Iron porphyrins migrations

Diazoalkanes are u.seful is precursors to ruthenium and osmium alkylidene porphyrin complexes, and have also been investigated in iron porphyrin chemistry. In an attempt to prepare iron porphyrin carbene complexes containing an oxygen atom on the /(-carbon atom of the carbene, the reaction of the diazoketone PhC(0)C(Ni)CH3 with Fe(TpCIPP) was undertaken. A low spin, diamagnetic carbene complex formulated as Fe(TpCIPP)(=C(CH3)C(0)Ph) was identified by U V-visible and fI NMR spectroscopy and elemental analysis. Addition of CF3CO2H to this rapidly produced the protonated N-alkyl porphyrin, and Bit oxidation in the presence of sodium dithionitc gave the iron(II) N-alkyl porphyrin, both reactions evidence for Fe-to-N migration processes. ... 

Iron-porphyrin model reactions have been reported for several steps of metabolic oxidation of sydnones by cytochrome P450 [52,96]. Thus, diazoketones react with iron(II) porphyrins to give iron carbene complexes and then AT-alkylporphyrins after a one electron oxidation. In this case, a migration of the carbene moiety to the pyrrole nitrogen atom is observed (Scheme 10) [97]. Similar results were obtained with PhCH2CHN2 [53]. 

A.L. Balch (1981). Reversible migration of an axial carbene ligand into an iron-nitrogen bond of a porphyrin Implications for high oxidation states of heme enzymes and heme catabolism. J. Am. Chem. Soc. 103,4271-4273. 

Also, many new aryl porphyrine high- and low-spin iron complexes were obtained. The aryl group may migrate from the iron metal to the nitrogen atom. 

The reactions of cytochrome P450cam with aryldiazenes (ArN=NH) yield cr-bonded iron-aryl complexes, whose oxidation causes regioselectivc migration of the aryl group from the iron to the porphyrin nitrogens. The influence of high pressure on the formation and rearrangement of these Fe-aryl complexes was studied. The aryls are stable at atmospheric pressure but decompose in a pressure-dependent manner at pressures above 1,500 (Fe-phenyl) or 2,500 bar (Fe-(2-naphthyl) or Fe-(/>-biphenyl)) under formation of the A-aryl protoporphyrin adducts. ... 

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