Roelfes Gerard, Lubben Marcel, Chen Kui, Ho Raymond Y. N., Meetsma Auke, Genseberger Susan, Hermant Roel M., Hage Ronald, Mandal Sanjay K., Young Victor G., Zang Yan, Kooijman Huub, Spek Anthony L., Que Lawrence, Feringa Ben L.
Department of Organic and Molecular Inorganic Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, Unilever Research Laboratory, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands, and Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Inorg Chem. 1999 Apr 19;38(8):1929-1936. doi: 10.1021/ic980983p.
In an effort to gain more insight into the factors controlling the formation of low-spin non-heme Fe(III)-peroxo intermediates in oxidation catalysis, such as activated bleomycin, we have synthesized a series of iron complexes based on the pentadentate ligand N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine). The following complexes have been prepared: (N4Py)Fe(II)(CH(3)CN)(2) (1), (N4Py)Fe(II)Cl (2), (N4Py)Fe(III)OMe(2) (3), and (N4Py)(2)Fe(2)O(4) (4). Complexes 1 and 2 have low- and high-spin Fe(II) centers, respectively, whereas 3 is an Fe(III) complex that undergoes a temperature-dependent spin transition. The iron centers in the oxo-bridged dimer 4 are antiferromagnetically coupled (J = -104 cm(-)(1)). Comparison of the crystal structures of 1, 3, and 4 shows that the ligand is well suited to accommodate both Fe(II) and Fe(III) in either spin state. For the high-spin Fe(III) complexes 3 and 4 the iron atoms are positioned somewhat outside of the cavity formed by the ligand, while in the case of the low-spin Fe(II) complex 1 the iron atom is retained in the middle of the cavity with approximately equal bond lengths to all nitrogen atoms from the ligand. On the basis of UV/vis and EPR observations, it is shown that 1, 3, and 4 all react with H(2)O(2) to generate the purple low-spin (N4Py)Fe(III)OOH intermediate (6). In the case of 1, titration experiments with H(2)O(2) monitored by UV/vis and (1)H NMR reveal the formation of (N4Py)Fe(III)OH (5) and the oxo-bridged diiron(III) dimer (4) prior to the generation of the Fe(III)-OOH species (6). Raman spectra of 6 show distinctive Raman features, particularly a nu(O-O) at 790 cm(-)(1) that is the lowest observed for any iron-peroxo species. This observation may rationalize the reactivity of low-spin Fe(III)-OOH species such as "activated bleomycin".
为了更深入地了解控制氧化催化中低自旋非血红素铁（III）-过氧中间体形成的因素，如活化博来霉素，我们基于五齿配体N4Py（N4Py = N，N-双（2-吡啶甲基）-N-（双-2-吡啶甲基）胺）合成了一系列铁配合物。已制备了以下配合物：(N4Py)Fe(II)(CH(3)CN)(2)（1）、(N4Py)Fe(II)Cl（2）、(N4Py)Fe(III)OMe(2)（3）和(N4Py)(2)Fe(2)O(4)（4）。配合物1和2分别具有低自旋和高自旋的Fe（II）中心，而3是一种经历温度依赖性自旋转变的Fe（III）配合物。氧桥联二聚体4中的铁中心是反铁磁耦合的（J = -104 cm(-)(1)）。1、3和4的晶体结构比较表明，该配体非常适合容纳处于任何自旋态的Fe（II）和Fe（III）。对于高自旋Fe（III）配合物3和4，铁原子位于配体形成的腔体外，而对于低自旋Fe（II）配合物1，铁原子保留在腔体中间，与配体所有氮原子的键长近似相等。基于紫外可见光谱和电子顺磁共振观察结果表明，1、3和4均与H(2)O(2)反应生成紫色低自旋(N4Py)Fe(III)OOH中间体（6）。对于1，通过紫外可见光谱和(1)H核磁共振监测的H(2)O(2)滴定实验揭示了在生成Fe（III）-OOH物种（6）之前，(N4Py)Fe(III)OH（5）和氧桥联二铁（III）二聚体（4）的形成。6的拉曼光谱显示出独特的拉曼特征，特别是在790 cm(-)(1)处的ν（O - O），这是任何铁-过氧物种中观察到的最低值。这一观察结果可以解释低自旋Fe（III）-OOH物种如“活化博来霉素”的反应活性。
