Complexes of macrocyclic ligands

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

The study of the complexing of macrocycle ligands should be considered for its intrinsic importance rather than for its value in illuminating the mechanism of substitution. Kinetic (but much more thermodynamic °) data are available for the reactions of the different macrocycle ligand types, shown in Fig. 4.5, including azamacrocycles,crown ethers and cryp-tands, and porphyrins. ... 

Macrocyclic N-donor ligands. Nickel complexes of macrocyclic ligands have been studied by cyclic voltammetry, and the irreversible or quasi-reversible couples Ni" L Ni L Ni L have been established. The structure of (124) has been reported and the co-ordination is essentially square-planar with a slight tetrahedral distortion. The reaction of [Ni(pn)3] with... 

Cadmium complexes of macrocyclic ligands have not been as widely studied as the corresponding zinc complexes, but the fact that cadmium macrocycles undergo easy metal exchange should make them attractive subjects for future study. The crystal structure of [Cd(TPP)(dioxane)j and its 113CdNMR characteristics have been reported.1144 The formation... 

Template reactions between a-diketones and diamines have been used for the synthesis of complexes of macrocyclic ligands such as (38)78 and (39).79 Some insight into the mechanism of the formation of these macrocycles has been provided by some recent work which shows the value of the thermodynamic template effect (Scheme 6).80... 

The construction of suitable dialdehydes for macrocycle formation by metal template methods has more recently been extended to include a range of oxamides. In the first case, the simple 2,2 -(oxalyldiimino)bisbenzaldehyde underwent rather sluggish template reactions but yielded extremely stable macrocyclic complexes (Scheme 31).167 168 These products could be sulfonated in oleum, without destruction of the macrocyclic structure. This general synthetic route has been extended to include reactions of diketones and the formation of complexes of macrocyclic ligands such as (70) and (71). Attempts to incorporate a malonamide fragment in place of the oxamide... 

In addition to their thermodynamic stability, complexes of macrocyclic ligands are also kinetically stable with respect to the loss of metal ion. It is often very difficult (if not impossible) to remove a metal from a macrocyclic complex. Conversely, the principle of microscopic reversibility means that it is equally difficult to form the macrocyclic complexes from a metal ion and the free macrocycle. We saw earlier that it was possible to reduce co-ordinated imine macrocycles to amine macrocyclic complexes in order to remove the nickel from the cyclam complex that is formed, prolonged reaction with hot potassium cyanide solution is needed (Fig. 6-24). 

Template syntheses of complexes of macrocyclic ligands with the coordination units, containing N atoms, are examined in detail [316-318,322], An interesting example of... 

As well as in the above-described template reaction (3.168), the 2,6-diacetylpyridine is widely used for preparation of complexes of macrocyclic ligands having N,S-ligand environment [318]. An example of such syntheses is the reaction (3.173) ... 

Such syntheses are widely used for obtaining complexes of macrocyclic ligands [316-319]. For example, the interaction of metal acetylacetoniminates, containing electron-acceptor substituents in y-positions of the ligand, with ethylenediamine (3.180) [318,364-366] ... 

Complexation of macrocyclic ligands to lanthanide cations has been studied extensively [207,208], One main reason for the current interest in those macro-cyclic complexes are their intrinsic paramagnetic and luminescent properties. There is also the steadily increasing number of tailor-made macrocyclic ligands [209], This section will focus on complexes which contain macrocycles as discrete counterions and in particular on the coordination chemistry of phthalocyanine (Pc) and porphyrin (Por) ligands. Schiff base ligands which display another source of amine functionalities are usually not deprotonated under the prevailing reaction conditions [210]. 

Complexes of macrocyclic ligands known as tropocoronands (TC) have also been described.219 These were prepared by reaction of the Li2-ligand salt with the corresponding MC14. A variety of... 

Complexes of the Eu3+ and Tb3+ ions with different types of macrocyclic ligands have been obtained and their properties, in particular luminescence, have been reported by different authors [4, 15, 80-82]. For this class of complexes, we discuss only the complexes of macrocyclic ligands incorporating chromophores, since such ligands can play the role of antennas. Figure 11 schematically shows the macrocyclic ligands of the Eu3+ and Tb3+ complexes examined. Some photophysical data and the number of coordinated solvent molecules of these complexes are gathered in Table 2. 

Carbonyl Vibrational Frequencies and Carbon Monoxide Binding Constants for NickelII) Carbonyl Complexes of Macrocyclic Ligands... 

Preliminary kinetic results on cation exchange in cryptates [ligand (21)] show some correlation with thermodynamic parameters, but only go a small way towards the complete elucidation of the mechanism. Metal replacement in complexes of macrocyclic ligands is also illustrated by studies of several metalloporphyrins. ... 

Table 17. IR-, TG/DTA- and room temperature electrical conductivity data (powder, 1 kbar) for mono- and polynuclear cyano metal complexes of macrocyclic ligands...

The template synthesis of a number of complexes of macrocyclic ligands is carried out in protic media (Eq. 6.17 ). 

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