Institute of Organic Chemistry PAS, ul. Kasprzaka 44/52, 01-224, Warsaw, Poland.
Magn Reson Chem. 2013 Oct;51(10):662-70. doi: 10.1002/mrc.3997. Epub 2013 Aug 13.
The complexation of rhodium(II) tetraacetate, tetrakistrifluoroaceate and tetrakisoctanoate with a set of diamines (ethane-1,diamine, propane-1,3-diamine and nonane-1,9-diamine) and their N,N'-dimethyl and N,N,N',N'-tetramethyl derivatives in chloroform solution has been investigated by (1) H and (13) C NMR spectroscopy and density functional theory (DFT) modelling. A combination of two bifunctional reagents, diamines and rhodium(II) tetracarboxylates, yielded insoluble coordination polymers as main products of complexation and various adducts in the solution, being in equilibrium with insoluble material. All diamines initially formed the 2 : 1 (blue), (1 : 1)n oligomeric (red) and 1 : 2 (red) axial adducts in solution, depending on the reagents' molar ratio. Adducts of primary and secondary diamines decomposed in the presence of ligand excess, the former via unstable equatorial complexes. The complexation of secondary diamines slowed down the inversion at nitrogen atoms in NH(CH3 ) functional groups and resulted in the formation of nitrogenous stereogenic centres, detectable by NMR. Axial adducts of tertiary diamines appeared to be relatively stable. The presence of long aliphatic chains in molecules (adducts of nonane-1,9-diamines or rhodium(II) tetrakisoctanoate) increased adduct solubility. Hypothetical structures of the equatorial adduct of rhodium(II) tetraacetate with ethane-1,2-diamine and their NMR parameters were explored by means of DFT calculations.
三氟乙酸铑(II)、八氟乙酸铑(II)和辛酸铑(II)与一系列二胺（乙烷-1,2-二胺、丙烷-1,3-二胺和壬烷-1,9-二胺）及其 N,N'-二甲基和 N,N,N',N'-四甲基衍生物在氯仿溶液中的络合作用通过（1）H 和（13）C NMR 光谱和密度泛函理论（DFT）建模进行了研究。两种双功能试剂（二胺和铑（II）四羧酸盐）的组合产生了不溶性配位聚合物作为络合的主要产物和溶液中的各种加合物，与不溶性物质处于平衡状态。所有二胺最初在溶液中形成 2:1（蓝色）、（1:1）n 低聚物（红色）和 1:2（红色）轴向加合物，这取决于试剂的摩尔比。在配体过量的存在下，伯和仲二胺的加合物分解，前者通过不稳定的赤道配合物分解。仲二胺的络合作用减缓了 NH(CH3)官能团中氮原子的反转，导致可通过 NMR 检测到含氮手性中心的形成。叔二胺的轴向加合物似乎相对稳定。分子中长脂肪链的存在（壬烷-1,9-二胺或辛酸铑(II)的加合物）增加了加合物的溶解度。通过 DFT 计算探索了铑（II）四乙酸盐与乙烷-1,2-二胺的赤道加合物的假设结构及其 NMR 参数。
