Phenols coordination chemistry

Macrocyclic Schiff base compartmental ligands (750) (Robson-type ligands) derived from the [2 + 2] condensation of a 2,6-diformyl- or 2,6-diketo-substituted phenol and a diamine are very prominent in dinuclear Ni coordination chemistry.1901-1903 Particular interest lies in magnetic exchange interactions between the adjacent metal ions as well as in bioinorganic chemistry, where such dinuclear complexes have been proposed as synthetic analogues for bimetallosites. 

Figure 1. Ligands containing oxidizable dangling phenols. Their coordination chemistry is described in (3-13).

Figure 10. Coordination chemistry of ligands containing dangling phenols (138—141).

Due to the presence of hard anionic oxygen atoms, phenolate and carboxylate groups are often employed as donors in lanthanide coordination chemistry. Ligand [L18]4- is reported as an excellent triplet sensitizer for lanthanide luminescence (61). Indeed aqueous lifetimes of 0.57 and 1.61 ms are reported for europium and terbium, respectively quantum yields of 0.20 and 0.95 respectively refer to the efficiency of the energy transfer process alone. 

A broad application of phenolic Sehiff base ligands lies in the synthesis of heterobimetallic complexes. Extended functionalization of the L2 - ligand affords the so-called compartmental ligands which ensure rich coordination chemistry by accomodation of several metals [89, 146]. Some representative ligands are depicted in Fig. 25. 

The dinucleating ligand (58) has been prepared by standard methods via the bis-hydroxymethyl-ation of 4R-substituted phenols. It has been observed that modification of the R substituent induces a drastic effect on the catecholase activity of the dicopper(II) complexes containing (58) in the deprotonated form.85 A similar coordination pattern to those found in metal derivatives of (58) is realized in bis(triazacyclononane) systems bridged by a m-xylyl fragment (59)86 and in (60).87 /)-Xylyl ligands exhibit different coordination chemistry and reactivity 85... 

Much research have been focused on compartmental SB macrocycles derived from 2,6-diformyl (diacetyl)phenols as head units (see Scheme 19). The coordination chemistry of the phenol-based compartmental ligands was reviewed.2 A series of symmetrical and less extensively asymmetrical macrocycles (having dissimilar lateral chains) have been prepared (Scheme 19). The variation of the lateral chains of the macrocycle gives ligands with different cavity size and flexibility. Thus, the N202 cavity of the ethylenediamine derivative (65a) can accommodate only the small Cu11 and Ni11 ions because it has little flexibility. The replacement of the dimethylene by a trimethylene... 

In the hypervalent area of phosphorus chemistry a configurationally stable tris(tetrachlorobenzenediolato) phosphate ion has been synthesised. The growing importance of hydridophosphoranes in coordination chemistry has led to the apprearance of a useful review. The superbase properties of the commercially available proazaphosphatrane has been extended to the catalysis of the silylation of sterically hindered alcohols and phenols. 

Phosphorus(V) in its most stable oxidation state forms robust chelate complexes with the porphyrin, and retains the capability of binding two oxygen ligands in a frans-axial mode as outlined in Sect. 3. This strategy was used by Maiya [81,102-104] and Tanaka and Segawa [105]. The coordination chemistry of phosphorous(V) porphyrins is similar to germa-nium(IV), tin(IV), gallium(III), and aluminium(III) porphyrin coordination chemistry [102,106]. These metalloporphyrins were shown to form multiporphyrin complexes with phenol-substituted porphyrins. Because of the... 

Due to the presence of hard anionic oxygen atoms, phenolate and carboxylate groups are often employed as donors in lanthanide coordination chemistry. Ligand is reported as an excellent... 

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