Rachlewicz Krystyna, Wang Sian-Ling, Ko Jia-Ling, Hung Chen-Hsiung, Latos-Grazyński Lechosław
Department of Chemistry, University of Wrocław, Wrocław 50 383, Poland.
J Am Chem Soc. 2004 Apr 7;126(13):4420-31. doi: 10.1021/ja039792y.
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.
采用¹H和²H核磁共振波谱法对2-氮杂-5,10,15,20-四苯基-21-碳杂卟啉（CTPPH）H₂的铁（II）配合物（HCTPPH）Fe（II）Br进行了氧化和氧合研究。在没有 dioxygen的情况下，向（HCTPPH）Fe（II）Br溶液中加入I₂或Br₂会导致单电子氧化，生成[(HCTPPH)Fe(III)Br]+。与dioxygen发生单电子氧化，伴随着C(21)H片段的去质子化和Fe-C(21)键的形成，生成一个中间自旋的五配位铁（III）配合物（HCTPP）Fe(III)Br。在随后的步骤中，检测到氧原子插入预先形成的Fe(III)-C(21)键中，生成[(CTPPO)Fe(III)Br]-。在N₂原子处质子化得到（HCTPPO）Fe(III)Br。所考虑的（HCTPPH）Fe（II）Br氧合机制涉及dioxygen插入Fe-C键。研究了顺磁性铁（III）配合物的¹H NMR和²H NMR光谱。利用选择性氘代进行了官能团归属。已发现吡咯和2-NH共振的特征模式可诊断铁的基态电子状态以及位于C(21)中心的供体性质，如中间自旋（HCTPP）Fe(III)Br的¹H NMR光谱所示：β-H 7.2、-10.6、-19.2、-20.6、-23.2、-24.9、-43.2；2-NH -76.6（ppm，298 K）。通过X射线衍射研究确定了两种化合物（HCTPP）Fe(III)Br和（HCTPPO）Fe(III)Br的结构。在第一种情况下，铁（III）是五配位的，与三个吡咯氮原子键合（Fe-N距离：1.985(8)、2.045(7)、2.023(8) Å），以及吡咯三角碳（Fe-C：1.981(8) Å）。（HCTPPO）Fe(III)Br的铁（III）与三个吡咯氮原子形成键（Fe-N距离2.104(5)、2.046(5)、2.102(5) Å）。Fe-O 2.041(5) Å和Fe-C(21) 2.192(5) Å的距离表明铁中心与羰基上的π电子密度以η²方式直接相互作用。
