Time Positron Diagnostics of Metal β-Diketonates

The effects of the nature of the metal atom and -substituents in aluminum(III), chromium(III), cobalt(III), and iron(III) acetylacetonates on the lifetime and intensity of a long-lived component in positron and positronium annihilation were studied by the method of positron diagnostics. An addition of a positron to the -system of a chelate ring is supposed, which makes it possible to qualitatively estimate the basicities of the complexes. Annihilation of positrons and halogen-containing positronium -diketonates is accompanied by the formation of a protonated complex; for -organylthioacetylacetonates, annihilation follows the inhibition mechanism.     

Thermal decomposition of silicon-containing chromium and cobalt γ-[(alkylthio)(alkoxy)phosphorylthio]acetylacetonates

Thermal decomposition of silicon-containing chromium and cobalt γ-[(alkylthio)(alkoxy)phosphorylthio]acetylacetonates in air was studied by derivatography. Thermal decomposition of the monomeric metal chelates containing triethylsilyl groups starts from the elimination of the substituent at P, followed by oxidation of the γ-thioacetylacetonate group. Thermal oxidation of polyorganylsiloxanes with phosphorus-substituted γ-thioacetylacetonate fragments starts with the oxidation of the γ-thioacetylacetonate groups, followed by oxidation of the alkoxy and vinylthio groups at phosphorus.     

Phosphorylation of trivalent metal tris(3-bromo-2,4-pentanedionates)

Reactions of chromium(III) and cobalt (III) tris(3-bromo-2,4-pentandionates) with sodium dibutyl phosphate, sodium dibutylphosphinate, sodium dibutyl dithiophosphate, and sodium dibutyldithiophosphinate were studied. Oxygen-containing derivatives of phosphorus acids give metal polyphosphates and polyphosphonates, and in the case of sodium dibutyl phosphate, a bromine substitution product was isolated in 3% yield. The reactions of the chelates with sodium dibutyl dithiophosphate and sodium dibutyldithiophosphinate, substitution products were isolated in 54% and 65% yields, respectively. The reactions all involved reductive dehalogenation along with substitution.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1472–1475.Original Russian Text Copyright © 2004 by Shapkin, Apanasenko, Skobun, Ivanova.This revised version was published online in April 2005 with a corrected cover date.     

Positron lifetime diagnostics of β-diketonates of bivalent metals

Positron lifetime diagnostics was used to study manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II) acetylacetonates, γ-chloro and γ-bromo chelate complexes of cobalt and nickel, and similar halo and nitro chelate complexes of copper. The dependences of the annihilation lifetime τ₂ on the metal nature and the stability constant of the metal chelate ring were established. The annihilation lifetime and intensity were found to depend not only on the electronic effect of the γ-substituent in the chelate ring but also on the structure of the complex. A comparison of the dependences of the frequencies of the C-O and M-O stretching vibrations on τ₂ revealed that a positron interacts simultaneously with the γ-carbon atoms and the O atoms of the chelate ring, whose accessibilities are determined by the structures of bis(chelates). The plots of the ionization potentials of the n-orbitals of the bis(chelates) vs. τ₂ were similar to the plots of the quenching rate constant of the benzophenone triplet vs. τ₂ in the presence of the bis(chelates).