Seitz, Michael and Kaiser, Anja and Stempfhuber, Sabine and Zabel, Manfred and Reiser, Oliver (2005) Enantiomerically pure pentagonal-bipyramidal metal complexes with predetermined helicity in the solid and solution states. INORGANIC CHEMISTRY, 44 (13). pp. 4630-4636. ISSN 0020-1669, 1520-510X
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New metal complexes with pentagonal-bipyramidal geometry have been synthesized with the chiral, pentadentate bis(oxazoline) ligand (R,R)-1, including the metal ions magnesium(II), iron(II), and cadmium(II). In the solid state, a complete transfer of chirality from the ligand is observed to exclusively yield enantiomerically pure P-helical, isostructural pentagonal bipyramidal complexes, as determined by X-ray analysis of four compounds. This uncommon coordination geometry is likely to be driven by pi-pi-stacking of the terminal phenyl groups of the linear ligands. The complex cations in [Fe((R,R)-1)(H2O)(2)](ClO4)(2) (3), [Cd((R,R)-1)(H2O)(2)](ClO4)(2) (4), and [Mg((R,R)-1)(H2O)(2)(ClO4)(2) (5) are mononuclear with the two apical positions of the pentagonal bipyramide occupied by two water molecules. In contrast, the structure in dinuclear [Cd((R,R)-1)(MeOH)(mu-I)(Cdl(3))] (2c) can be described as pentagonal-bipyramidal around cadmium with MeOH and distorted-tetrahedral Cdl(4) (via one bridging iodo ligand) completing the coordination sphere in axial positions. The crystal packing of 3-5 shows a highly ordered orientation of the mononuclear helical cations into one-dimensional chains along the crystallographic axis a, stabilized by intermolecular pi pi-stacking. In contrast, the dinuclear helices in 2c are tilted relative to one another, and consequently, directed, one-dimensional helicity in the solid state is not observed. Studies using a combination of mass spectrometry and NMR and CD spectroscopy indicate the presence of only one C-2-symmetrical, mononuclear species in acetonitrile for each case, suggesting the formation of diastereo- and enantiomerically pure complexes also in the solution state. All compounds exhibit a very characteristic and almost identical CD pattern between 200 nm and 300 nm. This signal can be attributed to the P-helical, pentagonal arrangement of the ligand.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 2-AMINOETHYL PENDANT ARMS; SCHIFF-BASE COMPLEXES; X-RAY STRUCTURE; CRYSTAL-STRUCTURE; CADMIUM(II) COMPLEX; MAGNETIC-PROPERTIES; LIGAND; COORDINATION; ZINC(II); 2,6-DIACETYLPYRIDINE; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie > Lehrstuhl Prof. Dr. Oliver Reiser |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 10 May 2021 07:54 |
| Last Modified: | 10 May 2021 07:54 |
| URI: | https://pred.uni-regensburg.de/id/eprint/35985 |
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