Ligands encapsulating

Tricresyl phosphate, 11 493, 494 Tricyanocuprate(I), 7 578t Tricyanovinyl dyes, 9 258 Tricyclic encapsulating ligand, tetraprotonated form of, 24 44 cis,lrares-Tricyclodecanediamine physical properties of, 2 500t Tricyclohexyl citrate... 

The tris-hydroxamate encapsulating ligand (278) can be assembled by high dilution acylation of (279) with X = NHOBz by (279) with X = COCl, followed by removal of the benzyl protecting... 

Lanthanide Complexes of Encapsulating Ligands at Luminescent Devices... 

Sabbatini, N. Guardigli, M. Lehn, J.-M. Luminescent lanthanide complexes as photochemical supramolecular devices. Coord. Chem. Rev. 1993,123, 201-228. Sabbatini, N. Guardigli, M. Manet, I. Lanthanide complexes of encapsulating ligands as luminescent devices. Adv. Photochem. 1997, 23, 213—278. 

The encapsulating ligand with N4S2 donors (L,0) was prepared, and it coordinated to Ni(II) to give an octahedral complex (46). 

Reactions of this type are widely used for the preparation of encapsulating ligands (see Chapter 7). 

Although we approached this section in terms of kinetically inert metal centres, it is also possible to build such encapsulating ligands about relatively labile metal ions. For example, although the square-planar nickel(n) complex 7.2 may be formed, this can react with an excess of dimethylglyoximedihydrazone and formaldehyde to give the nickel(n) analogue of 7.3. 

Encapsulating Ligands from More Than Two Components... 

The reactions discussed above are akin to those we considered in the early part of Chapter 6 and involve only two different types of reactant. In the final parts of the previous chapter, we illustrated the power of metal ions in building macrocyclic ligands from a variety of components in programmed, stepwise reactions. Can we apply the same principles to the assembly of encapsulating ligands ... 

Figure 7-11. A cartoon representation of the multi-component assembly of an encapsulating ligand. The white disc represents a pre-formed cap within the starting ligand and the shaded disc the new cap that has been built from a number of components. For example, in the ligand 7.9, the shaded cap is built from three formaldehyde molecules and a nitromethane molecule.

Figure 7-15. Some reactions of cobalt(m) diamsar. The nitro groups of the ligand may be reduced to amino groups, which may then be diazotised and converted to halogen substituents. Throughout these conversions, the cobalt ion remains within the encapsulating ligand.

Some Mechanistic and Stereochemical Aspects of Sepulchrates and Related Encapsulating Ligands... 

Good reviews on the synthesis and properties of encapsulating ligands. 

The different products which are obtained due to hydroxybenzyl migration can be trapped by metal complexation. The thus formed trivalent, N403-encapsulating ligand adopts a pentagonal bipyramidal geometry at the ytterbium center with two aryloxide oxygens in the axial positions. 

In addition to the cryptates, which are synthesized apart from metal ions and then used to form complexes, there are other types of multicyclic ligands called encapsulating ligands, which are synthesized around the metal ion and cannot release it. Complexes of this sort are sometimes called sepulchrates. Two of these are (1-XXIII) and (1-XXIV). An encapsulation complex allows studies to be carried out under extremely acidic or basic conditions since the metal ion, though it cannot be removed, can be oxidized or reduced. Such ligands also can enforce unusual coordination geometries in the examples shown the coordination is much closer to trigonal prismatic than to octahedral. 

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