PREPARATION, STRUCTURE AND CATECHOLASE-MIMETIC ACTIVITY OF 2 MONONUCLEAR FERROCENECARBOXYLATE COPPER(II) COMPLEXES

The complexes trans-bis(ferrocenecarboxylato)bis(pyridine)copper(II) (2) and trans-bis(ferrocenecarboxylato)- copper(II) (3) have been prepared from the reaction of tetrakis(ferrocenecarboxylato)bis (tetrahydrofuran) dicopper(II) (1) and the appropriate base. trans-Bis(ferrocenecarboxylato)bis(pyridine) copper(II) crystallizes as two isomers - one in which the carboxylate group coordinates in a chelating mode (2a) and one in which the carboxylate group coordinates as a monodentate ligand (2b). Complex 2a crystallizes in the monoclinic space group P2(1)/c with a=14.761(5), b=5.922(2), c=15.913(6) Angstrom, beta=102.69(3)degrees, V=1357.1(8) Angstrom(3), Z=2. The structure is compressed rhombic octahedral with four equatorial carboxlate oxygen atoms and two axial pyridine nitrogen atoms. The two Cu-O distances differ by approximately 0.2 Angstrom suggesting that the carboxylate function bonds in an approximate chelating mode. Complexes 2b and 3 both crystallize in the triclinic space group P1 with a=5.986(2), b=8.038(2), c=15.512(3) Angstrom, alpha=104.42(2), beta=93.11(2), gamma=99.95(2)degrees, V=708.1(3) Angstrom(3) Z=1, and a=7.475(3), b=9.296(3), c=10.090(3) Angstrom, alpha=111.05(2), beta=92.35(4), gamma=101.69(3)degrees, V=635.7(4) Angstrom(3) Z=1 for 2b and 3, respectively. The structures of 2b and 3 are best described as square planar with a CuN2O2 core having remote, weakly interacting, carboxylate oxygen atoms from the carboxylate groups at 2.53 and 2.76 Angstrom 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 differences are described in terms of the proposed requirement that two proximate metal atoms are involved in the catalytic process and the possible dimerization of 2 and not 3.