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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Ring contraction of six-membered metallabenzynes to five-membered metal-carbene complexes: A comparison with organic analogues
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Ring contraction of six-membered metallabenzynes to five-membered metal-carbene complexes: A comparison with organic analogues

机译：六元金属labenzynes到五元金属卡宾配合物的环收缩：与有机类似物的比较。

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摘要

The ring contraction of six-membered metallabenzynes to five-membered metal-carbene complexes in comparison with the corresponding rearrangement of benzyne to cyclopentadienylidene carbene have been studied by computational quantum mechanical calculations. The rearrangement of benzyne to a cyclopentadienylidene carbene is endothermic by 27.8 kcal mol~(-1). The instability of the cyclopentadienylidene carbene is attributed to the electron deficient singlet carbene carbon atom. However, the isolobal replacement of a sp-hybridized carbon atom in benzyne by a 14 valence electron transition metal fragment (M(PH_3)_2Cl_2, M = Fe, Ru and Os) makes the corresponding rearrangement feasible. The first row transition metal iron shows thermodynamic (exothermic by 19.1 kcal mol~(-1)) and kinetic preference (energy barrier of 1.8 kcal mol~(-1)) towards the carbene complex. However, the preference reduces down the group. The coordination number of the metal as well as the low-lying in-plane M-C π*-MO play a crucial role for this rearrangement. The conversion of metallabenzynes to metal-carbene complexes is also associated with a ring plane rotation to attain an effective overlap between the metal d-orbital and the p-orbital on the carbene carbon atom.
机译：通过计算量子力学计算研究了六元金属戊烯至五元金属-卡宾配合物的环收缩，以及苯并相应地重排成环戊二烯亚基卡宾。苯并炔重排成环戊二烯亚基卡宾时吸热为27.8 kcal mol〜（-1）。环戊二烯亚基卡宾的不稳定性归因于缺电子的单线态卡宾碳原子。然而，用14价电子过渡金属片段（M（PH_3）_2Cl_2，M = Fe，Ru和Os）等价取代苯炔中的sp杂化碳原子使相应的重排成为可能。第一排过渡金属铁对卡宾络合物表现出热力学性质（放热19.1 kcal mol〜（-1））和动力学偏好（能量垒为1.8 kcal mol〜（-1））。但是，首选项减少了该组。金属的配位数以及低位的平面M-Cπ* -MO对这种重排起着至关重要的作用。金属戊烯酮向金属-卡宾配合物的转化还与环平面旋转相关联，以在卡宾碳原子上的金属d-轨道和p-轨道之间实现有效的重叠。

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