Anionic nitrogen ligands

Substituted nitrogen donors to copper(II) are much less common (Table Anionic nitrogen ligands, such as nitrite (Table 78c),azide (Table cyanate... 

Figure 1.27 Structure of the anionic, bidentate nitrogen ligands [hpp] and [tbo] ...

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. 

Other anionic nitrogen-containing ligands which have been examined in the search for new non-metallocene catalysts include macrocyclic porphyrins and tetraazaannulenes. However, activities with these catalysts are low. 

Important aspects of the coordination chemistry of binary chalcogen-nitrogen ligands include (a) the ability of metals to stabilize labile neutral and anionic binary S-N ligands, (b) the applications of metal complexes as reagents for the preparation of other S-N compounds, and (c) the possible incorporation of metals into sulfur-nitrogen chains to produce conducting materials. 

In recent studies See et al. (1998) and Shields et al. (2000) suggest that Rq sometimes depends on factors other than the oxidation states of the cation and anion. To obtain correct bond valence sums around transition metals with nitrogen ligands, it is necessary to use different values of Rq depending on the coordination number of as discussed in Section 9.2. 

Analogous to the work on dipicolinic acid reported in Section 31.5.2, a range of titanium(IV) peroxo complexes (35) have been prepared which encompass an oxygen-nitrogen anionic chelating ligand and hexamethylphosphortriamide.171 The crystal structure of... 

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