Internal Alkyne Isomerization to Vinylidene versus Stable π-Alkyne: Theoretical and Experimental Study on the Divergence of Analogous Cp*Ru and TpRu Systems

The activation of internal alkynes by Cp*Ru and TpRu complexes gives respectively π-alkyne and disubstituted vinylidene as stable species, even though both systems bear identical pyridylphosphine ligands (κ2P,N- iPr2PXPy, X = NH, CH2, S). The activation of the alkynones PhCCCOR (R = Me, Ph) by [TpRuCl(iPr2PXPy)] complexes allowed us to isolate and characterize metastable η1-OC(R)CCPh adducts. These complexes isomerize spontaneously to vinylidene both in solution and in the solid state. Kinetic studies have been carried out in solution by 31P{1H} NMR and in the solid state by IR spectroscopy, providing the Eyring and Avrami–Erofeev parameters, respectively. The activation of internal alkynes without ketone groups provided vinylidene species as well, but without isolable intermediates. In contrast with the TpRu system, the activation of alkynones by [Cp*RuCl(iPr2PXPy)] always results in stable π-alkyne species. Representatives of both Cp*Ru−π-alkyne and TpRu–vinylidene compounds have been characterized by X-ray diffraction. DFT calculations have been carried out with the actual experimental complexes, including solvent effects, in order to analyze the mechanism of the π-alkyne to vinylidene isomerization of internal alkynes and to explain the divergent results obtained for Tp and Cp*.

Cp*Ru与TpRu配合物对内炔烃的活化分别生成π-炔烃与二取代亚乙烯基作为稳定物种，尽管两个体系所使用的吡啶基膦配体完全一致，均为κ2P,N-配位模式的iPr2PXPy（X=NH、CH2、S）。[TpRuCl(iPr2PXPy)]配合物活化炔酮PhC≡CCOR（R=甲基、苯基）时，我们成功分离并表征了亚稳态的η1-O配位的O=C(R)C≡CPh加合物。这类配合物在溶液与固态环境中均可自发异构化为亚乙烯基物种。我们分别通过31P{1H}质子去耦核磁共振波谱（溶液相）与红外光谱（固态）开展了动力学研究，由此分别获得了埃林（Eyring）参数与阿夫拉米-叶罗菲耶夫（Avrami–Erofeev）参数。不含酮羰基的内炔烃经活化后同样生成亚乙烯基物种，但无法分离得到中间产物。与TpRu配合物体系不同，[Cp*RuCl(iPr2PXPy)]配合物活化炔酮时，始终生成稳定的π-炔烃物种。我们通过X射线衍射对Cp*Ru−π-炔烃与TpRu–亚乙烯基两类代表性化合物进行了结构表征。本研究采用实际实验所用的配合物开展了密度泛函理论（DFT）计算，并纳入溶剂化效应，以此分析内炔烃从π-炔烃异构化为亚乙烯基的反应机理，同时解释了Tp与Cp*体系所得实验结果的差异性。