Weber Michael, Kuppert Dirk, Hegetschweiler Kaspar, Gramlich Volker
Institut für Kristallographie, ETH Zentrum, CH-8092 Zürich, Switzerland.
Inorg Chem. 1999 Mar 8;38(5):859-868. doi: 10.1021/ic980867m.
The ligands all-cis-2,4,6-trimethoxycyclohexane-1,3,5-triamine (tmca) and all-cis-2,4,6-tribenzoxycyclohexane-1,3,5-triamine (tbca) were prepared almost quantitatively by using Ni(taci)(2) (taci = 1,3,5-triamino-1,3,5-trideoxy-cis-inositol) as precursor, where Ni(2+) acted as a very efficient protecting group for the nitrogen donors. The structure of tmca in solution was investigated by NMR spectroscopy. A strongly solvent-dependent conformational equilibrium was observed. In CD(3)CN, a chair conformation with three axial amino groups formed exclusively, whereas in D(2)O, the conformation with three equatorial amino groups predominated. This effect, as well as conformational changes in the course of stepwise protonation, is discussed in terms of hydrogen bonding effects. The crystal structure of H(3)tmca(3+) exhibits a chair conformation with three equatorial ammonium groups and three axial methoxy groups. The trihydrochloride hydrate crystallizes in the monoclinic space group P2(1)/n, a = 11.057(5) Å, b = 9.960(6) Å, c = 14.671(6) Å, beta = 93.79(3) degrees, Z = 4 for C(9)Cl(3)H(26)N(3)O(4). A variety of bis complexes M(tmca)(2) (M = Ni, Cu, Zn, Cd) and M(tbca)(2) (M = Ni, Cu) were prepared and they were isolated as solid, crystalline trinitrate or trichloride salts. Crystal data: Ni(tmca)(2)(2).4H(2)O, triclinic, space group P&onemacr;, a = 8.919(11) Å, b = 9.293(9) Å, c = 9.942(11) Å, alpha = 96.73(9) degrees, beta = 100.66(9) degrees, gamma = 101.95(9) degrees, Z = 1 for C(18)H(50)N(8)NiO(16); Cu(tmca)(2)(2), tetragonal, space group P&fourmacr;2(1)c, a = 13.017(6) Å, c = 15.985(10) Å, Z = 4 for C(18)CuH(42)N(8)O(12); Ni(tbca)(2)(2).MeCN.H(2)O, monoclinic, space group P2(1)/c, a = 12.930(8) Å, b = 19.324(10) Å, c = 22.724(14) Å, beta = 97.21(5) degrees, Z = 4 for C(56)H(71)N(9)NiO(13). The formation constants of M(tmca) and M(tmca)(2) were determined by means of a series of potentiometric titration experiments. A comparison of the taci complexes with the corresponding tmca complexes revealed an unexpected increase of stability for the latter. This increase is more than 2 orders of magnitude for the 1:1 complexes and about 5 orders of magnitudes for the 1:2 complexes. Possible reasons for this unexpected increase in stability are discussed.
以Ni(taci)(2)（taci = 1,3,5 - 三氨基 - 1,3,5 - 三脱氧 - 顺式 - 肌醇）为前体，几乎定量地制备了配体全顺式 - 2,4,6 - 三甲氧基环己烷 - 1,3,5 - 三胺（tmca）和全顺式 - 2,4,6 - 三苄氧基环己烷 - 1,3,5 - 三胺（tbca），其中Ni(2+)作为氮供体的一种非常有效的保护基团。通过核磁共振光谱研究了tmca在溶液中的结构。观察到一种强烈依赖于溶剂的构象平衡。在CD(3)CN中只形成了具有三个轴向氨基的椅式构象，而在D(2)O中，具有三个赤道面氨基的构象占主导。从氢键效应的角度讨论了这种效应以及逐步质子化过程中的构象变化。H(3)tmca(3+)的晶体结构呈现出具有三个赤道面铵基和三个轴向甲氧基的椅式构象。三盐酸盐水合物结晶于单斜空间群P2(1)/n，对于C(9)Cl(3)H(26)N(3)O(4)，a = 11.057(5) Å，b = 9.960(6) Å，c = 14.671(6) Å，β = 93.79(3)°，Z = 4。制备了多种双配合物M(tmca)(2)（M = Ni、Cu、Zn、Cd）和M(tbca)(2)（M = Ni、Cu），并将它们分离为固体结晶三硝酸盐或三氯化物盐。晶体数据：Ni(tmca)(2)(2).4H(2)O，三斜晶系，空间群P&onemacr;，对于C(18)H(50)N(8)NiO(16)，a = 8.919(11) Å，b = 9.293(9) Å，c = 9.942(11) Å，α = 96.73(9)°，β = 100.66(9)°，γ = 101.95(9)°，Z =
