Oxidation and oxygenation of (HCTPPH)Fe(II)Br an iron(II) complex of 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin (CTPPH)H2 have been followed by 1H and 2H NMR spectroscopy. Addition of I2 or Br2 to the solution of (HCTPPH)Fe(II)Br in the absence of dioxygen results in one-electron oxidation yielding [(HCTPPH)Fe(III)Br]+. One electron oxidation with dioxygen, accompanied by deprotonation of a C(21)H fragment and formation of an Fe-C(21) bond, produces an intermediate-spin, five-coordinate iron(III) complex (HCTPP)Fe(III)Br. In the subsequent step an insertion of the oxygen atom into the preformed Fe(III)-C(21) bond has been detected to produce [(CTPPO)Fe(III)Br]-. Protonation at the N2 atom affords (HCTPPO)Fe(III)Br. The considered mechanism of (HCTPPH)Fe(II)Br oxygenation involves the insertion of dioxygen into the Fe-C bond. The 1H NMR and 2H NMR spectra of paramagnetic iron(III) complexes were examined. Functional group assignments have been made with use of selective deuteration. The characteristic patterns of pyrrole and 2-NH resonances have been found diagnostic of the ground electronic state of iron and the donor nature localized at C(21) center as exemplified by the 1H NMR spectrum of intermediate-spin (HCTPP)Fe(III)Br: beta-H 7.2, -10.6, -19.2, -20.6, -23.2, -24.9, -43.2; 2-NH -76.6 (ppm, 298 K). The structures of two compounds (HCTPP)Fe(III)Br and (HCTPPO)Fe(III)Br, were determined by X-ray diffraction studies. In the first case, the iron(III) is five-coordinate with bonds to three pyrrole nitrogen atoms (Fe-N distances: 1.985(8), 2.045(7), 2.023(8) A), and the pyrrolic trigonal carbon (Fe-C: 1.981(8) A). The iron(III) of (HCTPPO)Fe(III)Br forms bonds to three pyrrole nitrogen atoms (Fe-N distances 2.104(5), 2.046(5), 2.102(5) A). The Fe-O 2.041(5) A and Fe-C(21) 2.192(5) A distances suggests a direct interaction between the iron center and the pi electron density on the carbonyl group in a eta2 fashion.

Iron(II) 2-aza-21-carbaporphyrins have been characterized by paramagnetically shifted 1 H and 2 H NMR spectra. The high-spin iron(II) complex (HCTPPH)Fe II Br displays the β-H resonances which reflect the combination σ and π routes of spin density delocalization. The uniquely large isotropic shift of the inner H(21) hydrogen (812 ppm, 298 K) indicates an Fe II −{C(21)−H} agostic interaction.

The nitrosylation of Co(HCTPP) (1) in CH2Cl2 afforded [Co(CTPPC2H2Cl)(NO)] (2) with a chlorovinyl group substituent on the inner carbon atom of the N‐confused porphyrin ring. The spectroscopic data suggest that 1 exhibits an {Co(NO)}8 electronic structure. The nitrosylation of 1 in the presence of oxygen leads to [Co(CTPPO)(NO)] (3), which is a {Co(NO)}7 cobalt nitrosyl complex. A bent axial Co–N–O conformation was observed in both nitric oxide complexes with an angle of 128.5(7)° for 2 and 146.9(11)° for 3. An sp3 hydride carbon atom was evidenced in the crystal structure of 2, and an η2 interaction between the cobalt center and the inner carbonyl group was observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)