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Eingeladener Vortrag
- nein (5)
Reaction between an aqueous ethanol solution of tin(II) chloride and that of 4-propanoyl-2,4-dihydro-5-methyl-2-phenyl-3 H-pyrazol-3-one in the presence of O2 gave the compound cis-dichlorobis(4-propanoyl-2,4-dihydro-5-methyl-2-phenyl-3 H-pyrazol-3-onato) tin(IV) [(C26H26N4O4)SnCl2]. The compound has a six-coordinated SnIV centre in a distorted octahedral configuration with two chloro ligands in cis position. The tin atom is also at a pseudo two-fold axis of inversion for both the ligand anions and the two cis-chloro ligands. The orange compound crystallizes in the triclinic space group P 1 with unit cell dimensions, a = 8.741(3) Å, b = 12.325(7) Å, c = 13.922(7) Å; = 71.59(4), = 79.39(3), = 75.18(4); Z = 2 and Dx = 1.575 g cm-3. The important bond distances in the chelate ring are Sn-O [2.041 to 2.103 Å], Sn-Cl [2.347 to 2.351 Å], C-O [1.261 to 1.289 Å] and C-C [1.401 Å] the bond angles are O-Sn-O 82.6 to 87.7° and Cl-Sn-Cl 97.59°. The UV, IR, 1H NMR and 119Sn Mössbauer spectral data of the compound are reported and discussed.
Self-assembly of Fe(II) and the ditopic ligand 1,4-bis(2,2':6',2"-terpyridine-4'-yl)benzene results in equilibrium structures in solutions, so-called metallosupramolecular coordination polyelectrolytes (MEPEs). It is exceedingly difficult to characterize such macromolecular assemblies, because of the dynamic nature. Therefore, hardly any structural information is available for this type of material. Here, we show that from dilute solutions, where small aggregates predominate, it is possible to grow nanoscopic crystals at an interface. A near atomic resolution structure of MEPE is obtained by investigating the nanoscopic crystals with electron diffraction in combination with molecular modeling. The analysis reveals a primitive monoclinic unit cell (P21/c space group, a = 10.4 Å, b = 10.7 Å, c = 34.0 Å, α = γ = 90°, β = 95°, ρ = 1.26 g/cm³, and Z = 4). The MEPE forms linear rods, which are organized into sheets. Four sheets intersect the unit cell, while adjacent sheets are rotated by 90° with respect to each other. The pseudooctahedral coordination geometry of the Fe(II) centers is confirmed by Mössbauer spectroscopy. The combination of diffraction and molecular modeling presented here may be of general utility to address problems in structural materials science.