Energy-Minimized Structures and Calculated and Experimental Isomer distributions in the hexaamine-cobalt(III) system [Co(L)2]3+ with the chiral facially-coordinating triamine (l = butane-1,2,4-triamine)
作者:Peter Comba、Marcel Maeder、Luc Zipper
DOI:10.1002/hlca.19890720520
日期:1989.8.9
(trab) is the smallest tridentate aliphatic unsubstituted chiral triamine. With optically pure trab, there are three, with racemic trab five isomers of [Co(trab)2]3+, One of the five isomers is centrosymmetrical, the others are chiral. For one of the isomers, there are four possible conformations (all combinations of chair and skew boat conformations for the chelate six ring of each ligand), for the others
丁烷1,2,4-三胺(trab)是最小的三齿脂族未取代手性三胺。对于光学纯的trab,有三个,而对于外消旋的trab,有[Co(trab)2 ] 3+的五个异构体,五种异构体之一是中心对称的,其他异构体是手性的。对于一种异构体,存在四种可能的构象(每种配体的螯合六环的椅子和斜小船构象的所有组合),对于其他异构体,仅存在三个独立的构象子。通过应变能最小化已经计算出所有十六个独立结构。基于通过统计熵贡献校正的总应变能,计算出的异构体分布(对于外消旋和光学纯净trab,分别为21%:16%:16%:4%:43%和40%:30%:30%)与基于HPLC和13的实验数据非常吻合在活性炭存在下通过水溶液的氧化制得的六胺-Co(III)化合物的平衡溶液的13 C-NMR分析。还简要讨论了将光学纯的trab和外消旋手性配体络合至过渡金属中心时可能的立体选择性的结果。