ELECTROCHEMISTRY AND SPECTROELECTROCHEMISTRY OF SIGMA-BONDED IRON(III) PORPHYRINS WITH NONPLANAR PORPHYRIN RINGS - REACTIONS OF (OETPP)FE(R) AND (OETPP)FECL, WHERE R=C6H5, C6F4H, OR C6F5 AND OETPP IS THE DIANION OF 2,3,7,8,12,13,17,18-OCTAETHYL-5,10,15,20-TETRAPHENYLPORPHYRIN

A variety of nonplanar sigma-bonded phenyl- and (fluorophenyl)iron(III) porphyrins are characterized as to their electrochemical and spectroscopic properties in nonaqueous media. The investigated compounds are represented as (OETPP)Fe(R), where R = C6H5, C6F4H, or C6F5 and OETPP is the dianion of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin. All three porphyrins contain a low-spin Fe(III) central metal ion and in the case of (OETPP)Fe(C6F5) and (OETPP)Fe(C6F3H) provide the first examples of low-spin iron sigma-bonded (fluorophenyl)porphyrins. The site of electron transfer was assigned on the basis of the spectroscopic and electrochemical data for these compounds and by comparison with a related (OETPP)In(C6H5) derivative which was also synthesized and characterized. Comparisons of the results on (OETPP)Fe(R) are also made to data on earlier reported (OEP)Fe(R) derivatives where R = C6H5, C6F4H or C6F5, the latter two of which contain high-spin Fe(III) as compared to the low-spin (OEP)Fe(C6H5) species. (OETPP)Fe(C6H5) undergoes three one-electron oxidations to give a Fe(IV) pi dication species. Our results show, for the first time, that the spin state of the iron(III) porphyrin is not a key factor which governs migration of the axial ligand of the electrooxidized species as has previously been proposed.