Corrinoids metal complexes

The synthetic procedures leading to corrinoid metal complexes have been developed in order to use them as models of the biosynthetic pathway to Vitamin B12. Their chemical and structural properties were expected to be very similar to those of the natural coenzyme and this is probably the reason why very few detailed investigations on their spectroscopic or electrochemical features and their reactivity towards axial coordination have been carried out. 

Licoccia S, Paolesse R (1995) Metal Complexes of Corroles and other Corrinoids. 84 71-134 Lin Z, Fan M-F (1997) Metal-Metal Interactions in Transition Metal Clusters with n-Donor Ligands. 87 35-80... 

This group of compounds is widely found in nature as metal complexes in the chlorophylls, the haem groups of many iron proteins and the corrinoids. They have in common a macrocyclic structure which provides four N donor atoms at the comers of a square plane. Metal coordination to the N atoms results in the displacement of two H+ ions. An extremely important feature of these molecules is their extensive -electron delocalization. The complexation of these and synthetic analogues has been the subject of a number of texts.143-145 Some of these aspects are also covered by Dolphin (Chapter 21,1), and biological related properties by Hughes (Chapter 62.1). 

Corroles and corrinoids - For results on the noble metal complexes of this interesting class of tetrapyrroles, see the article by S. Licoccia in this volume [105]. 

The chemistry of corroles and their metal complexes has been reviewed by different authors in the past [7-11] and apart from necessary clarifications this paper will deal with the contributions to the chemistry of metallocorrolates and corrinoids published in the last ten years. 

The presence of a metal salt is generally necessary to achieve the macrocycle some corrinoids have been isolated only as metal complexes since the metal-free ligand is not stable enough to be isolated. The reasons for such instability have not been clarified, but it is noted to increase with the unsaturation level of the macrocycle. 

Table 19. Synthetic metal complexes of corrinoid macrocycles...

Licoccia, S. Paolesse, R. Metal Complexes of Corroles and Other Corrinoids. Vol. 84, pp. 71-134... 

Licoccia, S. Paolesse, R Metal Complexes ofCorroles and Other Corrinoids. Vol. 84, pp. 71-134 Linares, C., Louat, A., Blanchard, M. Rare-Earth Oxygen Bonding in the IJ1MO4 Xenotime Structure. Vol.33,pp. 179-207. 

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