Demonstration of remote steric differentiation of cis/transalkene coordination in copper(i) complexes of aryl-substituted bis(2-pyridyl)amine
作者:John J. Allen、Andrew R. Barron
DOI:10.1039/c0dt01301c
日期:——
Complexes of the type [Cu(R-dpa)(η2-olefin)]BF4 (R = Mes and 2-iPrC6H4) for cis- and trans- isomers of 3-octene, as well as those for cis- and trans-4-octene (R = 2-iPrC6H4) have been prepared and characterized by 1H and 13C NMR, FTIR, and TGA. The crystal structure of [Cu(Mes-dpa)(η2-trans-3-octene)]BF4 (2) has been determined via X-ray crystallography. The asymmetric unit in the crystal lattice of 2 contains two unique conformations of the complex cation related by a pseudo center of symmetry, which differ primarily in the orientation of the olefin with respect to the rest of the molecule. The 1H and 13C NMR spectra of [Cu(Ar-dpa)(η2-olefin)]BF4 exhibit olefin resonances shifted upfield with respect to free olefin. The difference in Δδ(13C) relative magnitudes between cis- and trans- complexes, i.e., the binding, correlates with the degree of substitution at the amine nitrogen. The identity of the remote ligand substituent (Ar) controls the differentiation of binding between cis and trans isomers as a consequence of increased folding of the Ar-dpa ligand along the Cu⋯N axis.
已合成并表征了类型为 [Cu(R-dpa)(η2-烯烃)]BF4 的配合物(R = Mes 和 2-iPrC6H4),用于顺式和反式 3-辛烯,以及顺式和反式 4-辛烯(R = 2-iPrC6H4),采用的表征技术包括 1H 和 13C NMR、FTIR 和 TGA。通过X射线晶体学确定了 [Cu(Mes-dpa)(η2-trans-3-octene)]BF4 (2) 的晶体结构。晶体格子中 2 的不对称单元包含两个独特的配合物阳离子构象,这两个构象由一个伪中心对称关系联系,主要在于烯烃相对于分子其余部分的取向存在差异。[Cu(Ar-dpa)(η2-烯烃)]BF4 的 1H 和 13C NMR 光谱显示,烯烃的共振峰相对于游离烯烃向上移位。顺式与反式配合物之间的 Δδ(13C) 相对大小的差异,即结合,与氨基氮原子的取代程度相关。远端配体取代基 (Ar) 的特性控制了顺式与反式异构体之间结合的差异,这源于 Ar-dpa 配体沿 Cu⋯N 轴的折叠程度增加。