Macrocycle kinetic

Such modifications can be produced either in the kinetic aspects (proton transfer) or in the equilibrium constant. Both effects are mediated by intramolecular hydrogen bonds. For instance, Navarro et al. (93MI69) showed that the rate of proton transfer between the two nitrogen atoms of pyrazole (annular tautomerism) is considerably reduced in macrocycles containing oxygen or nitrogen atoms in the macroring. 

Lamb, J. D., Izatt, R. M., Christensen, J. J., Eatough, D. J. Thermodynamics and Kinetics of Cation-Macrocycle Interaction, in Coordination Chemistry of Macrocyclic Compounds (ed. Melson, G. A.), p. 145-217, New York, Plenum Press 1979... 

Kinetics and mechanisms of substitution reactions of octahedral macrocyclic amine complexes. C. K. Poon, Coord. Chem. Rev., 1973,10,1-35 (130). 

It is appropriate to identify our approach to developing the present review in the context of the Co chapter in CCC(1987). The first-edition chapter on Co featured a focused discussion and tabulation of synthetic methods, and many of these basic methods are still employed in synthesis today. Consequently, to avoid repetition, there will be diminished description here where prior appropriate methods have been provided, and only newer developments featured. The last two decades feature the development of many mixed-donor and sophisticated multidentate and macrocyclic ligands, which found limited coverage in the previous edition, and these will be discussed in more detail herein. Reaction kinetics and mechanism were also described thoroughly in the previous edition. We shall not reiterate this material, since the core mechanisms of many reactions involving Co compounds are now adequately defined. 

Methylation of [Co(tmt)]2+ with Mel leads to the potent methyl carbanion donor trans-[Co(tmt)Me2]+ (186). Reaction of this complex with variety of methyl-lead(IV) compounds in MeCN is rapid, leading to the same monomethylcobalt(III) product, but resulting in different methylated Pb derivatives depending on the reaction stoichiometry and Pb compound.839 The same complex rapidly transfers Me groups to Zn2+ and Cd2+ in MeCN,840 or Pb2+ and Sn2+ in water.302,841 The kinetics of Co—C bond formation in the reactions with primary alkyl and substituted primary alkyl radicals has been found to be influenced more by the structure of the macrocycle than by the nature of the radicals.842... 

C-functionalization of azamacrocycles is in general more difficult to achieve than N-functional-ization. The latter has been developed to an extent that macrocycles carrying side chains with various ligating groups are accessible, and Ni11 complexes can be prepared with high selectivity and predisposition for high thermodynamic and kinetic stability. 

To gain insight into electron-transfer kinetics of copper(II/I) complexes of macrocyclic thioethers,446,447 Rorabacher and co-workers reported448,4 7 structures of five complexes (complexes (548)-(552)). 

Hawthorne and co-workers have also produced a series of macrocyclic Lewis acid hosts called mercuracarborands (156, 157, and 158) (Fig. 84) with structures incorporating electron-withdrawing icosahedral carboranes and electrophilic mercury centers. They were synthesized by a kinetic halide ion template effect that afforded tetrameric cycles or cyclic trimers in the presence or absence of halide ion templates, respectively.163 These complexes, which can bind a variety of electron-rich guests, are ideal for catalytic and ion-sensing applications, as well as for the assembly of supramolecular architectures. 

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