Blaženka Foretić

Reactions of the aquapentacyanoferrate(II) ion with 2-nitroso-1-naphthol and 2-nitroso-1-naphthol-4-sulphonic acid

Abstract The aqua ligand of the aquapentacyanoferrate(II) ion was replaced by 2-nitroso-1-naphthol and its sulphonate derivative giving the analogous mononuclear nitroso-naphtholpentacyanoferrate(II) complex in the first stage of the reaction. In the second stage, a cyano-bridged binuclear product was obtained and characterized as pentacyanoferrate(II)-μ-cyano-tricyanonitrosonaphtholferrate(II). The latter reaction was catalysed by mercury(II) ions. The complexes were characterized on the basis of analytical, IR and UV-vis spectral data and have in the solid state and in solution a predominately quinone oximic structure. The preparation of the tris(2-nitroso-1-naphthol)ferrate(II) complex is also reported.

Tandem β-Elimination/Hetero-Michael Addition Rearrangement of an N-Alkylated Pyridinium Oxime to an O-Alkylated Pyridine Oxime Ether: An Experimental and Computational Study

A novel OH(-)-promoted tandem reaction involving C(β)-N(+)(pyridinium) cleavage and ether C(β)-O(oxime) bond formation in aqueous media has been presented. The study fully elucidates the fascinating reaction behavior of N-benzoylethylpyridinium-4-oxime chloride in aqueous media under mild reaction conditions. The reaction journey begins with the exclusive β-elimination and formation of pyridine-4-oxime and phenyl vinyl ketone and ends with the formation of O-alkylated pyridine oxime ether. A combination of experimental and computational studies enabled the introduction of a new type of rearrangement process that involves a unique tandem reaction sequence. We showed that (E)-O-benzoylethylpyridine-4-oxime is formed in aqueous solution by a base-induced tandem β-elimination/hetero-Michael addition rearrangement of (E)-N-benzoylethylpyridinium-4-oximate, the novel synthetic route to this engaging target class of compounds. The complete mechanistic picture of this rearrangement process was presented and discussed in terms of the E1cb reaction scheme within the rate-limiting β-elimination step.

Reaction of 1-benzoylethylpyridinium-4-aldoxime chloride with aquapentacyanoferrate(II)

The results of a spectrophotometric investigation of the reaction of the biologically active salt 1-benzoylethylpyridinium-4-aldoxime chloride with aquapentacyanoferrate(II) ion are presented. In spite of the presence of two donor sites, only the carbonyl group of the ligand coordinates to the iron centre. Reaction kinetics are consistent with a dissociative mechanism.

Spectroscopic Studies of Methimazole Reactivity toward the Aquapentacyanoferrate (II) Ion in Aqueous Solutions

Methimazole (2-mercapto-1-methylimidazole, MMI) and its pentacyanoferrate (II) complex have been charac- terized by means of UV/Vis, Raman, and NMR spectroscopy. The reaction of MMI with aquapentacyanoferrate (II), (Fe(CN)5(H2O)) 3� , in buffered aqueous solutions yielded the (Fe(CN)5(MMI)) 3� complex. It was found that only thione tautomer of MMI coordinates to the iron (II). The exceptionally stabile and inert complex was produced.

Spectrophotometric Studies of Reactions of the Aquapentacyanoferrate(II) Ion with Ketones. Kinetics and Mechanism of the Substitution Reaction of the Aquapentacyanoferrate(II) Ion with 1-Benzoylethylpyridinium Chloride

Abstract The carbonyl group of compounds of the phenacyl- and benzoylethyl-pyridinium type is recognized as a potential σ donor ligand which can produce complexes with the aquapentacyanoferrate(II) ion. Its reactive form is the ionized one i.e. the enolate ion. A detailed spectrophotometric investigation has been made for the reaction of the aquapentacyanoferrate(II) ion with 1-benzoylethylpyridinium chloride. The equilibrium constant of the produced complex was derived using two literatury available additional types of processing the molar ratio method’s experimental data which were not found to be applied to this type of complexes. The kinetics of this substitution reaction were studied in buffered solutions at pH = 8.0 and I = 0.05 M. The obtained results are consistent with a dissociative mechanism.

Vibrational analysis of 1-methyl-pyridinium-2-aldoxime and 1-methyl-pyridinium-4-aldoxime cations.

Pyrimidinium aldoximes are administered intravenously in cases of acute organophosphate poisoning. Since questions regarding their morphology and active conformation in the solution are still open, an effort was made to establish correspondence between their crystal state conformers and vibrational spectra, thus facilitating the future work on the assignment of bands in solution. Normal coordinate analysis including the potential energy distribution for all modes was performed for 1-methyl-pyridinium-2-aldoxime (PAM2AN) and 1-methyl-pyridinium-4-aldoxime (PAM4AN) cations (charge=+e, spin=0). Positions of infrared and Raman bands of corresponding chloride salts agree rather well with predicted values, except for modes taking part in hydrogen bonding to anions. The strength of hydrogen bonding is estimated to be of medium strength in both salts, the bonding in PAM2AN being stronger. The calculated and observed values of the characteristic stretching modes for the aldoxime moiety have been in accordance with the stronger acidity of PAM2AN structural isomer.

Thetris(2-nitroso-1-naphtholato)ferrate(II) ion

SummaryThetris(2-nitroso-1-naphtholato)ferrate(II) complex is isolated in the form of its ferrous salt and characterized by analytical, infrared, and UV/Vis data. In the solid state and in solution the complex has predominantly a quinone oximic structure. The oxime group is deprotonated and bound to ironvia the nitrogen atom.ZusammenfassungDertris(2-Nitroso-1-naphtholato)ferrat(II)-Komplex wurde in der Form seines Ferrosalzes isoliert und durch Analyse und Spektroskopie (IR, UV/Vis) charakterisiert. Im festen Zustand und in Lösung hat der Komplex vorwiegend Chinonoximstruktur. Die Oximgruppe ist deprotoniert und über das Stickstoffatom an das Eisen gebunden.