Schiff bases pentadentate

Mn2 (0)2(02)(Me3tacn)2] +, and [Mn2 0(E)2] with a Schiff-base pentadentate monoanionic ligand (F = N,N-bis(2-pyridyhnethyl)-iV -salicyliden-1,2-diaminoethane). The one-electron oxidized complex [Mn2 0(F)2] + has been electrochemically prepared and crystallized and is the only example of a structurally characterized mono-oxo bridged Mn2(III,IV) complex. 

S. Chandra, D. Jain, A. K. Sharma, and P. Sharma, Coordination modes of a Schiff base pentadentate derivative of 4-aminoantipyrine with cobalt(II), nickel(II) and copper(II) metal ions synthesis, spectroscopic and antimicrobial studies, Molecules, vol. 14, no. 1, pp. 174-190, 2009. 

Schiff bases provide useful mixed donor sets. The carbonyl function of the most frequently used ligands is derived from either 1,3-dicarbonyl compounds or salicylaldehyde. Favourable combinations involve O-, N- and S-donor atoms. A range of technetium and rhenium complexes exist with bi-, tri-, tetra- and pentadentate ligands. The geometry of these complexes depends on the number and type of coordinating atoms as well as on the chain length between the donor atoms in the SchifF-base ligands. 

In the only instances where spin crossover has been observed for a system involving a pentadentate ligand this has been an N302-donating Schiff base and the sixth coordination site has been occupied by a nitrogen donor, giving rise to an FeN402 coordination core. Most examples involve salten (Fig. 17). 

Fig. 17 Pentadentate N302-donating Schiff base ligands...

A high-spin manganese(II) complex of the sulfur containing, potentially pentadentate Schiff base derivative (218) has been reported. 

Fig. 6 A planar pentadentate SchifF-base that forms bimetallic complexes.

Figure 18 Some potentially pentadentate Schiff bases...

The potentially pentadentate Schiff bases of Figure 19a actually act as bis-tridentate ligands with respect to a single metal centre, giving dinuclear Cu11 complexes as in Figure 19b.132,133 Furthermore,... 

Figure 19 Some pentadentate Schiff bases (a) which act as bis-tridentate ligands in copper(ll) complexes (b) pentadentate...

A popular method for immobilizing Schiff base complexes involves covalent linking. Sutra and Brunei (85) constructed a pentadentate Schiff base in the pores of a mesoporous silicate, starting from grafted aminopropyl groups. After complexation with Mn, material 5 catalyzed the epoxidation of cyclohexene with PhIO in 58% selectivity. 

The trianion of a pentadentate Schiff base, 2-hydroxy-l,3-propanediylbis (acetylacetoneimine) (hpbaa), reacts with copper(II)... 

A number of similar trinuclear complexes were prepared with Mn(II) using the pentadentate macrocycle maodp as a planar blocking ligand. The reaction between [Mn°(maodp)(H20)2l and [Fe CN)6]" results in the neutral product [Mn maodp)(H20)]2[Fe CN)6] (101). As in the case of the complexes formed with Mn(III) Schiff base building blocks, the H2O molecule coordinated to each peripheral Mn(II) center is arranged trans to the bridging cyanide [Fig. 16(a)]. 

NMR and ESR studies have been carried out (72) on the O2 and CO adducts of the pentadentate Schiff base complex Co(salMeDPT) [11 ]. 

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