Eric Hosten

Interactions of uranium and thorium with arsenazo III in an aqueous medium

Complex formation of arsenazo III with U(IV), U(VI) and Th(IV) was examined using spectrophotometric techniques together with computational methods. U(VI) (added as UO22+) forms only a 1: 1 complex at pH 1.5, and in 6 M HCl and HClO4. Both U(IV) and Th(IV) form ML and ML2 complexes in 6 M HCl. The arsenazo III-U(IV) and Th(IV) system in 6 M HCl has isosbestic points, although there are more than two absorbing species in equilibrium.

Spectrophotometric study of arsenazo III and its interactions with lanthanides

Abstract Complex formation between arsenazo III and the lanthanides was examined. Spectrophotometric methods were used, in particular mole ratio and mole fraction (Jobs plot) methods, to show that only the 1:1 complex forms at low arsenazo III concentrations and in dilute acidic medium (pH 3.5).

Synthesis and characterization of rhenium(III) and (V) pyridylimidazole complexes

Reaction of trans-[ReOCl3(PPh3)2] with 2-(2′-pyridyl)imidazole (pimH) in methanol led to the isolation of the rhenium(III) salt [ReCl2(pimH)(PPh3)2](ReO4) (1). However, with 2-(2′-pyridyl)-1-methylimidazole (pimMe) as ligand, the complex [ReCl3(pimMe)(PPh3)] (2) was obtained. The monooxorhenium(V) complexes [ReOCl3(pimR)] (R = H, Me) could only be prepared by the reduction of [ReO4]− with an equimolar amount of PPh3 in the presence of pimR and hydrochloric acid in acetic acid. With four equivalents of PPh3, compounds 1 and 2 were obtained. Using (n-Bu4N)[ReOCl4] as starting material, the μ-oxo dimers [Re2O3(pimR)2Cl4] were isolated as the only products. These new compounds have been characterized by X-ray crystallography, 1H NMR and IR spectroscopy. In 1 the [ReO4]− counterion is tightly associated with the cationic complex through N–H ···  hydrogen bonding. Despite being paramagnetic, 1H NMR spectra for 1 and 2 could be fully assigned.

pH dependence of the reactions of arsenazo III with the lanthanides

Abstract Spectrophotometric techniques, together with computer simulations, were used to show that the 1 : 1 arsenazo III (3,6-bis[(2-arsonophenyl)-azo]-4,5-dihydroxy-2,7-naphthalenedisulphonic acid)-lanthanide(III) complex has four protonation states which respectively dominate at pH 3.3, 6.0, 8.3 and >10. Formation and molar absorptivity constants were calculated for the various complexes. Acid dissociation constants for free arsenazo III were also calculated from Spectrophotometric data.

The separation of rhodium and iridium. II. Chloridation and chlorination of iridium(III) and (IV)

Abstract The chloridation of iridium(III) chloro aquo complexes was studied at different aqueous HCl concentrations and temperatures to determine the optimum conditions which upon chlorination will lead to the most convenient method to produce an aqueous solution which only contains the [IrCl6]2− species required for very efficient separation of iridium from rhodium by separating agents like quaternary ammonium species. The interdependency of the two processes of chloridation and chlorination is indicated.

Synthesis and Structural Characterization of Dinuclear Oxorhenium(V) Complexes with Bidentate Imidazole Derivatives

The oxo-bridged dinuclear complexes [(μ-O){ReOCl2(L)}2] [L = 2-(1-ethylaminomethyl)-1-methylimidazole (eami); 2-(1-methylaminomethyl)-1-methylimidazole (mami); 2-(1-ethylthiomethyl)-1-methylimidazole (etmi)] were prepared by reaction of trans-[ReOCl3(PPh3)2] with L in acetone. X-ray crystallographic studies of the eami and etmi complexes show that these ligands coordinate in a bidentate manner, and that the cis, cis-N2Cl2 and cis, cis-NSCl2 equatorial planes are nearly orthogonal to the O=Re-O-Re=O backbone.

2,2′-dipyridylamine complexes of rhenium(V)

The reactivity of oxorhenium(V) precursors with the potentially N,N-donor ligand 2,2′-dipyridylamine (dpa) has been investigated. Reaction of a two-fold molar excess of dpa with trans-[ReO(OEt)Cl2(PPh3)2] in ethanol led to the isolation of [ReOCl2(OEt)(dpa)] (1). Spectroscopic measurements indicate that dpa is coordinated as a bidentate in the equatorial plane cis to the oxo group, with the ethoxide in the trans position. Treatment of trans-[ReOCl3(PPh3)2] with a tenfold molar excess of dpa in ethanol at reflux yielded the trans-dioxo complex [ReO2(dpa)2]Cl (2), but with a twofold molar excess (μ-O)[{ReOCl2(dpa)}2] (3a) was isolated. The latter reaction with (n-Bu4N)[ReOCl4] as starting material in ethanol at room temperature led to a dark green product, also with the formulation (μ-O)[{ReOCl2(dpa)}2] (3b). These compounds were characterised by common spectroscopic techniques, and the crystal structures of 2·3H2O, 3a and 3b·2DMSO were determined. The structure of 3b presents a nearly linear O=Re–O–Re=O group, with the two [ReOCl2(dpa)] halves of the dimer rotated by 180.0° about the Re–O–Re fragment away from an eclipsed conformation. In 3a, the two halves are only rotated by 61.4°.

Interaction of anions with arsenazo III-lanthanide (III) complexes

Abstract Spectrophotometric techniques, together with computer simulations, were used to investigate the interaction of selected anions on the complex formation of arsenazo III with the lanthanides in solutions of pH 3.3. The anions influence complexation by reacting with both the free lanthanide ion and the arsenazo III complex.

Monodentate imido coordination of 2-aminodiphenylamine to rhenium(V)

The complex trans-[Re(ada)Cl3(PPh3)2] (H2ada = 2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre solely through a dianionic imido nitrogen, with distorted octahedral coordination geometry around the metal ion. Surprisingly, the Re–Cl bond trans to the Re=N bond is shorter than the two equatorial Re–Cl bonds. The Re = N–C bond angle of the phenylimido moiety equals 178.7(4)°.

Bis diallyl dithiocarbamate Pt(II) complex: synthesis, characterization, thermal decomposition studies, and experimental and theoretical studies on its crystal structure

Platinum dithiocarbamate (DTC) complex has been synthesized from the ligand diallyl DTC, and its structure was established from elemental analysis, IR, NMR, and single-crystal X-ray analyses to be Pt[S2CN(C3H5)2]2. The thermal properties were studied using a simultaneous thermal analyzer, and showed two main steps of decomposition. The structural geometry analysis was determined using X-ray diffraction and Density Functional Theory (DFT) calculations. The single-crystal X-ray analysis showed that the complex has a square planar geometry. The diallyl groups of the DTC ligands are not symmetrical making the complex non-centrosymmetric, and the complexes are stacked with intermolecular ring–ring interactions. The DFT calculations were performed to obtain the theoretical information and compared with the experimental data obtained from the experimental crystal structure. GRAPHICAL ABSTRACT