Acetylene to vinylidene rearrangements on electron rich d6 metal centers: a density functional study
Acetylene to vinylidene rearrangements on electron rich d6 metal centers: a density functional study
复制标题
DOI：
10.1039/b408452g
复制
发表时间：
2004-01-01
影响因子：
4
通讯作者：
Re, N
中科院分区：
文献类型：
--
作者：
De Angelis, F;Sgamellotti, A;Re, N
用密度泛函理论计算方法研究了几种金属中心电子丰度不同的Ru(II)d(6)金属碎片上乙炔与偏乙烯的异构化。我们考虑了[(eta(5)-C5Me5)Ru(dippe)](+), [(eta(5)-C5Me5)Ru(dmpe)](+), [(eta(5)-C5H5)Ru(PMe3)(2)](+), [(eta(6)-C6Me6) Ru(CO)(PPh3)](+), [(eta(5)-C5H5)Ru(CO)(PPh3)]（+）和[(eta(6)-C6H6)(PMe3)ClRu](+)，这些物质在阳离子Ru（II）配合物化学中非常常见，并且跨越了广泛的电子丰度范围。对于每一个考虑的片段，势能面上的最小值对于两种可能的异构化机制，即通过1,2-氢的直接移位或通过羟基-炔基中间体，已经定位。在乙烯配合物的C=C伸展频率之间发现了线性相关关系，作为电子丰富度的估计，与相应的羟基炔基中间体的稳定性。对于考虑的碎片中最富电子的[(Cp*)(dippe)Ru(HCCH)](+)，已经发现羟基-炔基与炔配合物基本上是等能的（仅高1.9千卡摩尔（-1）），这与实验证据一致，表明该体系在这两种物质之间达到平衡。对于相同的[(Cp*)(dippe)Ru]（+）碎片，详细分析了两种可能的乙炔重排途径的反应谱。我们的研究结果表明，一旦进入eta(2)-C-H配位乙炔中间体，该体系很容易演变为氢炔基中间体，这一过程在动力学上更有利于直接1,2移位生成偏乙烯产物。
The acetylene to vinylidene isomerization on several Ru(II)d(6) metal fragments with different electron richness of the metal center has been investigated by means of density functional theory calculations. We considered the [(eta(5)-C5Me5)Ru(dippe)](+), [(eta(5)-C5Me5)Ru(dmpe)](+), [(eta(5)-C5H5)Ru(PMe3)(2)](+), [(eta(6)-C6Me6)(PMe3)ClRu](+), [(eta(5)-C5H5)Ru(CO)(PPh3)](+) and [(eta(6)-C6H6)(PMe3)ClRu](+), species which are quite common in the chemistry of cationic Ru(II) complexes and span a wide range of electron-richness. For each of the considered fragments, the minima on the potential energy surfaces for the two possible isomerization mechanisms, i.e. through a direct 1,2-hydrogen shift or through a hydrido-alkynyl intermediate, have been localized. A linear correlation has been found between the C=C stretching frequencies of the vinylidene complexes, as an estimate of the electron richness, and the stability of the corresponding hydrido-alkynyl intermediates. For the most electron-rich among the considered fragments, [(Cp*)(dippe)Ru(HCCH)](+), the hydrido-alkynyl species has been found essentially isoenergetic with the alkyne complex (only 1.9 kcal mol(-1) higher), in agreement with the experimental evidence showing for this system an equilibrium between these two species. For the same [(Cp*)(dippe)Ru](+) fragment, a detailed analysis of the reaction profiles for the two possible acetylene rearrangement pathways has been performed. Our results show that once the eta(2)-C-H coordinated acetylene intermediate is accessed, the system can easily evolve towards a hydrido-alkynyl intermediate, this process being kinetically favored with respect to the direct 1,2-shift leading to the vinylidene product.