SUBSITE-DIFFERENTIATED ANALOGS OF NATIVE [4FE-4S]2+ CLUSTERS - PREPARATION OF CLUSTERS WITH 5-COORDINATE AND 6-COORDINATE SUBSITES AND MODULATION OF REDOX POTENTIALS AND CHARGE-DISTRIBUTIONS
SUBSITE-DIFFERENTIATED ANALOGS OF NATIVE [4FE-4S]2+ CLUSTERS - PREPARATION OF CLUSTERS WITH 5-COORDINATE AND 6-COORDINATE SUBSITES AND MODULATION OF REDOX POTENTIALS AND CHARGE-DISTRIBUTIONS
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DOI：
10.1021/ja00163a028
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发表时间：
1990-03-28
影响因子：
15
通讯作者：
HOLM, RH
中科院分区：
文献类型：
--
作者：
CIURLI, S;CARRIE, M;HOLM, RH
亚位分化簇[Fe4S4（LS3)Cl]2- （1,ls3 = 1,3,5-三（（4,6-二甲基-3-巯基）硫）-2,4,6-三（对甲基硫）苯（3-）））在Me2SO溶液中与多种双齿和三齿配体反应生成取代簇[Fe4S4(LS3)L'']z-。制备了10个这种类型的团簇，以考察团簇电荷和独特子位配位数对氧化态的相对稳定性和57Fe异构体位移感应的电荷分布的影响。这是第一次对Fe4S4簇的这种效应进行全面研究。所制备的簇包括L′= ph -(4)、Me2NCS2-(5)、吡啶-2-硫代酸酯(6)、1,4,7-三氮杂环壬烷(8)、三吡唑硼酸酯(9)和1,2-二取代苯，如苯-1,2-二硫代酸酯（11）。LS3配体的H - NMR各向同性位移对L′′高度敏感。给出了移位表。所有簇在解中都具有有效的三角对称性。取代团簇具有以下重要性质：(i)化学可逆的[Fe4S4]3+/2+氧化还原偶，电位约为300-700 mV，比参考团簇4负；（ii） [Fe4S4]3+/2+和[Fe4S4]2+/3+对在单负簇8 vs 1和4上的电位负移；（iii）与对称离域相比，独特子位上的电子分布向“类铁”（5,6,11）和“类铁”（8,9）特征倾斜。其他考虑的问题包括某些取代团簇的稳定性来源以及团簇电荷和核心电荷密度对氧化还原电位的影响。这些数据显示了原生簇中单个亚位点上各种潜在配体的内在效应。这项工作可能的生物学意义是用氮酶的p簇来说明的，它的末端连接可能不同于现在经典的天然簇Fe4S4(S.cntdot.Cys)4。
The subsite-differentiated cluster [Fe4S4(LS3)Cl]2- (1, LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-)) in Me2SO solution reacts with a variety of bidentate and tridentate ligands to afford the substituted clusters [Fe4S4(LS3)L'']z-. Some ten clusters of this type were prepared in order to examine the effects of cluster charge and coordination number at the unique subsite on relative stabilities of oxidation states and charge distributions as sensed by 57Fe isomer shifts. This is the first comprehensive study of such effects with Fe4S4 clusters. Clusters prepared include those with L'' = PhS- (4), Me2NCS2- (5), pyridine-2-thiolate (6), 1,4,7-triazacyclononane (8), hydrotris(1-pyrazolyl)borate (9), and 1,2-disubstituted benzenes such as benzene-1,2-dithiolate (11). Cluster formation is detected by H NMR isotropic shifts of the LS3 ligand, which are highly sensitive to L''. A tabulation of shifts is presented. All clusters have effective trigonal symmetry in solution. Among the more significant properties of the substituted clusters are the following: (i) chemically reversible [Fe4S4]3+/2+ redox couples at potentials ca. 300-700 mV more negative than that of reference cluster 4; (ii) negative shifts of the potentials of the [Fe4S4]3+/2+ and [Fe4S4]2+/3+ couples on mononegative cluster 8 vs 1 and 4; and (iii) skewing of electron distribution at the unique subsites toward "ferric-like" (5,6,11) and "ferrous-like" (8, 9) character vs symmetrically delocalized 4. Other matters considered include the source of stability of certain substituted clusters and the effects of cluster charge and core charge density on redox potentials. The data presented approximate the intrinsic effects of various potential ligand sets at a single subsite in native clusters. The possible biological implications of this work are illustrated with the P-clusters of nitrogenase, whose terminal ligation may depart from that of the now-classical native clusters Fe4S4(S.cntdot.Cys)4.