The intrinsic catalytic activity of a hybrid gel-derived ZrO2-acetylacetonate (HSGZ) material towards the oxidative degradation of phenanthrene (PHE), in aqueous solution and in the dark, was revealed for the first time. The HSGZ catalyst is a polymeric network of zirconium oxo-clusters on the surface of which part of Zr4+ ions are involved in strong complexation with acetylacetonate (acac) ligands. The HSGZ gave significant PHE degradation rates acting as radicals initiator without any light irradiation at 30 °C. Free radicals were formed on the solid surface by the coexistence of Zr(IV)-acac and Zr(III)-acac• complexes in equilibrium at a given temperature, from which reactive oxygen species were produced in the presence of molecular O2. A direct evidence of radical's presence on HSGZ solid surface was obtained by EPR spectroscopy. The analysis of the degradation products confirmed that the reaction goes on through the formation of intermediate free radicals, leading to the first ring-opening and to the formation of phthalates as main intermediates. Subsequently, low molecular weight alkanes are produced. Finally, a deep oxidation of the intermediates occurs completing the mineralization process. The HSGZ catalyst showed a good stability under the reaction conditions, retaining its catalytic activity after repeated tests.

Oxidative degradation of phenanthrene in the absence of light irradiatiion by hybrid ZrO2-acetylacetonate gel-derived catalyst

Styrene has been polymerized by a Quinone Transfer Radical Polymerization (QTRP) based on the redox reaction of an ortho-quinone and a metal catalyst. Several metal acetylacetonates have been tested in this work. The radical polymerization of styrene is largely controlled when phenanthrenequinone (PhQ) is used with catalytic amounts of Co(acac)2, Ni(acac)2, Mn(acac)2 or 3, and Al(acac)3. As a rule, in the presence of all these metallic complexes, the polystyrene molar mass increases with the monomer conversion, and polydispersity (Mw/Mn) is in the 1.3–1.6 range (at least until 40% monomer conversion). Styrene polymerization has also been resumed by polystyrene chains prepared by QTRP. In the specific case of manganese acetylacetonates, an amine or phosphine ligand has to be added for the control to be effective. Finally, two mechanistic hypotheses have been proposed, depending on whether the oxidation state of the metal can be easily changed or not. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2723-2733, 2005

Quinone transfer radical polymerization (QTRP) of styrene: Catalysis by different metal complexes

Polymerization of methyl methacrylate by metallocenes

New adducts of manganese(II)βdiketonate: An example of strong magnetic exchange coupling between the manganese(II) ions

Zur polymerisationsauslösenden Wirkung von Molybdän(V)‐oxid‐chlorid in Gegenwart von Diphenylsulfoxid

Manganese(III) acetylacetonate, in the presence of a suitable electron donor such as dimethyl sulphoxide, is an active, selective, initiator of free-radical polymerization at 25°, the order for the monomers studied being acrylonitrile > methyl methacrylate > styrene: suggested mechanisms for selective and nonselective components of the reaction involve ligand displacement.

C. H. Bamford

Papers

Initiation of polymerization by ligand displacement