The molybdenum and tungsten 2,4,6-trimethylbenzylidyne complexes [MesC≡M{OC(CF₃)_nMe_3–n}₃] (M = Mo: MoF0, n = 0; MoF3, n = 1; MoF6, n = 2; MoF9, n = 3; M = W: WF3, n = 1; Mes = 2,4,6-trimethylphenyl) were prepared by the reaction of the tribromides [MesC≡MBr₃(dme)] (dme = 1,2-dimethoxyethane) with the corresponding potassium alkoxides KOC(CF₃)_nMe_3–n. The molecular structures of all complexes were established by X-ray diffraction analysis. The catalytic activity of the resulting alkylidyne complexes in the homometathesis and ring-closing alkyne metathesis of internal and terminal alkynes was studied, revealing a strong dependency on the fluorine content of the alkoxide ligand. The different catalytic performances were rationalized by DFT calculations involving the metathesis model reaction of 2-butyne. Because the calculations predict the stabilization of metallacyclobutadiene (MCBD) intermediates by increasing the degree of fluorination, MoF9 was treated with 3-hexyne to afford the MCBD complex [(C₃Et₃)Mo{OC(CF₃)₃}₃], which was characterized spectroscopically.

中文翻译：

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用氟代醇盐配体OC（CF ₃）_n Me _{3– n}（n = 0–3）调节钼和钨2,4,6-三甲基苄二炔配合物的催化炔烃复分解活性

钼和钨2,4,6-三甲基苄二炔络合物[MesC≡M{OC（CF ₃）_n Me _{3– n} } ₃ ]（M = Mo：MoF0，n = 0；MoF3，n = 1；MoF6，n＝ 2；MoF 9，n＝ 3； M ＝ W：WF 3，n＝ 1； Mes ＝ 2,4,6-三甲基苯基）通过三溴化物[MesC ₃ MBr ₃（dme）]（dme ＝ 1）反应制备。，2-二甲氧基乙烷）和相应的烷氧基钾KOC（CF ₃）_n Me _{3– n}。通过X射线衍射分析确定了所有配合物的分子结构。研究了在内部和末端炔烃的复分解和闭环炔烃复分解反应中生成的亚烷基配合物的催化活性，显示出对烷氧化物配体氟含量的强烈依赖性。通过涉及2-丁炔的复分解模型反应的DFT计算合理化了不同的催化性能。由于计算结果预测了通过增加氟化度可稳定金属环丁二烯（MCBD）中间体，因此用3-己炔处理MoF9可得到MCBD配合物[（C ₃ Et ₃）Mo {OC（CF ₃）₃ } ₃]，通过光谱表征。