A. B. Shapiro

Paramagnetic complexes of 4-trifluoroacetoacetyl-2,2,5,5-tetramethyl-Δ3-imidazolin-1-oxyl

Conclusions1.4-Trifluoroacetoacetyl-2,2,5,5-tetramethyl-Δ3-imidazolin-1-oxyl and its complexes with Cu(II), Co(II), and Eu(III) have been synthesized.2.On the basis of a study of the magnetic properties of the paramagnetic complexes that have been prepared, it has been established that there is a weak exchange interaction between the unpaired electrons of the nitroxyl fragments and the variable-valence metal ions.

Hydrogenation of stable nitroxyl radicals with acetylenic bonds on Ni, Pd, and Pt catalysts

Conclusions1.We have examined the liquid-phase hydrogenation of stable iminoxyl radicals with acetylenic bonds — 4-ethynyl-4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl and 4-phenylethylnyl-4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl on Raney Ni, Pt, and Pd catalysts.2.On Raney Ni the paramagnetic center and the C=C bond of the radicals are reduced simultaneously; in the presence of Pt the iminoxyl group is preferentially hydrogenated, while on Pd black the C≡C bond is reduced (via the olefinic compound) without affecting the paramagnetic center.3.In the course of this work we have prepared several new stable iminoxyl radicals: 4-ethynyl-4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl and 4-phenylethynyl-4-hydroxy-2,2, 6,6-tetramethylpiperidin-1-oxyl, 4-vinyl-4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-(5-phenylvinyl)-4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, and 4-(β-phenylethy1)-4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, together with 4-vinyl-1,4-dihydroxy-2,2,6,6-tetramethylpiperidine and 4-ethyl-1,4-dihydroxy-2,2,6,6-tetramethylpiperidine.

Investigation of the stepwise mechanism and selectivity of the hydrogenation of stable nitroxide free radicals on a Pt catalyst

1. The kinetics and stepwise mechanism of the catalytic hydrogenation of nitroxide biradicals on Pt-black in the liquid phase were investigated. 2. Biradicals with distant (noninteracting) nitroxide fragments are reduced selectively through the step of formation of the corresponding hydroxylamino radicals. 3. The selectivity of the process is due to the stronger adsorption of the biradicals on Pt in comparison with the monoradicals formed intermediately. 4. In the noncatalytic reduction of the biradical by phenylhydrazine, the reaction proceeds nonselectively, with the simultaneous formation of a hydroxylamino radical and a dihydroxylamine.