2,2 ,6 ,2"-Terpyridyl , as ligand

The Chemistry of Complexes Containing 2.2 -Bipyridy 1, 1,10-Phenanthroline, or 2.2. 6. 2"-Terpyridyl as Ligands W. R. McWhinnie and J. D. Miller Olefin Complexes of the Transition Metals... 

THE CHEMISTRY OF COMPLEXES CONTAINING 2,2 -BIPYRIDYL, 1,10-PHENANTHROLINE, OR 2,2, 6, 2"-TERPYRIDYL AS LIGANDS... 

Tricapped trigonal prismatic is the most familiar example of nine-coordinate geometry, adopted for the [Ln(H20)9] + ions of all lanthanides in a number of crystalline salts. It is also found in a number of chlorides LnCls (Ln = La-Gd) and bromides LnBrs (Ln = La-Pr). This geometry is also sometimes adopted where polydentate ligands are involved, such as the [Ln(terpy)3] + ion (terpy = 2,2 6 ,2 -terpyridyl see Figure 4.7). 

Complexes of the lanthanides with the rather similar terdentate hgands 2,2 6, 2"-terpyridyl (terpy), 2,4,6-tris-2-pyridyl-l,3,5-triazine (tptz), 4-amino-bis(2,6-(2-pyridyl))-1,3,5-triazine (abptz), and related ligands have been studied iu cousiderable detail aud uumber, as these terdentate N-donor ligands are efficient in separating actinides from lanthanides selectively by solvent extraction, of obvious relevance to processing nuclear waste. 

For the better part of two decades, the chemistry of self-assembled systems containing lanthanides has been dominated by hehcate systems [20, 21]. Simple tridentate ligands such as 2,6-dipicolinate, terpyridyl and 6-(diaminocarbonyl)-picolinic acid form stable and luminescent triple helicate complexes in water [21-24]. Polymetallic chelates can be assembled by using related ligand structures that can bridge between two metal centres. 

Kinetic studies of the reaction of a CH2S(CH2)3SCH2-linked bis-terpyridyl ligand (bterpy) with [Fe(terpy)2] revealed a very slow two-step process. The mechanism suggested consists of slow loss of one terpy, rapid formation of [Fe(terpy)(bterpy)], and finally slow displacement of the second terpy as the partially bonded bterpy becomes hexadentate. " Replacement of the 2,4,6-tri(2 -pyridyl)-l,3,5-triazine, 2,4,6-tptz (66), in [Fe(2,4,6-tptz)2] " " by phen or bipy is alleged to occur by an associative mechanism. ... 

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