Rao P Venkateswara, Bhaduri Sumit, Jiang Jianfeng, Holm R H
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Inorg Chem. 2004 Sep 20;43(19):5833-49. doi: 10.1021/ic040055s.
Sulfur bridging interactions between three cis-planar NiII-S2N2 complexes and NiII, CuI,II, ZnII, and HgII reactants were investigated by synthesis and X-ray crystal structures of some 24 complexes. This work was stimulated by recent crystallographic structures of the A-cluster of carbon monoxide dehydrogenase/acetylcoenzyme A synthase. This bridged biological assembly has the minimal formulation [Fe4S4]-(micro2-SCys)-[M((micro2-SCys)2Gly)Ni] with M = NiII, CuI, and ZnII at sites distal and proximal, respectively, to the iron-sulfur cluster. Bridges supported by representations of the distal nickel site were sought by reactions of the complexes [NiII(LH-S2N2)]2- and [NiII(LR-S2N2)], with 5-5-5 chelate ring patterns. Reaction products implicate the bridges Ni-(micro2-S)1,2-M in a variety of molecular structures, some with previously unknown connectivities of bridge atoms. The most frequently encountered bridge units are the nonplanar rhombs Ni(2-S)2M involving both sulfur atoms of a given complex. Those with M = NiII are biologically relevant inasmuch as the catalytic metal at the proximal site is nickel. The complex [Ni(L-655)]2-, containing the 6-5-5 ring pattern and coordination sphere of the distal nickel site, was prepared and structurally characterized. It was shown to sustain Ni2(micro2-S)2 rhombic interactions in the form of trinuclear [[Ni(L-655)]2Ni]2- and [[Ni(L-655)]Ni(R2PCH2CH2PR2)] (R = Et, Ph) in which the second NiII simulates the proximal site. Bridging interactions of NiII-S2N2 complexes are summarized, and geometrical features of Ni2(2-S)2 rhombs in these complexes, as dependent on ring patterns, are considered (LH-S2N2 = N,N'-ethylenebis(2-mercaptoisobutyramide)(4-); LR-S2N2 = trans-rac-N,N'-bis(2-mercapto-2-methylprop-1-yl)-1,2-cyclohexanediamine(2-); L-655 = N-(2-mercaptopropyl)-N'-(2'-mercaptoethyl)glycinamide(4-)).
通过约24种配合物的合成及X射线晶体结构，研究了三个顺式平面NiII - S2N2配合物与NiII、CuI,II、ZnII和HgII反应物之间的硫桥连相互作用。这项工作受到一氧化碳脱氢酶/乙酰辅酶A合酶A簇最近晶体结构的启发。这种桥连生物组装体的最简形式为[Fe4S4]-(μ2 - SCys)-[M((μ2 - SCys)2Gly)Ni]，其中M分别在铁硫簇的远端和近端位点为NiII、CuI和ZnII。通过具有5 - 5 - 5螯合环模式的配合物[NiII(LH - S2N2)]2-和[NiII(LR - S2N2)]的反应，寻找由远端镍位点表示所支持的桥连。反应产物表明在各种分子结构中存在Ni-(μ2 - S)1,2 - M桥连，其中一些具有以前未知的桥连原子连接方式。最常遇到的桥连单元是非平面菱形Ni(2 - S)2M，涉及给定配合物的两个硫原子。那些M = NiII的在生物学上具有相关性，因为近端位点的催化金属是镍。制备并对含有6 - 5 - 5环模式和远端镍位点配位球的配合物[Ni(L - 655)]2-进行了结构表征。结果表明它以三核[[Ni(L - 655)]2Ni]2-和[[Ni(L - 655)]Ni(R2PCH2CH2PR2)]（R = Et，Ph）的形式维持Ni2(μ2 - S)2菱形相互作用，其中第二个NiII模拟近端位点。总结了NiII - S2N2配合物的桥连相互作用，并考虑了这些配合物中Ni2(2 - S)2菱形的几何特征，其取决于环模式（LH - S2N2 = N,N'-亚乙基双(2 - 巯基异丁酰胺)(4 - )；LR - S2N2 = 反式 - 外消旋 - N,N'-双(2 - 巯基 - 2 - 甲基丙 - 1 - 基)-1,2 - 环己二胺(2 - )；L - 655 = N-(2 - 巯基丙基)-N'-(2'-巯基乙基)甘氨酰胺(4 - )）。
