Synthesis of pure iron(II) mesotetraphenylchlorin complexes via a versatile general method of iron insertion into chlorins

Abstract

An original synthesis of pure (tetraphenylchlorinato)iron(III) chloride (1) is reported. Insertion of iron is achieved using 1.2 equivalents of cadmium acetate in DMF at 110°C, followed by a transmetallation reaction (in situ) using 8 equivalents of iron(II) chloride tetrahydrate in acetone at 60°C. The 1H NMR shifts at 25°C of the pyrrole protons varied from 60 to 100ppm. The absence of the signal at 80ppm related to undesired (tetraphenylporphirinato)iron(III) chloride is a purity criterion and shows the importance of the method used.Reaction of (tetraphenylchlorinato)iron(III) chloride (1) with four equivalents of tert-butyl isocyanide, 2,6-xylyl isocyanide and dimethylphenylphosphine in the presence of zinc amalgam in dichloromethane (DCM) afforded pure FeII(TPC)(t-BuNC)2 (2), FeII(TPC)(2,6-xylylNC)2 (3) and FeII(TPC)[P(Me)2Ph]2 (4) respectively.