Pawlicki Miłosz, Latos-Grazyński Lechosław
Department of Chemistry, University of Wrocław, 50 383 Wrocław, Poland.
Inorg Chem. 2002 Nov 4;41(22):5866-73. doi: 10.1021/ic025718p.
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)Fe(III)Cl(2) complex. The reduction of (OTPP)Fe(III)Cl(2) has been accomplished by means of moderate reducing reagents producing high-spin five-coordinate (OTPP)Fe(II)Cl. The molecular structure of (OTPP)Fe(III)Cl(2) 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)Fe(III)Cl(2) 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)Fe(III)Cl(2) or (OTPP)Fe(II)Cl with n-BuLi (toluene-d(8), 205 K) resulted in the formation of (OTPP)Fe(II)(CH(2)CH(2)CH(2)CH(3)). (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(yz))(2)(d(z)(2)(1)(d[(x)(2)-(y)(2)])(0) ground electronic state of iron(I) oxaporphyrin (g(1) = 2.234, g(2) = 2.032, g(3) = 1.990). The (1)H NMR spectra of (OTPP)Fe(III)Cl(2), (OTPP)Fe(III)(CN)(2), ((OTPP)Fe(III))O)(2+), and (OTPP)Fe(II)Cl have been analyzed. There are considerable similarities in (1)H 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)Fe(III)Cl(2) is unprecedented in the group of iron(I) porphyrins.
对5,10,15,20 - 四苯基 - 21 - 氧杂卟啉（OTPP）H的铁配合物进行了研究。插入铁（II）后经单电子氧化生成高自旋、六配位的（OTPP）Fe（III）Cl₂配合物。（OTPP）Fe（III）Cl₂的还原是通过适度的还原剂实现的，生成高自旋五配位的（OTPP）Fe（II）Cl。（OTPP）Fe（III）Cl₂的分子结构已通过X射线衍射确定。铁（III）21 - 氧杂卟啉骨架基本呈平面状。呋喃环通过氧原子以η¹方式配位，该氧原子具有三角几何构型。铁（III）以顶端方式配位两个氯配体。向（OTPP）Fe（III）Cl₂在氘代甲醇 - d₄中的溶液中加入氰化钾，会使其转化为六配位、低自旋的配合物[OTPP）Fe（III）（CN）₂]，该配合物会被过量的氰化物自发还原为[OTPP）Fe（II）（CN）₂]⁻。[OTPP）Fe（III）（CN）₂]的光谱特征对应于常见的低自旋铁（III）卟啉（d（xy））²（d（xz）d（yz））³电子构型。用正丁基锂（甲苯 - d₈，205 K）滴定（OTPP）Fe（III）Cl₂或（OTPP）Fe（II）Cl会生成（OTPP）Fe（II）（CH₂CH₂CH₂CH₃）。（OTPP）Fe（II）（n - Bu）通过铁 - 碳键的均裂分解生成（OTPP）Fe（I）。电子顺磁共振谱（甲苯 - d₈，77 K）与铁（I）氧杂卟啉的（d（xy））²（d（xz））²（d（yz））²（d（z²）¹（d[（x）² - （y）²]）⁰基态电子构型一致（g₁ = 2.234，g₂ = 2.032，g₃ = 1.990）。对（OTPP）Fe（III）Cl₂、（OTPP）Fe（III）（CN）₂、（[（OTPP）Fe（III）]）₂O）²⁺和（OTPP）Fe（II）Cl的¹H核磁共振谱进行了分析。在每个铁（n）氧杂卟啉 - 铁（n）常规卟啉或N - 甲基卟啉对（n = 2, 3）中，¹H核磁共振性质存在相当大的相似性。与该观察结果相反，在（OTPP）Fe（III）Cl₂的双电子还原产物中检测到的吡咯共振在156.2、126.5、76.3 ppm处的低场位置模式以及呋喃共振在161.4 ppm（273 K）处的模式在铁（I）卟啉组中是前所未有的。
