Synthesis, characterization and catalytic activity of peripherally tetra-substituted Co(II) phthalocyanines for cyclohexene oxidation

Abstract

New 3,3-diphenylpropoxyphthalonitrile (5) was obtained from 3,3-diphenylpropanol (3) and 4-nitrophthalonitrile (4) with K2CO3 in DMF at 50 degrees C. The novel cobalt(II) phthalocyanine complexes, tetrakis-[2-(1,4-dioxa-8-azaspiro[4.5]dec-8-yl)ethoxy]phthalocyaninato cobalt(II) (2) and tetrakis-(3,3-diphenylpropoxy)phthalocyaninato cobalt(II) (6) were prepared by the reaction of the phthalonitrile derivatives 1 and 5 with CoCl2 by microwave irradiation in 2-(dimethylamino) ethanol for at 175 degrees C, 350 W for 7 and 10 min, respectively. These new cobalt(II) phthalocyanine complexes were characterized by spectroscopic methods (IR, UV-visible and mass spectroscopy) as well as elemental analysis. Complexes 2 and 6 are employed as catalyst for the oxidation of cyclohexene using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA), aerobic oxygen and hydrogen peroxide (H2O2) as oxidant. It is observed that both complexes can selectively oxidize cyclohexene to give 2-cyclohexene-1-ol as major product, and 2-cyclohexen-1-one and cyclohexene oxide as minor products. TBHP was found to be the best oxidant since minimal destruction of the catalyst, higher selectivity and conversion were observed in the products. Copyright (C) 2012 John Wiley & Sons, Ltd.