Amines polydentate

L = aromatic amines, picolinic acids, picolinate N-oxido anions, dicarboxylic acids, O and N containing polydentate ligands etc. 

Figure 1.66 Gold(lll) complexes with polydentate amine complexes.

Zirconium(IV) and hafnium(IV) halides form adducts with a variety of monodentate and polydentate amines. Typical complexes are listed in Table 3. In general, these compounds are air- and moisture-sensitive white solids (yellow when the halide is iodide), thermally stable and insoluble in most organic solvents. 

Polydentate amines, diethylenetriamine, triethylenetetramine and facultative ligands... 

Finally, polydentate ligands can affect the geometry of a complex merely as a result of their own steric requirements. For example, we find some tetradentate ligands such as tris(2-dimethylaminoethyl)amine, [Me6tren = ((CHj NCHjCH N], form only five-coordinate complexes (Fig. 12.10), apparently because the polydentate ligand cannot span a four-coordinate tetrahedral or square planar complex and cannot conform ( fold ) to fit a portion of an octahedral coordination sphere. 

Numerous nickel(II) complexes with a variety of polydentate amines have been described. Selected examples of such complexes are collected in Table 42. In general, solid complexes have been easily obtained by direct synthesis from nickel salts and the appropriate ligand using H20, MeOH, EtOH or butanol as reaction medium. Most of the complexes with the fully TV-alkyl-substituted ligands are conveniently prepared under anhydrous conditions. 

NEW POLYDENTATE Mo(VI) - GRAFTED POLY(AMIDO AMINE) RESINS AS HETEROGENEOUS EPOXIDATION CATALYSTS... 

The design of polydentate ligands containing imines has exercised many minds over many years, and imine formation is probably one of the commonest reactions in the synthetic co-ordination chemist s arsenal. Once again, the chelate effect plays an important role in stabilising the co-ordinated products and the majority of imine ligands contain other donor atoms that are also co-ordinated to the metal centre. The above brief discussion of imine formation will have shown that the formation of the imine from amine and carbonyl may be an intra- or intermolecular process. In many cases, the detailed mechanism of the imine formation reaction is not fully understood. In particular, it is not always clear whether the nucleophile is metal-co-ordinated amine or amide. Some intramolecular imine formation reactions at cobalt(m) are known to proceed through amido intermediates. A particularly useful intermediate (5.24) in metal-directed amino acid chemistry is... 

Myriad polydentate aza-macrocycles have been reported 41. The extent of the subject forces limitation of this discussion to only macrocycles containing a pyridine or dipyridine subunit. Most of these coronands have been synthesized by a SchifF base condensation of an aldehyde or ketone with a hfc-primary amine in the presence of a metal ion. The metal ion acts as a template, resulting in dramatic increases in yield of the desired cyclic product over linear polymerization products42 46. Lindoy and Busch45 have described this effect in two ways, kinetic and thermodynamic. If the metal ion controls the steric course of a series of stepwise reactions, the template effect is considered to be kinetic. If the metal ion influences an equilibrium in an organic reaction sequence by coordination with one of the reactants, the template effect is termed thermodynamic. It is the kinetic effect that is believed to be operative in most metal ion-assisted (in situ) syntheses of... 

We consider here the remarkably small number of complexes of osmium with primary and aromatic amines RNH2 all these involve phosphines as coligands. For complexes of pyridine and its analogues see p. 533 complexes of polydentate amines are considered in the sections which follow this one (p. 534). 

---