ROLE OF THE LIGAND IN THE COBALT(II)-CATALYZED DECOMPOSITION OF TERT-BUTYL HYDROPEROXIDE - EVIDENCE FOR THE PARTICIPATION OF BRIDGED DICOBALT COMPLEXES

In the cobalt(II)-catalysed decomposition of t-butyl hydroperoxide at 25 degrees C in a 5:1 mixture (v/v) of chlorobenzene and dioxane, coba lt 2-ethylhexanoate is more active as a catalyst than the cobalt(II) c omplexes of a number of 1,3-dicarbonyl compounds. These complexes beco me deactivated and, in general, a decrease in the acidity of the paren t 1,3-dicarbonyl compound lowers the rate of deactivation. This relati onship, as well as the high activity of the 2-ethylhexanoate, is consi stent with the radical chain decomposition of the hydroperoxide being initiated by a catalytic cycle which involves bridged dicobalt complex es. This cycle differs from the currently accepted Haber and Weiss cyc le in that it does not directly generate an alkoxy radical. (C) 1997 E lsevier Science Ltd.