Schiff-base ligands cleavage

Clearly, for oral activity to be achieved, the chelator must also be designed so as to resist the acidity of the stomach and enzymatic cleavage. Thus esters, amides, Schiff-base ligands and simplex hydroxamates should be avoided. 

The Schiff base ligand prepared from pentafluorobenzaldehyde and 1,2-diaminobenzene reacted with [W(CO)3(EtCN)] to give [W°(CO)3(NI I2C6H4NCI IC6F5-A%V )(EtCN)] immediately and then the metallacycle [WlT (CO)3(NH2C6H4NCIIC6F4-A, , C )] by cleavage of a C—F bond. The cleaved fluoride atom coordinated to tungsten ion. 01... 

The stability of the D-I-I complex and the cleavage of the I-I bond depend on the donor activity of the ligand and the solvent. The formation of a complex between I2 and three pentadentate Schiff bases, 1,3-bis (salicylideneamino)-2-propanol, 1,3-bis (2-hydroxy-l-naphthylideneamino)-2-propanol, and 1,3-bis [l-(pyridine-2-yl) methylideneamino]-2-propanol results only in polarization of the I-I bond [13]. The formation of a complex between pyridine and molecular iodine (I2) leads to the polarization of the I-I bond in some non-polar solvents such as liquid alkanes and is accompanied by cleavage of the I-I bond in low-density polyethylene [14]. 

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