Hsu I-Jui, Hsieh Chung-Hung, Ke Shyue-Chu, Chiang Kuo-An, Lee Jenn-Min, Chen Jin-Ming, Jang Ling-Yun, Lee Gene-Hsiang, Wang Yu, Liaw Wen-Feng
Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
J Am Chem Soc. 2007 Feb 7;129(5):1151-9. doi: 10.1021/ja065401e.
The neutral trinuclear iron-thiolate-nitrosyl, (ON)Fe(mu-S,S-C(6)H(4)) (1), and its oxidation product, (ON)Fe(mu-S,S-C(6)H(4))[PF(6)] (2), were synthesized and characterized by IR, X-ray diffraction, X-ray absorption, electron paramagnetic resonance (EPR), and magnetic measurement. The five-coordinated, square pyramidal geometry around each iron atom in complex 1 remains intact when complex 1 is oxidized to yield complex 2. Magnetic measurements and EPR results show that there is only one unpaired electron in complex 1 (S(total) = 1/2) and no unpaired electron (S(total) = 0) in 2. The detailed geometric comparisons between complexes 1 and 2 provide understanding of the role that the unpaired electron plays in the chemical bonding of this trinuclear complex. Significant shortening of the Fe-Fe, Fe-N, and Fe-S distances around Fe(1) is observed when complex 1 is oxidized to 2. This result implicates that the removal of the unpaired electron does induce the strengthening of the Fe-Fe, Fe-N, and Fe-S bonds in the Fe(1) fragment. A significant shift of the nuNO stretching frequency from 1751 cm(-1) (1) to 1821, 1857 cm(-1) (2) (KBr) also indicates the strengthening of the N-O bonds in complex 2. The EPR, X-ray absorption, magnetic measurements, and molecular orbital calculations lead to the conclusion that the unpaired electron in complex 1 is mainly allocated in the Fe(1) fragment and is best described as {Fe(1)NO}7, so that the unpaired electron is delocalized between Fe and NO via d-pi* orbital interaction; some contributions from [Fe(2)NO] and [Fe(3)NO] as well as the thiolates associated with Fe (1) are also realized. According to MO calculations, the spin density of complex 1 is predominantly located at the Fe atoms with 0.60, -0.15, and 0.25 at Fe(1), Fe(2), and Fe(3), respectively.
合成了中性三核铁硫醇盐-亚硝酰基配合物[(ON)Fe(μ-S,S-C₆H₄)]₃ (1)及其氧化产物[(ON)Fe(μ-S,S-C₆H₄)]₃[PF₆] (2)，并通过红外光谱、X射线衍射、X射线吸收、电子顺磁共振(EPR)和磁性测量对其进行了表征。当配合物1被氧化生成配合物2时，配合物1中每个铁原子周围的五配位四方锥几何结构保持完整。磁性测量和EPR结果表明，配合物1中只有一个未成对电子(S总 = 1/2)，而配合物2中没有未成对电子(S总 = 0)。配合物1和2之间详细的几何比较有助于理解未成对电子在该三核配合物化学键合中所起的作用。当配合物1被氧化为2时，观察到Fe(1)周围的Fe-Fe、Fe-N和Fe-S距离显著缩短。这一结果表明，未成对电子的去除确实导致了Fe(1)片段中Fe-Fe、Fe-N和Fe-S键的加强。νNO伸缩频率从1751 cm⁻¹(1)显著移至1821、1857 cm⁻¹(2)(KBr)也表明配合物2中N-O键的加强。EPR、X射线吸收、磁性测量和分子轨道计算得出结论，配合物【1】中的未成对电子主要分布在Fe(1)片段中，最好描述为{Fe(1)NO}7，因此未成对电子通过d-π*轨道相互作用在Fe和NO之间离域；也认识到[Fe(2)NO]和[Fe(3)NO]以及与Fe(1)相关的硫醇盐的一些贡献。根据分子轨道计算，配合物1的自旋密度主要位于Fe原子上，在Fe(1)、Fe(2)和Fe(3)处分别为0.60、-0.15和0.25。
