Frank Dietze

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.

HEAVY METAL EXTRACTION WITH THIOCARBAMIC-O-ALKYLESTERS

ABSTRACT Two types of thiocarbamic-O-alkylesters, four bidentate ligands HL and one bis-bidentate ligand H2L, were used as extractants for heavy metal ions from aqueous solutions. Silver(I) was extracted as neutral complexes in a yield > 99 %. The underlying stoichiometry and the extraction constants are discussed. The extraction of silver&I) by the bis-bidentate ligand is significantly more effective than the extraction by the analogous bidentate compound. In a dioxane/water mixture neutral, cationic and anionic silver complexes were found by means of pAg and pH potentiometric titrations. The extraction behavior is discussed with regard to the calculated stability constants.

Thermochemical and structural studies of Cu(II) and Ni(II) complexes with N, N-diethyl-N'-pivaloylthiourea

Abstract The standard (p0=0.1 MPa) molar enthalpies of formation of crystalline bis(N,N-diethyl-N′-pivaloylthioureato)copper(II), Cu(PVET)2, and bis(N,N-diethyl-N′-pivaloylthioureato)nickel(II), Ni(PVET)2, were measured, at T=298.15 K, by solution–reaction isoperibol calorimetry. The standard molar enthalpies of sublimation, at T=298.15 K, of both complexes were obtained using a Knudsen effusion technique. These values were used to derive the standard molar enthalpy of formation of Cu(PVET)2 and Ni(PVET)2 in gaseous phase, and to evaluate the difference between the mean metal–ligand and the hydrogen–ligand bond dissociation enthalpies, in these compounds. The NH homolytic bond dissociation enthalpy in N,N-diethyl-N′-pivaloylthiourea ligand (HPVET) was calculated by high-level density functional theory based calculations. The three-dimensional structures of Cu(PVET)2 and Ni(PVET)2 are presented and show a planar coordination around the metal in both molecules.

Protonation, complexation and thermochemical behaviour of N-benzoylthiocarbamic-O-alkylester anions in solution

Abstract Enthalpies of protonation and metal complex formation of anions of a series of five N -benzoylthiocarbamic- O -alkylesters (R=Et, i -Pr, n -Bu, n -Hex, n -Dodec; 1–5 ) have been measured by titration calorimetry. Using known stability constants the reaction entropies have been calculated. The free ligands HL are verified to react as NH-acids. The remarkable gain of entropy mainly depends on the high number of lost molecules from the extended solvation shell of the reacting species in the 1,4-dioxane/water mixture. The nickel(II) cations are bound in the complex through similar forces than the NH-proton in the ligand.

1-Ethoxycarbonyl-3-ferrocenyl-propan-1,3-dion und Ferrocen-1,1'bis(2,4-dioxobutansäureethylester) als Liganden für Übergangsmetallionen. Kristallstruktur von Bis(1-ethoxycarbonyl-3-ferrocenyl-propan-1,3dionato)kupfer(II)

Die Liganden 1-Ethoxycarbonyl-3-ferrocenyl-propan-1,3-dion und Ferrocen-1,1′-bis(2,4-dioxobutansaureethylester) werden durch Reaktion von Acetylferrocen bzw. 1,1′-Diacetylferrocen mit Oxalsaurediethylester dargestellt. Sie bilden unter Deprotonierung neutrale Chelate mit CuII, NiII, ZnII, CoII und MnII . Die Sauredissoziationskonstanten der Liganden und die Stabilitatskonstanten ihrer Metallkomplexe, einschlieslich der FeII-Komplexe, werden angegeben. Die Struktur von Bis(1-ethoxycarbonyl-3-ferrocenyl-propan-1,3-dionato)kupfer(II) wurde rontgenographisch bestimmt. Es liegt eine cis-Anordnung mit nahezu quadratisch-planarer Koordinationssphare am Cu-Atom vor. 1-Ethoxycarbonyl-3-ferrocenyl-propane-1,3-dion and Ferrocene-1,1′bis(2,4-dioxobutanoic acid ethylester) as Ligands for Transition Metal Ions. Crystal Structure of Bis(1-ethoxycarbonyl-3-ferrocenyl-propane-1,3dionato)copper(II) The ligands 1-ethoxycarbonyl-3-ferrocenyl-propane-1,3-dion and ferrocene-1,1′-bis(2,4-dioxo-butanoic acid ethylester) have been prepared by reaction of acetylferrocene or 1,1′-diacetylferrocene and diethyl oxalate. They yield neutral chelates with CuII, NiII, ZnII, CoII, and MnII. The acid dissociation constants of the ligands and the stability constants of their metal complexes including FeII complexes are reported. The structure of bis(1-ethoxycarbonyl-3-ferrocenyl-propane-1,3-dionato)copper(II) was determined by X-ray structure analysis. A cis arrangement with a nearly square planar coordination sphere at the Cu atom is found.

Flüssig–Flüssig‐Extraktion von Silber(I) mit Aroylthiocarbamidsäure‐O‐estern – Einfluss von Solvens und Struktur der Extragentien

Funf bisbidentate (H2L) und zwei bidentate (HL) Aroylthiocarbamidsaure-O-ester wurden synthetisiert und zur Flussig–Flussig-Extraktion von Silber(I) verwendet. Ein Silber(I)-Komplex wurde in fester Form charakterisiert. Die Verteilungsverhaltnisse DAg und Zusammensetzungen der extrahierten Komplexe wurden fur die Silber(I)-Extraktion aus salpetersaurer wasseriger Losung in Abhangigkeit von pH-Wert und organischem Losungsmittel bestimmt. Die DAg-Werte verringern sich in der Reihe der Losungsmittel Decan, Decan/Toluen, Toluen, Chloroform. Dabei erweisen sich die bisbidentaten Vertreter als wirkungsvollere Extragentien als die bidentaten. Heteroatome in der verbruckenden Molekulgruppe der bisbidentaten Verbindungen erhohen die DAg-Werte. Saurekonstanten und Stabilitat der Silber(I)-Komplexe werden in Zusammenhang mit den Extraktionseigenschaften diskutiert. Liquid–Liquid Extraction of Silver(I) with Aroylthiocarbamic-O-esters Influence of the Solvents and of the Structure of Extractants Five bisbidentate (H2L) and two bidentate (HL) aroylthiocarbamic-O-esters were synthesized and used for the liquid–liquid extraction of silver(I). A silver(I) complex was characterized in solid state. The distribution ratio DAg and the compositions of the extracted complexes were obtained for the silver extraction from nitric acid solutions depending on the pH value and the organic solvent. DAg values are decreasing in the sequence of the solvents decane, decane/toluene, toluene, chloroform. The bisbidentate extractants are more effective than the bidentate ones. Hetero atoms in the bridging molecule group of the bisbidentate compounds increase the DAg values. The extraction behavior is discussed with regard to the calculated protonation constants and stability constants.

Tris{2-[N-(diethylaminothiocarbonyl)benz(-amidino;-imidoxy;-imidothio)-N′-yl]ethyl}amine - neue tripodale Liganden. Darstellung, Komplexstabilität und Extraktionsverhalten ihrer Silber(I)-Komplexe

Die Reaktion von N-(Thiocarbamoyl)-benzimidoylchloriden mit dreiwertigen Nukleophilen fuhrte zu vier neuen tripodalen Liganden, von denen zwei mittels Rontgenbeugungsmethoden strukturell charakterisiert werden konnten. Die Liganden bilden mit Silber(I) unter S-monodentater Koordination aller drei Ligandarme geladene Einkernkomplexe, die durch FAB- und ESI-Massenspektrometrie sowie ESCA- und NMR-Untersuchungen bestatigt wurden. Die Protonierungskonstanten von Liganden und die Stabilitatskonstanten der Silber(I)-Komplexe wurden potentiometrisch ermittelt. Die neuen tripodalen Verbindungen sind geeignete Extraktanden fur Silber(I). Tris{2-[N-(diethylaminothiocarbonyl)benz(-amidino; imidoxy; -imidothio)-N′-yl]ethyl}amines – New Tripodal Ligands. Synthesis, Complex Stability, and Extraction Behaviour of their Silver(I) Complexes N-(Thiocarbamoyl)-benzimidoylchlorides react with trivalent nucleophiles to give four novel tripodal ligands. Two of them have been characterized by X-ray methods. The ligands form with silver(I) cationic mononuclear complexes in which the three arms of the ligand are coordinated monodentately via sulfur. The results of FAB and ESI mass spectrometry as well as ESCA and NMR investigations verify this binding mode. The protonation constants of the ligands and the stability constants of silver(I) complexes have been determined potentiometrically. The novel tripodal compounds behave as powerful extractands for silver(I).

Synthesis, characterization and thermochemical properties of N-acyl-N′,N′-diethylthioureas

Three N-acyl-N′,N′-diethylthioureas, RCONHCSNEt2, R = iPr, iBu, tBu, have been prepared and characterised. The standard (po = 0.1 MPa) molar enthalpies of combustion in oxygen of the three crystalline compounds, at T = 298.15 K, have been measured by rotating bomb-combustion calorimetry, and the standard molar enthalpies of sublimation of the compounds by microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively. The derived standard molar enthalpies of formation in the gaseous state are discussed comparatively. Acid constants and some complex stabilities have been measured pH-potentiometrically in dioxane–water mixture. The crystal structure of N,N-diethyl-N′-isovaleroylthiourea is presented and shows a delocalization of the π electrons of the CS group over the carbon–amine nitrogen bond, CS–NEt2, stabilising the molecule, in accordance with the thermochemical results.