Active states of rhodium in zeolite catalysts after rhodium(III)-exchange

Zeolite-X exchanged with Rh^III compounds and activated at 450 °C in O₂ contains two paramagnetic species involving rhodium: these, detected by e.s.r, are Rh^II and superoxides of Rh^III. Superoxo-rhodium(III) is formed by the oxidation with O₂ of Rh^II generated in the heat treatment.     

3D high-resolution contrast enhanced MRI of carotid atheroma — a technical update

Objective

Development of a fast 3D high-resolution magnetic resonance imaging (MRI) protocol for improved carotid artery plaque imaging.

Methods

Two patients with carotid atherosclerosis disease underwent 3D high-resolution MRI which included time-of-flight and T₁-weighted variable flip angle, fast-spin-echo (FSE) imaging, pre- and post-intravenous gadolinium-based contrast agent administration.

Results

Good quality images with intrinsic blood suppression were obtained pre- and post-contrast administration using a 3D FSE sequence. The plaque burden, lipid core volume, hemorrhage volume and fibrous cap thickness were well determined.

Conclusions

3D high-resolution MR imaging of carotid plaque using TOF and 3D FSE can achieve high isotropic resolution, large coverage, and excellent image quality within a short acquisition time.     

Optically active coordination compounds---XLVIII. Synthesis, resolution and interconversions of isomers of tris-salicylatocobaltate(III)

Stable aqueous solutions of the green ion [Co(sa1)₃]³⁻ (sa1 = dianion, C₆H₄( )(CO ), of salicylic acid, 2-hydroxybenzoic acid) are obtained from [Co(NH₃)₅ C1]C1₂ and an excess of salicylic acid. Several salts, [C][Co(sa1)₃] have been characterized, where C = [Co(NH₃)₆]³⁺ and [M(en)₃]³⁺ (M = Co or Rh, EN = 1,2-diamino-ethane). By using (+)-[Rh(en)₃]³⁺, optical resolution via less soluble diastereoisomeric salts has been achieved, and isomerization and racemization have been studied. Resolved tris-malonatocobaltate(III) has been used as a model. A novel thermochromism (77-293 K) in solid Δ(+)-[Rhen₃]Λ[Co(sa1)₃ is described.     

Palladium (II) chloride as a reagent for the mild aromatization of piperidine and cyclohexanone

Summary Piperidine may be rapidly converted into pyridine using palladium(II) Chloride or tetrachloropalladate(II) ion in aqueous medium at pH 10-11 and in the absence of oxygen. Cyclohexanone may be aromatized under the same conditions, although more slowly. The products fromo-cyclohexenylcyclohexanone are also described.     

Equilibria in complexes of n-heterocyclic compounds—LI. Synergic solubility and x-ray crystal structure analysis of mer-chloro-oxalato-tris-pyridine-iridium(III), [IrCl(py)3(C2O4)]

The title compound, mer-[IrCl(py)₃(C₂O₄)], has been made by the reaction of the known trans-dichloro-tetrapyridine-iridium(III) chloride with ethanedioate ion(oxalate) in aqueous ethanol. A non-electrolyte, it resembles its rhodium eutrope in showing extraordinary synergic solubility in water: pyridine. An X-ray structure determination has confirmed the mer geometry.     

6-alkoxy-3,4-dihydro-2h-pyrans from substituted α,β-unsaturated esters

Cycloaddition reactions of substituted α,β-unsaturated esters with various electronich olefins lead to 6-alkoxy-3,4-dihydro-2H-pyrans.     

Dimorphism in a 2,2′,2″-terpyridyl compound

Chloro-(2,2,2-terpyridine)platinum(II) chloride dihydrate, [Pt(terpy)Cl]Cl · 2H₂O, crystallizes from aqueous EtOH (1:1) as a yellow dimorph, but from dilute (1 M) HCl as its less stable red dimorph. X-ray powder photography shows that, above 100 °C, the red form converts into the yellow form.     

Equilibria in complexes ofn-heterocyclic molecules,part XXVI. Reactions of hydroxide and water with the tris-(2,2′-bipyrazine)iron(II) and tris-[2,2′-bis-(5,6-dihydro-4-H-1,3-oxazine)]iron(II) ions

Summary The reactions of [Fe(bipyz)₃]²⁺ (bipyz = 2,2-bipyrazine) and [Fe(box)₃]²⁺ [box = 2,2-bis-(5,6-dihydro-4-H-1,3-oxazine] with H₂O and HO^– in aqueous solution have been followed. The [Fe(bipyz)₃]²⁺ ion is attacked at the ligand with both nucleophiles and the ligand is cleaved. A similar reaction between HO^– and [Fe(box)₃]²⁺ is observed. Detailed kinetics for all reactions are reported.phen 1,10-phenanthroline - bipy 2,2-bipyridyl - bipym 2,2-bipyrimidine Part XXV: R. D. Gillard, W. S. Walters and P. A. Williams,J. Chem. Soc. Dalton Trans., in press.     

Automatic measurement of pesticides in drinking water using on-line solid-phase extraction, HPLC and chemometry

Using an automated on-line phase extraction device, followed by HPLC, various pesticides groups can be separated and quantified chromatographically in a single run. By using a diode-array detector capable of automatically identifying components and determining their homogeneity by utilizing multiple, non subjective spectral comparison techniques, correct results can be obtained. For peaks that co-elute due to inadequate resolution, Multi Component Analysis (MCA) provides quantitative accuracy with a determination limit as low as 0.010 g/L with few exceptions.