Alkyl-metal porphyrin anion

Only the (F20TPPT)Fem/ alkyl-metal porphyrin anion exhibits another reversible couple ( 1/2, —1.63 V) to yield a dianion [the four electron-withdrawing pentafluorophenyl groups on the porphyrin ring make possible the addition of an election to give the (F2oTPP2-)Fe dianion within the voltage limit of the solvent]. 

The alkyl-metal porphyrin anion [(porT)Fem/ ] is oxidized reversibly on reversal of a cathodic scan (—1.36 to —0.54 V, Table 13.8). The further oxidation of (por)Fem does not occur when is a tertiaiy-butyl group [apparently steric effects weaken the (por)Fein—R bond]. The oxidation potentials for the iron porphyrins (with the same porphyrin ring) are in the order (por)Fem > (por)Feu > (porT)Fem > (por) Fe- > (porT)nFe- (most negative). 

Other o-bonded metal porphyrins have electronic absorption spectra belonging to the hyperclass. The o-bonded complexes of iron , indium gallium exhibit such typical spectra. Thus, replacement of the anionic axial ligand on the halogenated complexes M(Por)X by an alkyl (or aryl) o-bonded ligand results in a splitting of the Soret band into two bands. One of the bands is red shifted and the other is blue shifted with respect to the same porphyrin complex with anionic axial ligands. This is illustrated in Fig. 2 for In(OEP)Cl and In(OEP)(C(CH3)3). 

Cobalt Porphyrins. The primary synthetic method for generating cobalt porphyrins with a metal carbon a-bond is to react a chemically or electrochemically generated cobalt(I) anion, [(P)Co] , with an alkyl or an aryl halide(19-26). [(P)Co] is stable and... 

Iron, as found in the porphyrin derivative hemoglobin, complexes CO to form a stable metal carbonyl. Iron also forms a variety of metal carbon monoxide derivatives such as the homoleptic Fe(CO)5, Fe2(CO)9 and Fe3(CO)i2, the anionic [Fe(CO)4] and its covalent derivative Fe(CO)4Br2, [CpFe(CO)2] and its alkylated covalent derivatives CpFe(CO)2-R with its readily distinguished n (and and a (and / ) iron carbon bonds. By contrast. Mg in its chlorin derivative chlorophyll, which very much resembles porphyrin, forms no such bonds with CO nor is there a rich magnesium carbonyl chemistry (if indeed, there is any at all). 

The metal-centered reduction of iron and cobalt porphyrins [(por)Afn] yields metalloporphyrin anions [Eq. (13.13)]. The reduction potential for this reaction is 13, and is equivalent to the N- value for the oxidation of the metal-centered nucleophile [(por)uM-]. The one-electron reduction of alkyl halides yields the... 

---