Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Inorg Chem. 2023 Feb 6;62(5):1911-1918. doi: 10.1021/acs.inorgchem.2c01353. Epub 2022 Jun 15.
Reported herein are alkyne and alkene adducts of synthetic [FeS] clusters that model intermediates and inhibitor-bound states in enzymes involved in isoprenoid biosynthesis. Treatment of the -heterocyclic carbene-ligated cluster [(IMes)FeS(OEt)][BAr] (IMes = 1,3-dimesitylimidazol-2-ylidene; [BAr] = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) with phenylacetylene (PhCCH) or -cyclooctene (COE) results in displacement of the EtO ligand to yield the corresponding π complexes, [(IMes)FeS(PhCCH)][BAr] and [(IMes)FeS(COE)][BAr]. EPR spectroscopic analysis demonstrates that both clusters are doublets with > 2 and thus are spectroscopically faithful models of the analogous species characterized in the isoprenoid biosynthetic enzymes IspG and IspH. Structural and Mössbauer spectroscopic analysis reveals that both complexes are best described as [FeS] clusters in which the unique Fe site engages in modest back-bonding to the π-acidic ligand. Paramagnetic NMR studies show that, even at room temperature, the alkyne/alkene-bound Fe centers harbor minority spin and therefore adopt an Fe valence. We propose that such valence localization could likewise occur in Fe-S enzymes that interact with π-acidic molecules.
本文报道了模拟异戊烯生物合成酶中中间体和抑制剂结合态的 [FeS] 簇的炔烃和烯烃加合物。用 -杂环卡宾配体的簇 [(IMes)FeS(OEt)][BAr]（IMes = 1,3-二异丙基咪唑-2-亚基；[BAr] = 四（3,5-双（三氟甲基）苯基）硼酸酯）处理苯乙炔（PhCCH）或环辛烯（COE），导致 EtO 配体被取代，生成相应的π 配合物 [(IMes)FeS(PhCCH)][BAr] 和 [(IMes)FeS(COE)][BAr]。电子顺磁共振波谱分析表明，两个簇均为 > 2 的二重态，因此是异戊烯生物合成酶 IspG 和 IspH 中特征类似物的光谱忠实模型。结构和穆斯堡尔谱分析表明，两个配合物都可以最好地描述为 [FeS] 簇，其中独特的 Fe 位点与 π-酸性配体适度地发生反馈键合。顺磁 NMR 研究表明，即使在室温下，炔烃/烯烃结合的 Fe 中心也含有少数自旋，因此采用 Fe 价态。我们提出，在与 π-酸性分子相互作用的 Fe-S 酶中也可能发生这种价态定位。
