The interaction of (chloro)-μ-nitrido-bis[(tetra-tert-butyl-phthalocyaninato)iron(IV)] Cl(FePc)2N with organic N-bases L as electron–donors (L = diethylamine, imidazole, 1-methylimidazole, 2-methylimidazole) with the formation of one-electron reduced species (L)PcFeIII–N=FeVIPc(L) was investigated in benzene at 298 K by UV-visible spectroscopy. The reaction was established to be stepwise process including fast reversible axial binding of two substrate molecules onto iron cations followed by slow one-electron metal-centered reduction. The results of IR, ESI-MS and EPR study support the formation of final product with Fe+3–N=Fe+4 unit and two substrate molecules in the first coordination sphere. The reaction kinetics was studied, the pre-equilibrium constants Keq and rate constants k were obtained. The Keq and k values were found to be linearly correlated with basicity of substrates pKa. The possibility of the transition Fe4+ → Fe3+ is promoted by electron–donor properties of substrate combined with the presence of both electron-rich macrocycle and π-backdonation Fe ← NPc.
