Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840, USA.
Inorg Chem. 2010 Jun 7;49(11):4814-9. doi: 10.1021/ic9014509.
A new hexanuclear iron-selenium nitrosyl cluster, (n-Bu)(4)N[Fe(6)Se(6)(NO)(6)] (1), and a hexanuclear iron-sulfur nitrosyl cluster, (n-Bu)(4)N[Fe(6)S(6)(NO)(6)] (2), were synthesized by the solvent-thermal reactions of [(n-Bu)(4)N][Fe(CO)(3)NO] with selenium or sulfur in methanol, while a tetranuclear iron-sulfur nitrosyl cluster, (Me(4)N)[Fe(4)S(3)(NO)(7)] (3), was also prepared by the solvent-thermal reaction of FeCl(2).4H(2)O with thiourea in the presence of (CH(3))(4)NCl, NaNO(2), and methanol. Complexes 1-3 were characterized by IR, UV-vis, (1)H NMR, electrochemistry, and single-crystal X-ray diffraction analysis. IR spectra of complexes 1 and 2 show the characteristic NO stretching frequencies at 1694 and 1698 cm(-1), respectively, while the absorptions of complex 3 appear at 1799, 1744, and 1710 cm(-1). The UV-vis spectra of complexes 1-3 show different bands in the range of 259-562 nm, which are assigned to the transitions between orbitals delocalized over the Fe-S cluster, the ligand-to-metal charge transfer, pi*(NO)-d(Fe), and the metal-to-ligand charge transfer, d(Fe)-pi*(NO). Single-crystal X-ray structural analysis reveals that complex 1 crystallizes in the monoclinic P2(1)/n space group with two molecules per unit cell. Two parallel "chair-shaped" structures, consisting of three iron and three selenium atoms, are connected by Fe-Se bonds with an average distance of 2.341 A; each iron center is bonded to three selenium atoms and a nitrogen atom from the nitrosyl ligand with a pseudotetrahedral center geometry. Cyclic voltammograms of complexes 1 and 2 display two cathodic and three anodic current peaks with an unusually strong cathodic peak. Further electrochemical investigations demonstrated that the intensity of the unusually strong peak is a result of at least three processes. One is the quasi-reversible reduction, and the other two are from an irreversible electrochemical process, in which the compound goes through a typical electron transfer and chemical reaction mechanism. Compound 3 shows three quasi-reversible reductions.
一种新的六核铁-硒亚硝酰簇合物，(n-Bu)(4)N[Fe(6)Se(6)(NO)(6)]（1）和一种六核铁-硫亚硝酰簇合物，(n-Bu)(4)N[Fe(6)S(6)(NO)(6)]（2），是通过甲醇中[(n-Bu)(4)N][Fe(CO)(3)NO]与硒或硫的溶剂热反应合成的，而四核铁-硫亚硝酰簇合物，(Me(4)N)[Fe(4)S(3)(NO)(7)]（3），也是通过 FeCl(2).4H(2)O 在 (CH(3))(4)NCl、NaNO(2)和甲醇存在下与硫脲的溶剂热反应制备的。配合物 1-3 通过 IR、UV-vis、(1)H NMR、电化学和单晶 X 射线衍射分析进行了表征。配合物 1 和 2 的 IR 光谱分别在 1694 和 1698 cm(-1)处显示出特征的 NO 伸缩振动频率，而配合物 3 的吸收出现在 1799、1744 和 1710 cm(-1)处。配合物 1-3 的 UV-vis 光谱在 259-562nm 范围内显示出不同的谱带，这些谱带归因于轨道在 Fe-S 簇之间的离域、配体到金属的电荷转移、pi*(NO)-d(Fe)和金属到配体的电荷转移，d(Fe)-pi*(NO)。单晶 X 射线结构分析表明，配合物 1 结晶在单斜 P2(1)/n 空间群中，每个单元中包含两个分子。两个平行的“椅形”结构，由三个铁原子和三个硒原子组成，通过 Fe-Se 键连接，平均距离为 2.341A；每个铁中心与三个硒原子和一个来自亚硝酰配体的氮原子键合，具有伪四面体中心几何形状。配合物 1 和 2 的循环伏安图显示出两个阴极和三个阳极电流峰，其中一个阴极峰异常强烈。进一步的电化学研究表明，异常强峰的强度是至少三个过程的结果。一个是准可逆还原，另外两个来自不可逆电化学过程，其中化合物经历了典型的电子转移和化学反应机制。化合物 3 显示出三个准可逆还原。
