CATALYTIC OXYGENATION OF OLEFIN WITH DIOXYGEN AND TETRA-T-BUTYLPHTHALOCYANINE COMPLEXES IN THE PRESENCE OF SODIUM-BOROHYDRIDE

Catalytic oxygenation of styrene with dioxygen was performed by tetra- t-butylphthalocyanine complexes of manganese(III), iron(III), and coba lt(II) in the presence of sodium borohydride using ethanol as a solven t. The yield of 1-phenylethanol increased with the passage of time in the case of the manganese(III) and iron(III) complexes, but an inducti on period appeared in the case of the cobalt(II) complex. The initial reaction rate was 2.8 X 10(-3) or 3.4 X 10(-2) mmol min(-1) for the re action catalyzed by the manganese(III) or cobalt(II) complex respectiv ely. No oxygenation product was formed in anaerobic ethanol with any o f the complexes, but ethylbenzene was formed exclusively in the presen ce of the cobalt(II) complex. A radical scavenger, 2,2,6,6-tetramethyl piperidine-1-oxyl, inhibited the reaction considerably with the mangan ese(III) or iron(III) complex, but inhibited the reaction slightly wit h the cobalt(II) complex. The amount of oxygenation product from alpha -methylstyrene was larger than that from styrene in the case of the ma nganese(III) and iron(III) complexes, but the amount of oxygenation pr oduct from alpha-methylstyrene was almost the same as that from styren e in the case of the cobalt(II) complex. A radical mechanism is propos ed for the oxygenation reaction of olefin catalyzed by the complexes. In the case of the cobalt(II) complex, a sigma-bound intermediate may also contribute to the reaction. (C) 1998 Elsevier Science S.A. All ri ghts reserved.