The catalytic utility of [RuL¹(CO)₂I₂] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L¹), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBAr^F, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.

中文翻译：

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内和末端炔烃化学和立体选择性半加氢的退火介孔碳（MIC）基Ru（II）催化剂

评估[RuL ¹（CO）₂ I ₂ ]（1）的催化效用，该催化剂包含基于π-共轭咪唑-萘啶基的中性离子卡宾（MIC）配体（L ¹），用于E-选择性炔烃半氢化反应。预催化剂1与2当量的AgBAr ^F组合，可在水中与分子氢（5 bar）半氢化各种内部炔烃。（E）-烯烃的收率很高，并且可以容忍许多可还原的官能团。螯合MIC配体和两个顺式羰基在Ru中心为氢化和异构化提供了一个明确的平台。两种碘化物的损失和两种羰基的存在使Ru中心电子缺乏，因此避免了与末端炔烃形成金属亚乙烯基。通过在异丙醇中的相同催化系统，可以利用它来催化末端炔烃的半氢化反应。反应曲线，异构化，动力学和DFT研究表明，最初的炔烃氢化为（Z）烯烃，然后通过金属催化的Z → E异构化进一步异构化为（E）烯烃。