The iron complexes of 5,10,15,20-tetraphenyl-21-oxaporphyrin (OTPP)H have been investigated. Insertion of iron(II) followed by one-electron oxidation yielded a high-spin, six-coordinate (OTPP)(FeCl2)-Cl-III complex. The reduction of (OTPP)(FeCl2)-Cl-III has been accomplished by means of moderate reducing reagents producing high-spin five-coordinate (OTPP)(FeCl)-Cl-II. The molecular structure of (OTPP)(FeCl2)-Cl-III has been determined by X-ray diffraction. The iron(III) 21-oxaporphyrin skeleton is essentially planar. The furan ring coordinates in the eta(1) fashion through the oxygen atom, which acquires trigonal geometry. The iron(III) apically coordinates two chloride ligands. Addition of potassium cyanide to a solution of (OTPP)(FeCl2)-Cl-III in methanol-d(4) results in its conversion to a six-coordinate, low-spin complex [OTPP)Fe-III(CN)(2)] which is spontaneously reduced to [OTPP)Fe-II(CN)(2)](-) by excess cyanide. The spectroscopic features of [OTPP)Fe-III(CN)(2)] correspond to the common low-spin iron(III) porphyrin (d(xy))(2)(d(xz)d(yz))(3) electronic configuration. Titration of (OTPP)(FeCl2)-Cl-III or (OTPP)(FeCl)-Cl-II with n-BuLi (toluene-d(8), 205 K) resulted in the formation of (OTPP)Fe-II(CH2CH2CH2CH3). (OTPP)Fe-II(n-Bu) decomposes via homolytic cleavage of the iron-carbon bond to produce (OTPP)Fe-I. The EPR spectrum (toluene-d(8), 77 K) is consistent with a (d(xy))(2)(d(xz))(2)(d(z)(2))(1)(d(z2-y2))(0) ground electronic state of iron(I) oxaporphyrin (g(1) = 2.234, g(2) = 2,032, g(3) = 1.990). The H-1 NMR spectra of (OTPP)(FeCl2)-Cl-III, (OTPP)Fe-III(CN)(2), {[(OTPP)FeIII)](2)O}(2+), and (OTPP)(FeCl)-Cl-II have been analyzed. There are considerable similarities in H-1 NMR properties within each iron(n) oxaporphyrin-iron(n) regular porphyrin or N-methylporphyrin pair (n = 2, 3). Contrary to this observation, the pattern of downfield positions of pyrrole resonances at 156.2, 126.5, 76.3 ppm and furan resonance at 161.4 ppm (273 K) detected for the two-electron reduction product of (OTPP)(FeCl2)-Cl-III is unprecedented in the group of iron(I) porphyrins.