Eberhard Ludwig

Investigations on technetium and rhenium monothio-βdiketonate complexesand x-ray structure of tris(monothiodibenzoylmethanato)technetium(III)

Abstract Six-coordinated tris(monothio-β-diketonates) of Tc(III) and Re(III) have been synthesized by the reaction of M(III) thiourea complexes with the appropriate monothio-β-diketone ligands in methanol. Characterization of the compounds by IR, UV-Vis, 1H NMR and mass spectroscopy indicates that the ligands coordinate as bidentate. The 1H NMR spectra of the paramagnetic substances are well resolved and the chelate ring protons show a large high-field shift of the Tc complcxes and a low-field shift of the corresponding Re analogues. A complete crystal and molecular structure determination, performed on tris(monothiodibenzoylmethanato)technetium(III), is the first structural characterization of a Tc(III) compound with O and S chelate ligands.

Rotational barriers in metal chelates. Hindered rotation about the terminal NC(X)-bond in Ni-coordinated isomeric unsaturated 1,3-(S,O)-ligands

The barrier of hindered rotation about the terminal NC(X)-bond has been measured in the ligands as well as in the nickel(II) chelates using 1H NMR. The free energy of activation for hindered rotation is lower in the cases where charge delocalization occurs in the chelate ring (chelates with methine groups) and higher in the cases where it takes place in a smaller degree (aza-analogous chelates). Thus the bonding situation investigated by 1H NMR corresponds fairly well with that determined by other methods.

Synthesis and characterization of a new technetium complex tris(monothiodbenzoylmethanato)technetium(III)

The widespread use of 99mTc radiopharmaceuticals has stimulated investigations in the field of the coordination chemistry of the long-lived radionuclide technetium-99 [l]. Despite the fact that in recent years an increasing number of technetium compounds has been prepared and characterized in order to obtain more knowledge of the basic chemistry of this element, little is known about complexes of technetium with 1,3dicarbonyl ligands and their corresponding sulfur analogues.

Voltammetric studies of non-oxo vanadium(IV) chelates

A series of non-oxo vanadium(IV) chelates with tridentate diacidic ligands was studied by cyclovoltammetry using a platinum electrode and by differential pulse polarography using a hanging mercury drop electrode. The reversibility of the electrode processes was observed for the electrochemical redox reaction. A diffusion-controlled one-electron transfer was mostly found. The influence of structural parameters on the stability of the compounds was discussed considering the shift of the reduction potential of the complexes.

Zinn(IV)-Komplexe mit diaciden Azo(hydrazono)verbindungen. Kristallstruktur von Bis[4-(2′-hydroxyphenylazo)-3-methyl-lphenyl- pyrazol-5-onato(2-)]zinn(IV)/ Tin(IV) Complexes with Diacidic Azo(hydrazono) Compounds. Crystal Structure of Bis[4-(2′-hydroxyphenylazo)-3-methyl-l-phenyl-pyrazol-5-onato(2-)]tin(IV)

Abstract Tin(IV) complexes of diacidic azo and hydrazono compounds were synthesized by the reaction of these ligands with SnCl2acac2 and SnCl2 · 2H2O , respectively. The complexes were further characterized by Mössbauer spectroscopy. For bis[4-(2′-hydroxyphenylazo)-3-methyl-l-phenyl-pyrazol-5-onato(2-)]tin(IV) force field calculations have been performed and the crystal structure was determined by X-ray analysis.

Titan- und Vanadiumkomplexe mit 4-[1-(N′-Benzoylhydrazino)-l-phenylmethyliden]- 3-methyl-1-phenyl-pyrazol-5-on. Röntgenkristallstruktur von 4-[1-(N′-Benzoylhydrazino)-1-phenyl-methyliden]-3-methyl-1-phenyl- pyrazol-5-on / Titanium- and Vanadium Complexes of 4-[1-(N′-Benzoylhydrazino)-1-phenylmethylidene]-3-methyl-1-phenyl-pyrazol-5-one. Structure of 4-[1-(N′-Benzoylhydrazino)-1-phenyl-methylidene]-3-methyl-1-phenyl-pyrazol-5-one

By reaction of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one with benzoylhydrazine the tridentate diacidic ligand 4-[1-(N′-benzoylhydrazino)-1-phenyl-m ethylidene]-3-m ethyl-lphenyl-1-pyrazol-5-one (H2L) is formed which gives complexes ML2 with tetravalent titanium and vanadium ions. The ligand and its complexes were characterized by mass spectroscopy. The vanadium(IV) complex can be oxidised and reduced electrochemicallv. The chemical bonding in the titanium(IV) complex and in the ligand was studied by IR and 13C NMR spectroscopy. The molecular structure of 4-[1-(N′-benzoylhydrazino)-1-phenyl-methylidenel-3-m ethyl-lphenyl- pyrazol-5-one was determined by X-ray analysis. Crystal data: a = 9.159(3) Å, b = 11.014(4) Å, c = 11.136(5) Å, a = 90.11 (2)°, β = 101.84(3)°, γ = 113.01 (2)°; space group P1̄, Z = 2.

Hydrolyse von Trifluoracetylaceton-salicylhydrazon / Hydrolysis of Trifluoroacetylacetone Salicylhydrazone

Abstract The reaction of trifluoroacetylacetone with salicylhydrazone gives acetone salicylhydra zone besides the expected trifluoroacetylacetone salicylhydrazone. The resulting mixture was analyzed by mass spectroscopy. The structure of acetone salicylhydrazone was determined by X-ray analysis. Crystal data: a = 12,8493(12) Å, b = 6,1084(8) Å, c = 12,757(3) Å; space group Pna21; Z = 4; R = 0,051 ; 750 unique reflexions.

Molekülstrukturen von Tautomeren des Benzoylaceton-benzoylhydrazons / Moleculare Structures of Tautomeric Forms of Benzoylacetone Benzoylhydrazone

Abstract By crystallization from benzene two tautomeric forms of benzoylacetone benzoylhydra zone were isolated side by side. They were found to be the pyrazoline(III) and the enhydrazine(II) form. Crystal data: II: a = 9,247(2) Å , b = 9,953(2) Å , c = 16,112(4) Å , α = 81,79(1)°, β = 82,74(1)°, γ = 89,94(2)°; space group P1; Z = 4; R = 0,0584; 6197 unique reflexions; III; a = 17,357(6) Å, b = 21,190(7) Å , c = 7,908(5) Å; space group Pccn; Z=8; R = 0,0553; 1152 unique reflexions.