Preparation, structure and catecholase-mimetic activity of two mononuclear ferrocenecarboxylate copper(I1) complexes

Abstract

The complexes trans-bIs(ferrocenecarboxylato)bls(pyridIne)copper(II) (2) and trans-bls(ferrocenecarboxylato)- bis(lmldazole)copper(II) (3) have been prepared from the reaction of tetrakis(ferrocenecarboxylato)bis(tetrahydrofuran) dlcopper(II) (1) and the appropriate base. trans-Bis(ferrocenecarboxylato)brs(pyridlne)copper(II) crystallizes as two isomers - one in which the carboxylate group coordinates m a chelating mode (2a) and one in which the carboxylate group coordinates as a monodentate ligand (2b). Complex 2a crystallizes in the monochnlc space group F2,/c with a = 14.761(5), b=5.922(2), c = 15.913(6) A, p= 102.69(3)“, V= 1357.1(S) A’, Z=2. The structure is compressed rhombic octahedral with four equatorial carbo late oxygen atoms and two axial pyrldme nitrogen atoms. The two Cu-0 distances differ by approximately 0.2 2 suggesting that the carboxylate function bonds m an approximate chelating mode. Complexes 2b and 3 both crystalhze m the trlchmc space roup Piwith a =5.986(2), b = 8 038(2), c = 15X2(3) A, cy=104.42(2), /3=93.11(2), y=99 95(2)“, V=708.1(3) 13 Z=land n = 7.475(3), b = 9.296(3), c = 10.090(3) A, (Y= 11105(2), p=92.38(4), y= 101.69(3)“, V=635.7(4) A’, Z=;for 2b and 3, respectively The structures of 2b and 3 are best described as square planar with a CuN,O, core having remote, weakly interacting, carboxylate oxygen atoms from the carboxylate groups at 2.53 and 2.76 8, from the copper atom for 2b and 3, respectively. The catalytic activities of 1, 2 and 3 toward the aerobic oxidation of catechol to o-quinone were determined The activity of 2 is similar to that of 1 but much greater than that of 3 These drfferences are described in terms of the proposed requirement that two proximate metal atoms are involved in the catalytic process and the possible dlmerization of 2 and not 3