One- and two-electron oxidative pathways leading to cyclopropane-containing oxidized porphyrinogens and C-C-coupled porphyrinogens from alkali cation and transition metal meso-octaethylporphyrinogen complexes
One- and two-electron oxidative pathways leading to cyclopropane-containing oxidized porphyrinogens and C-C-coupled porphyrinogens from alkali cation and transition metal meso-octaethylporphyrinogen complexes
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DOI：
10.1021/ja982178f
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发表时间：
1999-03-03
影响因子：
15
通讯作者：
Rizzoli, C
中科院分区：
文献类型：
--
作者：
Crescenzi, R;Solari, E;Rizzoli, C
本文研究了中辛乙基卟啉原四阴离子[Et8N4]（4-）的不同过渡金属和碱阳离子辅助氧化途径。[Et8N4Mn{Na(thf)(2)}(2)]， 4与Cp2FeBPh4的双电子氧化得到相应的单环丙烷衍生物[Et8N4(Delta)Mn], 6, [Delta =环丙烷]，而与CuCl2或O-2的单电子氧化得到Mn(III)-卟啉原[Et8N4Mn][Li(thf)(4)], 5，过量的CuCl2可进一步氧化为[Et8N4(Delta)(2)Mn- cl](+)[Cu9Cl11](0.5), 7。7的形成不遵循预期的顺序Mn（II）—> Mn（III）—> Mn（II）—单环丙烷—> Mn（II）—双环丙烷—卟啉原。在铁(II)-卟啉原的情况下，[Et8N4Fe{Li(thf)(2)}(2)], 9，氧化在初步阶段导致铁（III）衍生物[Et8N4Fe][Li(thf)(4)], 10，然后导致双环丙烷-卟啉原的金属化形式[Et8N4(Delta)(2)Fe-Cl]{mu-Cu4Cl5}], 11。通过将[Cy4N4Fe{Li(thf)(2)}(2)]， 11氧化为[Cy4N4(Delta)(2)Fe-Cl][Cu2Cl4], 14，排除了铜(I)团簇对双环丙烷的稳定化作用。[Et8N4M(thf)(4)]的逐步氧化[M = Li, 1；M = Na， 2]与Cp2FeBPh4共合成[Et8N4(Delta)Li(2)thf(2)], 15, [Et8N4(Delta)Li]BPh4, 16和[Et8N4(Delta)Na]BPh4, 17。由1和16生成15的反应表明环丙烷中的C-C部分是如何参与分子间电子转移的。17与18-冠-6的反应允许释放双环丙烷-卟啉原[Et8N4(δ(2))]特别有趣的是15至19的热重排通过环丙烷的C-C键转位到两个相邻吡罗的-位置上的C-C桥，通过分子内和分子间的电子转移发生。在金属的情况下，如Ni(II)，其不经历氧化态的变化，金属-中介辛烷基卟啉原的主要氧化产物是单环丙烷衍生物，它与起始材料反应掩盖了整体的单电子氧化。事实上，[Et8N4Ni{Li(thf)(2)}(2)]， 20与2个等量的Cp2FeBPh4反应得到了预期的[Et8N4(δ)Ni], 21，而20与1等量的Cp2FeBPh4反应得到了二聚体[(β - β)(Et8N4)(2)Ni-2], 22，它们在20和21的反应中同样好地形成。配合物22是一种非常独特的金属卟啉原二聚体，其中两个单体单元在吡咯的β位置通过C-C键连接。这样的反应表明，该方法可以加入金属卟啉原的低聚形式。
This report deals with the different transition metal- and alkali cation-assisted oxidation pathways of the meso-octaethylporphyrinogen tetraanion [Et8N4](4-). The two-electron oxidation of [Et8N4Mn{Na(thf)(2)}(2)], 4, with Cp2FeBPh4 led to the corresponding monocyclopropane derivative [Et8N4(Delta)Mn], 6, [Delta = cyclopropane], while the one-electron oxidation with CuCl2 or O-2 led to the Mn(III)-porphyrinogen [Et8N4Mn][Li(thf)(4)], 5, which can be further oxidized by an excess of CuCl2 to [Et8N4(Delta)(2)Mn-Cl](+)[Cu9Cl11](0.5), 7. The formation of 7 does not follow the expected sequence Mn(II) --> Mn(III) --> Mn(II)-monocyclopropane --> Mn(II) - biscyclopropane-porphyrinogen. In the case of iron(II)-porphyrinogen, [Et8N4Fe{Li(thf)(2)}(2)], 9, the oxidation led in a preliminary stage to the iron(III) derivative [Et8N4Fe][Li(thf)(4)], 10, then to the metalated form of the biscyclopropane-porphyrinogen [Et8N4(Delta)(2)Fe-Cl]{mu-Cu4Cl5}], 11. The supposed stabilization of the biscyclopropane by the copper(I) cluster was ruled out by carrying the oxidation of [Cy4N4Fe{Li(thf)(2)}(2)], 11, to [Cy4N4(Delta)(2)Fe-Cl][Cu2Cl4], 14. The stepwise oxidation of [Et8N4M(thf)(4)] [M = Li, 1; M = Na, 2] with Cp2FeBPh4 led to [Et8N4(Delta)Li(2)thf(2)], 15, [Et8N4(Delta)Li]BPh4, 16, and [Et8N4(Delta)Na]BPh4, 17. The reaction of 1 with 16 leading to 15 showed how the C-C moiety in cyclopropane can be engaged in an intermolecular electron transfer. The reaction of 17 with 18-crown-6 allowed the release of biscyclopropane-porphyrinogen [Et8N4(Delta(2))] Particularly interesting is the thermal rearrangement of 15 to 19 occurring via intra- and intermolecular electron transfers with the transposition of the C-C bond of the cyclopropane to a C-C bridge across the beta position of two adjacent pyrroles. In the case of metals, such as Ni(II), which do not undergo oxidation state changes, the primary oxidation product of a metalla-meso-octaalkylporphyrinogen is the monocyclopropane derivative, which reacting with the starting material masks an overall one-electron oxidation. In fact, the reaction of [Et8N4Ni{Li(thf)(2)}(2)], 20, with 2 equiv of Cp2FeBPh4 led to the expected [Et8N4(Delta)Ni], 21, while the reaction of 20 with 1 equiv of Cp2FeBPh4 led to the dimer [(beta-beta)(Et8N4)(2)Ni-2], 22, which forms equally well from the reaction of 20 and 21. Complex 22 is a quite unique metallaporphyrinogen dimer, where the two monomeric units are joined via a C-C bond in the beta position of a pyrrole. Such a reaction shows that the methodology can accede to oligomeric forms of metallaporphyrinogens.