ON THE MECHANISM OF AUTOXIDATION OF IRON(II) PORPHYRINS - DETECTION OF A PEROXO-BRIDGED IRON(III) PORPHYRIN DIMER AND THE MECHANISM OF ITS THERMAL-DECOMPOSITION TO THE OXO-BRIDGED IRON(III) PORPHYRIN DIMER
ON THE MECHANISM OF AUTOXIDATION OF IRON(II) PORPHYRINS - DETECTION OF A PEROXO-BRIDGED IRON(III) PORPHYRIN DIMER AND THE MECHANISM OF ITS THERMAL-DECOMPOSITION TO THE OXO-BRIDGED IRON(III) PORPHYRIN DIMER
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DOI：
10.1021/ja00533a009
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发表时间：
1980-01-01
影响因子：
15
通讯作者：
BALCH, AL
中科院分区：
文献类型：
--
作者：
CHIN, DH;LAMAR, GN;BALCH, AL
在-80℃下，向FeIIP(P=a-卟啉双阴离子)的甲苯溶液中加氧。C导致了新中间体1的形成，可见光和核磁共振氢谱检测到了该中间体。根据方程1+2FeIip·fwdarw，1与FeIIP发生定量反应。2PFeOFeP。提出了一种过氧桥联的二聚体结构PFeIII-0-0-FeIIIP，它的组成、反铁磁性(由~1H核磁共振接触位移的温度依赖性和181℃时的磁化率2.1µB决定)。K，在222度时为2.7微巴。K)和检测到包含2个不同取代的卟啉的混合配体物种。升温时，1通过反应2 1.fwdarw定量分解。2PFe0FeP+02，反应过程中未检测到其他物种。用质谱仪及其与FeIIP的反应对产物进行了鉴定。在-22~-40℃范围内测定了该反应的动力学。C.反应为1级反应，具有**图形**。=14.5.+-1千卡/摩尔和**图形**。=-15。+-。1 EU[熵单位]。用于生成1的02的同位素标记表明，由于1的分解而释放的02的同位素组成与其形成时使用的相同。当两个标记物种PFe02FeP和P‘’Fe02FeP‘’被分解时，卟啉配体确实发生了扰乱：PFe0FeP，P‘’Fe0-FEP‘’和PFe0FeP‘’都形成了。在此基础上，提出了1分解为PFe0FeP的机理。
Addition of dioxygen to toluene solutions of FeIIP (P = a porphyrin dianion) at -80.degree. C leads to the formation of a new intermediate 1 which was detected by visible and 1H NMR spectroscopy. 1 reacts quantitatively with FeIIP according to the equation 1 + 2FeIIP .fwdarw. 2PFeOFeP. A peroxo-bridged, dimeric structure, PFeIII-0-0-FeIIIP, is proposed for 1 on the basis of its composition, its antiferromagnetism (as determined by the temperature dependence of the 1H NMR contact shifts and the magnetic susceptibility, 2.1 .mu.B at 181.degree. K, 2.7 .mu.B at 224.degree. K) and detection of a mixed ligand species involving 2 differently substituted porphyrins. Upon warming 1 decomposes quantitatively by the reaction 2 1 .fwdarw. 2PFe0FeP + 02 with no other species detected during the reaction. The 02 produced was detected by mass spectroscopy and its reaction with FeIIP. The kinetics of this reaction were determined over the temperature range -22 to -40.degree. C. The reaction is 1st order in 1 with .**GRAPHIC**. = 14.5 .+-. 1 kcal/mol and .**GRAPHIC**. = -15 .+-. 1 eu [entropy unit]. Isotopic labeling of the 02 used to form 1 reveals that the isotopic composition of the 02 released due to decomposition of 1 is identical with that used in its formation. When 2 labeled species PFe02FeP and P''Fe02FeP'' are decomposed, the porphyrin ligands do scramble: PFe0FeP, P''Fe0-FeP'' and PFe0FeP'' all are formed. Based on these observations, a mechanism for the decomposition of 1 to PFe0FeP is proposed.