Department of Chemistry, Inha University, Incheon 402-751, Korea.
J Comput Chem. 2010 Sep;31(12):2248-57. doi: 10.1002/jcc.21514.
We investigated the transition metal-catalyzed reaction mechanisms of NBD dimerization to Binor-S using cationic Co(I), Rh(I), and Ir(I) catalysts, using mPW1PW91, mPW1K, and B3LYP density functional methods. Our results indicate that the monomeric metal center has the ability to bind with four double bonds of two NBD molecules with a syn spatial geometry to form a penta-coordinated complex. We designed three possible pathways, but found two of them blocked. The favored pathway involves three steps from the reactant precursor to the product precursor: the first step is the formation of a single bond to connect two NBD units, the second is the alkene insertion leading to the formation of the three-membered ring structure, and the final step is the formation of the final product precursor. Orbital analysis showed metal...C-C sigma agostic interaction in the product precursor, which is in agreement with the previous experimental findings. In addition, we found that the solvent and counter-ions had significant effects on the dimerization reactions.
我们使用阳离子 Co(I)、Rh(I) 和 Ir(I) 催化剂，通过 mPW1PW91、mPW1K 和 B3LYP 密度泛函方法研究了 NBD 二聚化到 Binor-S 的过渡金属催化反应机制。我们的结果表明，单体金属中心能够与两个 NBD 分子的四个双键以顺式空间几何构型结合，形成五配位配合物。我们设计了三种可能的途径，但发现其中两种途径受阻。有利的途径包括从反应物前体到产物前体的三个步骤：第一步是形成单键连接两个 NBD 单元，第二步是烯烃插入导致三员环结构的形成，最后一步是形成最终产物前体。轨道分析表明，产物前体中存在金属...C-Csigma 桥接相互作用，这与先前的实验结果一致。此外，我们发现溶剂和抗衡离子对二聚反应有显著影响。
