Template reaction kinetic

The kinetic template effect is observed in reactions in which the metal ion acts by coordinating the reactants. This effect has also been described as a coordination template effect. A more direct description of a kinetic template reaction is one which involves Combination of two Ligands Attached to the same. Metal ion. Such a description leads to the useful acronym CLAM reaction , which graphically portrays the key reaction step. The process can be generalized and compared with the non-template reaction in Scheme 30. 

Numerous kinetic template reactions have been employed in the formation of porphyrins, corrins and phthalocyanins (see Section 61.1.3). The most instructive examples from a mechanistic point of view are those employed by Eschenmoser and his coworkers in the formation of corrins and... 

The most dramatic formation of cages has been provided by kinetic template reactions of ligands attached to cobait(III). The deprotonated amine ligands undergo reaction with formaldehyde to produce bound imines which can be trapped by a variety of nucleophiles (Schemes 66 and 67).205-208 The synthesis of cages of this type will be considered further in Section 61.1.2. 

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... 

Cyclization of coordinated primary amines on to coordinated aminoacetone has also been investigated in bis(l,2-diaminpethane)cobalt(ni) complexes, and the results show selectivity with respect to attack of the monoamine or 1,2-diaminoethane (equation 38).218 A similar complex with two coordinated aminoacetone molecules undergoes the same type of stereoselective kinetic template reactions and yields complexes primarily of a new quadridentate ligand (Scheme 48).219... 

Define the terms "equilibrium template reaction and "kinetic template reaction as applied to reactions involving transition metal ions, giving an example of each. 

The term equilibrium template reaction is defined in Box 5.4, and an example is provided in Scheme 5.3, The term kinetic template reaction is defined in the margin note on page 93 and an example is provided in Scheme 5.4. 

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