Macrocyclic nitrogen ligands

Complexes with larger macrocyclic nitrogen ligands 379... 

Silver(I) complexes with macrocyclic nitrogen ligands are also very numerous. Mono- or homodi-nuclear silver-containing molecular clefts can be synthesized from the cyclocondensation of functionalized alkanediamines or triamines with 2,6-diacetylpyridine, pyridine-2,6-dicarbalde-hyde, thiophene-2,5-dicarbaldehyde, furan-2,5-dicarbaldehyde, or pyrrole-2,5-dicarbaldehyde in the presence of silver(I).486 97 The clefts are derived from bibracchial tetraimine Schiff base macrocycles and have been used, via transmetallation reactions, to complex other metal centers. The incorporation of a range of functionalized triamines has provided the conformational flexibility to vary the homodinuclear intermetallic separation from ca. 3 A to an excess of 6 A, and also to incorporate anions as intermetallic spacers. Some examples of the silver(I) complexes obtained are shown in Figure 5. 

There are a number of Ni111 complexes with macrocyclic nitrogen ligands. They are usually made by one-electron oxidation of the Ni11 species the ring size and size of cavity in the macrocycles has an influence on the Nin/Niin redox potential. Some Ni111 macrocycles can also be oxidized to NiIv. A structurally characterized example of a Nim macrocycle is the deep purple complex (17-G-XV) which contains a square-planar NiN4 core.12... 

Complexes with macrocyclic nitrogen donor ligands 482... 

Complexes with Nitrogen Donor Ligands 63.5.2.1 Complexes with macrocyclic nitrogen donor ligands... 

Macrocycles attached to redox responsive groups such as ferrocene (78) can give selective transition metal ion receptors. The X-ray structure reveals a five-coordinate zinc with distorted square-pyramidal geometry bound to the four macrocycle nitrogens and an iodide. In the solid state the two ferrocenyl groups are positioned on the same side of the ligand with distances to the metal center of 5.347(7) and 6.120(8) A and these distances can be related to the redox behavior.689... 

Figure 6-13. The templated formation of a hydrazone macrocycle. This ligand contains five nitrogen donor atoms and was designed to investigate the properties of metal complexes containing a pentagonal planar donor set. In practice, the complexes of these ligands usually acquire one or two axial ligands to give six- or seven-co-ordinate complexes.

Oxidation of Organic Substrates Using Metal Centers With Macrocyclic Nitrogen and Oxygen Ligands, Including Porphyrins... 

Transition-metal systems with macrocyclic nitrogen and oxygen donors are more analogous to biological 02-oxidation centers than the more organometallic type systems considered thus far. Studies on the macrocyclic ligand systems follow earlier ones such as Udenfriend s systems (e.g., Fe(II)-EDTA), and the use of other transition-metal salts, sometimes with added ligands (43, 113). 

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