Synthesis of N‑Heterocycle Substituted Silyl Ligands within the Coordination Sphere of Iron

N-Heterocycle-substituted silyl iron complexes have been synthesized by nucleophilic substitution at trichlorosilyl ligands bound to iron. The homoleptic (tripyrrolyl)- and tris­(3-methylindolyl)­silyl groups were accessed from (Cl3Si)­CpFe­(CO)2 (Cl3SiFp) by substitution of chloride with pyrrolide or 3-methylindolide, respectively. Analogously, nucleophilic substitution of Cl with pyrrolide on the anionic Fe(0) synthon Cl3SiFe­(CO)4– generates the (tripyrrolyl)­silyl ligand, bound to the iron tetracarbonyl fragment. The bulkier 2-mesitylpyrrolide substitutes a maximum of 2 chlorides on Cl3SiFp under the same conditions. The tridentate, trianionic nucleophile tmim (tmimH3 = tris­(3-methylindol-2-yl)­methane) proves reluctant to perform the substitution in a straightforward manner; instead, ring-opening and incorporation of THF occurs to form the tris-THF adduct tmim­(C4H8O)3SiFe­(CO)4–. The bidentate, monoanionic nucleophile 2-(dipp-iminomethyl)­pyrrolide (DippIMP, dipp = 2,6-diisopropylphenyl) shows chloride displacement and addition of a second DippIMP moiety on the imine backbone. The heterocycle-based silyl ligands were shown to be sterically and electronically tunable, moderately electron-donating ligands. The presented approach to new silyl ligands avoids strongly reducing conditions and potentially reactive hydrosilane intermediates.氮杂环取代的甲硅烷基铁配合物（N-Heterocycle-substituted silyl iron complexes）可通过对与铁配位的三氯甲硅烷基配体（trichlorosilyl ligands）进行亲核取代反应制备得到。均配型三吡咯基甲硅烷基和三(3-甲基吲哚基)甲硅烷基配体对应的配合物，可由(三氯甲硅烷基)二羰基环戊二烯基铁（Cl3SiFp）通过分别以吡咯负离子（pyrrolide）和3-甲基吲哚负离子（3-methylindolide）取代氯原子得到。类似地，以吡咯负离子对阴离子型Fe(0)合成子（anionic Fe(0) synthon）Cl3SiFe(CO)4– 中的氯原子进行亲核取代，可得到与四羰基铁片段结合的三吡咯基甲硅烷基配体对应的配合物。在相同条件下，位阻更大的2-均三甲苯基吡咯（2-mesitylpyrrolide）仅能对Cl3SiFp中的最多2个氯原子发生取代反应。三齿三阴离子亲核试剂tmim（tmimH3=三(3-甲基吲哚-2-基)甲烷）难以直接发生取代反应，反而会使四氢呋喃（THF）开环并参与配位，最终生成三(四氢呋喃)加合物tmim(C4H8O)3SiFe(CO)4–。双齿单阴离子亲核试剂2-(二异丙基苯基亚胺甲基)吡咯（2-(dipp-iminomethyl)pyrrolide，简称DippIMP，其中dipp=2,6-二异丙基苯基）可发生氯原子置换反应，并在亚胺骨架上引入第二个DippIMP单元。实验表明，此类基于杂环的甲硅烷基配体具有空间和电子可调性，属于中等强度的给电子配体。本研究开发的新型甲硅烷基配体合成方法，避免了强还原条件以及高活性的氢硅烷中间体。