SYNTHESIS, CRYSTAL-STRUCTURE AND POLYMORPHISM OF A MU-OXO BRIDGED BINUCLEAR IRON(III) COMPLEX OF 2,2'6',2''6''2''-QUATERPYRIDINE

Aqueous solutions of iron(III) perchlorate and 2,2':6'2 '': 6 '',2'''- quaterpyridine (L, C20H14N4) in the presence of triethylamine gave dee p red crystals of two polymorphic phases of [{FeL(H2O)}(2)(mu-O)][ClO4 ](4) . 2H(2)O 1, a mu-oxo derivative of iron(III). One has been identi fied as a monoclinic phase, space group P2(1)/n, with unit cell a = 13 .080(3), b = 14.045(3), c = 13.778(3) Angstrom, beta = 105.52(3)degree s and the other as an orthorhombic one, space group Pbca with unit cel l a = 14.175(2), b = 15.463(1) and c = 20.949(3) Angstrom. The crystal structures of both polymorphs have been studied and shown to correspo nd to slightly different geometries of the same cation. To reduce some degree of disorder in the perchlorate anions, the monoclinic phase ha s also been studied at -150 degrees C, giving an ordered pattern. The crystal structures of the two phases are compared. The two iron atoms are at the centre of corner-sharing octahedra, with the water trans to the mu-bonded oxide.