Johannes G. Vos

Synthesis, separation, and NMR characterisation of the fac- and mer-isomers of tris(1-methyl-3-(pyridin-2-yl)-1,2,4-triazole)ruthenium(II) hexafluorophosphate

Abstract The preparation of tris(1-methyl-3-(pyridin-2-yl)- 1,2,4-triazole)ruthenium(II) hexafluorophosphate is described. The separation of facial and meridional isomers has been achieved through crystallisation methods. The isomers can be clearly distinguished by their 1 H NMR and 13 C NMR spectra. NMR evidence suggests that the triazole ring is bound to the central metal atom by the N4 donor atom. The title compound does not show any emission at room temperature or liquid nitrogen temperature. Electrochemical data suggest that the ligand (1-Mepytr) is a weaker π-acceptor than 2,2′-bipyridine, but has strong σ- donor properties.

Acid-base chemistry of some 1,2,4-triazole and imidazole complexes of ruthenium(II)bis(2,2'-bipyridyl)

Abstract The acid-base chemistry of [Ru(2,2′-bipyridyl) 2 (imidazole) 2 ] 2+ and [Ru(2,2′-bipyridyl) 2 (1,2,4-triazole) 2 ] 2+ has been studied in both the ground and the excited state. From the pH dependence of emission and absorption spectra it was found that both complexes are stronger acids in the excited state compared to the ground state. In sulphuric acid media the 1,2,4-triazole complex is a stronger base in the excited state than in the ground state. pK values for the different proton-equilibria are reported.

GROUP VI METAL PENTACARBONYL COMPLEXES OF 1,2,4-TRIAZOLES

Abstract The synthesis of chromium and tungsten pentacarbonyl complexes with 4-methyl and 4-phenyl-1,2,4-triazole is reported. The nature of the lowest energy absorption in the ultraviolet spectra of these complexes has been examined and shown to be principally a ligand field band. The triazoles are shown to be acting as monodentate ligands by infrared and 1 H nuclear magnetic resonance spectroscopy. The compounds show strong solvent dependence in the 1 H NMR and these effects are explained by solvent—solute interaction. The temperature dependence of the 1 H NMR spectrum of W(CO) 5 (4-phenyl-1,2,4-triazole) has also been examined.

Carbonyl complexes of 1,2,4-triazoles ☆: II. The crystal structure of pentacarbonyl-4-methyl-1,2,4-triazolechromium(0), Cr(CO)5(C3H3H5). Chromium-to-triazole π-bonding

Abstract The crystal structure of pentacarbonyl-4-methyl-1,2,4-triazolechromium [Cr(CO) 5 (C 3 N 3 H 5 )] has been determined by single-crystal X-ray techniques. The compound crystallizes in the space group Pbca with a 10.899(2), b 17.572(2), c 11.877(2) A and Z = 8. The compound consists of monomeric units in which the chromium atom is coordinated octahedrally to five CO groups and one monodentate coordinating 4-methyl-1,2,4-triazole ligand (CrN 2.111(2) A). Full matrix least-squares refinement resulted in a final R = 0.025 ( R w = 0.0324). There appears to be no or little π-interaction between the triazole ligand and the chromium atom.

Ruthenium(II)bis(2,2-bipyridyl) complexes of some 1,2,4-triazoles☆

Abstract The first example of ruthenium complexes of 1,2,4-triazoles are reported. Compounds of the types [(bpy)2RuL2]2+ (bpy = 2,2′ bipyridyl, L = 1,2,4- triazole (Htrz), 4-phenyl-1,2,4-triazole (Phrz), 4 methyl -1,2,4-triazole (Metrz) and 4-allyl-1,2,4- triazole (Altrz) and of the types (bpy)2RuL2 (L = triazolato anion) have been prepared. The complexes are characterised by UV/VIS infrared and 1H NMR spectra and their redox chemistry has been investigated using cyclic-voltammetry. In all complexes reported the tiazole ligands are acting as monodentate

Non-stationary processes at polymer coated rotating disk electrodes: Part I. Model and simulation

Abstract A time dependent model for the mediated oxidation of a substrate in bulk solution at a polymer modified rotating disk electrode is proposed and a numerical solution is found by orthogonal collocation. The mediation system consists of a surface bound redox species which can accept electrons from a substrate in solution. In the model considered here the substrate can enter the film freely but does not react at the electrode surface. The effect of the variation of substrate concentration, mediator concentration, effective charge transfer diffusion coefficient of the bound species and homogeneous rate constant on the electrochemical behaviour of the modified electrode is considered. Good qualitative agreement was found between simulated current-potential curves and experimental curves using [Fe(CN) 6 ] 4− a substrate and [Ru(bpy) 2 Cl(PVP) 5 ]Cl as the polymer coating.

A kinetic investigation of the hydrogenation of acetone by [Ru(2,2′-bipyridyl)2(CO)H]PF6·0.5acetone

A kinetic investigation of the hydrogenation of acetone to propan-2-01 by [Ru(2,2’-bipyridyl)2(CWI + in buffered aqueous solutions has been carried out. The dependence of the pseudo-first order rate constant of the reaction, kobs, on acetone, buffer and H+ concentration, has been studied. No dependence of k,, on temperature was observed. The kinetic data support a mechanism involving general acid catalysis.

Iron(III) complexes of N-donor ligands. Part II. The reaction of [Fe(L)2Cl2][FeCl4] with 1,2,4-triazole, 4-Allyl-1,2,4-triazole and 4,4′-bipyridyl; Rearrangement of the chelating ligands☆

Abstract [Fe(bpy)2Cl2][FeCl4] and [Fe(dmbpy)2Cl2][FeCl4] were reacted with 1,2,4-triazole (Htrz), 4-allyl-1,2,4,-triazole (Altrz) and 4,4′-bipyridyl (44bpy). The products obtained have been characterised by elemental analyses, infrared spectroscopy and Mossbauer spectroscopy. A rearrangement of the bipyridyl ligands was found and the products obtained are probably mononuclear for Htrz, dimeric for 44bpy and dimeric or polymeric for Altrz.

A spectroscopic and polarographic investigation of the complexation of cefazolin with copper(II) ions

Etude IR et polarographique de la formation du complexe Cu(CEF) 2 vert; il semblerait y avoir une coordination pontante des groupes acide carboxylique

The crystal and molecular structure of tetracarbonyl(6-p-styryl-2,2'-bipyridyl)tungsten(0): an examination of the affect of a bulky group α to one coordinating nitrogen atom in a bidentate ligand

Abstract The crystal and molecular structure of tetracarbonyl(6- p -styryl-2,2′-bipyridyl)tungsten(0) have been determined by single crystal X-ray techniques. Cell dimensions are a 13.735(17), b 8.839(6) and c 17.105(12) A for the monoclinic unit cell with β 109.06(8)° and Z = 4. The space group was determined as P 2 1 / n . The structure was solved by conventional Patterson and Fourier methods and refined to a final R -value of 0.055 (1734 unique reflections) by block diagonal least squares. The molecule consists of monomeric units containing one tungsten atom bound to four terminal carbonyl groups and to one 6- p -styryl-2,2′-bipyridyl ligand via its two nitrogen atoms. The presence of the styryl group α to one coordinating nitrogen causes a significant difference in the bond lengths between the central tungsten atom and the nitrogen atoms (WN(1), 2.29(1) A; WN(2) 2.23(1) A).