Rhodium In Solution Research Articles

Specific Features of Dissolution of Metallic Rhodium in Acid Oxidative Media under Hydrothermal Conditions

Dissolution of metallic rhodium in solutions of hydrochloric acid was studied under hydrothermal autoclave conditions. The influence exerted by various factors on the depth of rhodium(0) transfer to solution was examined. It was found that the quantitative dissolution of rhodium(0) is reached in a mixture of hydrochloric and hydrobromic acids in the presence of manganese dioxide at 20°C in autoclaves. The results obtained can be used both for an analytical determination of rhodium and for processing of rhodium-containing raw materials and synthesis of complex rhodium compounds.

Electrochemical behaviour and electrowinning of rhodium in acidic chloride solution

The electrochemical behaviour and recovery of rhodium in an acidic solution were investigated using a rotating disc electrode system and a modified electrochemical cyclone cell, respectively. The electrochemical polarization data indicated that the Rh3+ ions were reduced to metallic Rh below −0.1 V, and the limiting current density for rhodium deposition was observed at around −0.3 V (vs. SCE) with a diffusion coefficient of 6.3 × 10−6 cm2 s−1 using the Levich equation. The effects of the applied voltage and the initial concentration of rhodium were examined using the modified cyclone cell, and more than 91 % of the rhodium in solution was recovered within 2 h under the optimal conditions.

Improved synthetic routes to rhodium bipyridine complexes: Comparison of microwave vs. conventional synthesis

We report here two new, high purity, high yield, one-step syntheses of cis-[Rh(bpy) 2X 2][PF 6] {X = Cl, Br, I, bpy = 2,2′-bipyridine} directly from the RhX 3 · nH 2O starting materials – one conventional and one microwave. The key to obtaining the pure complexes appears to be maintaining a 2:1 ratio of bipyridine to rhodium in solution; thus all reactants must be completely dissolved prior to the start of the reaction. Comparison of the two methods is also discussed. These complexes are pure enough for emission spectroscopy after minimal work-up. The complete characterization of all the halide complexes and the first cyclic voltammetry data on the cis-[Rh(bpy) 2I 2][PF 6] complex are reported. The irreversible Rh(III)–Rh(I) redox potential becomes more positive from Cl to I. All three complexes show two reversible redox potentials corresponding to the bipyridine reductions. These data are consistent with the loss of the two halide ligands and formation of [Rh(bpy) 2] + upon reduction of Rh(III) to Rh(I).

ChemInform Abstract: Catalytic Selective Cleavage of a Strong C—C Single Bond by Rhodium in Solution.

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Catalytic selective cleavage of a strong C–C single bond by rhodium in solution

Reaction of [RhCl(C8H14)2]2 with an excess of the diphosphine 1,3-bis(diisopropylphosphinomethylene)mesitylene 1 in dioxane under mild H2 pressure (25 psi) or with an excess of HSi(OEt)3 results in catalytic selective cleavage of a strong C–C single bond.

Determination of rhodium in organic solutions by flame atomic absorption spectrometry, with methyl isobutyl ketone and ethanol as solvents

A flame atomic absorption spectrometric method for the determination of rhodium in organic solutions containing toluene, 1-hexene, 1-heptanol and 1-heptanal is described. Methyl isobutyl ketone (MIBK) and ethanol were used as solvents and 1-heptanal as buffering agent. In addition to burner position, the composition of the organic solution significantly affected the absorbance. The recovery of 5 μg/ml rhodium was only 60% in a solution containing 75% MIBK, 20% toluene and 5% hexene, but improved as the ratio of alcohol or aldehyde to hexene increased. When the amount of hexene was reduced to zero and 5% heptanol, 5% heptanal or 2.5% heptanol + 2.5% heptanal was used instead, recoveries were 97%, 92% and 95%, respectively. The recoveries of 10 μg/ml rhodium in solutions containing 75% ethanol, 20% toluene and 2.5% hexene + 2.5% heptanol, heptanal or their mixtures were 97%, 104% and 103%, respectively. Ethanol has several advantages over MIBK as a solvent: it is cheaper, the smell is less unpleasant, the burner and chamber assembly keep cleaner and sensitivity is slightly better.

Rhodium elution from polymer-bonded hydroformylation catalysts

The concentration of rhodium in solution over polymer-bonded hydroformylation catalysts was measured, and the factors influencing that concentration were identified. Rhodium dissolution exhibited an equilibrium behavior which' decreased with increasing temperature or hydrogen pressure and with decreasing CO pressure. Solvent effects were particularly pronounced with amine resins and the sequential reaction, olefin-aldehyde-alcohol, led to significant redistribution of rhodium within a reactor bed. The implications of these effects in catalysis are noted.

Dissociation of nitrosyltris(triphenylphosphine)rhodium in solution

Dissociation of nitrosyltris(triphenylphosphine)rhodium in solution

Nature of chlorotris(triphenylphosphine)rhodium in solution and its reaction with hydrogen

Nature of chlorotris(triphenylphosphine)rhodium in solution and its reaction with hydrogen

Hydride transfer reactions catalysed by metal complexes

Chloro-complexes of rhodium(III) catalyse the dehydrogenation of isopropyl alcohol to acetone. During the reaction rhodium metal is precipitated, and the rate of dehydrogenation decreases as rhodium is removed from solution. The reaction kinetics agree with the rate of evolution of hydrogen being proportional to the concentration of rhodium in solution. It is suggested that the catalysis proceeds via the reactions: Me2CHOH +[RhIIICl]⇌ Me2CO +[HRhIII]+ HCl, HCl +[HRhIII]→ H2+[RhIIICl]

A SPECTROPHOTOMETRIC DETERMINATION OF RHODIUM WITH TIN (II) BROMIDE

Rhodium salts react with a solution of tin (II) bromide in hydrobromic acid to produce an intense yellow color suitable for a spectrophotometric determination of rhodium. The method described is relatively simple and is the most sensitive for this metal published to date. Several factors influencing the intensity and stability of the colored species, whose nature is unknown, are described. Since the other platinum metals and base metals interfere it is necessary to isolate the rhodium prior to its determination. However, a fair estimation of rhodium can be made even when equivalent quantities of iridium are present. The procedure may be adapted, with a small loss in sensitivity, to determine rhodium in solutions which have been fumed with sulphuric acid.