occurs. 

Simple a-diimines are hydrolytically unstable, but can be stabilized as metal complexes by virtue of the formation of stable five-membered chelate rings.68 69 a-Diketones and glyoxal undergo metal template reactions with amines to yield complexes of multidentate ligands such as (34),70 (35)71 and (36).72>73 In the last case, the metal exerts its stabilizing influence on the a-diimine partner in an equilibrium process (Scheme 5). The same phenomenon occurs with amino alcohols74 75 in addition to amino thiols. The thiolate complexes (37) can be converted to macrocyclic complexes by alkylation in a kinetic template reaction (Scheme 5).76 77... 

Template reactions between malonaldehydes and diamines in the presence of copper(II), nickel(II) or cobalt(II) salts yield neutral macrocyclic complexes (equation 15).99-102 Both aliphatic102 and aromatic101 diamines can be used. In certain cases, non-macrocyclic intermediates can be isolated and subsequently converted into unsymmetrical macrocyclic complexes by reaction with a different diamine (Scheme ll).101 These methods are more versatile and more convenient than an earlier template reaction in which propynal replaces the malonaldehyde (equation 16).103 This latter method can also be used for the non-template synthesis of the macrocyclic ligand in relatively poor yield. A further variation on this reaction type allows the use of an enol ether (vinylogous ester), which provides more flexibility with respect to substituents (equation 17).104 The approach illustrated in equation (15), and Scheme 11 can be extended to include reactions of (3-diketones. The benzodiazepines, which result from reaction between 1,2-diaminobenzenes and (3-diketones, can also serve as precursors in the metal template reaction (Scheme 12).101 105 106 The macrocyclic complex product (46) in this sequence, being unsubstituted on the meso carbon atom, has been shown to undergo an electrochemical oxidative dimerization (equation 18).107... 

A key review of metal templated reactions in macrocyclic chemistry. Although it is a little old, it contains a great deal of interesting material. 

Metal templated reaction of P-ketoiminato complexes with 1,2-diaminoethane (en)... 

Fe(en)3]Cl2 (en = ethylenediamine) The complex forms when, under anhydrous and anaerobic conditions, an excess of ethylenediamine is added to a solution of iron(II) chloride in ethanol. The product may be condensed with acetone, producing a tetraazacyclotetradecadiene macrocycle by way of a metal template reaction (88). [Fe(en)3]Cl3 is produced in a similar manner by reacting anhydrous iron(III) chloride with ethylenediamine (89). 

The significance of the counteranion in metal template reactions has received little attention. Where reactions are carried out in solvents with low polarities and low dielectric constants, namely, most organic solvents, the effectiveness of the metal template ion will be related to its availability in solution, i.e., dissociation of the salt. For the Li+ ion in the template synthesis of XII, the order of yields, LiC104 > LiCl > Li2S04 (27, 115), has been correlated with the dissociation energies of the salts (115). 

More versatile reactions are being discovered in metal-templated reactions involving C-N bond formation.21-23 Co-condensation of formaldehyde, nitroethane and the aminothioether 26 in the presence of copper(II) yields an intermediate di-imino nitro macrocycle. Subsequent dissolving metal reduction with zinc in HC1 yields the saturated aza-thia macrocycle 27 in which the hydroxy group and amino groups are /rani-related (Scheme 3.10).22,23... 

Figure 5.11 A metal templated reaction (a) the reaction in the absence of ions (b) the reaction in the presence of Ni ions...

Black, D. S. C., Srivastava, R. C. Metal template reactions. I. Benzilic acid rearrangement of dipyridylglyoxal compounds promoted by nickel(ll) and cobalt(ll) ions./tust. J. Chem. 1969, 22, 1439-1447. 

The generality of the rearrangement is further illustrated by the reaction of 2,2 -furil with hydroxide ion in dry ether (Table 1). Likewise, 2,2 -pyridil is rearranged in hot methanol solution (40 min) to give the sodium salt of 2,2 -pyridilic acid (86%). Acidification, however, affords bis(2-pyridyl)methanol by decarboxylation since 2,2 -pyridilic acid (16) is structurally similar to a -keto acid. Benzilic rearrangement of 2,2 -pyridil with methanolic nickel(ll) and cobalt(II) acetates results in the formation of metal complexes of 2,2 -pyridilic acid (17 92%). A plausible mechanism is summarized in Scheme 4. Rearrangement is also observed with 2,2 -quinaldil, but benzil, 2,2 -furil or 1-phenyl-2-(2 -pyridyl)ethane-1,2-dione are not susceptible to these metal template reactions. 

Mercury, tris(l,10-phenanthroline)-structure, 64 Mercury(II) complexes masking agent, 536 Mercury electrodes potential range aqueous solution, 480 Metal carbonyls structure, 16 Metallocenes nomenclature, 126,127 Metallochromic indicators, 554 Metallofluorescent indicators, 558 Metallothionein proteins, 142 Mettd-metal bonding, 137,169 gravimetry, 525 history, 21,23 nomenclature, 122, 123 Metal nitrosyls structure, 16 Metal-phthalein metallochromic indicator, 557 Metal template reactions, 416,433 equilibrium kinetic, 434 thermodynamic, 434 Methane, dichloro-... 

Metal template reactions may be defined as reactions involving ligands which require, or can be significantly enhanced by, a particular geometrical orientation imposed by co-ordination to a metal. Many metal template reactions have resulted in the synthesis of macrocyclic compounds, such... 

Tetradentate and pentadentate macrocyclic systems based on o-aminobenzaldehyde and its derivatives can be obtained by metal-template reactions of diaminodicarbonyl compounds with diamines (Scheme 2-24(a)), and also by interaction of monoaminodicarbonyl compounds with primary diamines containing additional supporting nitrogen atoms in the chain (see Scheme 2-24(b)) [391],... 

For example, meso-tetraaryltetrabenzoporphyrin zinc complex results from heat treatment of the corresponding 3-benzylidenisoindolinone with zinc benzoate l Appropriately substituted methine and azomethine isoindolinones featuring substructure 24 were also converted into stable metal chelate pigments of general structure 26 via a metal template reaction with aromatic and heterocyclic a-hydroxy aldehyde or ketone hydrazone derivatives incorporating the structural element 25 . ... 

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