Kinetics of acid fission of substituted tris-[N-(2-pyridylidene)aniline]-iron(II) complexes

A series of tris-(Schiff base)iron(II) complexes has been prepared from pyridine-2-aldehyde and a variety of substituted anilines. Kinetics of acid fission of these complexes have been studied. Two reaction paths have been observed, one in which the rate of reaction is independent of acid concentration, the other in which the rate depends on the square of the acid concentration. In the first case acid fission takes place by simple iron–nitrogen bond breaking. The most likely mechanism for the second case involves protonation of two of the ligand molecules followed by rate-determining loss of the third ligand molecule.