Oxidation reaction of the copper(I) phenoxo complex [(phen)(Ph 3P)Cu(OPH)]: The formation of the copper(II) derivative [(phen)Cu(OPh(OC 6H 4-2-(OH)], having a catecholate group derived from phenol hydroxylation reaction

Abstract

The copper(I) bicarbonato complex [(phen)(Ph 3P)Cu(O 2COH)] (1) (phen = 1,10-phenanthroline) reacts under nitrogen with phenol giving the copper(I) phenoxo derivative [(phen)(Ph 3P)Cu(OPh)] (2). Complex 2 was shown to undergo a facile hydrolysis, PhOH being released. The action of moist CO 2 on 2 allowed the isolation of the starting bicarbonato complex 1. The reaction of 1 with excess phenol under an oxygen atmosphere, gave the unexpected copper(II) derivative [(phen)Cu(OPh)(OC 6H 4-2-(OH)] (3). The catecholate group, OC 6H 4-2-(OH), which is present in complex 3, originates from a phenol hydroxylation reaction assisted by the copper center. The same complex 3 has been also obtained by reacting 2 with excess PhOH under oxidative conditions. The bicarbonato complex 1 reacts with catechol under an oxygen atmosphere giving [(phen)Cu(cat)] (4) or the bis(catecholate)copper(II) derivative, (phen)Cu[OC 6H 4-2-(OH)] 2 (5), depending on the molar ratio copper/catechol. The copper(II) complexes 3, 4 and 5 were shown to be sensitive to water; in the case of compounds 3 and 5 a reaction takes place, the Cu OPh (complex 3) and one of the Cu OC 6H 4-2-(OH) (complex 5) groups being involved, phenol (complex 3) and catechol (complex 5) being respectively released. Complex 4, owing to its tendency to retain water of crystallization, converts into [(phen)Cu(cat)]H 2O (6). From the hydrolysis reactions of 3 and 5, [Display omitted] the catecholato derivative 6 was always obtained, probably through the intermediate formation of the copper(II) hydroxo-catecholate complex [(phen)Cu(OH)(OC 6H 4-2-(OH))].