New Trends in the Chemistry of Organometalloporphyrins

The evolution and the current trends in a new area of chemistry of organometalloporphyrins, in metalloporphyrin chemistry are reviewed. Synthesis and properties of out of plane, di—nuclear, and "Skewered" metalloporphyrins are described. The new chemistry of metalloporphyrins was initiated by the application of Cr(CO)6, metal carbonyl in general, for insertion of Cr ion (metal ions) into por— phyrins. Organometalloporphyrins in general are defined as synthetic metalloporphyrim complexes containing at least one direct metal—carbonyl bond. However, the coenzyme of Vitamin B 2 (Figure 1) containing an adenosyl group linked to cobalt by a direct cobalt-carbon o-bon[ is the first example of a naturally occurring orgamometallocorrin complex (similar to organomtllo— porphyrins in molecular structure) and the first—known stable organocobalt derivative. ' The determination of the structure of the vitamin B10 coemzyme by x—ray crystallography, prompted several studies of the synthesis and properties of cobalt—alkyl compounds. Johnson and his co—workers extended their studies to the porphyrin series by reaction of pyrid— inobromocobalt (III) aetiopor— phyrin-I with a variety of alkyland aryl-magnesium halides in anhydrous 1,2dimethoxyethane (DME) to give the corresponding alkyland rl—cobalt (III) derivatives. Ethyl and p-olyl-iron (III) derivatives of aetio— porphyrin-I were also prepared by a similar method. The first—row transition metal derivatives of organometallo— porphyrins were thus synthesized for the first time. In an alternative synthesis, Johnson and his co-workers were also able to prepare the identical alkyl cobalt(III)aetioporphyrin— I complexes as that mentioned above, by reduction of cobalt (II)aetioporphyrin—I with 1% sodium amalgam in DE to form cobalt(I) species, which then react with alkyl halides to give the final products. This SPATIAL STRUCTURE OF COENZYME B12 method was also used for the preparation of hydroxyalkylFIGURE 1 cohalt( IIIaetioporphyrin—I complexes. Both the cobalt(III) and the iron(III) orgamometalloporphrins are sensitive to light, especially in solution, and decompose by homolytic fission of the metal-carbon bond. The use of metal carbonyls for the ieion of metal ions into porphyrins was first introduced by Tsutsui and his co—workers ' in 1966 (Figure 2). This method is probably one of the most important developments in porphyrin chemistry within the last two decades. In addition to a number of previs pted metalloporphyrins, the reaction of metal carbonyls and metal carbonyl halides ' ' ' with neutral porphyrins has lead to the synthesis of new metal1oporphyrmn18olexes of chromium, molybdenum, technetium, ruthenium, rhodium, rhenium and iridium. — Except for the chromium and molybdenum complexes, carbonyl groups