Attenuation of substituent effects on reactivities of low-spin iron(II) complexes of Schiff base ligands

Substituent effects on reactivity are compared for base hydrolysis of tris-ligand-iron(II) complexes of Schiff base ligands derived from 2–acetylpyridine and substituted benzylamines and their aniline analogues. The methylene spacer in the former effectively isolates the iron from substituent effects in the phenyl ring, as indicated by the almost equal rate constants for base hydrolysis of the complexes derived from benzylamine and its 4–methyl, 4–fluoro, and 4– trifluoromethyl derivatives. Rate constants for base hydrolysis of the (substituted) benzylamine derivatives are also reported for some Me2CO-H2O and DMSO-H2O solvent mixtures. Reaction is faster in all these binary aqueous mixtures, mainly due to the higher chemical potentials of hydroxide ion.