The formation of linear hydrocarbon chains by sequential coupling of C₁ units on the metal surface is the central part of the Fischer–Tropsch (F-T) synthesis. Organometallic complexes have provided numerous models of relevant individual C–C coupling events but have failed to reproduce the complete chain lengthening sequence that transforms a linear C_n hydrocarbon chain into its C_n+1 homologue in an iterative fashion. In this work, we demonstrate stepwise growth of linear C_n hydrocarbon chains and their conversion to their C_n+1 homologues via consecutive addition of CH₂ units on a molecular diruthenium carbide platform. The chain growth sequence is initiated by the formation of a μ-η¹:η¹-C═CH₂ ligand from a C + CH₂ coupling between the μ-carbido complex [(Cp*Ru)₂(η-NPh)(μ-C)] (1; Cp* = η⁵-C₅Me₅) and Ph₂SCH₂. Then, the chain propagates via a general C═CHR + CH₂ coupling and subsequent hydrogen-assisted isomerization of the resulting allene ligand μ-η¹:η³-H₂C═C═CHR to a higher vinylidene homologue μ-η¹:η¹-C═CH(CH₂)R. By repeating this reaction sequence, up to C₆ chains have been synthesized in a stepwise fashion. The key step of this chain homologation sequence is the selective hydrogenation of the μ-η¹:η³-allene unit to the corresponding μ-alkylidene ligand. Isotope labeling and computational studies indicate that this transformation proceeds via the hydrogenation of the allene ligand to a terminal alkene form and its isomerization to the μ-alkylidene ligand facilitated by the coordinatively unsaturated diruthenium platform.

中文翻译：

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来自分子碳化二钌平台的线性烃链生长

通过在金属表面上连续偶联 C ₁单元形成线性烃链是费托 (FT) 合成的核心部分。有机金属配合物提供了许多相关单个 C-C 偶联事件的模型，但未能重现以迭代方式将线性 C _n烃链转化为其 C _{n +1}同系物的完整链延长序列。在这项工作中，我们展示了线性 C _n烃链的逐步增长及其通过连续添加 CH ₂转化为 C _{n +1}同系物分子碳化二钌平台上的单元。链增长序列由形成了μ-η的发起¹：η ¹ -C═CH ₂从C + CH配体₂的μ-碳化复合物之间的耦合[（CP * Ru）的₂（η-NPH）（ μ-C)] ( 1；Cp* = η ⁵ -C ₅ Me ₅ )和Ph ₂ SCH ₂。然后，链通过一般的 C=CHR + CH ₂偶联和随后得到的丙二烯配体 μ-n ¹ :η ³ -H ₂ C =C=CHR 的氢辅助异构化扩展为更高的亚乙烯基同系物 μ-η ¹:η ¹ -C=CH(CH ₂ )R。通过重复该反应序列，最多可逐步合成C ₆链。该链同源序列的关键步骤是将 μ-n ¹ :n ^{3 -}丙二烯单元选择性氢化成相应的 μ-亚烷基配体。同位素标记和计算研究表明，这种转化是通过丙二烯配体氢化为末端烯烃形式以及在配位不饱和二钌平台的促进下异构化为 μ-亚烷基配体来进行的。