Multidentate ligands coordination polymers

Alternatively, bi- or multidentate ligands can also be used for support. As an additional benefit, the latter offer greater stability for the coordinatively bound metal center against leaching through ligand dissociation and substitution reactions. The first, somewhat remarkable, approach to this is shown in Figure 42.11, based on numerous examples of the support of bidentate phosphines on polymers [1-5]. 

Scheme 6 represents coordinate polymers. A low-molecular-weight compound with multidentate groups on both ends of the molecule grows into a linear polymer with metal ions, and the polymer chain is composed of coordinate bonds. The parquetlike polymer complexes, poly(metal-phthalocyanine) and poly(metal-tetracyano-ethylene), are classified into Scheme 7. They are formed by inserting metal ions into planar-network polymers or by causing a low-molecular-weight ligand derivative to react with a metal salt and a condensation reagent.

In the first step, a substrate coordinates to a metal catalyst and forms an intermediate mixed complex (LMS in Scheme 13). The substrate is then activated by metal ions and dissociates from the catalyst. The complex catalyst, having accomplished its purpose, is regenerated to the original complex. The catalytic action of a metal ion depends substantially on the nature of the ligands in the intermediate mixed complex. Certain ligands induce an increase in catalytic activity, while others, e.g. multidentate ligands such as ethylenediaminetetracetic acid, inhibit the catalytic action of a metal ion. Therefore, if a polymer ligand is used as one component of a metal-complex catalyst, its properties may affect the catalytic action of the metal ion. 

Coordination Polymers with N-containing Multidentate Aromatic Ligands... 

Multidentate ligands for transition metals based on 1,3,5-triazine still attract great attention. The leading position here belongs to 2,4,6-tris(pyridin-2-yl)-l,3,5-triazine 44. An interesting example is its application in bimetallic porous coordination polymers with spin-crossover properties, [Fe(44)2/3 M(CN)2 2] (M=Ag(I),Au(I)) (13CEJ6851). 

The synthesis, structures, and luminescence properties of polynuclear lanthanide complexes and lanthanide coordination polymers, which are formed from multidentate oxygen and nitrogen-containing Schiff-base ligands, are described in this chapter. 

Another strategy involving metal coordination reactions is shown in Scheme 13. In this case, the metal coordination reactions actually yield the metal-containing polymer (98). It can be seen that the reaction of a multidentate ligand (96) with a ruthenium complex (97) led to the formation of polymer 98 with the Ru atoms as an integral part of the polymer backbone. ... 

Argent SP, Adams H, Riis-Johannessen T, Jeffery JC, Harding LP, Clegg W, Harrington RW, Ward MD (2006) Complexes of Ag(I), Hg(I) and Hg(II) with multidentate pyrazolyl-pyridine ligands from mononuclear complexes to coordination polymers via helicates, a mesocate, a cage and a catenate. Dalton Trans 4996-5013... 

A multidentate ligand incorporating aromatic carboxylate and pyridine donors separated by a flexible spacer (Lg = 5-[(Pyridin-4-ylmethyl)-amino]-isophthalic acid) forms the coordination polymer, Mn(Lg)(H20)](H20)1.5(DMF) [57] in aqueous DMF under solvothermal condition. Each Mn(II) ion shows a distorted octahedral geometry with one water molecule bound to the metal (Figure 53). 

Fig. 10.1. Upper. Synthesis of multidentate polymer ligands with a balanced composition of thiol (—SH) and amine (—NH2) coordinating groups grafted to a linear polymer chain. Lower Procedures for achieving self-assembly of multidentate hgands...

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