Donor atom sets tridentate ligands

The number of tridentate ligands meeting the identification criteria is small. These ligands exhibit S3, S2N, or S2C donor atom sets and are summarized in Scheme 1. 

Schiff Bases as Acyclic Polydentate Ligands Table 8 Typical Tridentate Schiff Bases with Different Donor Atom Sets... 

As for V(III), trigonal prismatic complexes, and trigonally distorted octahedral complexes are not uncommon for V(IV) [56]. The ligand set exerts a stronger influence on the redox potentials, whether the coordination geometry is octahedral or trigonal prismatic, at least to a first approximation. A series of compounds made with tridentate and tetradentate ligands with N- and O-donor atoms such as the azophenol derivative shown in Fig. 8 has both reversible oxidations and reductions. 

Tridentate ligands of the linear type having donor sets P3, AS3 or P As3. t, where the donor atoms are connected by o-phenylene, ethylene or trimethylene chains, were found to form stable complexes with nickel(II) salts.1350 Listings of the most common ligands and nickel(II) complexes are given in Tables 67 and 68, respectively. 

Tridentate SB ligands having a NPO donor set, combining hard and soft donor atoms, are prepared either by reacting the appropriate (aminoalkyl)diphenylphosphine with sal16 (20, R = -CH2 (20a), -(CH2)3-, (20b), o-C6H4 (20c)), or by reacting 2-(diphenylphosphino)benzaldehyde... 

One role of spectator ligands is to block certain sites, say of an octahedron, to leave a specific set of sites available for the actor ligands so the desired chemistry can occur. These spectator ligands are commonly polydentate with the donor atoms arranged in specific patterns. A small sample of such ligands is shown in Fig. 1.10. The tridentate ligands can bind to an octahedron either... 

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