EFFECTS OF PHENOXIDE LIGATION ON IRON SULFUR CLUSTERS - PREPARATION AND PROPERTIES OF [FE4S4(OAR)4]2- IONS AND THE STRUCTURE OF [(C2H5)4N]2[FE4S4(OC6H5)4]
EFFECTS OF PHENOXIDE LIGATION ON IRON SULFUR CLUSTERS - PREPARATION AND PROPERTIES OF [FE4S4(OAR)4]2- IONS AND THE STRUCTURE OF [(C2H5)4N]2[FE4S4(OC6H5)4]
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DOI：
10.1021/ja00357a011
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发表时间：
1983-01-01
影响因子：
15
通讯作者：
AVERILL, BA
中科院分区：
文献类型：
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作者：
CLELAND, WE;HOLTMAN, DA;AVERILL, BA
通过[Fe4S4(SR)4]2-或[Fe4S4Cl4]2-分别与HoAr或NaOAr反应，合成了苯氧基连接的四核铁硫簇合物[Fe4S4(OAr)4]2-(I，R=苯基；II，R=对甲苯基)。报道了这些化合物的合成、反应活性、电子性质和晶体结构。[Et4N]2[Fe4S4(OPh)4]属单斜晶系，空间群为-P2xjn，晶胞参数为a=17.610(4)，b=11.600(3)，c=22.810(6)，？=106.41(1)，V=4469.9×3**(-150C)。利用F02和Gt；3a(F02)的6032个独立反射，将结构细化到R=0.066和/？“=0.107。I的结构是由[Fe4S4]2+立方烷核向Z)M对称扭曲而成，末端的酚氧配体完成了每个铁原子的近似四面体配位。最显著的构造特征是Fe-O距离较短(平均为1.865(17)α)。在I和II的~H核磁共振谱中观察到各向同性位移的共振，这些位移的方向和相对大小与自旋在苯环的it系统中的显著离域相一致。在任何温度下，各向同性位移的大小大约是芳硫醚类似物观察到的两倍。各向同性位移的大小随着温度的升高而增加，这与反铁磁耦合系统是一致的。变温磁化率测量结果与核磁共振数据相吻合，在25℃时的Jucff/Fe为~1.3微米。固体I的零场穆斯堡尔谱显示为单四极双峰，其参数为0.50，AEq为1.21 mm/S。电化学数据表明，酚类配体取代芳硫酸盐导致[Fe4S4]2+核的第一和第二还原电位显著负移。在核磁共振波谱的监测下，I与PhSH反应生成了[Fe4S4(Oph)4“(Sph)]2”(=0-4)混合配位物种，配体在物种中的分布具有近似的统计分布.累积的结果与I和II中相对共价的Fe-0相互作用相一致.讨论了酪氨酸与4Fe-4S中心配位的生物学意义.
The phenoxide-ligated tetranuclear iron-sulfur clusters [Fe4S4 (OAr) 4] 2-(I, R= phenyl; II, R= p-tolyl) have been synthesized by reaction of [Fe4S4 (SR) 4] 2-or [Fe4S4Cl4] 2-with HOAr or NaOAr, respectively. The preparation, reactivity, and electronic properties of these compounds are described, as is the crystal structure of the Et4N+ salt of I.[Et4N] 2 [Fe4S4 (OPh) 4] crystallizes in the monoclinic space group—P2xjn with Z= 4 and unit-cell parameters a= 17.610 (4) Á, b= 11.600 (3) Á, c= 22.810 (6) Á, ß= 106.41 (1), and V= 4469.9 Á3**(-150 C). The structure was refined to R= 0.066 and/?„= 0.107, using 6032 independent reflections with F02> 3a (F02). The structure of I consists of an [Fe4S4] 2+ cubane core distorted toward Z) M symmetry, with a terminal phenoxide ligand completing the approximately tetrahedral coordination about each iron atom. The most notable structural feature is the short Fe-O distance (mean 1.865 (17) Á). Isotropically shifted resonances are observed in the* H NMR spectra of I and II; the directions and relative magnitudes of these shifts are consistent with significant delocalization of spin into the it system of the phenyl rings. At any temperature, the magnitude of the isotropic shifts is approximately twice that observed for the arenethiolate analogues. The magnitude of the isotropic shifts increases with increasing temperature, consistent with an antiferromagnetically coupledsystem. Variable-temperature magnetic susceptibility measurements are in agreement with the NMR data and give values of jucff/Fe of~ 1.3 µ at 25 C. Zero field Mossbauer spectra of solid I show a single quadrupole doubletwith parameters= 0.50 and AEq= 1.21 mm/s. Electrochemical data indicate that substitution of arenethiolate by phenolate ligands results in substantial negative shifts of first and second reduction potentials of the [Fe4S4] 2+ core. Reaction of I with PhSH, monitored by NMR spectroscopy, generates the mixed-ligand species [Fe4S4 (OPh) 4_ „(SPh)„] 2"(= 0-4), with an approximately statistical distribution of ligands among the species present. The accumulated results are consistent with a relatively covalent Fe-0 interaction in I and II. The biological implications for tyrosyl coordination to 4Fe-4S centers are discussed.