A theoretical study of the activity in Rh-catalysed hydroformylation: the origin of the enhanced activity of the p-acceptor phosphinine ligand
A theoretical study of the activity in Rh-catalysed hydroformylation: the origin of the enhanced activity of the p-acceptor phosphinine ligand
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Rh催化加氢甲酰化活性的理论研究：p受体膦配体活性增强的根源
DOI：
10.1039/c3cy00956d
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Aguado-Ullate S
中科院分区：
文献类型：
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作者：
Aguado-Ullate S
利用一组计算工具研究了铑催化加氢反应中影响活性的因素。我们对膦改性的Rh催化剂[HRh（CO）3（PC 5 H2 R3）]进行了DFT计算，并将其与膦改性的HRh（CO）3（PR 3）和HRh（CO）2（PR 3）2配合物进行了比较。π-受体膦配体优先在五配位Rh络合物的赤道位点与垂直于赤道平面的杂环配位，尽管配体围绕Rh-P键自由旋转。总的能垒可以分为以下贡献：烯烃络合物的形成，烯烃旋转和烯烃插入。在没有空间效应（模型系统）的情况下，整体势垒与烯烃旋转的计算势垒相关。这证明了π-受体配体减少了对烯烃的反馈，导致较低的旋转势垒，从而导致较高的活性。Rh-P供体-受体相互作用使用能量分解分析（EDA）的修改版本进行定量。在Rh-膦体系中，π-反馈的有效方向性，而不是整体受体能力，是高催化活性的原因。引入空间效应增加了与烯烃配位所需的能量，从而增加了整体势垒。控制Rh-单磷烷催化剂活性的因素似乎与QSAR模型开发过程中推导出的Rh-二磷烷相关（Catal. Sci. 2012，2，1694）。为了研究mono-的发现是否可以外推到二膦配体，我们使用基于易于解释的2D描述符的拓扑最大互相关（TMACC）方法重新检查了我们以前的QSAR模型。TMACC描述符突出显示接近磷的杂原子作为活性增加原子，而高度取代的碳原子基团突出显示为活性降低基团。
The factors governing the activity in Rh-catalyzed hydroformylation were investigated using a set of computational tools. We performed DFT calculations on the phosphinine-modified Rh catalyst [HRh(CO)3(PC5H2R3)] and compared it to the phosphane-modified HRh(CO)3(PR3) and HRh(CO)2(PR3)2 complexes. The π-acceptor phosphinine ligand coordinates preferentially at the equatorial site of the pentacoordinated Rh complex with the heterocycle perpendicular to the equatorial plane, although the ligand freely rotates around the Rh–P bond. The overall energy barrier can be divided into the following contributions: alkene complex formation, alkene rotation and alkene insertion. In the absence of steric effects (model systems), the overall barrier correlates with the computed barrier for alkene rotation. This proves that π-acceptor ligands reduce back-donation to the alkene, leading to a lower rotational barrier and, consequently, to a higher activity. The Rh–P donor–acceptor interactions were quantified using a modified version of energy decomposition analysis (EDA). In Rh–phosphinine systems, the efficient directionality of the π-back-donation, rather than the overall acceptor ability, is responsible for the high catalytic activity. Introducing steric effects increases the energy required to coordinate the alkene, increasing the overall barrier. The factors governing the activity in Rh–monophosphane catalysts seem to be related to those derived for Rh–diphosphane during the development of a QSAR model (Catal. Sci. Technol. 2012, 2, 1694). To investigate whether the findings for mono- can be extrapolated to diphosphane ligands, we re-examined our previous QSAR model using the Topological Maximum Cross Correlation (TMACC) method based on easy-to-interpret 2D-descriptors. The TMACC descriptors highlight heteroatoms close to phosphorus as activity-increasing atoms, whereas highly substituted carbon atom groups are highlighted as activity-decreasing groups.