Oxygen-nitrogen chelates

The presence of functional groups containing oxygen-, nitrogen-, and phosphorus-chelating heteroatoms does frequently have regiochemical consequences in the... 

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... 

When K[PtX(acac)2] (X = Cl, Br) is treated with a strong proton add the uncoordinated 0,0 site is protonated and complex (170) is formed.1606,1607 If the alkyl groups on the 0,0 -bonded acac ligand are non-equivalent, exchange can be observed. Although the mechanism has not been definitively proven, a dissociative mechanism is favored.160 This proposal correlates with the observations that the 0,0 -bonded chelate complex Pt(acac)2 will react with tertiary phosphines and nitrogen bases with substitution of one of the oxygen-bonded chelate arms.1609,1610 A variety of products are formed as outlined in Scheme 17. 

Oxygen donors to copper(II) are nearly as frequent in occurrence as nitrogen donors (Table 79). They have a lower tendency to form oxygen chelate ligands, compared to the nitrogen chelates (Section 53.4,9.3), but adequately compensate for this limitation in the occurrence of hydrates and oxygen donors in oxyanions (see Chapter 15.5). 

There are many hundreds of published reports on the use of achiral lanthanide tris(/3-diketonates) as NMR shift reagents. Essentially any substrate with an oxygen, nitrogen or sulfur atom is a potential candidate for analysis with lanthanide shift reagents. These include sulfur- and phosphorus-containing functional groups that have oxygen atoms. Carboxylic acids and phenols were observed to decompose lanthanide chelates of dpm, whereas solutions with chelates of fod were stable for several days and suitable for study. 

---