Polyamine ligands

Crystal stmcture data are available for an indole—trinitroben2ene complex (2) and for the lithium and sodium salts in the presence of polyamine Ligands (3). The crystal stmcture of indole itself is evidendy disordered (4). Table 1 gives the and C-nmr assignments in CDCl (5). C-nmr assignments have been tabulated for many other indole derivatives (6). 

Open chain polyamine ligands have been widely studied. Often the coordination of zinc is compared with other first row transition metals and factors, such as behavior across a pH range, studied. The protonation patterns and stability constants are of particular interest. Octahedral zinc tris(ethylenediamine) structures have been characterized by X-ray diffraction with a number of different counter anions.94 The X-ray structure of zinc tris(ethylenediamine) with fluoride counter ions reveals extensive hydrogen bonding.95... 

Although the vast majority of this review has been concerned with homogeneous systems, supported catalyst and single-crystal studies of rhodium are important topics that have also been considered by some researchers. This topic extends and dovetails nicely with the discussion of the interactions of acyclic and cyclic polyamine ligands and Schiff... 

Most systems considered in this section contain bridging oxo- or hydroxo ligands with water occupying the non-bridging sites, but recent developments in this area also involve ammonia and polyamine ligands... 

Other structural features that have acceleratory influences in the base hydrolysis of Co(III) systems are (i) the incorporation of a pyridine ligand in the coordination sphere and (ii) the incorporation of a flat secondary nitrogen donor system in the polyamine ligand skeleton (5) (structures C and D in Fig. 17). 

All the linear triamines (27)-(31) are commerically available and there are others, such as 6,6-tri, which, as yet, do not appear to have been used in the preparation of coordination complexes. These linear polyamine ligands can coordinate in either meridional or facial topology and both bis(tri-amine) and mono(triamine) complexes are possible for octahedral central metal ions. 

Table 9 Linear Tridentate Polyamine Ligand Configurations in M(triden-...

Scheme 3 Topological forms for linear N4 polyamine ligands in an octrahedral complex...

Polyamine ligands such as (118)-(120) which contain terminal aniline residues have also been reported.896-898... 

Nucleophilic reactions, in particular ligand replacement by EDTA and polyamine ligands, readily occur with Ni and Cu11 peptide complexes, the most reactive nucleophiles being those that contain an amine group to give an associative-type intermediate. The presence of histidine as the third residue in a peptide appears to reduce the susceptibility of Cu complexes to nucleophilic attack. 

With most metal ions the complex stability decreases as the size of the chelate rings formed by open-chained polyamine ligands increases from five to six membered. Examples of this effect are presented in Table 8.1, where experimental data are com-... 

Pu(IV) and Am(III) at the appropriate denticity can be achieved. The polyamines used have been linear or aromatic polyamines or cyclic polyamines. For the linear polyamines ligand (29) is separated by 3 and 4 methylene units or 3, 4 and 3 methylene units, thus resulting in the acronyms 3,4-LICAM254), 3,4-LICAMC260) and 3,4-LICAMS261), (30, 3,4,3-LICAMC, R as in 29). Alternatively various cyclic polyamines were used e.g., (31, R as in 29) which leads to an acronym series CYC AM257). 

The pH-dependent reactivity of 25 and 26 resembles that of related complexes with other polyamine ligands (55) and may be summarized as follows The peroxo complexes may be transformed into the dinuclear superoxo complexes plus a mononuclear halo species by addition of a suitable acid. In aqueous alkaline solution (pH > 12), the peroxo complexes are stable over several hours, whereas the superoxo complexes will react immediately even with dilute aqueous ammonia to reform the peroxo complexes. 

Only a handful of reports on iron(II) and iron(III) complexes of opertrchain aliphatic polyamine ligands had previously existed in... 

Macropolycyclic polyamine ligand (a form of cryptand leading to extremely inert metal ion complexes)... 

There are also systematic trends in stability constants when frve-memberedpolyamine rings are replaced by six-membered rings, or when linear polyamine ligands are replaced by macrocyclic ligands of a similar strain see Chelate Effect). These effects can be well accounted for in terms of enthalpy contributions to the formation constant. ... 

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