Dioxygen-Derived Nonheme Mononuclear FeIII(OH) Complex and Its Reactivity with Carbon Radicals

A new tetradentate, monoanionic, mixed N/O donor ligand (BNPAPh2O–) with second coordination sphere H-bonding groups has been synthesized for stabilization of a terminal FeIII(OH) complex. The complex FeII(BNPAPh2O)­(OTf) (1) reacts with O2 to give a mononuclear terminal FeIII(OH) complex, FeIII(OH)­(BNPAPh2O)­(OTf) (2), both of which were characterized by X-ray diffraction, electrospray ionization mass spectrometry, UV–vis, 1H and 19F nuclear magnetic resonance, 57Fe Mössbauer, and electron paramagnetic resonance spectroscopies. Treatment of 2 with carbon radicals (Ar3C·) gives Ar3COH and the FeII complex 1, in direct analogy with the elusive radical “rebound” process proposed for nonheme iron enzymes.本研究合成了一种带有第二配位层氢键基团的单阴离子四齿氮氧混合给体配体（BNPAPh2O–），用于稳定末端羟基铁(III)配合物。配合物FeII(BNPAPh2O)(OTf)（1）可与氧气反应生成单核末端羟基铁(III)配合物FeIII(OH)(BNPAPh2O)(OTf)（2），上述两种配合物均通过X射线衍射、电喷雾电离质谱、紫外-可见光谱、1H与19F核磁共振波谱、57Fe穆斯堡尔谱及电子顺磁共振波谱进行了表征。采用碳自由基（Ar3C·）处理配合物2，可得到Ar3COH与二价铁配合物1，该反应与非血红素铁酶中提出的难以观测的自由基"回弹"过程直接类比。