Homogeneous catalysis by tetra-t-butylphthalocyanine iron: intermediates in the oxidative dimerization of 2,6-di-t-butylphenol

The oxygen-bridged dinuclear complex derived from tetra-t-butylphthalocyaninato-iron efficiently catalyses the oxidative dimerization of o,o'-disubstituted phenols such as 2,6-di-t-butylphenol to yield 3,3',5,5'-tetra-t-butyl-p-bisphenoquinone. UV and NMR spectroscopy, as well as an independent synthesis of the product, clearly indicate that the intermediate 3,3',5,5'-tetra-t-butylbiphenyl-4,4'-diol (3) is accumulated at high substrate to catalyst ratios, i.e. about 1550, whereas at ratios of about 100 the bisphenoquinone 4 is exclusively formed. (C) 1998 Elsevier Science S.A. All rights reserved.