Schiff bases tetradentate

Structural aspects of metal complexes with some tetradentate Schiff bases. M. Calligaris, G. Nardin and L. Randaccio, Coord. Chem. Rev., 1972, 7, 385-403 (56). 

John E, Bott A, Green M. Preparation and biodistribution of copper-67 complexes with tetradentate Schiff-base ligands. J Pharm Sci 1994 83 587-590. 

The P-N chelate (91) (dapdmp) exhibits a variety of coordination geometries in complexes with divalent Co. Pseudotetrahedral Co(dapdmp)X2 (X = C1, Br, I, NCS), low-spin five-coordinate [Co(dapdmp)2X]+ (X = C1, Br, I), planar [Co(dapdmp)2]2+ and pseudo-octahedral Co(dapdmp) (N03)2 were all identified.390 The tetradentate P2N2 Schiff base complex (92) is formed by reacting the free ligand with CoI2. The iodo complex is low spin and square pyramidal.391... 

The ability of the ubiquitous Co(salen) complex and its tetradentate Schiff base analog complexes to bind 02 reversibly has been central to most investigations of its coordination chemistry. A density functional computational investigation has been carried out on the 02 carriers... 

A range of tetradentate Schiff-base ligands have also been employed to prepare discrete aluminum alkoxides. The most widely studied system is the unsubstituted parent system (256), which initiates the controlled ROP of rac-LA at 70 °C in toluene. The polymerization displays certain features characteristic of a living process (e.g., narrow Mw/M ), but is only well behaved to approximately 60-70% conversion thereafter transesterification causes the polydispersity to broaden.788 MALDI-TOF mass spectroscopy has been used to show that even at low conversions the polymer chains contain both even and odd numbers of lactic acid repeat units, implying that transesterification occurs in parallel with polymerization in this system.789... 

Table 3 Average Fe-donor atom bond lengths for Fe(III) compounds of tetradentate N202-donating Schiff base ligandsa,b,c,d... 

Five-Coordinate Complexes of Tetradentate N202-Donating Schiff Base Ligands... 

The use of appropriate tetradentate N202-donating Schiff base ligands (Fig. 14) together with the incorporation of the N-donating nitrosyl anion has resulted in the formation of a unique series of five-coordinate Fe(III) spin crossover materials containing FeN302 chromophores. 

Fig. 14 Tetradentate N202-donating Schiff base ligands. The use of NO as co-ligand yields FeN302 chromophores...

Fig. 15 Tetradentate N202-donating Schiff base ligands...

The most common tetradentate Schiff base ligands used are Salen (where H2Salen = A,A -ethylene-bis(salicylideneamine) and its derivatives (see (Figures 3, 18 and 19) for structures). 

Tetradentate, potentially triacidic Schiff base ligands with N2OS donor sets (type (134) with R = R = H R =-(CH2) NHC(0)CH2SH = 2-4)) react with [Re02(py)4]Cl or [ReOCl3(PPh3)2] under complete deprotonation and the formation of five-coordinate [ReO(L)] complexes when n = 2 or six-coordinate products of the compositions [ReO(L)(py)] or [ReO(L)(PPh3)] when n = 3 or 4. ... 

Planar tetradentate Schiff-base ligands are extremely common for VO(IV) complexes. The prototypal example, VO(salen), has been studied under a variety of conditions. Under nonaqueous acidic conditions the chemistry is complicated by dimerization driven by the release of water (Eq.4) [84]. 

Optically active Schiff-base oxovana-dium(IV) complexes catalyze the asymmetric oxidation of sulfides to sulfoxides by peroxides [86]. The catalytically active species is VO(V) rather than VO(IV) and is formed in situ under the reaction conditions. A series of related complexes based on the optically active ligand shown in Eig. 15 shows linear dependence of their oxidation Ef values on the Hammett parameters of functional group X. These values ranged from 0.18 V versus Cp2Ee/DMSO for X = NO2 to —0.18 V for X = OCH3 [87]. A few complexes of planar tetradentate non-Schiff base ligands have also been investigated [88]. 

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