Iron porphyrin, coordinative groups types

The last three of these D, E, and F) take account of the negative charges resulting from the loss of the two protons by the porphyrin as a result of coordination with iron, and the last represents an ionic bond of the type discussed in the case of the cyanide linkage. It is evident that there must certainly be a substantial reduction in the formal charge transferred to the ferrous ion by the six coordinated groups from the maximum value of —6 possibly to as little as —3, which would make the net formal chaise of the iron —1. 

In iV-confused porphyrins, this agostic coordination mode has been observed frequently. To date, monomeric complexes of this macrocycle with divalent manganese (35, 26), divalent iron (36, 29), lanthanides (57), rhodium carbonyl (55), and group 12 elements (34), have been structurally characterized that exhibit this peculiar type of metal binding. A generic structure for several of... 

Structure 5.17. Tetraphenylporphyrin Iron(III) chloride, with basket-handle of the picket-fence type with secondary amide groups in close vicinity to the porphyrin ring. Reprinted from Structure 16 J. Costamagna, G. Ferraudi, J. Canales and J. Vargas, Carbon dioxide activation by aza-macrocychc complexes, Coordination Chemistry Reviews 148 (1996) 221-248. Copyright 1996, with permission of Elsevier. 

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