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首页> 外文期刊>Catalysis science & technology >A theoretical study of the activity in Rh-catalysed hydroformylation: the origin of the enhanced activity of the π-acceptor phosphinine ligand
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A theoretical study of the activity in Rh-catalysed hydroformylation: the origin of the enhanced activity of the π-acceptor phosphinine ligand

机译：RH催化氢甲基化活性的理论研究：π-受体磷酸配体的增强活性的起源

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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 n-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.
机译：使用一组计算工具研究了控制RH催化的氢甲酰化活性的因素。我们对磷酸修饰的RH催化剂[HRH（CO）3（PC5H2R3）]进行了DFT计算，并将其与磷酸化的HRH（CO）3（CO）3（PR3）和HRH（CO）2（PR3）2（PR3）2复合物进行了比较。 N-Apceptor磷酸配体配体在五角齿RH复合物的赤道位点优先与垂直于赤道平面的杂环坐标，尽管配体围绕RH-P键自由旋转。总体能屏障可以分为以下贡献：烯烃复合物的形成，烯烃旋转和烯烃插入。在没有空间效应（模型系统）的情况下，总体屏障与烯烃旋转的计算屏障相关。这证明π受体配体将反向浓度减少到烯烃，从而导致较低的旋转屏障，从而导致较高的活性。使用改良版的能量分解分析（EDA）对RH-P供体的相互作用进行了量化。在Rh磷氨酸系统中，π-背对抑制的有效方向性，而不是总体受体能力，是高催化活性的原因。引入空间效应增加了协调烯烃所需的能量，从而增加了整体屏障。控制Rh-磷酸催化剂活性的因素似乎与QSAR模型开发过程中Rh-二磷酸的催化剂有关（Catal。Sci。Technol。2012，2，1694）。为了研究单声道的发现是否可以外推到双磷酸配体，我们使用易于间隔的2D-Descriptors使用拓扑最大互相关（TMACC）方法重新检查了以前的QSAR模型。 TMACC描述符突出显示了接近磷的杂原子作为活性吸收原子，而高度取代的碳原子基团被突出显示为活性降低的基团。

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