Trans-dioxo manganese(V) Porphyrins
Trans-dioxo manganese(V) Porphyrins
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DOI：
10.1021/ja0761737
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发表时间：
2007-10-17
影响因子：
15
通讯作者：
Groves, John T.
中科院分区：
文献类型：
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作者：
Jin, Ning;Ibrahim, Mohammed;Groves, John T.
在碱性溶液中，锰(III)卟啉在过氧化氢的作用下氧化生成相对稳定的oxoMn(V)卟啉，明确地确定为反式二氧物种。拉曼光谱显示，五种卟啉配合物的O=Mn-v=O伸缩频率在741-744 cm(-1)之间对称，而二氧代-MnV-四氟卟啉[Mn-V(O2)(TPFPP)]的红外光谱在805 cm(-1)处出现反对称伸缩。制备了半标记和全标记的180-Mn-v卟啉配合物，其拉曼光谱和红外光谱符合线性三体O=Mn=O振子模型。数据排除了末端的单氧式，如Ho-Mn-v=O或五配位的Mn-v=O。[Mn-V(O2)(TMP)]-的H-1核磁共振谱显示了两个邻甲基的单一尖锐共振，也符合D(4h)对称性的八面体配位。计算得到Mn=O双键的力常数F为454N/m，拉伸-拉伸力常数k=67.2N/m，与其它Mn-O力常数相比，在五个氧化态范围内与Badger定律符合得很好。结果表明，这些二氧代锰钒卟啉不能与本体水溶液进行氧原子交换。二氧代MNV卟啉是阴离子物种[Por-Mn-V(O)(2)h]，在过量碱存在的情况下对烯烃不起反应，但在-70℃质子化时有效地环氧化环辛烯。这些化合物是唯一具有这种特征的反式二氧锰配合物，从而扩展了已知的第一排过渡金属的TL键排列。
The relatively stable oxoMn(V) porphyrins generated by oxidation of Mn(III) porphyrins in alkaline solutions using peroxides are unambiguously identified as trans -dioxo species. Raman spectra revealed symmetric O=Mn-v=O stretching frequencies between 741 and 744 cm(-1) for five porphyrin complexes while the IR of dioxo-Mnv-tetrapentafluoroporphyrin [Mn-V(O2)(TPFPP)]displayed an antisymmetric stretch at 805 cm(-1). Both half-labeled and fully labeled 180-Mn-v porphyrin complexes were prepared, and the Raman and IR shifts correspond well with a linear, three-body O=Mn=O oscillator model. Terminal, monooxo formulations such as HO-Mn-v=O or five-coordinate Mn-v=O are excluded by the data. The H-1 NMR spectrum of [Mn-V(O2)(TMP)]-, which shows a single, sharp resonance for the two ortho methyl groups, is also consistent with octahedral coordination of D (4h) symmetry. The force constant F for the Mn=O double bond was calculated to be 454 N/m with a stretch-stretch force constant k = 67.2 N/m. Comparison with other Mn-O force constants revealed a very good agreement with Badger's rule spanning five Mn oxidation states. These dioxo-Mn-v porphyrins were shown to not exchange the oxo oxygens with bulk water solvent. Dioxo Mnv porphyrins, which are anionic species [Por-Mn-V(O)(2)h] are unreactive toward olefins in the presence of excess base but efficiently epoxidize cyclooctene upon protonation at -70 degrees C. These compounds are the only trans-dioxomanganese complexes of any type to be characterized as such, thus extending the known TL-bonding arrangements for first-row transition metals.