Reaction of μ-oxobis(phthalocyaninatoiron(III)) in pyridine/water. Evidence for a slow reacting oxophthalocyaninatoiron(IV) compound

Abstract

The reaction of μ-oxobis(phthalocyaninatoiron(III)) in pyridine containing small amounts of water has been investigated. The reaction occurs in two consecutive steps. The first step is a disproportionation equilibrium ( K = 1.0×10 −3 mol dm −3 at 35 °C) yielding [(py) 2Fe(II)(pc)] and the ferryl compound [(py)Fe(IV)(pc)O]. The spectrum of the latter in the 600–700 nm range shows the shape characteristic of phthalocyaninato derivatives with a high intensity Q band ( ϵ = 7.5 × 10 4) at 670 nm. During the succedding step, that requires several hours to be completed, the FeO oxygen is transferred to peripheral sites of the macrocycle, very likely to form C-OH groups. This fact does not modify appreciably the electronic properties of the complex, if compared to those of [(py) 2Fe(pc)], and can be revealed only by FAB experiments which show the presence of phthalocyaninato derivatives of mass 568 + 16 and 568 + 32 (568 being the mass of the molecular ion [Fe(pc) +]. The first step of this reaction representes a convenient method for preparing pyridine solutions of the ferrylic species, suitable for reactivity studies.