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

The complexes s-bis(ferrocenecarboxylato)bis(pyridine)copper(II) (2) a nd trans-bis(ferrocenecarboxylato)- copper(II) (3) have been prepared from the reaction of tetrakis(ferrocenecarboxylato)bis (tetrahydrofura n) dicopper(II) (1) and the appropriate base. trans-Bis(ferrocenecarbo xylato)bis(pyridine) copper(II) crystallizes as two isomers - one in w hich the carboxylate group coordinates in a chelating mode (2a) and on e in which the carboxylate group coordinates as a monodentate ligand ( 2b). Complex 2a crystallizes in the monoclinic space group P2(1)/c wit h 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 oc tahedral with four equatorial carboxlate oxygen atoms and two axial py ridine nitrogen atoms. The two Cu-O distances differ by approximately 0.2 Angstrom suggesting that the carboxylate function bonds in an appr oximate chelating mode. Complexes 2b and 3 both crystallize in the tri clinic space group P1 with a=5.986(2), b=8.038(2), c=15.512(3) Angstro m, alpha=104.42(2), beta=93.11(2), gamma=99.95(2)degrees, V=708.1(3) A ngstrom(3) Z=1, and a=7.475(3), b=9.296(3), c=10.090(3) Angstrom, alph a=111.05(2), beta=92.35(4), gamma=101.69(3)degrees, V=635.7(4) Angstro m(3) Z=1 for 2b and 3, respectively. The structures of 2b and 3 are be st 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 d escribed in terms of the proposed requirement that two proximate metal atoms are involved in the catalytic process and the possible dimeriza tion of 2 and not 3.