Dialkyl effect on enantioselectivity:: π-stacking as a structural feature in P,N complexes of palladium(II)
Dialkyl effect on enantioselectivity:: π-stacking as a structural feature in P,N complexes of palladium(II)
复制标题
DOI：
10.1021/om020314q
复制
发表时间：
2002-07-08
期刊：
影响因子：
2.8
通讯作者：
Albinati, A
中科院分区：
文献类型：
--
作者：
Dotta, P;Magistrato, A;Albinati, A
合成了一种含3，5-二叔丁基苯基的P，N-双齿膦基恶唑啉配体4。在Heck芳基化的二氢呋喃，4显示出提供更高的ee的比2或3，未取代的和m-二甲基苯基类似物，分别。报道了4的几种Pd（0）配合物。Pd（4）（dba）的交换动力学表明，涉及通过分子内过程的非对映异构体的相互转化。用X射线衍射方法测定了PdCl_2（4），8的X射线结构。与PdCl 2（2），9和PdCl 2（3），10的数据比较表明，不同量的堆叠影响这些相对简单的Pd络合物的结构，9和10揭示了最强的π-π相互作用。对相互作用中涉及的货车范德华能的估计支持了一个ca. 4 kcal/mol通过pi-pi堆积稳定。
A phosphino,oxazoline P,N-bidentate ligand, 4, containing 3,5-di-tert-butylphenyl groups has been prepared. In the Heck arylation of dihydrofuran, 4 is shown to afford higher ee's than either 2 or 3, the unsubstituted and m-dimethylphenyl analogues, respectively. Several Pd(0) complexes of 4 are reported. The exchange dynamics of Pd(4)(dba) are shown to involve an interconversion of diastereomers via an intramolecular process. The X-ray structure for PdCl2(4), 8, was determined by X-ray diffraction methods. Comparison of data with PdCl2(2), 9, and PdCl2(3), 10, suggests that differing amounts of stacking influence the structures of these relatively simple Pd complexes, with 9 and 10 revealing the strongest, pi-pi interactions. An estimation of the van der Waals energies involved in the interaction supports a ca. 4 kcal/mol stabilization via pi-pi stacking.